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Cast 3d printer
Introduction to Metal Casting and Ways to Combine 3D Printing With Casting Workflows
Metal casting is an age-old metalworking process in which molten metal cools and solidifies in a mold to form metal parts. Despite its ancient roots, metal casting is still one of the most popular processes for companies looking to produce metal parts.
This article will cover what metal casting is, how it works, and walks you through the most common metal casting processes and the benefits manufacturers can attain by combining modern digital tools like 3D printing with traditional casting workflows.
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Get design guidelines for creating 3D printed patterns, walk through the step-by-step direct investment casting process, and explore guidelines for indirect investment casting and sand casting.
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Metal casting step-by-step from the original design through final casting.
Since the advent of metal casting, the methods have evolved and varied. Its core techniques, however, have remained constant. Here is a general step-by-step process for metal casting:
Ring patterns 3D printed in Castable Wax 40 Resin.
In order to begin the metal casting process, a manufacturer first must develop a representation of the desired pattern. This pattern is essential in designing the mold used for the cast. It is traditionally made from wood, foam, plastic, or wax and ensures that the mold accurately produces the finished metal part. Today, 3D printing is also a common method to produce patterns, which allows designers to create accurate patterns directly from digital CAD software tools.
A pattern is not an exact replica of the desired part. It has additional elements that make the casting process possible, including gates that allow molten metal to flow at a steady rate and vents for gas to escape. Additionally, patterns are also larger than the parts they represent to account for the shrinkage that occurs during cooling.
When the casting piece is hollow, the manufacturer also creates a core of sand or metal to shape the internal form.
This core gets removed upon completion of the casting.
The next step is creating a casting mold, which can be either reusable (non-expendable) or non-reusable (expendable). Non-reusable molds are usually made out of sand, plaster, wax, or by 3D printing, and just as the name suggests, they get destroyed in the casting process. Reusable molds are made out of metal and other durable materials and can be reused for multiple casting cycles.
Ceramic shells after burnout and 3D printed patterns in Clear Resin.
Molten pewter poured into a High Temp Resin 3D printed mold for metal casting.
During this step, the metal gets heated in a furnace until it melts. Depending on the application, manufacturers can use a variety of different metals, with the most commonly cast metals being iron, aluminum, aluminum alloy, steel, copper, and zinc, as well as precious metals like gold and silver. Once the metal melts, the manufacturer pours it into the mold cavity and allows it to cool and solidify.
Metal casting post-production.
Once the metal cools down and solidifies, the parts get removed from the mold. Depending on the mold type, this can be done by vibrations in a shakeout process, washing away the investment material, or by ejector pins. Then, excess material, such as vents, gates, and feeders, are removed from the parts. Finally, the parts get filed, grated, machined, or sandblasted to smooth the surface and reach the final shape requirements.
Though all metal casting techniques share the same core process, there are various methods better suited for different applications. Some of the most common methods include die casting, investment casting, and sand casting.
Die casting uses a steel mold and high pressure. (Source: buhlergroup.com)
Die casting is a metal casting process in which a manufacturer pushes molten metal into a steel mold cavity at a high pressure to quickly produce metal parts. In die casting, the manufacturer fixes two halves of a die or reusable mold together and uses a nozzle to inject pressurized molten metal into the die.
When the metal cools, the die opens, and ejector pins push out the cast.
The two most common die casting processes are hot-chamber and cold-chamber casting. While the specifics of these processes vary, there are several shared characteristics of the die casting process as a whole.
Hot-chamber die casting is the most common of the two main die casting processes. Hot-chamber die casting machines have a built-in furnace to heat the metal within the machine. Once the metal reaches a molten state, the machine lowers a cylindrical chamber into the molten metal. The gooseneck shape of the metal injection system allows the chamber to quickly fill itself, and then push the material into the mold with air pressure or a piston.
Immersing the injection mechanism to fill it allows for rapid and streamlined mold injection in this casting process. Because the chamber is subject to direct heat from the molten metal, however, hot-chamber die casting systems are at risk for corrosion, making them a less viable option for metals with high melting points.
Instead, it is better suited for materials with low melting points and high fluidity, like lead, magnesium, zinc, and copper.
By contrast, the cold-chamber die casting process works more slowly to avoid corrosion. With this method, a foundry worker ladles molten metal into the injection system. A piston then pushes the metal into the mold.
This process limits the corrosion that is more common in hot-chamber die casting. It is an ideal option for metals with high melting points, like aluminum and aluminum alloy.
The die casting process is rapid and produces highly detailed parts. It is ideal for the production of high volumes of complex parts and can also produce strong parts with smooth surface finishes. Die casting’s capacity to produce a high volume of parts makes it a crucial process in the automotive and aerospace industries.
As die casting tooling and equipment are expensive, this process is not cost-effective for smaller production runs. In addition, the malleability of metals used in the process can impact the complexity of the product.
Cast parts from SLA patterns printed in Clear Resin on a Formlabs 3D printer.
Investment casting, also known as lost-wax casting, is a process that uses wax, slurry, and molds to produce complex parts. It is one of the oldest metal casting techniques but is still valued for its ability to create precise metal parts with intricate shapes.
