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Finish 3d printed parts


Ultimate Guide to Finishing 3D Printed Parts

Time to read: 13 min

The purpose of this article is to detail the different finishing methods for FDM and PolyJet 3D printed parts and the techniques/tips that can elevate the look and feel of your prototypes.

A simple Apple Watch stand design will be utilized as a case study. This stand is a model with pockets and internal and external features that needs to be surface finished to a standard that complements the shiny exterior of an Apple Watch put on it.

Here’s a quick overview of the main points this article covers:

  • PLA: If you’re working with a tight budget then PLA is going to be your best material choice; the results aren’t as polished but the price is cheapest.
  • ABS: If your budget is moderate then go with ABS. It’s not as cheap as PLA but still at a low price point and the material is more reliable than PLA.
  • VeroBlack or VeroWhite: For the highest quality parts go with VeroBlack/VeroWhite. This will give you the best dimensional accuracy and best overall polished look.

Overview of Post-Processing

The 3d printing post-processing needed for the watch stand parts involves a combination of repairing and preparing the print for post-processing, sanding, and painting.

The finished sample 3D printed parts with all three materials should be smooth, matte black surfaces. Inherent to the 3D printing process, with every print are unique challenges and considerations to arrive at the best finish possible. Although there are ways to mitigate the challenges, experience in 3D printing goes a long way.

The print settings process for each material is detailed separately and a summation of the results may be found in the conclusion of this article.

ABS (Printed on a Dimension Elite)

The Dimension Elite prints are smooth, clean, and ready to sand out of the NaOH bath.

There are, however, clear stepping lines between the printed layers. If we don’t remove these stepping lines, they’ll show up in the final paint coat which will ruin our smooth finish. Thankfully, removing these will be easy thanks to ABS’s high melting point and easy sandability.

Materials Needed

The materials we’ll be using:

  • Sandpaper (grits 100 to 600)
  • Medium, fine, and extra-fine sanding sponges
  • XTC-3D brush-on coating (As an alternative, Bondo putty is a common solution to fill holes in parts. We chose XTC-3D for its viscosity, sandability, and ability to penetrate small perforations, which makes it desirable over Bondo putty)
  • Razor blade
  • Foam brush, mixing cups and popsicle sticks
  • Sandable Krylon Primer
  • Montana Acrylic Primer in Shock Black
  • Matte Acrylic Varnish

Sanding

Sanding the ABS print is simple and straightforward. First start with 100 – 200 grit sandpaper to remove stepping lines and then gradually increase up to 600 grit to achieve a smooth finish without sanding lines.

Pro Tip: Sand in small circular movements evenly across the surface of the part. Avoid sanding in one direction only, especially in the direction of the stepping lines to prevent striations or “trenches” in the print.

Beware that ABS is very easy to sand, so be careful not to overdo it. Removing as little as .010” can be enough to completely remove any stepping layers and oversanding can compromise critical dimensions.

After sanding the parts, some holes are revealed on our part left by an incomplete layer around the letters DIM. These holes can perforate through the finished paint coat to create ugly sinkholes, so we need to find a solution.

As you can see in the Catalyst tray to the right, there are large holes between the DIM and the edge of the part. Moving the DIM up in our Solidworks model would solve this, but for now we’ll have to find a way to fill these holes with a sandable filler.

Repairing the Incomplete Layer

We’re going to use a thin, sandable epoxy called XTC-3D to fill the tiny holes and crevices in our print. XTC-3D is cheap (a 24 oz bottle costs about $25), quick, thin, and effective. Note that a small amount goes a long way (within the 10 minute pot life).

Pro Tip: Be sure to maintain a weight ratio of 100 Part A to 42 Part B. Mix thoroughly for one minute and coat your part within the 10 minute pot life. For more details, check Smooth-On’s technical bulletin here, and a great instructional example here.

Before applying the XTC-3D, wash the part with soap and dry with compressed air to ensure your part is thoroughly clean and free of any oils or sanding dust. Also make sure to wear gloves so as not to get any hand oils or sweat on your part.

Fill in holes or gaps in your print with a very thin (1/64”) coat; a thin layer of XTC-3D will level itself out. We used a razor blade to scrape excess XTC-3D into the unwanted holes and gaps, making sure to avoid any areas we didn’t want filled (like the letters DIM).

Allow the XTC-3D sufficient time to become tack-free dry (approximately 2 hours). Now we’re ready to continue sanding away at the excess XTC-3D layer with 300 to 600 grit to reveal the repaired surface.

Then, after another thorough wash, we’re ready to begin preparing our repaired surfaces for painting.

Priming and Painting

Painting 3D printed parts is a vast world of acrylics, enamels, sprays, and airbrushes.

In this example, we’ll be using Montana spray can paints to follow a relatively straight forward process: prime, dry, paint, dry, varnish, dry.

Standard spray painting principles apply:

  1. First make sure your surface is oil-free, dust-free and hole-free
  2. Shake your cans for at least two minutes prior to painting
  3. Ensure your cap is clean to prevent drips
  4. Be aware of how the paint is accumulating on the part and look for any pooling or dripping
  5. Paint in many light coats rather than fewer heavy coats; this is especially important for 3D printed parts with internal and obscured geometries
  6. Paint in controlled, well-ventilated and well-lit areas

The Dimension prints started with very obvious stepping between layers. If you’ve sanded properly up until now to create as smooth a surface as possible, these layers shouldn’t show up in your final paint finish.

The Final Result

The finished ABS part is matte black and smooth to the touch with very little evidence of layering in most surfaces. A few important results to note here:

  • Sharp internal pockets are tough to sand. After about 30 minutes of sanding, we still had a hard time removing all the layering and the stepping shows up even after priming, painting, and varnishing the print.
  • Because we had to remove more surfaces from the sanding, there is some sacrifice in regards to the final geometry of the part.
  • Filling the incomplete layer with a thin coat of XTC-3D worked very well; those holes are invisible in the final paint layer.

