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3D printed mold making
Ultimate Guide to Silicone Molding for 3D Printing (Part 1)
Download the full Guide
as a PDF!
The simple post-processing techniques presented in this guide are an excellent way for professionals to create low-cost silicone molds, threaded inserts for enclosures, vacuum formed parts, and more.
Silicone molding is a powerful production method that, when combined with 3D printing, can allow you to make several copies of one product. You can also create a product in a material that is not supported by your 3D printer.
In this How To, we will show you some of the best practices associated with creating silicone molds around 3D printed parts.
Working time will vary depending on a number of factors. Creating a mold around our 3D printed part took us about 1.5 hours. Casting into our mold took about 15 minutes.
Supplies
3D printed mold box, hardware, vents & keys (read on for more info).
Master (the print you are molding)
Silicone
Resin and dye
Mixing cups
Mixing sticks
Mold release spray
Hot glue or cyanoacrylate glue
Funnel
Ex acto knife
Rubber bands, tape, or straps
Gloves
Respiratory mask
Eye protection
Need some of these products? We've curated an Amazon wish list for you.
Step 1: Choose a file to cast a mold around
Obtain a file that you would like to either make several of, or create in a material not supported by your printer.
We chose the cap to a perfume bottle to understand what the process would look like for a product development team attempting to produce several concept models of a prototype.
The next step is to create your mold box. This is the structure that will hold the silicone in place around your part when pouring. Your master will need to be suspended in this structure.
You can create mold boxes from:
Foam core board
Legos
3D printing
We chose to design and print ours as this method has a few benefits. Designing and 3D printing mold boxes allows you to:
Print in pour holes and vents
Easily calculate the volume of our mold
Create boxes that perfectly fit the parts you plan to create a mold of
Re-use mold boxes to create multiple molds
While 3D printing your mold box isn’t necessary, it provides you with a reusable customizable mold box that the other methods cannot produce.
Step 3: Prepare and Print
Because the silicone molding process is not very demanding on the 3D printed mold box or master, you can select standard print settings.
The 2021 Guide to 3D Printing Materials
Learn about polymers, composites, and metals all available for 3D Printing!
Supplies Used:
3D printed mold box, 3D printed master, Cyanoacrylate glue, Mold release spray, Vents & Keys
A: Spray your mold box, master, vents, and keys with mold release.
B: Choose points across model to glue vents
C: With our 3D printed mold box we were able to glue our master directly onto the pour hole during preparation.
D: Spray again with mold release for good measure
You can suspend your master using popsicle sticks, skewers, or 3D printed rods glued to the surface of the master in an inconspicuous place. The holes left in their place after your mold has cured will aid in resin flow through the mold.
Step 5: Open Bottles of Silicone (Parts A and B) and Stir Thoroughly
Supplies Used: Silicone (Part A & B), Mixing Sticks
As silicone comes in two parts, it needs to be mixed both individually and once combined with its hardener.
Mix slowly using separate mixing sticks.
Supplies Used: Measuring cups
A: Determine the volume of silicone needed to fill your mold
B: Measure desired amount of silicone and hardener separately in two measuring cups.
We calculated our mold volume by filling our 3D printed mold box with water and pouring the water into a measuring cup to find exact volume.
For two part molds like the one shown, you only need to mix enough silicone to fill half of the volume of your mold.
Once you have measured each part, combine the two parts into one mixing cup and stir slowly with a mixing tool.
Be cautious not to stir in air bubbles. Be sure to scrape the sides of the cup to mix in all material.
Once your parts are thoroughly mixed the curing process will begin.
TIP
Read instructions on your silicone for “pot-life”. This is how long you have to work with the silicone before it cures.
Supplies Used: Mixed silicone, prepared mold box and master
Pour silicone into the first half of your mold box.
When pouring, pour slowly into one corner of the mold box and allow the silicone to run to other parts of the mold box as it fills.
Stop when the silicone reaches the top of the first half of your mold box.