This process is still widely used for producing jewelry, dentistry, and art. Its industrial form, investment casting, is a common way to create precision metal parts in engineering and manufacturing.
Investment casting patterns are typically made out of wax or 3D printed polymers. The patterns are assembled into a tree-like structure and dipped into a slurry of silica, or put into a flask and surrounded by the liquid investment plaster. After the investment material dries, the flask is placed upside down into a kiln, which melts the pattern, leaving a negative cavity in the shape of the original model. Metal is melted and then poured, using gravity or vacuum pressure to pull the metal into the cavity.
The casted parts are filed, ground, machined, or sandblasted to achieve final geometry and surface finish.
Sprue trees with cast rings.
Investment casting is a versatile process. It allows manufacturers to produce accurate and repeatable parts out of nearly any metal available for casting and complicated shapes that would be difficult or impossible with other casting methods. Casted parts also have excellent surface qualities and low tolerances, with minimal surface finishing or machining required.
These features make investment casting ideal for complex parts in automotive, aerospace, and industrial applications, medical tools, dental implants, as well as fine jewelry and art.
Investment casting is a complex and labor-intensive process. It requires specialized equipment, costly refractories and binders, as well many manual operations to make a mold. It can be difficult to cast parts that require cores and the process is better suited to small parts.
One half of a sand casting mold.
Sand casting is a metal casting method that was first in use 3,000 years ago but remains the most widely used casting method to this day. This process allows manufacturers to cast metal without relying on machining.
In the sand casting process, the manufacturer first creates a foundry pattern, or replica of the casting, most commonly from wood or plastic. The pattern is oversized to allow for shrinkage. Parts with features on one side only require an open-faced mold. For parts with multiple detailed surfaces, the manufacturer separates the foundry pattern into two mold boxes to form a closed cavity mold. The top half is called a cope and the bottom a drag.
Once the manufacturer creates the pattern, they tightly pack sand around the pattern. Then, they add sprues and gates to ensure that the molten metal flows smoothly through the mold cavity. The manufacturer removes the pattern then clamps the two halves of the sand mold together. Once the metal melts to a molten state, it is poured into the mold and left to cool.
From here, the sand mold is removed using vibrations or high-pressure water. Finally, the manufacturer refines the part by removing sprues and gates, and polishing the cast metal part.
Sand casting is an adaptable process that functions outside the limitations of machinery. Because of this, it can create complex parts of virtually any size. Sand is inexpensive and plentiful, which lowers the setup cost and makes modifications possible. It is the only practical or economical way to produce very large castings. The lead time of sand casting is also short, making it a viable process for short production runs.
Sand casting’s versatility makes it a manufacturing option across a wide array of industries. It can produce medical equipment, automobile parts, electronic equipment, gas tanks, and engine blocks, and more.
Sand casting creates highly porous, textured metals. The shrinkage and rough surface finish also lower the dimensional accuracy of parts. This results in a low-strength final product that requires time-consuming post-processing to achieve a higher quality finish.
In order to choose the right industrial metal casting process, several factors must be considered. We’ve created this comparison table to help you compare die casting, investment casting, and sand casting in terms of types of metals, production volume, costs, production time, part complexity, and for which industries they are generally used.
| Die Casting | Investment Casting | Sand Casting | |
|---|---|---|---|
| Compatible metals | Aluminum, copper, lead, magnesium, zinc | Most metals | Most metals |
| Production volume | High volume | Low to high volume | One-off to medium volume |
| Unit costs | Low | Moderate to high | Moderate |
| Tooling costs | High | Moderate | Low |
| Cycle time | Rapid | Long | Moderate |
| Industries | Automotive, aerospace, consumer products, furniture, power tools | Automotive, aerospace, jewelry, medicine, dentistry, art | Automotive, aerospace, industrial equipment, electronics, consumer products |
3D printed jewelry ring pattern and cast metal part.
Engineers, designers, jewelers, and hobbyists can capitalize on the speed and flexibility of 3D printing by combining castings processes like indirect investment casting, direct investment casting, pewter casting, and sand casting with 3D printed patterns or casting metal into 3D printed molds. Cast metal parts using 3D printed rapid tooling can be produced in a fraction of the time invested in traditional casting and at a significantly lower cost than metal 3D printing.
Stereolithography (SLA) 3D printers offer high precision and a broad material library that is well-suited for casting workflows and can produce metal parts at a lower cost, with greater design freedom, and in less time than traditional methods.
Webinar
In this webinar, we will look at how desktop stereolithography (SLA) 3D printers are being used to directly print patterns, how to work with SLA patterns for investment casting, and how the benefits of generative design are increasing the demand for printed patterns.
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A 3D printed mold in Clear Resin for wax injection.
The process of making patterns from molds or tooling is referred to as indirect investment casting because it requires creating molds for producing the patterns in addition to final investment molds.
Rigid molds for wax (often referred to as tools) are commonly fabricated by machining aluminum or steel. Machined metal molds cost thousands of dollars to produce and take weeks of machining and polishing work before first shots can be run and pattern parts evaluated within a casting process.
