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3D printing nuts and bolts


A Step by Step guide to 3D printing Threads and Screws

 Category Engineering

3d printing Threads and screws are present all around us. You have them in our bathrooms, kitchens, gardens and in your cars, even in our computers. These small components are important cogs that run the world. But 3D printing threads and screws that fit properly might feel like a daunting task. That is why we have this simple guide to learn how to design and 3D print screws and threads.

Before we begin with this 3D Printing service in India, you need to know the exact difference between a screw and thread.

Well, a screw is the fastening element that is used to form a joint, such that it can be dismantled if the need arises.  Whereas a thread is the main fastening feature of a screw. It is defined as a ridge of uniform section in helical form on either the external or internal surface of a screw. That said, threads are not an exclusive feature of screws. You might have seen them on pipes, worm gears, and many other devices. Every thread is a continuous helical groove of a specific cross-section. 

Most commonly, the cross-section is either triangular or trapezoidal. Triangle thread forms find their use as fasteners, while the trapezoidal thread forms are used for power transmission purposes and as linear drives on lead screws. To make things a little bit specific, in this article we’ve discussed the triangular-shaped threads only, but everything applies to both the types.

The triangular thread forms can be further classified on the basis of the shape of the triangle and the pitch of the helical curve. On this ground they can be categorized as metric threads or inch threads. The former is used in Europe and Asia, while the latter are used in America and the UK. Next, we’ll be taking a look at the fundamental knowledge one should have before designing and 3D printing threads and screws.

  • Metric threads: The ‘M’ designation of a metric thread in 3D Printing online indicates the nominal outer diameter of a thread in millimetres. For example, the M4 thread has a nominal outer diameter of 5 mm. The nominal outer diameter is the same as the major diameter, In an external thread. Whereas, in an internal thread, the nominal outer diameter has to be determined by measuring the minor diameter and consulting a metric thread table.
  • Inch threads: Inch threads of 3D Printing in India are denoted using a number of standards, the most prominent being Unified Thread Standard (UTS). It uses numbers to name standard thread sizes for example #4. The two most significant measurements in the UTS are the major or minor diameter in external or internal threads, respectively, and the threads per inch i.e. TPI.

Before we Begin

There are concepts of online 3D Printing Bangalore we need to make ourselves familiar with, before we start designing threads.  

  • External or internal thread: An external also known as ‘male’ thread extends from a cylindrical surface. An internal or ‘female’ thread is the exact opposite of an external thread in terms of orientation, in that it is carved into a negative cylindrical surface. Bolts are a good example of employing external threads, while nuts make use of internal threads.
  • Thread axis: In online 3D Printing India, this is the central axis or imaginary line that runs through the centre of the cylinder around which the thread is formed.
  • Root: This is the bottom of the groove which runs around the thread body.
  • Crest: The topmost point of the thread profile is known as crest.
  • Major diameter: The diameter of the cylinder that encompasses the crest of the external thread or the root of the internal thread, is known as the major diameter in the terminology of online 3D Printing India. This cylinder is coaxial to the thread axis.
  • Minor diameter: The diameter of the cylinder that encircles the root of the thread in an external thread or the crest in an internal thread. This cylinder is coaxial to the thread axis and the major diameter. The minor diameter is also referred to as the ‘drill size’ diameter with relation to inner threads.
  • Pitch: The pitch is the distance between corresponding points on adjacent threads. Such as the length between two neighboring crests of a triangular thread is referred to as the pitch.

Planning and Crafting Threads

Let’s get down to the task at hand now. Let us demonstrate the process of designing external and internal threads using Fusion 360. We chose this software of online 3D Printing Bangalore because it provides a simple-to-use thread generation function.

There are other CAD programs having tools of varying degrees of similarity. But, the most important thing is to familiarize yourself with the basics, we discussed in the previous section of 3D Printing service in India. With that knowledge, it is easy to use any capable modelling tool and provide the necessary and accurate values to create the desired threads.

Let’s begin with the external thread of a bolt.

External Thread

  1. First, draw a circle. The diameter of the circle is taken as the desired thread’s major diameter.
  2. Then make it into a cylinder by extruding the circle to the required thread’s length.
  3. Move your cursor to “Create”, then select the “Thread” option from there.
  4. Finally, select the cylinder you just created to make sure that the “Modelled” checkbox is ticked or checked. Then, set the thread parameters as desired. Hit “OK” after it is done.

And, Voila! You have created your external thread! To make it into a fitting bolt, you’ll have to attach it to a bolt head suitable to your needs.