VeroBlack (Printed on an Objet30)

Thanks to .0011” resolution, the Objet30 prints have some stepping between layers, but nowhere near as obvious as in our FDM prints.

The Objet30 prints come out of the printer with a thick layer of support structure material so before we can begin finishing our VeroBlack part, we’ll need to remove this support structure and the residue it leaves behind.

VeroBlack 3D Printed Part Materials Needed

The materials needed for post-3D printing finishing:

  1. Sandpaper (grits 100 to 600)
  2. Medium, fine, and Extra fine Sanding Sponges
  3. Sandable Krylon Primer
  4. Montana Acrylic Primer in Shock Black
  5. Matte Acrylic Varnish

VeroBlack 3D Printed Part Sanding

Start with 100 grit sandpaper to wet sand the residue and gradually move to wet sand with 300 grit sandpaper; the residue will fall off in small soft white chunks. This is the hardest part of the VeroBlack finishing process and it took us about 30 to 40 minutes to remove all the residual layer.

After removing the residual layer by wet sanding utilizing 300 grit sandpaper, the surface of the part will begin to feel smooth. If you rub the part with your fingernail, you’ll feel it’s harder and more plastic-like beneath the gummy residual coat. Continue wet sanding through to 600 fine grit sandpaper until the part is fully smooth.

Pro Tip: Water breaks up the residue, so wet sanding is a highly effective method to get a smooth, residue-free, paintable, and homogenous surface.

Thoroughly clean your part with soap and water before you move on to the next step to remove any additional residue. Again, we recommend using compressed air to dry the part and clear any accumulated dust.

Beware that VeroBlack is like ABS: very easy to sand, so be careful not to overdo it. Once you break through the residual layer, the actual VeroBlack will sand very easily. Removing as little as .005” can be enough to completely remove any stepping layers. Be careful as oversanding can compromise critical dimensions.

VeroBlack 3D Printed Part Priming and Painting

Next, we’re going to paint the VeroBlack part just as we did the ABS part: using Montana spray can paint with the following process: prime, dry, paint, dry, varnish, dry.

Standard spray-painting principles apply:

  1. First make sure you have a good surface quality which is oil-free, dust-free and hole-free
  2. Shake each paint can for at least two minutes prior to painting
  3. Ensure your cap is clean to prevent drips
  4. Be aware of how the paint is accumulating on the part and look for any pooling or dripping
  5. Paint in many light coats rather than fewer heavy coats; this is especially important for 3D printed parts with internal and obscured geometries
  6. Only paint in controlled, well-ventilated, and well-lit areas

VeroBlack 3D Printed Part Final Results

The finished VeroBlack part is matte black and smooth to the touch. A couple points to note here:

  • Some of the internal corners were not sanded enough to remove the residue, so you can see how the paint powdered up in these areas. This will likely result in peeling paint over time.
  • Although very little stepping is visible on the part, you can see slight evidence of it here. This part could have probably used 30 more minutes of thorough sanding.

PLA (Printed on a 5th gen. Replicator)

Now for the dreaded PLA, a notoriously difficult material to finish. But with some tricks and patience, it too can join ABS and VeroBlack in the ranks of matte black glory!

This Replicator print came off the plate with severe striations: see the parallel grooves in the layers of the part above. This could be a result of machine quality, but for now we’ll just have to find a way to maneuver these striations to a smooth part.

Sanding PLA is difficult, in part because of how soft and gummy it becomes if you try to sand too aggressively or quickly, so we’ll explore options on how to smooth 3d prints with minimal effort and abrasion.

PLA 3D Printed Part Sanding

If you choose to sand the PLA directly, the process is straightforward. Note: PLA acetone smoothing is not advisable. PLA smoothing is not as forgiving as ABS when it comes to sanding and abrasion, so you will likely spend more time removing the stepping between layers, especially with the severe striations in a print like ours.

Begin with a low (100 – 200) grit sandpaper, sanding away at the bumpy striations and any raft or support material (aluminum foil) left behind. Particularly in the case of MakerBot support, it’s easiest to remove them with a flush cutter or pair of pliers and brush them with a rotary multi-tool first before sanding away at them.

Depending on the size and geometry of your part, you’ll likely be stuck in the 100 – 300 grit sandpaper range for a while to smooth out striations and pesky support structure remnants.

Once layering and striations are less prevalent, move through finer grits (400 – 600) sandpaper to achieve a shiny surface ready for priming and painting.

Pro Tip: Patience is key when sanding PLA. Turn on a movie or your favorite show, but don’t zone out! Sand in small circles evenly across the surface of the part. If you’re using a sanding multi tool on PLA, be careful not to overheat/melt your 3D printed part. 

An alternative method to sanding PLA prints directly is smoothing the PLA print with the XTC-3D first and then sand on top of the coating.

PLA 3D Printed Part Finishing

We’re going to use XTC-3D to create a smooth, sandable, paintable layer of epoxy clear coat glossy finish around our PLA print.

Before applying XTC-3D, ensure that your part is thoroughly clean, free of any oils and sanding dust (sensing a pattern yet?). Wash the part with soap and dry with compressed air to clear any dust. Again make sure to wear gloves to protect both your part and your hands.

Brush on the XTC-3D in a thin (1/64”) coat; as long as the coat is thin enough, it will level itself out. Between coats, leave 1.5 hours for the XTC-3D to dry.

It may be difficult to coat an entire part at once, so don’t be afraid to do it in sections, making sure to keep overlapping to a minimum between sections. Wait 90 minutes between first and second coats and after you’ve finished wait 2 hours to allow the shiny surface to become tack-free.

With striations as severe as ours, it will take multiple coats to get a smooth uniform surface, so patience is key. Remember that multiple thin glossy finish coats will level better than thick coats.