With 3D printing, manufacturers can directly 3D print the mold for their pattern using materials like High Temp Resin or Rigid 10K Resin, resins with high-temperature resistance. For an optimal surface finish of molded parts, treat the interior surfaces of the mold by sanding and polishing for a smooth look, or bead blasting if a uniform matte look is desired. To ensure the final cast parts are dimensionally accurate, compensate for shrinkage by scaling up the printed mold.
The exact shrinkage of the wax and the casting process can be obtained from supplier specifications.
3D printed molds for metal casting shorten the time between concept and first tests to a matter of days because manufacturers can directly print the tooling necessary for running and evaluating parts.
While molded pieces must follow design rules for moldability (e.g., no undercuts, draft is beneficial, etc.), you can achieve increased pattern complexity by using assembly jigs to combine multiple components into a single structure.
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3D printed jewelry patterns and metal casted rings.
Direct investment casting is a version of investment casting where the process moves directly from pattern creation to surrounding the pattern with investment material.
It is ideal for producing parts with geometries that are too complex to be molded or for parts with extensive undercuts and fine surface texture details, where molding is possible but carries high tooling costs.
Traditionally, patterns for direct investment casting are carved by hand or machined if the part is a one-off or expected to be only a handful of units. With 3D printing, however, manufacturers can directly print the patterns, removing the design and time constraints common in other processes.
With 3D printing, engineers, designers, and jewelers can direct 3D print patterns in order to achieve shorter lead times and geometric freedom that exceeds the design for manufacturability constraints of molding processes. Formlabs developed a range of castable materials suitable for direct investment casting, in particular for the jewelry industry.
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The way jewelers work is changing, and castable photopolymer resins are leading the way.
In this guide, learn how to cast fine jewelry pieces 3D printed on Formlabs printers.
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Sample part
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Grey Resin printed pattern and finished aluminum casting from an open-faced sand mold.
Similar to investment casting, 3D printing can be used to create patterns for sand casting.
In comparison to traditional materials like wood, 3D printing allows manufacturers to create complex shapes and go straight from digital design to casting.
Metal Miniatures made with pewter casting and 3D printing.
Pewter is a malleable metal alloy with a low melting point that can be used for making fully metal objects for decorative applications such as detailed metal miniatures, jewelry, scale models, and replicas of antiques.
With recent developments in temperature-resistant 3D printing materials, like High Temp Resin for Formlabs SLA 3D printers, it’s now possible to 3D print molds for direct pewter casting.
There are two options for mold designs: a sacrificial or pull-apart mold. In a sacrificial mold, there is a shell designed to be broken apart in the process. Pull-apart molds function with separate halves so the mold can be reused.
Compared to directly printing metal, the casting pewter in 3D printed molds offers significantly better detail and surface finish at a small fraction of the cost. Compared to wax casting, directly 3D printing a mold has fewer steps and requires less manual effort, while preserving the most possible detail.
Webinar
Watch our webinar to learn how moldmaking using 3D printed masters and reusable or sacrificial molds can allow you to produce parts in porcelain, precious and non-precious metals, silicone and biocompatible flexible materials, and more.
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Jewelry investment casting process with 3D printed patterns.
Businesses looking to boost design freedom or cut costs and lead times have a strong solution in metal casting with 3D printing.
Certain types of complex metal castings, such as large shapes with cross-sections and pieces with multiple cores, are difficult to create using traditional metal casting methods. 3D printing allows manufacturers to produce these complex designs. For example, jewelers can create intricate and custom designs that might be impossible without a 3D printed pattern.
3D printing also eliminates reliance on multiple machines or service providers to create parts. Instead, companies just need a digital file, a 3D printer, and printing material. This can cut costs and waste, as all the material used goes into the final product.
Finally, the combination of 3D printing with metal casting can cut costs and lead time.
Rather than waiting weeks for expensive tooling before being able to cast a final product, a 3D printer can create a pattern or mold in hours.
Metal casting combined with 3D printing help companies quickly and efficiently create metal parts. With a Formlabs SLA 3D printer, you can expedite the metal casting process and cut costs along the way.
Learn more about the Form 3 desktop SLA 3D printer and request a free sample part to evaluate the quality firsthand.
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Custom 3D-Printed Casts and Splints
You Have Casting Options!
When you have a broken bone, you can choose a custom fit, waterproof 3D printed cast for the remainder of your healing, just as soon as your fracture is stabilized and your swelling goes down.
Your Clinic Can Provide ActivArmor Today!
No equipment or inventory to buy. Get started now with our free iPhone app!
What is ActivArmor™?
ActivArmor is the only waterproof, breathable, sanitizable custom plastic cast in the U.
S. consumer marketplace. It empowers patients with the freedom to be able to stay safe and maintain their active lifestyles.
No rubbing or slipping. Custom fabricated to within 1mm of your body map.
Clips are locked on like a cast or easily removable like a splint, per doctor’s orders.
Kids love the colorful options and comfort. It’s breathable and does not trap bacteria.
Shower, bathe or swim as you normally would. Easy to clean dirt, sweat and grime.