Once you have poured your silicone place small keys into the silicone. These will create negative spaces and allow the mold halves to fit together once poured. We will remove them before pouring the second half of our mold.
Depending on what type of silicone you are using it can take anywhere from 75 minutes to overnight to cure.
Temperature and humidity will affect curing times, so we recommend this process be done in a room temperature environment.
Step 10: Attach and Prepare Mold Part Two
Supplies Used: Mold box part two, hardware (nuts & bolts)
Once our mold has set, we will prepare to pour the second half of our mold.
A: Remove the keys you inserted in step 9.
B: Attach and secure second half of mold box.
C: Spray with mold release
Next, repeat steps 5-9 and create the second half of your mold using the methods mentioned above.
Step 12: Let Cure
Supplies Used: Pliers or Ex-Acto knife
Once both halves of your mold have cured you are ready to remove them from the mold box and begin using them to recreate parts.
A. Remove the hardware
B: Remove the mold from the mold box and open.
C: Remove the master and vents.
Supplies Used: Cured mold, mold release spray, rubber bands
Next, you will need to reassemble your mold.
A: Ensure that all parts of your mold are correctly aligned, and plug any holes created by vents.
B: Secure mold pieces using rubber bands, straps, or tape.
Tip
Another great application for 3D printing would be to design and print a box to hold the mold together when pouring resin, or modify the mold box we used to serve the same purpose.
TIP:
If your vents leave holes in areas where resin can spill out during the pour, they will need to be plugged.
Supplies Used: Resin (Part A & B), measuring cups, measuring sticks, dye.
Just as with silicone you will need to measure each part of the mixture taking into account the volume needed to create a part.
If you have made several molds, you can mix a larger quantity of resin and pour several molds at once.
Add dye to the part of the resin mixture specified in the instructions.
Step 16: Mix Resin
Combine both parts of the resin mixture and mix thoroughly being sure not to stir in air bubbles.
TIP:
Resins typically have a shorter “pot-life” than silicone meaning they will cure faster.
Step 17: Pour Resin
Supplies: Funnel
Once mixed, pour immediately into the opening of your mold using a funnel.
Pour slowly as not to overfill and spill resin.
Any resin that remains in the mixing cup will harden, but can typically be removed afterwards.
Step 18: Let Cure
Once poured, allow the resin to cure for the appropriate amount of time.
Supplies Used: Pliers
Once your resin has cured, you can open the mold and remove your cast part.
Any resin that escaped through seams or voids and cured is called “flash”. Flash will need to be removed from the part through post processing.
Below, you can see that we were able to recreate our perfume bottle cap in several different colors and opacities using silicone molding.
Visit one of our other applications pages for tips on how to take your print even further.
We recommend that you visit our pages on:
Silicone Molding Part II
Vacuum Forming
Sanding
Last but not least, remember to share your work with us on Thingiverse and social media @MakerBot.
We can’t wait to see what you make!
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How to Use 3D Printing for Injection Molding
The majority of plastic products in the world today are manufactured by injection molding. However, fabricating molds can be prohibitively expensive and time-consuming.
Fortunately, molds don’t always need to be machined out of metal—they can be 3D printed.
Stereolithography (SLA) 3D printing provides a cost-effective alternative to machining aluminum molds. SLA 3D printed parts are fully solid and isotropic, and materials are available with a heat deflection temperature of up to 238°C @ 0.45 MPa, meaning that they can withstand the heat and pressure of the injection molding process.
Download our free white paper to learn how to create 3D printed injection molds.
Download the White Paper
Webinar
In this webinar, we'll show you how to use stereolithography (SLA) 3D printed molds in the injection molding process to lower costs, reduce lead times, and bring better products to market.
Watch the Webinar Now
3D printed injection molds in an aluminum frame with the finished injection molded part.
With affordable desktop 3D printers, temperature resistant 3D printing materials, and injection molding machines, it is possible to create 3D printed injection molds in-house to produce functional prototypes and small, functional parts in production plastics.