Next, let’s get down to designing the nut with an internal thread.

Internal Thread

  1. First of all, you need to draw a hexagon. Only for this tutorial, just make sure it’s bigger than the thread you want to create.
  2. Then go ahead and extrude it to the desired height, like we did for the external thread.
  3. Go to the “Create” menu and make a hole in the centre by selecting the “Hole” option there. The hole diameter should be the required thread’s major diameter.
  4. Highlight the internal surface of the hole you just created then go to “Create”, and select the “Thread” option.
  5. It is important to always remember to check the “Modelled” option. Set the thread parameters such as size etc. Click “OK”.

With that your first thread is all ready to get printed. All that remains is printing it. Then you may marvel at your creation

Is Your Printer up to the task?

While we might have made it seem simple, printing threads isn’t always easy, especially if you are working to get small diameters.

Let’s say for example, you’re working with a 0. 4-mm nozzle and a 0.2-mm layer height. With that, the smallest possible pitch you’ll be able to print will be somewhere around 0.5 mm ± 0.1 mm. Such a pitch is good enough to get an M3 thread and isn’t much of a problem if you’re trying to print an internal thread in a comparatively larger part. That’s because the thread will have plenty of time to cool down while the nozzle is working elsewhere.

But things get a bit trickier if you want to create an external thread on a screw or a bolt, for example with 3D Printing service in India. In such cases, your nozzle doesn't have a lot of space to travel around to go, this means that you’re probably in need of some extra cooling. Hence, it is important to properly test your printer beforehand. Then you may decide to print many thin external threads.

We’re linking a  thread test here for you to properly test your 3D printer’s capabilities.

Optimising your 3D Printer

Here are some comprehensive guidelines for priming your printer for 3D printing threads.

  • With online 3D Printing Bangalore, it is important to make sure your printer is properly calibrated. Thankfully, we already have a couple of handy articles for making it easy for you. You might want to check them out
  • Properly level your 3D printer bed, it is very important to get the desired results.
  • Try to print your threads vertically, whenever possible. The thread axes should be perpendicular to the print bed, for best results.
  • Supports of online 3D Printing Bangalore can be a real pain especially in parts as small as these don’t go inside the thread. So, print without supports whenever possible. Otherwise, it could prove to be a daunting task, to remove them and preserve its utility, especially with internal threads.
  • Use at least 4 vertical layers or at least 2-mm thick vertical walls, if possible. This will ensure a sturdy thread.
  • Try to set Infill density to at least 25%, even though it mostly depends on your application.
  • Layer height is another parameter of utmost importance of 3D printing service in India when printing threads. For slick operation, layers should be set as low as possible. Very important to note that, threads larger than M12 or 1/2″ can be efficiently printed with 0.2-mm layers, whereas smaller threads should be printed with thinner layers.

Advantages

A wide range of accessibility:

You can have a 3D printer that works for low cost next to your home computer – about half that if you can buy a kit and bring the printer together.

You can buy all sorts of filaments, regular and special, online. There are many free and open access modeling services that you can use right off the internet, not to mention pre-designed patterns and thousands of message boards devoted to tips, tricks, and questions about 3D printing service in India.

If you are an instructor or a designer, you might make a strong case for adding 3D printing to your career as a means to educate or develop. Online 3D printing Bangalore is an easy-to-use digital extension to every form of a creative hobby in your life.

Also, it's just as easy to go pro once you're comfortable – you'll find advanced 3D printers right next to the smaller ones, and as long as you've done your research on products and models, you can make that leap anytime you feel confident.

Individual adaptations:

3D printing service in India is useful for playing with the design. As long as you have patience (and filament) for designs, printing temperatures, and finishing methods, you can refine the object until it's just what you want during the actual 3D printing process.

Many 3D printers also let you stop in the middle of printing, make changes, and start printing again in the same place you left off. It's a flexible way to learn about designs.

Prices:

Even at its highest price, the upfront costs of online 3D printing Bangalore would come at significantly smaller prices than those of mass processing. Plus, replacement and material costs will also be relatively cheap.

A variety of materials:

You can print 3D with filaments that combine anything from thermoplastics to glass pieces, in any color you can think of (and a handful you haven't heard of yet).

Your item will shine in the dark, smell like oak, or carry water without spilling a drop. The options are infinite, and all you've got to do is pick your filament.