ActivArmor™ allows you to continue to be active while you are healing from your injuries, and can reduce downtime in your active lifestyle and/or training.
ActivArmor™ is covered by most insurance plans and is affordable or even free depending on your individual coverage.
ActivArmor™ is the only commercially available, 3D printed custom splint in the United States and is FDA listed.
Participate in daily activities such as bathing and showering; convenient for children or those with mobility problems.
No need for a 3D printer in the doc’s office. All you need is an Rx pad and you can prescribe from the comfort of your own desk.
Listed with FDA as a Class 1 splint, doctors love the patient outcomes and patients love the faster recovery. ISO-10993 certified for biocompatibility.
ActivArmor is designed and made in Pueblo, Colorado in a United States EDWOSB, and was developed by an American entrepreneur.
When you no longer have a need for your ActivArmor™ custom splint, rest assured you can recycle it and help keep our planet beautiful.
Doctors Love ActivArmor™
ActivArmor saves physicians time and increases clinic efficiencies by reducing cast removals, material inventory, recasting, and skin irritation complaints.
Custom RX Pad
Scan with your iphone in your office, or just write a script to have our certified staff fill your patient’s DME order.
Very Easy to Prescribe
it really is…
You can also become an ActivArmor partnering clinic
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Increase Traffic to Clinics
Your patients become walking billboards for your practice, marketing for you while they heal.
Zero Upfront Costs
Help more patients
Clinics are viewed as innovative, and are given the opportunity to provide patients with the latest in high tech healing options with no upfront equipment cost.
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Advanced Treatments
Provide your patients with the latest in high-tech immobilization, custom adapted for advanced healing technologies like ultrasound, bone and muscle stimulators and TENS units.
Advanced Treatments
Any doctor can do it
Because ActivArmor™ devices are custom designed and fabricated, physicians and patients now have an infinite number of unique design options.
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Improve Patient Satisfaction
Patients prefer ActivArmor™ over traditional casting and splinting options.
Patient Satisfaction
Patients can stay active
Referring physicians for ActivArmor™ have reported that their patients prefer it over traditional casting and splinting options.
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Actor
ActivArmor has changed my life! When I was diagnosed with severe never damage by my doctor and needed to be put into a cast, it really hurt me because I knew what they meant. My nerve damage is extensive and will take a year or more to heal, but I still wanted to work out, shower, wash. This is making my healing process so much more enjoyable and while I have a long road of healing ahead, I’m very happy with the cast I have, seeing what I can do with it! These should be all across America and replace fiberglass casts everywhere!
Pro Circuit Rider
"My brace has given me the freedom to do things I couldn't do with a standard cast while giving me the support I need to protect my wrist fracture. I love it and would recommend it to anyone with any problem requiring extra support!"
Mother
"My son, Robert, is a very active child: water skiing, climbing, baseball, swimming, you name it and as such he injured his arm the first week of summer vacation.
Knowing his injury required a cast, we assumed Robert would miss out on all of the summer fun with his friends. He was going to have to wear a stinky itchy cast like his sister did before him. given that Robert had just been invited to a pool party, I asked the doctor if there were any options. When the doctor prescribed an ActivArmor™ cast we were thrilled! ActivArmor™ was the answer to what would've been a dreary summer otherwise. My son said it was very comfortable to wear. He loved being able to shower with the cast on. No smell, no discomfort, and no irritated/itchy skin."
Patient
"Out and about with my ActivArmor™ cast... I have sent more people to your site than you can believe. Everyone asks about it and I love telling your story. Thank you for giving me back my summer. I have been boating, swimming everyday, paddleboarding, kayaking, and rafting since I got my cast. I am able to shower, and unfortunately do dishes. I can wash my dogs, and hose down my hogs. If when I am throwing hay, it shakes out of the cast.
It is not smelly either. My baby Toy Chihuahua loves to chew on it. I just wish I had more than one color to coordinate with my clothes. But I am always answering questions about it and sending people to your site."
MD
"The ActivArmor™ brace is the next generation of patient immobilization. Custom fit, 3D printed, waterproof, and breathable! All of the previous problems of inability to shower, swim or workout, itching, hygiene, and incision exposure are solved. Patients will love the comfort and convenience of going back to a more normal life!"
19
"After breaking my wrist and having to have surgery, I thought I wouldn't be able work as a lifeguard this summer. But thanks to ActivArmor™, I'm able to be in a cast to heal my wrist and still be able to lifeguard and get in the water whenever, and however many times needed!"
Ironman World Championships Competitor
"Literally couldn't do it without you!!!"
Injection molding from 3D printed molds
Study of low-volume production of small plastic parts
BRIEF INFORMATION
Form 2 printer and injection using a Galcom Model-B100 injection molding machine.
Two transparent resin molds were tested: one large butterfly mold and one mold with four small butterflies in one block. A third mold for the USB stick case was tested in high temperature polymer. These molds were 3D printed by Formlabs and the castings were made by Galomb Inc and Formlabs in a variety of materials.
Formlabs and Galomb, Inc.