For low-volume production (approximately 10-1000 parts), 3D printed injection molds save time and money compared to expensive metal molds. They also enable a more agile manufacturing approach, allowing engineers and designers to prototype injection molds and test mold configurations or to easily modify molds and continue to iterate on their designs with low lead times and cost.
SLA 3D printing technology is a great choice for molding. It is characterized by a smooth surface finish and high precision that the mold will transfer to the final part and that also facilitates demolding. 3D prints produced by SLA are chemically bonded such that they are fully dense and isotropic, producing functional molds at a quality not possible with fused deposition modeling (FDM). Desktop and benchtop SLA printers, like those offered by Formlabs, simplify workflow as they are easy to implement, operate, and maintain.
Formlabs Rigid 10K Resin is an industrial-grade, highly glass-filled material that serves as an ideal molding material for a wide variety of geometries and injection molding process conditions.
Rigid 10K Resin has an HDT of 218°C @ 0.45 MPa and a tensile modulus of 10,000 MPa, making it a strong, extremely stiff, and thermally stable molding material that will maintain its shape under pressure and temperature to produce accurate parts.
Rigid 10K Resin is Formlabs' go-to material for printing sophisticated molds for injection molding, which we showcase with three case studies in our white paper. French industrial technical center IPC ran a research study and printed thousands of parts, contract manufacturer Multiplus uses it for low-volume production, and product development company Novus Applications has injected hundreds of intricately threaded caps with a single Rigid 10K Resin mold.
High Temp Resin is an alternative material that can be considered when clamping and injection pressures are not too high and Rigid 10K Resin cannot meet the required injection temperatures. High Temp Resin has a heat deflection temperature (HDT) of 238°C @ 0.45 MPa, the highest among Formlabs resins and one of the highest among resins on the market, allowing it to withstand high molding temperatures and minimize cooling time.
Our white paper goes through a case study with Braskem, a petrochemical company that ran 1,500 injection cycles with one mold insert printed with High Temp Resin to produce mask straps. The company printed the insert and placed it inside a generic metallic mold integrated in the injection system. This is a powerful solution to produce medium series quickly.
High Temp Resin, however, is quite brittle. In the case of more intricate shapes, it warps or cracks easily. For some models, reaching more than a dozen cycles can be challenging. To solve this challenge, French startup Holimaker turned to Grey Pro Resin. It has a lower thermal conductivity than High Temp Resin, which leads to a longer cooling time, but it is softer and can withstand hundreds of cycles.
Download our free white paper for the detailed case studies and to learn how to create 3D printed molds in-house for injection molding.
Download the White Paper
Injection molding with 3D printed molds can be used for a wide variety of applications. Download our white paper for five real-life case studies to learn how this hybrid manufacturing process enables on-demand mold fabrication to quickly produce small batches of thermoplastic parts:
- IPC conducted a technical study on injection molding with 3D printed molds
- Multiplus uses Rigid 10K Resin 3D printed molds for low-volume production
- Novus Applications injection molded hundreds of threaded caps with a Rigid 10K Resin three-parts mold
- Braskem fabricated 3000 mask straps in a week with a High Temp Resin mold insert
- Holimaker produces 100s of technical parts with Grey Pro Resin and Rigid 10K Resin molds
Textures on the Rigid 10K Resin 3D printed injection mold and the final molded part.
An injection mold 3D printed with Formlabs High Temp Resin.
Based on internal testing and case studies with our customers, we suggest to choose the 3D printing resin based on the criteria from the table below. Three stars means the resin is highly effective, one star is less effective.
| Criteria | High Temp Resin | Grey Pro Resin | Rigid 10K Resin | |
|---|---|---|---|---|
| High molding temperature | ★★★ | ★ | ★★ | |
| Shorter cooling time | ★★★ | ★ | ★★ | |
| High pressure | ★ | ★★ | ★★★ | |
| Increase cycle number for complex geometries | ★ | ★★ | ★★★ |
The complexity of the injection molding process is mostly driven by the complexity of the part and the mold structure. A broad range of thermoplastics can be injected with 3D printed molds such as PP, PE, TPE, TPU, POM, or PA. A low viscosity material will help reduce the pressure and extend the lifetime of the mold. Polypropylene and TPEs plastics are easy to process at a high amount of cycles. In contrast, more technical plastics like PA will allow a lower number of runs. The handling of a release agent helps to separate the part from the mold, in particular for flexible materials such as TPUs or TPEs.
