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How to 3D Print Molds for Vacuum Forming

Posted by Joaquin Laurel on

There are many ways to create your Vaquform molds. You may use sculpted clay, Lego pieces, found objects, and many more. As long as the mold can hold its shape under heat, is not wet or dusty, and will not stick to a formed sheet, you can #VaquformIt.

But there is one thing that makers out there use a lot and that’s FDM 3D printing. With 3D printing, you can easily and digitally modify your mold designs. 

This guide will teach you how to optimize your FDM 3D prints for vacuum forming.


Here's a bullet point summary if you’re here for a quick reference, don't have time to read through the whole article, or just have a short attention span just like most of us do.



    • Angles (draft angles & undercuts)
    • Vent holes in concave features



0.5mm Sheet & 1mm Sheet*

Layer Height


Wall Thickness


Top Thickness


Bottom Thickness


Infill Density


Infill Pattern


Increase wall thickness if:

  • You’re using a thicker sheet
  • You’re going beyond 10 pulls for 0.25mm - 0.5mm
  • You’re going beyond 5 pulls for 1mm or thicker



    • Sand your molds
    • Let your molds cool down in between forming cycles
    • Print multiple molds


Here, your ultimate guide to 3D printing your Vaquform molds

A smart and powerful machine, and a good mold leads to a successfully formed sheet. 



To start things off, All Vaquform Molds should follow two basic principles:

  1. Angles 
  2. Vent Holes




Your molds ought to have draft angles along its vertical edges. Having draft angles on the appropriate surfaces will ensure that you will be able to separate your mold from the formed sheet.



When it comes to how much draft angle you should apply, a general range we recommend is between 3-5 degrees. A larger draft angle will make it easier to separate your mold from the formed sheet, but will also affect the overall shape and dimensions of your mold. It is up to you to find the balance based on your individual forming needs.



Watch out for any negative angles or “undercuts” to ensure that you can separate your 3D printed mold from the plastic sheet after forming.

Undercuts may include inward angles less than 90 degrees (such as in the photo above), overhanging protrusions, slots, holes, and other concave and convex features that are present on the sides of your mold



Vent holes

If your molds have any concave features, it is a good idea to drill vent holes in order to ensure that the plastic sheet forms evenly into the details of those features.

In the example above, the mold contains a basic box cut out in the center. Without the use of vent holes, the plastic sheet has difficulty getting down into the corners and crevasses of the concave feature as air gets trapped inside the concave feature.

The strategic placement of vent holes will allow air to escape from places where air might otherwise get trapped during the forming process.


When choosing what size of drill bit to use for your molds, the idea is to allow as much air to flow as freely as possible through the hole, without the hole being so big that it leaves a noticeable impression on your formed sheet.

In the photo above, we drilled 4 vent holes using 0.4mm, 0.6mm, 1.0mm and 2.0mm bits to give you an idea of the impressions that different sizes of vent holes may leave on your formed sheet.

For the best result, we recommend using between 0.4mm to 0.8mm size drill bits. Anything bigger, and you will begin to notice evidence of vent holes on the final form. It is up to you to determine if evidence of vent holes is relevant to your specific forming needs.




0.5mm Sheet & 1mm Sheet

Layer Height


Wall Thickness


Top Thickness


Bottom Thickness


Infill Density


Infill Pattern


The table above shows the standard parameters that we use at the lab for forming 0.5mm and 1mm sheets. Let’s discuss each parameter in detail.


Layer Height


The DT2 is a VERY powerful machine; great for getting those finer details that other desktop vacuum formers simply can't. This does mean however that fine details such as layer lines on your 3D prints will be seen on your form.



Now this may or may not be important to you and your forming goals, but if you prefer a form without those layer lines, we recommend using a 0.16mm layer height (for a standard 0.4mm nozzle) to get the best balance of surface finish and print speed for Vaquforming molds.


Wall and Top Thickness

As a general rule, the thicker the wall thickness of your printed mold, the longer the service life will be.


For example:

A wall thickness of 1.6mm might last you tens of cycles with sheet thicknesses of up to 1.0, and adequate mold cool down time (see adequate cool down), while a wall thickness of 3.2 might potentially last you much longer, with thicker sheets.

We use a wall thickness of 3.2mm for our general use PLA tools, which will hold up against sheets of up to 1.5mm thick


Tip: For thicker sheets you can use the formula

Sheet Thickness x 1.5 = *Wall Thickness

*Be sure to round the wall thickness to the nearest multiple of your nozzle size to ensure that the nozzle prints the exact amount of walls needed without overlap

A 0.4mm nozzle → wall thickness = 1.6mm, 2.0mm, 2.4mm, 2.8mm, 3.2mm, etc..