LOW-VOLUME 3D PRINTED PARTS PRODUCTION
Most of the plastic products in the world today are made by injection molding. Using inexpensive desktop 3D printers and injection molding machines, molds can be created to produce small functional parts from manufacturing plastics.
For low volume production (approximately 10-100 parts), 3D printed molds save time and money. They also allow for a more flexible approach to manufacturing, giving engineers and designers the ability to easily modify molds and continue iterating their designs at low time and cost.
The Form 2 Stereolithographic 3D Printer (SLA) produces completely solid, smooth parts that can withstand the temperature and pressure of desktop injection molding.
3D prints produced using SLA are chemically bonded so that they are completely dense and isotropic, producing functional shapes with a quality not possible with FDM.
Formlabs is partnering with Galomb Inc., a manufacturer of low cost injection molding machines, to test and demonstrate the viability of SLA injection mold printing.
Fig. 2 : 3D printed molds in aluminum frames.
METHOD
Both clear and high temperature resins can be used to print small functional forms, with high temperature resins offering compatibility with a wider temperature range of
thermoplastic melts. Formlabs Clear Resin was chosen for its strength, high detail and smooth surface Clear Resin is preferred for its transparency as you can easily see when forms are being filled, but any of the standard Formlabs Resins (clear, white, black and grey) can also be used as they have similar mechanical properties. The plates were printed with a layer height of 100 µm and took approximately 5 hours per plate.
Depending on the geometry, multiple shapes can be printed at once on the build platform to improve printing efficiency.
Fig. 3 : Printing setup in PreForm with cavities up.
Two forms were printed from transparent resin. Parts and subsequent molds were designed to match Galomb machine vise sizes, 1 in3 injection cylinder capacity, and Form 2 build volume. supports were polished.
The parts were then cured for one hour under a 405 nm UV lamp to achieve full mechanical strength and rigidity. For a better understanding of the impact of post-curing on parts, see the Formlabs UV post-curing booklet.
Fig. 4 : 3D printed molds in aluminum frames and die-cast parts.
The first was a large Formlabs butterfly logo and the second was four small Formlabs butterfly logos. Both molds had a cavity, narrow inlets, and sprue at the point of injection and were designed in Solidworks. The molds were inserted into aluminum frames to provide protection from the downward pressure and heating of the injection nozzle. Aluminum frames can also prevent the shape from deforming after repeated use. The frames shown in figures 2 and 4 were custom made by Whittaker Engineering in Scotland, but standard aluminum frames are readily available on request from injection molding machine manufacturers.
Plastic pellets can be purchased online or from suppliers such as IASCO-TESCO. To create different colors, the molten plastic was pre-mixed with powdered dyes prior to injection.
Using a Model-B100 benchtop injection molding machine, Galomb tested printing plates with 25 shots of LDPE. LDPE melts at approximately 325°F (163°C) and was chosen for its low melting point. Of note, Formlabs Clear Resin has an HDT at 0.45 MPa 73.1 ºC after post-cure (see Material Data Sheet). HDT is a measure of the thermal properties of a material, but does not rule it out for use, although LDPE has a higher melt temperature. Whether your 3D printed mold will withstand the injection molding process depends on the melt temperature of the injection material, part geometry, and cooling and cycle times.
RESULTS FOR CLEAR POLYMER
After 25 injections of LDPE, there was no noticeable deterioration in the surface of the molds (chips, cracks or scratches). LDPE is not prone to sticking to polymer molds when tested, but other plastics may require the use of a mold remover to assist in part removal. Adhesion of the part to the mold can cause mold wear during ejection. Release agent is widely available, and silicone release agent is compatible with Formlabs standard and high temperature resins.
The cycle time for each injection was approximately three minutes. This process was accelerated by using compressed air to cool the mold. Cyclic injection into forms printed on the Form 2 causes the form to heat up. To counteract this, the cooling time between open mold cycles must be increased. While the mold cannot deform, too much residual heat will reduce molding success if the mold is opened too early. Galomb also improved molding success by etching shallow (0.
05 mm deep) vent holes (not shown) leading from cavity edge to mold edge so that air does not enter the cavity during injection.
Some of the injections showed a leak in the parting line due to deformation of the polymer mold during the cooling phase after several injections. Increasing the clamping force in the vise can help mitigate leakage, as can polishing the parting plane of the mold to make it as flat as possible. Galomb proposed incorporating channels into the mold design to include metal tubes and fill them with aluminum epoxy, as a strategy to strengthen the mold, reduce warping, and improve cooling time.
Fig. 5 : A range of injection molding parts made using 3D printed molds.
FURTHER TESTING WITH HIGH TEMPERATURE POLYMER
Clear resin molds have been successfully tested using LDPE, which has a relatively low melt temperature. Higher melt temperatures can cause thermal shock in clear resin printed parts, which manifests itself as a deformed mold surface.
Transparent resin molds experience thermal shock when exposed to higher temperature molten plastic.