Conclusion

Don’t fret even if your first test is unsuccessful, have some faith in yourself and try again. Also heed these final words of wisdom:

  • Even if you do manage to print a decent looking external thread smaller than M6 (6 mm in diameter), be cautious before putting it to use and carry any weight. It’s small diameter and the nature of 3D printing services, makes this size of thread suitable only for visual models. If you desire functionality, go for a different design.
  • The smaller pitch of Internal threads, which is less than 4 mm in diameter, makes them difficult to print. At this size, you’d be better off printing a blank hole and then cutting the thread with a tap wrench. Anyway, it’s always a good idea to clean a thread properly before use, whether it’s cut or 3D printed.
  • Some materials have the tendency to shrink more than others. It’s always wise to first make some small samples to check the thread dimensions, before you print larger parts. Otherwise, you might end up with a stiff thread when printing internal threads or a very loose one when printing external threads.

And that’s a wrap, we hope your love affair with 3D printing continues!

Read More : A beginner’s guide to making 3D models using Paper

3D Printing Threads and Adding Threaded Inserts to 3D Printed Parts (With Video)

There are many ways to attach screws to 3D printed parts, including inserts, tapping, and even 3D printed screw threads.

Screws are among the most popular fasteners in any material. Can you use off-the-shelf screws with your 3D printed parts? The answer is a clear yes, for both stereolithography (SLA) and selective laser sintering (SLS) parts.

In this article, we explore different methods of using metal screws with 3D printed parts, and provide some tips for incorporating screw threads directly into your 3D design.

Watch our application video about 3D printing threads and threaded inserts for 3D printed plastics.

Video Guide

Having trouble finding the best 3D printing technology for your needs? In this video guide, we compare FDM, SLA, and SLS technologies across popular buying considerations.

Watch the Videos

Let’s take a look at the various design options for 3D printed threads, which we’ve collected over the years within Formlabs and based on feedback from our customers. Our test part is designed to showcase all these methods at once:

We’ve grouped these options based on the type of fastening, with pros and cons of each option listed for different use cases.

Sample part

See and feel Formlabs quality firsthand. We’ll ship a free sample part printed on an SLA or SLS 3D printer to your office.

Request a Free Sample Part

In this section, we look at three ways to incorporate inserts and nuts into your completed 3D prints for strong, long-lasting fastening that stands up to multiple cycles of assembly and disassembly.

Pros

  • Very good hold into 3D printed parts

  • Metal threads are strong and wear-resistant

  • Installs with a simple press fit

Screw-to-expand inserts are cylindrical, with a slight taper and knurling on the exterior surfaces. During the design stage, incorporate a boss with a depth and diameter based on the insert’s specs into your part. Print and post-process the part as normal, following the usual steps for SLA or SLS post-processing, taking care to make sure no extra material remains inside the cavity, and install the insert with a simple press fit. Adding a screw will press the knurled surface into the surrounding printed material, creating a strong friction fit.

Tip for using screw-to-expand inserts with 3D printed parts made with SLA 3D printing: Wash the part as normal, insert the screw-to-expand insert, install a screw, and post-cure the part with the screw in place. Saving this step for last reduces the chance that the insert will crack the surrounding material when expanded.

Heat-set threaded inserts are designed to be installed into thermoplastics using a soldering iron with an installation tip. They can also be used as glue-in inserts in thermoset materials, such as SLA parts. 

To install in a thermoplastic part, like one printed with SLS Powders, follow the installation instructions for your particular hardware. The typical process is to use a soldering iron, with or without a special attachment, to heat the insert, which conducts heat into the surrounding plastic. The surrounding material softens and, by pressing down with the soldering iron, you can gently press the insert into the printed part. Be sure to allow enough time for the material to cool down and regain strength before installing a screw.

To install in a thermoset part, like one printed with SLA Resins, glue can be used to hold a heat-set insert in place. Unlike with traditional installation, make sure to design your boss to match the widest diameter of the insert, and use a bead of cyanoacrylate (CA) glue or epoxy to hold it in place when installed. Be sure to allow enough time for your glue to fully cure before installing a screw.

Note: In the SLS 3D printed part photographed for this article, the boss is sized for a press-fit, as we recommend here for thermoset plastics. This also works, with a drop of glue or epoxy, for thermoplastic parts, but won’t have as strong a hold as a true heat-set installation.

Although an additional step of soldering or gluing is required, heat-set threaded inserts for both SLS and SLA parts offer improved security and strength compared to screw-to-expand inserts With either method, these are a great option to gain a little extra security and strength compared to screw-to-expand inserts, although the additional step and equipment may be inconvenient.