Here, we printed two cubes with identical slicer settings (our recommended parameters). The only difference between them is the wall thickness. We put both molds through a number forming cycles, using HIPS sheets heated to 160 degrees celsius.

This is the result after 10 pulls. As you can see, there is evidence of warping and deformation on the print with thinner walls (left), while the other mold with thicker walls still looks like it’s fresh off the printing bed. 

Bottom Thickness


We always keep the bottom thickness of our molds 0. This not only speeds up printing time, but more importantly, creates an open bottom where air can pass through more easily from the vent holes during forming.

The difference between the two forms is clear. The debossed Vaquform Logo can be seen more clearly and cleanly when formed over a mold with gyroid infill, even without the use of vent holes.


Infill Density

For the infill density of your Vaquform molds, 20% is a good place to start.


It's true that increasing the infill density will help increase the service life of your mold. However, with 100% infill, not only will it take you longer to print, it will also prevent air from escaping through your mold.


Infill Pattern

In 3D printing, the infill pattern can affect the durability of your print, how much material is used, and also the printing time. In vacuum forming, this also affects the structural integrity of your mold against multiple forming cycles.


We have found that the gyroid infill pattern has the perfect balance between good structural integrity and fast printing time.



With a gyroid infill, force from the vacuum suction is supported more evenly throughout the surface of the mold. The photo above demonstrates how having gyroid infill will help increase the mold’s service life, especially when compared to other patterns such as grid where you can see signs of deformation with the same number of forming cycles.


The gyroid infill pattern also has no air locks in any directions. This means that if you pour a liquid substance into a mold with this infill, the fluid will flow and distribute itself freely throughout.

A grid infill pattern and other similar infill patterns wont have the same benefit, and in the case of a grid infill, fluid will only be able to pass vertically through the spaces between the pattern. Air or any other fluid traveling horizontally is not possible with this infill pattern.

Filament Material

We use PLA to print nearly all of our Vaquforming molds because it’s rigid, durable, and easily accessible; as it is one of the most common types of filament used in 3D printing.

Other filament choices are available! But do take note of the following:

  • ABS tends to warp, and you may need a good printer and good conditions to print ABS well. However, because of ABS’ higher temperature resistance, molds printed with ABS may have a longer service life.

  • PETG printed molds will stick to a hot sheet and make it difficult to separate. More importantly. When forming PETG sheets over PETG printed molds, the heated plastic will fuse with the mold during the forming process, and make it nearly impossible to separate the mold from the sheet.



Now that you've followed our general guidelines for how to print your molds, they are nearly ready for forming! But before that, here are some techniques you can use to post-process your printed molds. Applying any of these post processing techniques may:

  • Extend the service life of your molds
  • Enhance the surface finish of your forms 
  • Improve the forming process as a whole 




It is a good idea to sand the surface of your 3D printed mold to help increase the surface quality. In the sample photo, we sanded the surface of the mold until the layer lines could no longer be seen.

When sanding your molds, sand in a circular motion. This will give you the smoothest surface finish. For the best results, we recommend multiple cycles of sanding using increasingly fine grit levels of sandpaper.

For example, starting first with 400 grit, then 800grit, and finishing with 1000 grit.

If you prefer to stick with only one grit level, we suggest that you avoid using anything rougher than 400 grit. 


A couple more advantages of sanding based on the forms above:

  • Smooth surfaces are less likely to leave an impression on your form.
  • Smooth surfaces are easier to demold.
  • Sanding after printing may allow you to get away with printing your molds with larger layer heights, as layer height greatly influences print time, a larger layer height means having to print a smaller number of layers, which decreases total printing time.

Adequate cool down

Allow your Vaquform molds to cool down between forming cycles. This will help lengthen the lifespan of your molds and prevent warping from constant heating.

Remember, your 3D printed molds are also thermoplastics just like your sheets!


Multiple molds

A surefire way to streamline your mass production is just to print several molds. Having multiple copies of the same mold while mass producing your forms will:
  • Make it possible to form several pieces of your design in one forming cycle, which is a more efficient use of the entire plastic sheet.
  • Allow you to cool down your molds in between each use, as you cycle through them, instead of waiting for one mold to cool down every cycle.
  • Mean that you have back-up molds in case anything goes wrong and one of your molds becomes unusable. 


There you go!

In some cases, you might need to tweak the settings according to your mold shape and design but these guidelines are a good place to start.

If you have questions, feel free to reach out through Facebook and Instagram, or by sending us a message at

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