Formlabs printed the shape of a USB device case in High Temp Resin to test
| Melting Point | Plastics | High Temp Polymer (HDT at 0.45 MPa = 289° C) | Clear Resin (HDT at 0.45 MPa = 73.1°C) | |
| LDPE | 163 °C | ||
| PP | 177 °C | ||
| TPE | 177 °C | ||
| PLA | 180 °C | ||
| ABS | 204 °C | ||
| HDPE | 204 °C | ||
| EVA | 204 °C | ||
| Polystyrene | 226 °C |
High temperature polymer molds showed no temperature degradation at the mold surface for any of the tested plastics.
*DURABLE RESIN polymer is under development and final specifications are subject to change.
High Temp and Standard are the polymers best suited for molding. Of the Formlabs resins, High Temp has the highest HDT at 0.45 MPa and low thermal expansion. It is also the stiffest material with the highest stretch factor.
The relatively high stiffness of High Temp Resin means that the mold will not deform when the part is removed. This makes the use of a release agent especially important for removing parts molded from rigid plastics such as polystyrene.
GENERAL TROUBLESHOOTING
Form overflow leak.
Leakage occurs when the injected plastic is forced out between the two mold halves. This can happen when the shape is overflowing, or if the split plane is not completely flat. Adding thin exit ports to the mold can help mitigate leakage from overpressure within the mold, facilitate part removal, and eliminate entrapped air that can cause bubbles in the molded part.
Although not shown, the plates were tested without the aluminum frame. The downside to this approach is that these parts use more material, which increases printing cost and time, and the forms can be more prone to warping. With this method, a steel washer placed between the printing plate and the nozzle of the injection molding machine protects the print from direct contact and helps distribute forces. In addition, pre-sealing the injection molding cylinder against a metal block helps ensure there are no air pockets to disrupt the plastic flow.
Printed lines visible on some parts; this can be reduced by printing the form with a lower layer height. The plates used in this study were printed at 100 µm, but 50 or 25 µm could also be used. This will improve the cleanliness of the plate surface, but increase print time and reduce tank life.
Final USB device case molded from high temperature resin.
DESIGN INSTRUCTIONS.
When designing a form, consider what will print successfully and what will form successfully.
- Adding one to three degrees of recess on surfaces perpendicular to the direction of the recess will allow easier part removal and minimize mold degradation. Fillets should be applied to the inside edges to reduce buckling from internal plastic stress and facilitate removal of the part.
- Embossed and engraved parts must be offset from the surface by at least 1 mm.
- If you plan on using an aluminum frame, The surfaces of the split planes can be polished with fine sandpaper to reduce flare. add an extra 12mm thick plate to the back of the mold plate to account for compressive forces and ensure complete sealing.
- Be sure to orient the mold halves in the PreForm so that the cavity is facing up. This will prevent reference marks inside the cavity and make post-print processing easier.
90° angle
2° recess
Optimum condition 2° recess and rounding.
PROCESS SUMMARY
STEP 1:
Part design in CAD.
STEP 2
Mold design in CAD.
STEP 3
3D print the forms on Form 2.
STEP 4
Remove support material from molds.
STEP 5
Insert the plastic into the mould.
STEP 6
Remove the part from the mold.
Steel 3D Printing - A Quick Guide
Any metal 3D printing technology can print with steel. This is the most popular material. But which steel grades and which technology is best for your application? Will printed steel parts really be as strong and durable as traditionally made parts?
Let's see how a 3D printed steel part revolutionizes manufacturing and opens the door to new applications in aerospace, medical equipment, automotive, tool making, heavy industry, architecture and more. In addition, more affordable desktop printers are expanding the scope and scope of real steel 3D printed parts.
Strength of steel printed parts.
Cast steel part (left), 3D printed version (center). On the right, a fully 3D printed hinge requires no assembly. (Source: Desktop Metal)The most common question when it comes to a 3D printed metal model is "Will it be as strong as a forged or cast part?" ?". The short answer is yes... and no.
3D printed steel parts can be just as strong, and sometimes even stronger, than those made in the traditional way. It depends on many factors such as: end use, type of steel, choice of 3D printing method, post-processing and shape of the part. Also, the comparison depends on which of the strength characteristics you focus on: tensile strength, static load strength, fatigue strength, etc.
Parts printed from steel are used in the aerospace industry, for the military, and also, for example, for the manufacture of a footbridge, shown below. Therefore, the strength of printed products is beyond doubt, but let's take a closer look.
A 3D printed or laser powder sintered (LPBF) steel part has a finer grain structure than cast metal products. This provides better tensile strength characteristics, but in other respects the cast parts are currently still stronger. Most often, LPBF 3D printing is used to replace cast components, but in some cases, 3D printed components can replace forged parts.
One study showed that, under certain conditions, stainless steel parts made using LPBF 3D printers were three times stronger than parts made from the same steel using the traditional method.
In experiments comparing 3D printed steel parts to traditionally made steel parts, researchers create identical parts using two methods and compare their performance. However, head-to-head comparison of details is only part of the big picture.
The main advantage of printing with steel is not only its strength, but also the unique ability to create internal channels and lattice fillings in parts, which is impossible using traditional manufacturing methods.