Pro Tip: Internal pockets are susceptible to pooling so be careful to suck up or remove any pooling that occurs before the XTC-3D begins to dry (that’s what we’re doing in the left picture above).

Beware that XTC-3D may compromise critical dimensions, but applying thin glossy finish coats will allow you to minimize the additional material.

After the XTC-3D layer has hardened (two hours after application of the last coat) it should be ready for sanding. Follow basic sanding guidelines, starting with 300 grit sandpaper (thanks to the smoothness of the XTC-3D) and sanding in small circular movements to even the surface. Any wavy patterns may require a coarser grit sandpaper to remove.

The sandpaper will scratch up the XTC-3D coat; focus on getting a level surface, moving through to 600 grit sandpaper.

After you’ve finished sanding 3D prints, make sure to thoroughly clean your part with soap and water and then dry using compressed air before moving on to the next step.‍

PLA 3D Printed Part Priming and Painting

Painting PLA parts follows the same process as the ABS and VeroBlack parts: prime, dry, paint, dry, varnish, dry.

Standard spray painting principles apply:

  1. Make sure your surface is oil-free, dust-free and hole-free
  2. Shake your cans for at least two minutes prior to painting
  3. Ensure your cap is clean to prevent drips
  4. Be aware of how the paint is accumulating on the part and look for any pooling or dripping
  5. Paint in many light coats rather than fewer heavy coats; this is especially important for 3D printed parts with internal and obscured geometries
  6. Paint in controlled, well-ventilated and well-lit areas

PLA 3D Printed Part Final Results

The XTC-3D coated PLA part is matte, black, and has a smooth surface to the touch with a few problems:

  • Although the XTC-3D has worked well to smooth the part and make sanding quicker and easier, it has left pooling in the internal pocket that has shown through the paint finish.
  • Striations are still visible on the part. 30 more minutes of sanding 3D prints could have prevented these from showing through the final paint finish.

Results and Closing Thoughts

After finishing all three parts to a smooth, matte black finish, let’s take a look at the differences in process, time, materials and finish.

Differences in Process
ABS (Dimension Elite)
  • Sand from 100 to 600 grit
  • Repair holes with XTC-3D (may not apply to your part)
  • Sand away XTC-3D with 300 to 600 grit
  • Prime, Paint, Varnish
VeroBlack (Objet30)
  • Sand from 100 to 600 grit
  • Prime, Paint, Varnish
PLA (Replicator 5th gen.)
  • Coat in 1 to 3 layers of XTC-3D (depending on how bad the striations on your print are)
  • Sand away XTC-3D with 100 to 600 grit
  • Prime, Paint, Varnish

Differences in Time

The part that took the longest to finish was PLA due to the XTC-3D coating time. Even without XTC-3D, however, PLA typically takes longer to sand than ABS or VeroBlack.

In our example, the VeroBlack was ultimately faster to finish since we repaired our ABS print with XTC-3D and stepping between layers was not as significant in the VeroBlack print.

All things considered, VeroBlack was the quickest to get to a smooth, matte black finish.

Pro Tip: If you’re in a rush to get from printer to photoshoot, pick the Dimension Elite or Objet30. Especially in models with overhangs and significant amounts of support material, the Dimension Elite and Objet30 both have support material that is quickly removable via dissolution, whereas the PLA support on a Replicator can significantly increase the time required to get to a smooth surface part.

Differences in Cost and Materials

It’s important to consider the amount of time it will take to finish your model as well as the overall look and dimension when considering the price.

PLA is the cheapest out of the three, at $20 per part, followed by ABS at $55, and VeroBlack at $110. In our opinion, VeroBlack is the best bang for your buck since it’s the shortest to surface finish and will give you the most accurate model.

Comparison of the Final Results

At first glance, all three models may look very similar, but there are a few key differences in the final finish.

Both the ABS and the PLA finished prints have evidence of stepping between layers that is visible in the final paint coat. The VeroBlack print requires much less effort to remove these steps, which ultimately are not as obvious in the final paint coat.

Although the ABS and the VeroBlack finished prints have very similar surface finishes, more material (approximately .020”) was lost in the sanding process for the ABS to remove stepping between layers. In contrast, the VeroBlack print required less sanding, so the final object dimensions are closer to the original design intent.

Individual Summary of Each Part

VeroBlack: High layer resolution (. 0011”) means little sanding is required to get a smooth, paintable part. Critical dimensions don’t need to be compromised to get a smooth surface quality part and no repairs are needed for fine detailed features.

ABS: Parts are easy to sand, but small fine detailed features may require repairing and careful sanding to remove stepping between layers. Once this stepping is removed, painting is straightforward.

PLA: The cheapest option, but also has the potential to be the most difficult to finish, depending on support structures and quality of the print. May require significant sanding and repairing via XTC-3D or Bondo filler.

Browse our website to learn more about our capabilities, such as 3D Printing and CNC Machining.

Quick Facts: 

  1. Finishing a 3D printed part often involves a combination of the following processes: smoother application, sanding, polishing, cleaning and painting. The process is unique to the material type.  
  2. A smooth finish with 3D printing is achievable but, post-processing will greatly improve the smoothness of parts. 
  3. Epoxy resins are an excellent choice for sealing PLA printed parts. 
  4. Acetone smoothing is not recommended for PLA prints.
  5. In general, IPA or rubbing alcohol will not dissolve PLA but there are some varieties that may be IPA soluble. Consult your filament material datasheet or technical datasheet for more information.
  6. PLA may be smoothed without sanding by dipping it or spraying it with a coating.
  7. ABS is tougher and lighter than PLA which is stronger and stiffer. Both have their ideal applications, but PLA is typically considered a hobby material whereas ABS is ideal for prototyping.

