The Formech 450DT is a thermoforming machine that makes light weight hollow copies of existing objects by pressing the object into a heated plastic sheet. The resultant product has a variety of uses including molds, packaging, prototyping, and even chocolatier work!
If you have an object you want to vacuum form, it must be designed with no undercuts and a minimum draft angle of 3 degrees for optimal removal. Our machine has an area limitation of 11x17 inches and a depth limitation of 6.3 inches, so please make sure that any object you bring is below this threshold. We have two reducing plates available for smaller objects.
All vacuum forming must be done through an appointment. Makerspace Staff can assist you with learning the equipment. If you need accommodations to use this equipment please contact us directly so we can assist you further.
Details:
From Formlabs.com: “Vacuum forming is a manufacturing method used to shape plastic materials. During the vacuum forming process, a sheet of plastic is heated and then pulled around a single mold using suction.” Vacuum forming can be done on a small scale for goods like chocolates and soap, and large scale like automotive parts.
Any object that can withstand the force of the vacuum former AND passes the design form criteria (explained below). Some examples of objects that cannot be vacuum formed include pottery, food, and un-fired/baked sculptures. If you are unsure, ask the Makerspace staff.
The MakerSpace offers these materials:
|
Material |
Thickness (actual size & forming size) |
12" x 18" 11” x 17” |
12"x12" 11” x 11” |
6"x6" 5” x 5” |
|
PETG (food safe, clear) |
0.02" |
$3.30 |
$2.50 |
$1.80 |
|
0.03" |
$4.20 |
$3.10 |
$2.10 |
|
|
0.04" |
$5.20 |
$3.80 |
$2.40 |
|
|
Polystyrene |
1/32" |
$4.00 |
$2.50 |
$1.80 |
|
1/16" |
$6.60 |
$3.80 |
$2.40 |
|
|
ABS |
1/16" |
$10.60 |
$3.80 |
$2.20 |
From Formlabs.com:
Clamp: A sheet of plastic is placed in an open frame and clamped into place.
Heat: The plastic sheet is softened using a heat source until it reaches the appropriate forming temperature and becomes pliable.
Vacuum: The framework containing the heated, pliable sheet of plastic is lowered over a mold and pulled into place via a vacuum on the other side of the mold. Convex molds need to have tiny holes drilled into crevices so that the vacuum can effectively pull the thermoplastic sheet into the appropriate form (more on this in Design Principles)
Cool: Once the plastic has been formed around/into the mold, it needs to cool.
Release and Trim: After the plastic has cooled, it can be removed from the mold and released from the framework. Edges may need to be trimmed or sanded.
Vacuum Forming Terminology and Design Principles
There are two types of molds when it comes to vacuum forming: positive, or convex, and negative, or concave. With positive molds, the sheet of plastic forms over the mold to contour the inside dimensions of the plastic part. With negative molds, the thermoplastic sheet forms inside the mold to form the outer dimensions of the part precisely.
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Vent holes are small holes in your 3D print (or object). With 3D prints, they can be integrated into the 3D model itself, or drilled in after the print is finished. Vent holes allow greater suction for the machine to pull the plastic closer to your object. Without them, your object may not be replicated as well. From Makyu: “This is especially relevant if your design has parts where the air can get stuck (aka concave designs). In those areas it’s recommended to add small holes where the air can move. A 1mm hole may not even be visible in the mold, but it will greatly improve the mold quality.”
The left mold doesn’t have vent holes, and the right mold does. Notice the curved inside where air is trapped in the left mold, and notice the sharp inside of the right mold.
From mayku.com: “A draft angle is a slant that is applied to the faces of your model and it helps when releasing the template from the plastic sheet. For 3D printing it’s recommended to add at least 1º of draft for every 2cm of height.” Drafts should be applied to all geometry, even the inside.
Here you can see what a difference a few degrees of draft angle can make. Because the top is smaller than the bottom, the object can pop right out. Removal of the 1 degree cube is harder than the 5 degree cube because the top and bottom are almost the same. Draft angles and vent holes give you the highest chance of mold success.
Undercuts are when part of your design moves inward, like ledges or indents. Undercuts should be avoided, or created intentionally (ex. One side has an undercut but the rest of the design is fine. See the orange dragon tooth as reference).
(Red represents the undercut, and blue the draft angle). Though the undercut is extreme on this model, so is the draft angle on the other side, Thus, the casted item can slide out from the draft angle side.
A good way of checking if your object has a forgivable undercut is imagining the object as it’s 3D printed. Does it need support to keep it up, or has an overhang? You need to reconsider your design. If you vacuum form a model that has undercuts, you’ll create a mechanical lock, aka, you won’t be able to remove the object once the plastic sheet cools down. In terms of depth, you should strive for no greater than 15mm.
This poor tree is mechanically locked, never to be free from its plastic prison. Meanwhile, this gummy bear will make an excellent soap mold.
From amtekcompany.com, webbing is “unwanted wrinkles that appear in your mold when the vacuum is applied and the plastic is stretched in a way you didn't plan.” Besides being unsightly, webbing can trap your original form, not adhere to it properly, and make casting more difficult for your form. Webbing can be avoided with vent holes and making sure your material isn’t too warm.
Vacuum forming is considerably easier to do when your object is more wide than tall. If you have a vertical object you need to vacuum form, place it on its side. Or, cut the model in half and vacuum form both sides and then assemble them together after forming. If you still want to try, give your object generous draft angles.
Here is a vacuum formed model of Beaumont tower. Because it doesn’t have sufficient
draft angles and it was vacuum formed vertically, it’s mechanically locked with unsightly webbing.
Every 3D print and object you vacuum form will have texture. PLA 3D prints have layer lines, and depending on the thickness of the vacuum form material, will show up no matter what unless the print is sanded and primed. To avoid the lines completely, you can print with Polysmooth filament and smooth your print with isopropyl alcohol vapor. This is a great solution for applications like soap or chocolate, where lines may distract from the design.
Due to it’s low melting point, PLA can’t be used for over 3 molds before it deforms. This can be mitigated slightly by increasing the infill of your 3D print to around 50%. That way, the internal structures won’t melt and deform under the heat and pressure. Additional perimeters or extra top layers are great options too. Let a staff member know if you are submitting a 3d print for vacuum forming and we can help you find the best solution.