Metal 3D printing makes it possible to produce parts faster than traditional production, since this method does not require the use of special equipment and tools, it allows you to create assemblies as a whole, eliminating the need for subsequent assembly and welding. Designing a printed part usually means that less metal is needed to make it, and therefore less weight, for the same strength.
Steel 3D printing is also more stable and cost effective as it reduces waste. When using subtractive manufacturing methods, such as CNC machining, you make a part by cutting it out of a large one, with a lot of waste. With additive manufacturing, you only use the material you need to make the finished product.
Steel 3D printing is not intended to replace traditional methods in all areas, but it may be a better choice for a wide range of applications. Particularly when the required parts are unique and designed for specific applications, such as rocket engines, racing cars or the oil and gas industry.
3D printing is the fastest and most flexible technology for mass production and prototype production. For military and industrial applications, steel 3D printing is a faster and more efficient way to create individual parts for vehicles and machines. Stainless steel 3D printing is rapidly finding applications in medicine to create unique surgical instruments and implants.
If you know what characteristics your final product should have (tensile strength, compressive strength, hardness, density, etc.), then all these parameters can be incorporated into the product at the production stage.
Types of steel for 3D printing
Metal powder is the most used metal material for 3D printing (Source: GKN Additive)There are thousands of different grades of steels and alloys with different mechanical properties, used in traditional manufacturing but in 3D printing there are only a few dozen of them, and some of them are unique, created specifically for this technology. Among the steel options, the following can be distinguished:
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Stainless steel (316L, 304L , 17-4PH, 15-5PH, 420, 254, Ph2, GP1, 630, 410).
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Tool steel (D2, M2, h23, h21, MS1, 1.2709).
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Low alloy steel (4140).
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Structural alloyed (20MnCr5).
Recently, unique alloys have been developed specifically for 3D printing, designed to solve the problems that occur with classical production methods.
For example, 3D printer manufacturer Desktop Metal released a patented stainless steel in 2022 that the company says combines the tensile strength, ductility, and corrosion resistance of 13-8 PH stainless steel, combined with the hardness low alloy steel like 4140. The company says customers can go to market with this material and skip the galvanizing step to protect products from corrosion.
ExOne offers two special blends of steel and bronze that the company says allows 3D printed steel parts to achieve increased corrosion resistance while being easy to machine and polish.
While most of the metal powders used in 3D printing are similar to those used for other manufacturing methods, their numbers are on the rise as more companies adopt the technology.
Some metal powder manufacturers, such as GKN, also make custom powders for specific 3D printing applications.
How to print with steel
The strength, properties, and applications of 3D printed steel products largely depend on which 3D printing technology you use. Some methods produce stronger parts, other methods provide better hardness or abrasion resistance, and some technologies are simply very fast.
Below are the main metal 3D printing methods, their properties and some of the most common application examples.
FDM printing
BCN3D's Epsilon printer extrudes metal filament from stainless steel (Source: BCN3D) as more printer manufacturers certify metallic filaments for use on their printers, such as Ultimaker, BCN3D, Makerbot, Raise3D. Raise3D has recently released a complete metal printing suite - Metalfuse (3D printer, debinding oven and sintering oven). This method is still much more popular for printing plastics, but with new plastic filaments filled with stainless steel powder, strong metal parts can be produced.
FDM media was once limited to thermoplastics. Companies like BASF Forward AM and The Virtual Foundry now offer metal filaments that can be used on almost any FDM printer as long as it has a hardened steel nozzle for abrasive media.
These materials are approximately 80% metal and 20% plastic. After printing, the post-processing process removes the plastic, resulting in 100% metal parts.
Due to the removal of the bonding plastic, FDM metal parts shrink during post-processing. The amount of shrinkage is constant and can be taken into account in CAD systems, which allows to obtain relatively accurate finished parts.
Forward AM's 316L Stainless Steel Ultrafuse filament produces finished parts with material properties that the company claims are comparable to injection molded metal parts.
(Source: BCN3D) While 3D printing with metallic materials may not be suitable for demanding applications such as aerospace, the economics of producing simple metal components without critical loads on an affordable FDM printer can outweigh the impossibility of applying them in some areas.
Metal prototype parts and finished parts that will not be subjected to extreme stress are ideal uses for this technology.
Bound Metal Deposition (BMD)
Desktop Metal's Studio System 3D printer used bonded metal bars that were extruded layer by layer to form a metal part (Source: Desktop Metal)Similar to FDM, Metal mesh deposition method (BMD) or bonded powder extrusion (BPE) is a 3D printing process based on extrusion. This method uses bonded metal rods or bonded powdered metal filaments, which consist of a much higher percentage of metal powder than the filaments used in FDM. As with FDM, post-treatment to remove the binder and heat treatment in a final sintering oven are required.
There are only a few 3D printers using this method such as Desktop Metal, Markforged and more recently 3DGence, but more companies are entering this market, so stay tuned. These printers are valued as a convenient solution for office 3D metal printing, they are more expensive than most FDM printers, but cheaper than the powder-based metal 3D printing technologies described below.
These printers use their own proprietary filament. Desktop Metal and Markforged offer four types of steel.