How to Finish Your 3D Prints - Ultimate Guide to Filling, Priming, Sanding & Painting 3D Printed Parts

Your 3D prints are now coming out great & looking as they should, but then again, they’re still looking like they’re 3D printed.  

Whether you’re printing for business, want to rescue a not-quite-perfect print, or just need some tips for finishing 3D printed parts, this guide on how to finish 3D prints will explain the various methods the experts use: allowing you to learn the full lowdown on how to smooth out 3D prints. 

In general, finishing is the post-printing process of smoothing the surface of a printed object so that it looks as perfect and professional as possible. Large industrial 3D printers accomplish this task by using acetone cloud chambers, multi-axis enamel jets, and agitating chemical baths.

Interior Painting Tips - Using a Ro...

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Interior Painting Tips - Using a Roller

However, I’m guessing you don’t have to have that kind of expensive equipment to finish 3D printed parts that are smooth and sharp.

In this article, we’re going to look at the various finishing techniques that you can use to get perfect-looking printed objects every time. Because every print material requires slightly different finishing techniques, we’re going to look at each of the common finishing techniques in turn and see how they apply to a material you may be using.

This will give you an opportunity to decide what may work for you given your individual setup, circumstances and printing practices.

Basic Best Beginning Practices for 3D Print Finishing

On the subject of printing practices, one of the best ways to minimize the amount of finishing work cleaning up 3D prints is by starting at the very beginning of the printing process. Your slicer settings have a lot to do with how your finished object looks.

For example, layer height contributes greatly to how a finished object looks. Layer height is the setting that establishes the height of each layer of filament in your print. In some sense, layer height in 3D printing is akin to resolution in photography or videography.

When you choose a thicker layer height, your object will have less fine detail and the layers will be more viable. When you choose a thinner layer height, a higher level of detail is possible and your layers will tend to blend into one another.

Print speed is another important setting that can contribute to overall object quality. Print speed is how fast the print head travels while extruding filament. Therefore, optimal speed depends on the object you are printing and the filament material that you are using to fabricate the object.

In general, simple objects with less detail can be printed faster without much loss of quality. On the other hand, more complex objects with more detail will benefit from a slower print speed. Because of this, it pays to experiment with your print speed to see what works best for the job you’re printing.

If you’re intending on painting 3D printed parts after you’ve finished printing, it may be best to use a lower layer height. You’ll spend more time printing, but less time sanding 3D printed parts before painting them. Read on to learn more about painting PLA and other 3D materials.  

You’re going to be sanding 3D prints after printing in order to obtain the smoothest surface possible. This means that your object is going to need to be a bit more robust in terms of thickness and infill than you previously planned for.

A shell is the outer wall of a designed object. Shell thickness refers to the number of layers that the outer wall will have before infill printing will begin. The higher the setting is for shell thickness, the thicker the outer walls of your object will be.

Obviously, thicker walls make for a sturdier object. So, when you’re planning to finish your object post-printing through sanding, you want to increase the shell thickness to account for the material that you will be removing later.

Fill density or infill is a measure of how much material will be printed inside the outer shell of the object in question. Fill density is usually measured as a percentage of whole, as opposed to a unit of measure. This means that if 100% fill density is selected, the printed object will be solid, with no empty space inside the outer shell. Likewise, if 0% is selected, the printed object will be empty inside.

Fill density is used to conserve filament while printing and speed up printing times. However, an object with more infill will be stronger and heavier than an object with less infill. Again, because sanding removes material from the surface of an object and requires the application of a certain amount of pressure to do so, you’re going to want to increase your fill density when printing the object. Doing so will insure that your object won’t be damaged or deform during the finishing process.

For more information on slicer settings, take a look at our article on the subject here. 

Slicer settings are not the only thing that affects the amount of potential finishing work that may need to be done once an object is printed. The quality of the printing filament that you are using can impact end quality as well. Poor quality filament contains impurities that will negatively affect how the material melts, extrudes and cools.

In addition, cheaper filament is not produced to the rigid tolerances necessary for high-quality end results. Specifically, variations in the diameter of the filament can lead to under extrusion and over extrusion problems during printing, both of which will produce a final object with serious surface flaws that will have to be dealt with through finishing.

Finally, consider using a color of filament that will closely match the desired color of the finished object. Doing so will reduce the amount of painting that needs to be done once printing is over and you’re finishing the object. 

Admittedly colour is less important for those truly professional-grade finishes though, because of the amount of primer paint coats needed. 

Support Structures

As you know, a 3D printer starts printing an object from the bottom up. This means that if you have a design that incorporates overhangs, upper areas in your model that don’t have any underlying material, you’re going to run into problems. After all, your printer filament is subject to the law of gravity. It can’t be extruded onto thin air.

In these cases, you will have used a support structure which supplies a surface onto which your overhangs could be printed. These structures, which may or may not be soluble, will need to be removed before the finishing process can begin.

Here you’ll notice Jon printed this helmet inverted, with minimal supports. 

If your support structure isn’t soluble, you will need to break or cut away the supporting material. A pair of flush cutters or an Exacto knife can help you get cuts that are flush with the printed surface of the object that you wish to retain. Once the supporting material has been removed, use a bit of 200 grit or 400 grit sandpaper to gently smooth the support marks.

You’ll notice in the image above, the model was printed upside down so that minimal support structures would be left – and so less work to remove them. It’s also easier going smoothing PLA on large, simple areas like the top of the helmet than potentially more intricate parts of the underneath.  

If your support structure is soluble, you’re likely dealing with either PVA or HIPS. In this case, simply submerge the object in the solvent in question – water for PVA and Limonene for HIPS. The water should completely dissolve the PVA support structure within several hours.

Limonene will take longer to dissolve the HIPS support structure, usually about 24 hours. In both cases, remember to give the containers containing the solvent and your object a gentle shake from time to time to help the process along.