Cons

  • Pocket or boss needs to be designed into the part, and accessible after printing

  • Depending on geometry, may require glue and curing time

Designing a pocket or boss that securely holds a nut into the part itself is another method to get metal-on-metal contact. Hexagonal or square nuts can be used, and even locking nuts are possible to accommodate. There are many design variations for this method—just make sure your pocket or boss is easily accessible (i.e. not on an interior surface) so that the nut can be installed. For extra security, a drop of cyanoacrylate (CA) glue will hold the nut in place.

White Paper

Stereolithography (SLA) 3D printers such as the Formlabs Form 3+ have high accuracy and precision, and offer a wide range of engineering materials. Download our white paper for specific recommended design tolerances.

Download the White Paper

For speed and simplicity, it might be preferable to forego inserts and nuts in favor of screwing directly into a 3D printed part. Whether tapping threads or using a self-tapping screw, off-the-shelf hardware designed for use with plastics work well with 3D printed materials like resins and thermoplastic powders.

Using a thread tap designed for plastic is a quick, economical way to add screw threads to 3D printed parts. It doesn’t require any extra design steps, and most shops that work with plastics will already have the equipment required.

Self-tapping screws, also called thread-forming screws, can be inserted into a negative feature with no preparation work done to the part. Follow the manufacturer’s guidelines for boss dimensions. 

It’s suggested to use these with materials that are ductile, or have high elongation. Formlabs Nylon 11 Powder or Nylon 12 Powder are both suitable for this, as are the Tough and Durable Resins in the Formlabs SLA material family. Brittle materials, or those with low elongation (such as the Rigid Resins in the Formlabs SLA material family), may crack when used with self-tapping screws, so take caution and wear eye protection when using these materials.

Including threaded geometries in your printed part can be effective if you follow certain guidelines. Stick to larger thread sizes, at least  ¼”–20 (imperial) or M6 (metric) or larger; reduce stress concentrations with fillets; and use thread profiles that are designed for plastics. For smaller screws, the threads should be customized to create a better fastener. For example, printing a semi-circular thread profile (on screw and nut) and using a 0.1 mm offset gives better thread engagement with improved wear characteristics. 

SLA and SLS 3D printing are generally preferable for this method over FDM, because they are more precise and can create parts with a smoother surface finish. Any material with particularly low surface friction, such as Durable Resin, is less likely to show wear over multiple cycles of assembly and disassembly.

When preparing your part for printing, it's important to minimize support structures on any threaded surfaces to ensure your parts will come together smoothly without additional post-processing.

There are many options for combining multiple 3D printed components using screws and threaded fasteners. From directly 3D printing threads to using off the shelf inserts, you can choose any of the methods outlined above, based on the chosen material, the number of cycles of assembly and disassembly you anticipate, the strength required, and the amount of extra steps your workflow can accommodate.

Curious to see what 3D printing material might be right for your application? Use our interactive wizard to choose the best 3D printing material or request a free 3D printed sample part to see the quality firsthand.

Explore 3D Printing MaterialsRequest a Free Sample Part

3D printing - threads and screws

First things first: what is the difference between a screw and a thread?

A screw is a fastener used to form a connection that can later be dismantled, while the thread is the main fastener of the screw. In this case, the thread is not only used for screws; they are also present on pipes, in linear drives, worm gears and many other devices.

All threads have in common the way they are formed. Each thread is a continuous spiral groove of a certain cross section, made on the outer or inner side of the cylindrical surface.

In most cases, the cross section or shape is triangular or trapezoidal. Triangular thread forms are primarily used for fasteners (screws), while trapezoidal thread forms, varieties of square threads, are used for power transmission and linear drives on lead screws. To keep things simple, this article only covers triangular shaped threads, but everything applies to both types.

A further level of categorization distinguishes metric threads from inch threads. The former are mainly used in Europe and Asia, while the latter are used in America and the UK. To the untrained eye, they look the same, but the difference exists in the shape of the triangle and the pitch of the spiral curve.

In this article, we will cover the basics of designing and 3D printing screws and threads.

Basic Terms

There are a few terms and concepts that you should be familiar with before you start designing a thread.

External or internal thread : external or external thread exits the cylindrical surface. The female thread is cut on the inner cylindrical surface. For example, bolts have external threads, while nuts have internal threads.

Thread axis : line through the center of the cylinder on which the thread is to be formed.

Base : the lower part of the groove that runs around the body of the thread.

Comb : The highest point of the thread profile.

Large diameter : The diameter of a cylinder enclosing the top of an external thread or the base of an internal thread. This cylinder is concentric with the axis of the thread.