The type of injection press does not have a significant influence on the process. If you are new to injection molding and are looking into testing it with limited investment, using a benchtop injection molding machine such as the Holipress or the Galomb Model-B100 could be a good option. Automated small scale injection molding equipment such as the desktop machine Micromolder or the hydraulic machine Babyplast 10/12 are good alternatives for mass production of small parts.
White Paper
Download our white paper for guidelines for using 3D printed molds in the injection molding process to lower costs and lead time and see real-life case studies with Braskem, Holimaker, and Novus Applications.
Read the White Paper
We recommend respecting the rules of design for additive manufacturing as well as the general rules for injection mold design, such as including two or three degrees of draft angles, maintaining a uniform wall thickness across the part or rounding up the edges. Here are a few helpful advice from users and experts, specific to polymer printed molds:
To optimize dimensional accuracy:
- Plan stock allowance on the mold to post-process and adjust sizes.
- Print one set of mold to understand dimensional deviations and account for this in the CAD model of the mold.
To extend the lifetime of the mold:
-
Open up the gate to reduce the pressure inside the cavity.
-
When possible, design one side of the stack flat while the other side carries the design. This will lessen chances of blocks misalignment and risk of flashing.
-
Include large air vents from the edge of the cavity to the edge of the mold to allow the air to escape. This yields a better flow into the mold, minimizes pressure and alleviates flashing in the gate area to decrease cycle time.
-
Avoid thin cross-sections: surface thickness less than 1-2 mm may deform with heat.
To optimize the print:
-
Adjust the back of the mold to minimize material: reduce the cross section in areas that are not supporting the cavity. It will save costs in resin and diminish risks of print failure or warpage.
-
Add chamfer to help to remove the piece from the build platform.
-
Add centering pins at the corners to align both prints.
If you have more questions about the workflow, make make sure to check our article FAQ: Injection Molding With 3D Printed Molds. For the complete process workflow and other best practices, download our white paper.
3D printed injection mold can accommodate side actions.
Combining moldmaking with desktop 3D printing allows engineers and designers to expand the realm of materials they’re using and bring the capabilities of their 3D printer beyond rapid rototyping and into the realm of production.
Using 3D printed molds, dies, and patterns to supplement molding and casting processes tends to be both faster and less expensive than CNC milling, and easier than working with silicone molds.
Beyond injection molding, 3D printed molds can be used for the following molding and casting processes:
- Thermoforming and vacuum forming
- Silicone molding (also overmolding, insert molding)
- Vulcanized rubber molding
- Jewelry casting
- Metal casting
Follow the links to download our white papers with the specific guidelines for each process.
White Paper
Interested in other applications of 3D printed molds? Download our white paper that also covers thermoforming and casting with elastomers.
Download the White Paper
White Paper
Download our white paper to see how to create complex molds with 3D printing fast and learn about tips and guidelines that you’ll want to follow when preparing your mold parts.
Download the White Paper
White Paper
Download this report for case studies featuring OXO, Tinta Crayons, and Dame Products that illustrate three different implementations of silicone molding for product design and manufacturing, including overmolding and insert molding.
Download the White Paper
How to use 3D printing for injection molding
Today, most plastic products in the world are made using injection molding. However, creating molds can be time consuming and costly. Fortunately, molds can not only be obtained on a metal milling machine, but also printed on a 3D printer.
Stereolithographic (SLA) 3D printing is an affordable alternative to milling aluminum molds on a machine. The 3D printed models are hard and isotropic, and the materials used have a thermal distortion temperature of 238°C at 0.45 MPa. This means that they can withstand the temperature and pressure of injection molding.