How to Clean Up 3D Prints With Filler

Before you sand and paint 3D printed models, it may be worth filling any small gaps, cracks, or underfilled sections with a 3D print filler solution. This is usually a variant of epoxy resin that is easy to work with, and can be sanded down afterward. 

We recommend using XTC-3D which you can get here. You’ll notice you can even use it for smoothing out 3D prints just by brushing it over as a 3D print coating.

Although you won’t get the same level of high-quality finish we’re aiming for in this article – it could be a quick way to improve a print. Think of it as the lazy man’s 3D printing finishing tip. 

The neater you are filling the gaps, the less sanding you’ll need to do afterward – so try to be as neat as possible. You’ll also need to leave it to cure for at least a few hours after filling. 

How to Sand 3D Prints (& Polishing)

Sanding is a simple and somewhat easy way to finish processing a 3D print, depending on the material in question. Some printing materials respond well to sanding, with other materials it may not be an option.

For example, PLA and ABS can respond very well to sanding. With harder materials, like Polycarbonate and PMMA, sanding is not an option. (We will discuss finishing options for harder materials in more detail below.)

If you’re looking for how to make 3D prints smooth and the material you’re using can’t be vapor smoothed, then sanding it is!

Among the few PLA finishing techniques, sanding gives the best result. Be sure to choose a good quality PLA filament, as poorer filaments can be more challenging to get a good smooth surface on.  

Sanding the surface of an object made from PLA or ABS is a fairly straightforward process – as long as you approach the job with some patience. For example, PLA’s lower melting temperature can make it get gummy and soft if it is sanded to aggressively and quickly. Therefore, patience and a bit of time are the keys to getting a smooth mirror finish on any object made with PLA.

Also, you need to be prepared to use multiple grit sizes of sandpaper. For example, with PLA be prepared to use every size from a 200 rough grit to a 3000 fine grit and every gradient in between.

Pro tip: With a material that’s a bit harder, like ABS, you may want to start with the same grit size but try wet sanding the object with a waterproof abrasive sheets such as “Wet & Dry.” A harder material can stand increased pressure while being sanded, but friction still is an issue.

Wet sanding helps reduce the heat that results from friction, allowing for more efficient removal of unwanted material with less deforming of the object due to frictional heat.

No matter the material, you want to start with the coarsest grit of sandpaper. Use a circular motion with a slow moderate pressure to remove unwanted material. The idea is to get rid of what you don’t want while leaving absolutely no trace that you’ve done any finishing work.

Once you’ve gone over the object once with coarse grit sandpaper, you want to repeat the process with a finer grit. For example, if you started with a 200 grit sandpaper, you want to switch to a 400 grit sandpaper on your next pass. Once you’ve patiently done a pass over the object with the 400 grit, you switch to 600 grit and repeat the process.

The idea is to slowly and carefully remove the features on the objects that you don’t want, while slowly and carefully retaining and highlighting the finish on the features that you do want to keep.

When you are scaling up the grit number on the sandpaper, remember that time is your friend when it comes to getting a mirror-smooth finish. In general, the more time that you spend sanding, the better the finish that you will obtain. This is especially true with the lower-numbered grit sandpapers.

Keep working your way up to finer and finer sandpaper grits – 600 to 800, 800 to 1000, and so on. As you get up over 1000 grit, the finish on your object will start to feel really smooth, but don’t stop here. To get a truly professional finish, take the time to carefully go over your object with 2000 girt and then 3000 grit. That extra attention will really pay off in the quality of the finish that you end up with.

Once you’ve sanded your object, it’s ready for either painting or simply polishing, depending on your preference. For more detail on this 3D sanding technique, view our guide on getting a mirror finish from sanding here.

Vapor Polishing

The before and after effects of a cold acetone smoothing bath.

An alternative to sanding is vapor polishing. With vapor polishing, a small amount of an applicable solvent is placed in a container. The printed object is also placed in the container on a platform that suspends it above the solvent. A non-airtight cover is placed on the container and the solvent is then heated until it begins to produce vapor.

This is an analogous process to what happens when water is heated to a point where it begins to form steam. Essentially, the solvent in question is brought to a temperature where it steams, or begins to transition from a liquid to a gas.

Once this happens, the solvent “steam” is allowed to surround, coat, and interact with the surface of the printed object. Ideally, the gaseous solvent begins to slowly and evenly dissolve the surface of the object, removing unwanted material and features.

Once the desired look of the surface of the object is achieved, the object is removed from the container and allowed to air dry. Drying stops the interaction of the solvent with the material the object is made of. The end result is an object with a smooth and professional finish.

As was the case with sanding, increasing shell thickness and fill density prior to printing will produce a more robust object that will be capable of withstanding vapor polishing without problems.

Vapor polishing softens the rough surface layers of the object so that they flow together to produce the desired finish. So if there are insufficient top layers present when using this process, just like with sanding, the undersurface of the object can be exposed and ruin the effect.

While industrial printers and finishers use cloud chambers to vapor polish projects, many makers replicate the process using common objects. For example, a wide-mouthed glass container with a lid or a simple saucepan can be used to hold the solvent. A raft or platform of aluminum foil can be used to suspend the object above the solvent. Finally, the heated bed of your printer or your home range can be used to carefully heat the solvent.

Now a word of caution. Every printing material is soluble is a different substance. Some of these substances are relatively benign, others are extremely toxic.

For example, in ascending order of toxicity, PVA is water-soluble. HIPS is soluble in Limonene. ABS and PMMA are soluble in acetone. PLA is most efficiently soluble in tetrahydrofuran or THF. Polycarbonate is soluble in dichloromethane. The list goes on.

Vaporizing any chemical solvent poses a number of hazards. First, solvent steam is much more readily absorbed by the body through respiration and contact. The more toxic the solvent, the worse the prolonged exposure to the substance will be. Therefore, any vapor polishing must be done in a well-ventilated environment. The use of a respirator, protective clothing and gloves is well neigh mandatory.