Minor Diameter : The diameter of a cylinder enclosing the root of a thread on an external thread or the crest of an internal thread. This cylinder is concentric to the thread axis and large diameter. The smaller diameter is also known as the drill diameter when handling internal threads.

Pitch : distance between equivalent points on adjacent threads. For example, the distance between two adjacent crests of a triangular thread.

Metric thread: The "M" designation of a metric thread indicates the nominal outside diameter of the thread in millimeters. For example, an M5 thread has a nominal outer diameter of 5 mm. For external threads, the nominal outside diameter is equivalent to the major diameter. For internal threads, the nominal outside diameter can be determined by measuring the minor diameter and referring to the metric thread table.

Inch threads: Inch threads are designated using a number of standards, including the Unified Thread Standard (UTS), which basically refers to standard thread sizes as numbers (eg #4). The two most important measurements in UTS are the major or minor diameter of external or internal threads, respectively, and threads per inch (TPI).

Thread Modeling

Let's look at the process of designing external and internal threads using Fusion 360, which provides a simplified threading feature.

Other CAD programs have tools with varying degrees of similarity. It is important to understand the basics presented in the previous section. With this knowledge, you will be able to use any available modeling tool for 3D modeling.

Let's start with the outer thread of the bolt.

External thread

- Draw a circle with a diameter equal to the largest diameter of the desired thread.

- Create a cylinder by extruding a circle to the desired thread length.

- Go to "Create" and select the "Thread" option.

- Select the newly created cylinder. Make sure "Modeled" is checked. Set the thread type and other thread options. Click OK.

That's it. You have an external thread! To make a good bolt out of it, you need to attach it to the head to your liking.

Now let's create a nut with an internal thread.

Internal thread

- Create a hexagon. For the purposes of this tutorial, just make sure it's larger than the carving you want to create.

- Push it out to the desired height.

- Make a hole in the center by selecting the "Hole" option from the "Create" menu. The hole diameter must match the largest thread diameter.

- Select the inner surface of the newly created hole, go to "Create" and select the "Thread" option.

- Don't forget to check the "Modeled" option. Set the thread size and other parameters. Click OK.

That's it. Your first carvings are ready for 3D printing!

Tips for 3D Printing Threaded Parts

This may seem like a simple task at first glance, but printing threads is not always easy, especially if you need small diameters.

Assume you are using a 0.4 mm nozzle and a 0.2 mm layer height. With this setting, the smallest pitch you can achieve during 3D printing is likely to be around 0.5mm (give or take 0.1mm). This pitch is suitable for M3 threads and you should have no problem trying to print an internal thread on a relatively large part. This is because your threads will have enough time to cool while the nozzle is in a different location.

Things get interesting if you need an external thread, for example on a screw or bolt. In this case, the nozzle has nowhere else to go, which means that you will probably need additional cooling. Check your 3D printer before you decide to print a lot of thin external threads.

One of the most practical options before starting thread printing is the M10 3D Printed Thread Test. Thanks to this special 3D model, you will be able to check exactly what your 3D printer is capable of.

Settings when 3D printing parts with threads

Below are some general guidelines for setting up your 3D printer when printing threads.

- Make sure your 3D printer is properly calibrated. Extruder calibration is also important.

- Always try to print threads vertically. For best results, the thread axes should be perpendicular to your 3D printer table.

- Print without the calipers, or at least make sure they don't go inside the threads. Otherwise, removing them and maintaining functionality can be a real problem, especially with internal threads.

- If possible, use at least 4 vertical layers or vertical walls at least 2 mm thick. This will ensure the strength of the thread.

- Try to set the filling density to at least 25%.

- Layer height is an important parameter when 3D printing threads. For smooth operation, the layers should be as thin as possible. As a guideline, threads larger than M12 or 1/2" can be successfully printed at 0.2mm, while smaller threads should be printed at thinner layers.

Resume

Even if your first test fails, don't despair! Here are some final tips for 3D printing threads:

- Even if you manage to print beautiful external threads smaller than M6 (6mm in diameter), think twice before using it for heavy duty use. Due to the small diameter and the nature of 3D printing, this thread size is best suited for visual models only. If it must be a functional piece, consider a different design.

- Internal threads less than 4 mm in diameter have a small pitch, which makes 3D printing difficult. Consider printing a blank hole and tapping with a wrench that size. In any case, it's always a good idea to clean threads before use, whether it's 3D printing or trimming.

- Some materials shrink more than others. Before 3D printing large threaded parts, make some small samples to check the thread dimensions.

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