Download our free white paper to learn how to 3D print injection molds.
Download white paper
3D printed aluminum framed molds and finished die-cast model.
With affordable desktop 3D printers, heat-resistant 3D printing materials and injection molding machines, you can create molds yourself to produce functional prototypes and small models from industrial plastics. In the case of small-scale production (approximately 10-1000 models), injection molds created using 3D printing save time and money by eliminating expensive metal molds. They also provide a more flexible approach to manufacturing, allowing engineers and design professionals to prototype injection molds, test mold configurations, or easily modify molds while continuing to iterate, thanks to short order lead times and turnaround times.
Stereolithography (SLA) technology is a great solution for injection molding. It is distinguished by the fact that it allows you to create molds with a smooth surface and high precision, giving these qualities to the finished model, as well as simplifying the process of removing from the mold. SLA 3D printing provides chemical bonding, density and isotropy of the manufactured models, which makes it possible to produce functional molds of a quality that cannot be achieved with Fused Deposition Modeling (FDM) printers. Desktop stereolithography printers, such as those offered by Formlabs, simplify your workflow because they are easy to implement, use, and maintain.
Formlabs created High Temp Resin for small production runs of injection molded models. It has the highest heat distortion temperature on the market and one of the highest among Formlabs resins: 238°C at 0.45 MPa. High Temp Resin can withstand high casting temperature and shorten the cool down time. Our white paper provides a case study from Braskem. She completed 1,500 casting cycles using a single 3D printed High Temp Resin profiling insert to make the face mask neck straps. The company printed the insert and placed it in a conventional metal mold integrated with the injection molding system. This is an effective solution for the production of medium batches of models. The printed insert can be replaced as the project parameters change or if it breaks. This solution allows molds to be created as needed with complex geometries that are difficult to create with traditional methods, and also provides the possibility of multi-stage casting.
However, High Temp Resin is quite brittle. In the case of more intricate shapes, it is easily deformed and cracked. For some models, it is difficult to complete more than a dozen cycles. To solve this problem, the young French company Holimaker used Gray Pro Resin. This polymer has a lower thermal conductivity than High Temp Resin, which increases the cooling time. However, it is softer and able to withstand hundreds of cycles.
Formlabs recently released Rigid 10K Resin, an industrial grade material with a high fiberglass content. It can convey a variety of geometric features and withstand injection molding processes. Rigid 10K Resin has a thermal distortion temperature of 218°C at 0.45 MPa and an elastic modulus of 10,000 MPa, making it strong, incredibly stiff and heat resistant. Novus Applications has cast hundreds of structurally complex threaded caps with just one Rigid 10K Resin mold. As more companies start using Rigid 10K Resin, we believe this resin will be a great help in 3D printing complex injection molds.
Download our free white paper to learn about practical use cases and how to 3D print your own injection molds.
Download white paper
Based on our customers' internal testing and case studies, we recommend selecting a 3D printing resin based on the criteria shown in the table below. Three stars mean that the polymer is very effective, one star means that it is not very effective.
The more complex the model and mold design, the more difficult the injection molding process. Using 3D printed molds, models can be molded from various materials such as polypropylene, polyethylene, thermoplastic elastomer, TPU or polyamide. Low viscosity material can reduce pressure and increase mold life. Polypropylene and thermoplastic elastomers are easy to process. Using them, you can perform a large number of cycles. In contrast, more technical plastics such as polyamide allow for fewer cycles. A release agent makes it easier to separate the model from the mold, especially for flexible materials such as TPU or thermoplastic elastomers.
The type of injection molding machine does not greatly affect the process. If you have little experience with injection molding and would like to try this method at no extra cost, we recommend using a desktop injection molding machine such as the Holipress or Galomb Model-B100.
White paper
Download our white paper to learn how to use 3D printed molds for injection molding to help you cut costs and order lead times, and see real world application examples 3D printed by Braskem, Holimaker, and Novus Applications.