Second, many solvents are flammable. Therefore, heating a solvent must be done under controlled conditions. You need to know the solvent’s boiling point and flame point beforehand and use a calibrated thermometer to ensure the temperature of the solvent stays within safe parameters. Always work with a fire extinguisher handy. To read more about vapor polishing, check out our in-depth guide here.

How to Paint 3D Printed Objects

No matter if you’re prototyping an object for use in a Kickstarter campaign or simply want to create something that’s absolutely stunning in its presentation and perfection, painting may be the way to go.

Successful finishing using paint actually involves two separate processes – priming and then painting. However, before looking at either, let’s take a look at a preliminary step that you need to take that will guarantee stellar results once you start painting.

If you’re wondering: can you paint 3D printed objects – the answers yes of course, but you need to do the right…

Preliminary Steps

When priming and painting an object, it’s best to first mount it on what’s known as a painting block using a dowel. A painting block is nothing more than a block of wood that supports the object while it is being primed and painted.How to paint PLA: Here you can see the helmet raised up, ready for finishing touches.

Simply take a wood dowel and, using a drill with a bit that is equivalent to the dowel’s diameter, drill a small hole into an inconspicuous area of your object. Insert the dowel into the hole you’ve drilled until it sets securely. (Alternatively, you can use a naturally occurring hole or declivity in your object to seat the dowel. )

Next, using the same size drill bit, drill a hole into a block of wood large enough to securely balance and support your object. Insert the other end of the wood dowel that you used on your object into the wood block. You now have a way to provide even and smooth coats of primer and paint to your object without having to touch it and risk leaving smears and fingerprints behind.

Also, remember that priming and painting an object can be a messy business. You want to stop the paint from getting on objects that it shouldn’t and you want to keep foreign objects, like dust, from settling on your printed object while it dries. Therefore, work in a well-ventilated area that is clean and well-lit.

Most spray-on paints contain solvents that can aerosolize and be inhaled. Consider wearing an approved respirator and nitrile gloves while priming and painting.

Also consider constructing a simple spray booth by hanging plastic sheeting around three sides of the surface you will be placing the object on while priming and painting.

This will contain the paint to the area around the object and will reduce the amount of dust and debris that will adhere to the object while the paint or primer is drying.

Priming before painting 3D prints

Primer for 3D prints is a special type of paint that comes in neutral colors. It is designed to provide a uniform surface that paint can easily bond to. Primer comes in both brush-on and spray-on varieties. When choosing a primer for your object, you are better off going with a spray-on variety.

It will cover the surface of your object with an even coat and will eliminate the use of brushes which can leave noticeable brush marks.

Best paint for 3D prints? For best results, use a primer (and paint) that are compatible with plastic and are of the same brand. Using a high-build filler primer like Krylon and Montana both are good choices.

Before priming your object, spend at least two to three minutes swirling the contents of the can of primer, using a circular motion. Doing so fully dissolves the pigment into the solvent within the can. You should never, under any circumstances, shake the can before you prime or paint. If you do, you will mix the pigment into the solvent, instead of dissolving it.

This will result in the formation of bubbles that will appear on the surface of your object while spraying. After about two or three minutes of swirling, you should hear the metal ball within the can moving smoothly. This indicates that the pigment is dissolved into the solvent and you are ready to begin priming your object.

Start with the nozzle of the can about 15 to 20 cm (6 to 8 in.) from the surface of the object. Using short and rapid strokes, begin spraying the object Start each stroke before the beginning of the object and end each stroke after the end of the object. Move quickly, rotating the object as needs. Avoid over-spraying. The goal is to start with a very thin initial coat that can be built up over time.

Once the initial coat of primer is dry, it’s time to add a second coat. Again, use short rapid strokes that start before the beginning of the object and end after the end. In the vast majority of cases, your object will only need two coats of primer to ensure an even cover that will improve the adherence of the paint you have chosen.

Once your second coat of primer is dry, you want to buff and polish the primer coat. A great and easy way to do this is to use nail buffing sticks, the kind that are available in any chemist or drug store and are used in manicures and pedicures. They come with a three grit surface.

You can skip the roughest surface and use the buffing and polishing surfaces to bring the primer coat up to glossy shine. As you did with the sandpaper, take your time and use a circular motion where possible. The goal is uniformity. When you’ve finished, gently wipe the object with a tack cloth to remove any dust created during the buffing and polishing.

Once you’ve buffed and polished the primer coat, you’re ready to begin painting. The painting process itself involves three distinct steps – undercoating, top coating and clear coating. As was the case with the primer coat, your best bet when painting is to use a spray-on variety. It will give you greater control over uniformity and layer thickness. It will also allow you to avoid brush marks.

You want to choose a painting that goes on as thinly as possible. One of the best choices is Tamiya. Tamiya paints are specifically designed for use by modelers and radio control enthusiasts. This makes them a perfect choice for finishing painting 3D printed objects.

Undercoating

Applying an undercoat layer will allow you to get the richest and deepest color when painting your object. An undercoat should not be confused with the primer coating. The two serve entirely different purposes. The primer coat is there to give the paint something even to adhere to. It prevents blotching and uneven coverage.

The undercoat layer is there to block the neutral and flat color of the primer. Undercoat layers are usually either solid black or white. Black is used for objects that will be a painted with darker toned colors. Obversely, white is used for objects that will be painted with lighter-toned colors. No matter the color, the undercoat will shine through the topcoat layers, giving the finish a luster and depth that is unmatched.

As was the case with the application of the primer, you want to use a respirator and gloves while painting. Spend two or three minutes swirling the paint can in a circular motion until the pigment dissolves in the solvent. You’ll know that this happened when you feel the metal ball in the can revolve around the inside without resistance.