Ideal niches for this technology are metal prototype parts, where it is necessary to test the functionality of a part before mass production using traditional methods. Popular applications are molds, punching dies, nozzles, impellers, fasteners and heat exchangers.
For example, Shukla Medical uses Markforged's Metal X printer to print steel prototypes of its orthopedic implant removal instruments.
Laser powder sintering.
Laser powder sintering technology uses one or more lasers to melt powdered metal into a desired shape layer by layer (Source: GE Additive) metal printing. This technology is used by 80% of all metal 3D printers on the market.This method uses powerful lasers to selectively sinter metal powder layer by layer.
LPBF 3D printers are available in a wide range of sizes, prices and laser powers. These and other characteristics affect the properties of the finished part, print speed and other parameters of the finished products.
Steel and steel alloys are the most popular material for LPBF equipment and, unlike FDM and BMD, metal powders are commercially available as they are most commonly used in traditional production methods.
LPBF is a technology that maximizes the quality of a 3D printed part. Applications include aerospace components such as monolithic thrust chambers, rocket engine components and heat exchangers, molds, tools and other applications, as well as high wear parts and surgical instruments.
Binder Jetting
Binder 3D printing technology uses metal powder and a binder to form metal parts (Sorrce: ExOne) binder, and not with a laser. During post-processing, the binder is removed.Binder application stands out for its high printing speed compared to other 3D printing methods or traditional manufacturing, and metal parts made with this technology have material properties equivalent to those made by metal injection molding.
The number of manufacturers producing metal-bonded inkjet 3D printers is much smaller than that of LPBF machines.
Leading manufacturers include ExOne, Desktop Metal, Digital Metal, GE Additive and HP.
Binder blasting is ideal for medium to high volume production of metal tools and spare parts.
In fact, HP claims that its Metal Jet 3D printer was designed specifically for mass production of 316L stainless steel products. HP has partnered with Parmatech to produce metal parts for the medical industry. Pennsylvania-based ExOne uses this technology to manufacture hard metal cutting tools and tool steels.
Electron Beam Melting (EBM)
(Source: GE Additive)Electron Beam Melting (EBM) is another powder cladding technology. It works in a similar way to selective laser melting (SLM), but instead of using a laser as the energy source, it uses a much more powerful beam of charged particles.
The recoater moves the powder onto the printing plate and an electron beam selectively melts each layer of powder. After each layer is printed, the plate is lowered and another one is applied on top of the previous layer.
EBM can be much faster than SLM, but SLM produces smoother and more accurate pieces. The electron beam is wider than the laser beam, so EBM cannot produce the same precise parts as SLM. Another difference is that the manufacturing process takes place in a vacuum chamber, which reduces the amount of impurities in the material that can lead to defects. That is why EBM is often chosen for printing components for the aerospace, automotive, defense, petrochemical and medical implant industries.
Titanium is the most popular metal for most EBM applications, however steel can be used.
Cold Spray
(Source: Impact Innovations)Cold spray 3D printing is done by injecting metal powders through a jet nozzle into a supersonic stream of pressurized gases such as air, nitrogen, or helium. The process is called "cold" because the metal particles do not melt, but hit the metal substrate and adhere to its surface during the so-called plastic deformation.
Cold spray printed products are not prone to porosity, thermal cracking and other defects associated with melt-based technologies.
This method has several advantages over other production methods. The technology is used in the military and aerospace industries around the world. For example, the US Army uses cold spray to repair the mounts of a worn Bradley 25mm steel turret gun.
In the automotive industry, cold spray steel is used for crash repairs because the high strength steel substrates in cars can be susceptible to thermal repair methods such as welding.
Direct Energy Deposition (DED) and Wire Arc Additive Manufacturing (WAAM)
WAAM Steel Parts from MX3D (Source: MX3D) Direct Energy Deposition (DED) uses welding powder or wire that enters through a nozzle and is fed into the power source to melt the metal. A melt region is created and applied to the substrate. DED is a new process, reminiscent of an old building technology known as "cladding", in which a coating is applied to a substrate, often for thermal insulation or weather resistance. DED is useful for fabricating large objects as a whole, as well as complex geometries that require extensive machining.
DED can get such parts much closer to finished than traditional CNC machining.
Because DED uses a coating process, it can be used to add complex geometries to existing steel parts, thus combining complexity with cost reduction. For example, the French company AddUp advertises a rocket nozzle that uses a preformed large 304 stainless steel hopper cone printed with an isogrid structure, usually made from a larger piece by traditional methods.
A technology related to DED is wire-arc additive manufacturing (WAAM). Instead of powder, WAAM uses a metal wire that is melted by an electric arc. The process is controlled by robotic arms. WAAM is also capable of producing large-sized metal parts, as demonstrated by the Dutch company MX3D and its nine thousand-pound 41-foot stainless steel bridge in Amsterdam, as well as an oil and gas equipment repair part, proving that parts can be made in the field.
Micro 3D printing
Micro parts printed from steel (Source: 3D MicroPrint) Micro scale additive manufacturing, or micro 3D printing, can produce products with a resolution of a few microns (or less).