Read white paper
We recommend that you follow the design rules for additive manufacturing as well as the general design rules for injection molding, such as 2 or 3 degree taper, uniform model wall thickness, and rounded edges. Here are some helpful tips from users and professionals regarding resin printed molds:
To optimize dimensional accuracy:
- Plan the mold allowance for post-processing and dimensional changes.
- Print one batch of a mold to learn about dimensional deviations and account for them in a CAD mold model.
To increase mold life:
-
Open the sprue to release pressure in the cavity.
-
If possible, design one side of the floor flat and the other as designed. This will reduce the chance of blocks shifting and splashing.
-
Create large air ducts from the edge of the cavity to the edge of the mold. This will improve the flow of material into the mold, minimize pressure, and reduce the chance of splashing in the sprue for faster cycle times.
-
Avoid thin cross-sections: under the influence of temperature, a surface with a thickness of less than 1-2 mm may be deformed.
For print optimization:
-
Modify the back of the mold to minimize the amount of material used: reduce cross-cuts in areas that do not support the cavity.
This will save resin and also reduce the chance of printing errors or warping.
-
Add a beveled edge to remove the product from the work platform.
-
Add centering holes at the corners to align both models.
If you have any questions about the workflow, please read our article in the FAQ section titled "Injection Molding in 3D Printed Molds". For full details of the workflow and recommended practices, download our technical white paper.
3D printed injection molds can withstand side loads.
By combining mold making with desktop 3D printing, engineers and designers can expand their 3D printer's range of materials and capabilities beyond rapid prototyping into industrial manufacturing.
3D printed molds, dies and samples to complement molding and casting processes are generally faster and cheaper than CNC milled models and easier than silicone molds.
In addition to injection molding, 3D printed molds can be used for the following molding and casting processes:
- Thermoforming and vacuum forming
- Silicone molding (including multilayer and insert molding)
- Molded using vulcanized rubber
- Jewelry casting
- Metal casting
To download our technical reports with specific recommendations for each process, use the appropriate links.
White paper
Are you interested in other uses for 3D printed molds? Download our white paper which also talks about thermoforming and injection molding of elastomers.
Download White Paper
White Paper
This white paper contains case studies from OXO, Tinta Crayons and Dame Products illustrating three different applications of silicone molding for product development and manufacturing, and multi-layer and insert molding.
Download white paper
3D printed molds
Injection molds are 3D printed using special durable materials. They are much cheaper than metal ones, but less durable and designed for the production of small batches of products (usually from 100 to 150 pieces).
Printing molds on a 3D printer is an ideal solution for small-scale production, fast production of test batches of products.
Printing molds on a 3D printer is an ideal solution for small-scale production, fast production of test batches of products.
How it works
How it works
Creating a computer model of a mold
Printing a mold on a 3D printer
Creating a computer model of a mold on a 3D printer02
Mold installation in injection molding machine
Result and comparison of printed and molded mold
Mold installation in injection molding machine
Result and comparison of printed and molded mold
Examples of using 3D printers to create molds
3D printing molds for the production of electrical switches
Berker (Germany), a leading manufacturer of electrical switches and sockets, uses Stratasys 3D printers to print plastic inserts in a press forms. With their help, the company produces small (20-30 pieces) batches of prototypes of new models for testing.
Examples of using 3D printers to create molds
3D printing of molds for the production of electrical switches
Berker (Germany), a leading manufacturer of electrical switches and sockets, uses Stratasys 3D printers to print plastic inserts into molds. With their help, the company produces small (20-30 pieces) batches of prototypes of new models for testing.
3D printing of molds from Objet materials
The history of the implementation of one of the CATI engineering service orders. The company's engineers complied with a customer's request to replicate a product sample using 3D printed molds created from various Objet materials. The cost of one form was less than $700.
3D printing of molds from Objet materials
The history of the implementation of one of the CATI engineering service orders. The company's engineers complied with a customer's request to replicate a product sample using 3D printed molds created from various Objet materials.