Once the paint is well mixed, hold the nozzle of the can 15 to 20 cm from the surface of the object and apply the undercoat in short and rapid strokes. Once again, start these strokes before the beginning of the object and end after the end of the object. As always, rotate the object on the painting block while applying the undercoat in the thinnest layer possible.

Once the initial undercoat layer is dry, buff and polish the undercoat layer using a nail buffing stick in the same manner as you did when buffing and polishing the primer. Once this is completed, you are ready to apply a second undercoat in the same manner as the first. Once the second undercoat is dry, buff and polish as you did before.

Top Coating

Now it’s time to apply the top coat. Top coating isn’t about complete coverage. In some sense, it’s the icing on the cake. It’s there to enhance and improve all the work that you’ve already performed. Ideally, the top coat will be a color that contrasts with the color of your undercoat. The top coat will add gradients of color which will allow the contrast of the undercoat to show through. The end result will be a depth and resonance that will make your object look amazing.

All of the steps that you’ve already used when applying the primer coat and the undercoat are also used when applying the top coat. You want to use a respirator and gloves. You want to keep your object mounted on the paint block. You want to keep and the nozzle of the paint can 15 to 20 cm from the surface of the object and use short rapid strokes while painting. You want to rotate your object rapidly on the paint block while applying the top coat. You want to polish and buff in between the first and second coats.

You want to make sure that you don’t apply the paint too thickly when doing the top coating. Remember, the goal is to let some of the contrast of the undercoat to show through the top coat in order to get a sense of depth. To that end, check that there is sufficient contrast showing after the first top coat layer has dried and been polished and buffed. Depending on what you find, apply the second top coat accordingly.

Clear Coating

Clear coating, also known as finish coating, is the last step in the painting process. The purpose of clear coating is twofold. First, the clear coat adds final layers which enhance the finished look of the object. Second, the clear coat protects all of the hard finishing work you’ve already done under a protective coating.

There are two types of clear coating available – glossy and matte. Obviously, glossy is shinier and matte provides a flatter-looking end appearance. The choice between the two is merely aesthetic. Practically, they both do the same thing.

Clear coat is applied in the same way that you’ve applied every other coating. Respirator, gloves, well-swirled coating, short rapid strokes, etc. You can apply either one or two coats of clear coating depending on the circumstances and the finished look that you’re trying to achieve.

I hope this guide has been a comprehensive breakdown of the available options to you for 3D printing post-processing and gives you a clear layout on how to paint 3D printed models. If you’re willing to put in a little time, truly exceptional finishes can be achieved. But if you’re just looking for tips on smoothing out 3D prints, then this guide will at least have given you some food for thought.

Related:

  • How to sand PLA to a smooth finish
  • Best infill settings
  • How to prevent filament stringing and pillowing

Finish: How to take your 3D printed parts to the next level

At ProtoFab we offer a wide range of post-processing options that produce very different finishes. Some options are primarily about improving the mechanical properties of the part, while others are purely for aesthetics. Let's take a closer look at the available options.

We offer many impressive finishes

galvanized
review

Although 3D printing materials are quite versatile, finished parts still lack certain mechanical properties and are not suitable for all applications. In many cases, the solution to this problem is electroplating, which greatly improves the properties of the part and gives it a hard metal-like finish. Electroplated parts have a much wider range of uses than conventional 3D printed parts and look absolutely amazing.


Electroplating provides the advantages of metal without the disadvantages of traditional manufacturing

Technique

Electroplating works by applying a thin layer of metal ions to the surface of a part using an electric current. Different metals can be used and different effects can be achieved by varying the thickness of the coating and different types of grinding and polishing.

Benefits

Electroplated parts feel much more substantial, and when held in the hands, many people swear it feels like solid metal. Needless to say, this greatly improves the aesthetics of the part and makes it much more usable by the consumer.

In terms of mechanical properties, the improvement is even greater. Generally speaking, there are three areas where the improvement is most noticeable: strength, thermal performance, and chemical resistance.

The specific strength improvement depends on the metal used, but typically the tensile strength will be somewhere around 10 times greater and the bending strength will be more than 20 times greater. These improvements completely transform the part and give it a whole range of new uses.

The improvement in thermal performance is easy to understand because electroplating creates a physical barrier between the photosensitive resin and the wider environment. The same goes for chemical resistance - electroplating prevents potentially corrosive substances from getting into 3D printed materials. The same applies to UV light, which will gradually degrade and discolor parts printed on 3D SLA over time.

Color electroplating

Standard electroplating gives impressive results, but if you want to take aesthetic enhancement to the next level, you can consider color electroplating. This involves the same process as the normal electroplating described above, but then the metal surface is then sprayed with a special paint. The end effect is stunningly upscale and completely transforms the detail.


Adding color to plating creates a truly stunning finish

Vacuum plating
overview

Vacuum plating is similar to electroplating but with a much thinner metallic finish. Although the galvanized parts seem solid and substantial, in some cases the added mass may be undesirable. Vacuum coating reduces weight while providing an attractive metallic finish and improved mechanical properties.


Vacuum coating creates an attractive, light metallic coating

Technique

First of all, the part is sprayed with primer and placed inside the vacuum chamber. The metallic material is then added to the chamber where it evaporates. Due to the vacuum, the metal atoms condense onto the part, and when the process is complete, the part will have an even coverage of the material.

Benefits

In addition to weight savings, vacuum coating also allows you to coat parts with a high degree of detail. The use of electroplated coatings on ultra-precise parts may result in a loss of clarity, and in some cases may simply not be possible.

As with electroplating, mechanical properties are greatly improved in all areas, although the improvement in strength is likely to be somewhat behind that of electroplating. However, the thin coating still provides very effective resistance to UV radiation and aggressive substances. The main disadvantage of vacuum electroplating is that, due to its thinness, it is prone to scratches and may not withstand a long period of wear.

