How to 3d print a mold

Ultimate Guide to Silicone Molding for 3D Printing (Part 1)

Download the full Guide

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.

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:

1. Open up the gate to reduce the pressure inside the cavity.

2. 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.

3. 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. 

4. Avoid thin cross-sections: surface thickness less than 1-2 mm may deform with heat.

To optimize the print:

5. 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. 

6. Add chamfer to help to remove the piece from the build platform.

7. 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

3D printing mold making

Desktop 3D printing molding allows engineers and designers to get more functionality out of a 3D printer beyond prototyping. Molding opens up a world of production materials and provides the opportunity to produce small batches and sample test molds before using expensive
tools.

This booklet covers the following three mold making strategies: injection molding, high temperature molding and injection molded elastomers. Typically, molds are made from Formlabs clear resin, which is preferred for its transparency, although any standard resin can be used, and high temperature resin is ideal for processes with high temperature requirements. It should be noted that these processes are best suited for stereolithographic 3D printing (SLA) because the printed parts are isotropic and waterproof.

Prototyping and small-scale production with 3D printing tools

Silicone molding and some desktop molds are available using Formlabs Standard Resins High Temp, which has the highest HDT at 0. 45 MPa for any 3D printed materials currently on the market and allows print parts that can be used for high temperature forming such as thermoforming and injection molding of materials with higher melt temperatures

Injection molding

High-resolution SLA 3D printing on the Form 2 can be used to quickly prototype inexpensive injection molds that can be used to make real parts from a wide variety of

thermoplastic materials. Injection molds can be used to test mold designs prior to metal tooling or to produce low-volume parts

3D Printed Injection Molding covers injection molding using Formlabs clear resin printed molds. Following the release of Formlabs High Temperature Resin, designed to achieve higher heat resistance and stiffness, the booklet has been updated to describe the benefits of High Temperature Resin plates that are less likely to break due to thermal shock or temperature-related deformation

USB Device Enclosure Mold, 3D Printed on Form 2 High Temperature Resin

This mold contains a core, a cavity, and two "gates" leading to the two halves of the enclosure. High temperature resin molds can be used to mold a wide range of thermoplastics without thermal stress or temperature-related deformation

Formlabs High Temperature Resin can be used to injection mold a wide range of plastics.

3D printed mold tools reproduce the exact quality of the SLA print finish on the Form 2. Forms can be printed at 100 microns for faster prototyping or the recommended 50 microns for fine detail and smoothness

electronics molded in HDPE with a High Temp tool.

This shape of the USB case has been adjusted over three iterations to remove cavities, entrapped air, and partial shrinkage. Total cost of materials for prototyping this high temperature resin mold tool: $25

Thermoforms

Form 2 3D printed thermoformed dies are a fast and efficient way to create high quality vacuum formed parts for low volume production. Printed thermoformed dies can be used to make packaging prototypes, clean orthodontic retainers, and food-safe molds for chocolate confectionery.

Thermoforming dies experience less pressure than injection molds, but still reach high surface temperatures.

High temperature polymer resists deformation and surface degradation from the combined heat and pressure of thermoforming for most plastics. Standard resins may also be suitable for thermoforming with some low temperature plastics such as vinyl.

APPLICATION EXAMPLE

Formech thermoformed prototype packaging.

Thermoforming a thin sheet of polycarbonate over a high temperature polymer matrix produces a transparent detail by matching the geometry and detail of the matrix. Thermoformed packaging can be easily prototyped and incorporated into the design process along with 3D printed product prototypes, and all this is achievable on the Form 2. The printed matrix was used without additional processing and the need for UV curing. Texture is recommended in thermoforming design to prevent air trapping under the sheet - layer lines on the printed thermoforming die can be helpful in this regard.

TEMPERATURE CONTROL

High Temperature Polymer Cycle Thermoforming

The surface temperature of the die reaches 130°C. The high temperature resin is highly resistant to deflection, whereas with standard resins you must allow the print matrix to cool between cycles, otherwise warping and degradation may occur.