Hydrographic printing
overview

This is a relatively recent technique that has been abundant in recent years. This is a great method for creating detailed, vibrant designs in a short amount of time.


Hydrographic printing is ideal for complex models

Technique

The technique works by immersing the part in water with a pre-designed film floating on the surface. When the part enters the liquid, the pattern moves from the floating membrane to the part. The part must be pre-sprayed with a primer and an activator agent applied to the membrane prior to dipping. This technique was first introduced in 1980s, but it lacked precision and only repetitive patterns were possible. Currently, the software can create accurate designs that can be transferred with a high degree of accuracy.

Benefits

Hydrographic printing can produce stunningly vibrant colors that take the finish of any part to the next level. It also takes into account the level of design complexity that is difficult to achieve with other methods. Hand-painting very intricate patterns is extremely time-consuming, not to mention complex. With hydrographic printing, no design is too complex and can be applied very quickly. The part is only immersed in water for a few moments, and the whole process from start to finish takes only a few hours, including preparation and drying time.

Painting
overview

Spray painting may seem low-tech compared to some of the other finishes available, but the benefits of painting 3D printed parts should not be underestimated. Painting is cost effective and provides significant improvements without any major downsides. Of course, painting is often done purely for aesthetic reasons, but it also offers physical benefits. There are also different types of paint coatings, each with its own unique characteristics and applications.


Two-tone painting example

Technique

Painting SLA 3D printed parts is a complex and time-consuming process. It's not just about applying paint, it usually takes several coats and several sanding cycles. First, the part is carefully sanded to prepare it for applying the primer. The undercoat is then sprayed in the laboratory, taking great care to ensure that the coat is smooth and even. Then another round of sanding is applied before applying the top coat. If the part is to be painted in several colors, it is necessary to carefully apply masking tape, and do each of the colors in turn. Once the paint is dry, the surface is polished to achieve the desired finish.

Benefits

Painting parts not only looks amazing, but also coats them with UV protection. Color change and degradation over time are some of the main disadvantages of photosensitive resin printing, and coloring solves this problem to a large extent. It also helps protect against other types of corrosion such as chemical attack.

Coloring also helps mask any joints or imperfections that may have occurred during the printing process. For example, some parts need to have drainage holes that are subsequently filled in during post-processing, and some designs need to be printed piecemeal and glued together. Painting is a great way to give such details a perfect smoothness and smoothness

Various paints

At ProtoFab we offer three basic paint styles: glossy, matte and leather effect. Let's look at each one in turn.

Gloss paint has an attractive sheen that emphasizes the lines and curves of the design. A layer of glossy paint and a period of high-quality polishing can make even a very simple detail attractive.

Gloss paint creates an attractive sheen

Matte finish adds textural depth and can bring a sense of quality and strength to details. While not as shiny as a glossy finish, when well crafted, it can be equally eye-catching.

A matte finish makes the details look and feel

We also offer more sophisticated finish styles such as leather paint. This gives the details a very detailed textured appearance. Not all parts suit this style, but when used correctly, they can turn the main body into something that looks and feels high quality. Different paint options have a significant impact on the final look of a part, so it's important to consider the different options and determine which one works best for your part.

Skin effect painting completely transforms the look of a part

(There is a solution) How do I give 3D printed parts in PLA a shiny smooth finish?

So we know what doesn't work, but what works (but not very well) is alcohol! Only isopropyl alcohol 90% (and above) will work! Also at Walmart you can get things called Goo Gone or even better - Oops!

What you are doing is chemically melting plastic. Since PLA is made from corn (more or less), the same chemicals won't work with this kind of bioplastic, which is PLA. ABS is an oil based product, which is why acetone works.

I use these two mentioned products because they are designed to remove glue and wax and don't evaporate right away so it has time to do its job and dissolve the plastic. The alcohol will evaporate, especially with less water content, and I absolutely definitely don't want anyone doing this in the bedroom or kitchen, especially don't do it without ventilation! Vapors are highly flammable and build up quickly at room temperature, they take a little time to ignite and that's just bad!

With rubbing alcohol, I dip and soak the parts until I see they look soft like leather or, depending on the PLA used, silky. I print hotter than recommended with a hot table with little to no fan and more feed because it thickens over a certain pace and it will look like it messes up and doesn't print straight like it clogs or doesn't feed fast enough and it's true but when zoomed in feed rate to say 108 or 115 it compensates for the shrinkage and you get the same fill.

Now that being said you will have smoother prints because it gets like watery but with a higher speed and a small fan will snap into place but the hot registration will keep it too hard for the next hotend pass and new layer, The next layer will not go on cold surfaces and can easily get under the press and melted down to the last layer and two layers of 0. 15 mm act like three, but tighter and smoother.

Then Oops! chemicals or alcohol, I just remove what is left of the flaws. I take a dust-free cloth, apply the solution to it and rub in the same direction with very little pressure until I feel the cloth get stuck or bite, then leave it alone for 15 seconds and wash it off by dipping it in a bucket of cold soapy water, then I rinse with fresh water and repeat if necessary. It's best if you use a string to hold or hang parts because it's easy to leave prints.

Also even better (and I don't suggest this because any liquid being sprayed can be flammable - except water) - use spray cans instead and lightly spray the same process and dip and dip to take it off - instead of to wipe off and risk imprints with traces on the finished parts.

Sanded. Heavy sanding is another way to smooth details.

I have also tried conformal coating my parts which works but gets messy when trying to apply over a pre-coat.

Then there is body filler or if you are using paint I recommend either car paint with primer-filler, or paint from the "Automotive" section specifically for plastic and vinyl, or heavy thick paints, but not latex, but varnish paints that are heavy and fill imperfections but dry flat! There are Lexan paints for RC and model plastics, but they need a primer.

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