select
navigate
switch tabs
Esc close

How to deal with shrinkage issues in polyurethane resin parts during vacuum casting

0
J
2

Hi,  I am concerned about shrinkage in polyurethane vacuum-cast parts during the curing process. These parts have tight tolerances, such as ±0.2 mm, and some features are designed carefully to fit together, such as snap joints or press-fit inserts. Should I make adjustments to my CAD model sizes to account for shrinkage, or is this something that the mold manufacturer automatically takes care of?  

Solved by David Y
Jumping in to add that the manufacturer makes adjustments for shrinkage based on material properties, thermal expansion effects, and moisture sensitivity. Shrinkage also depends on the geometric shape of a particular part: thin-walled sections usually shrink more than thick ones, and the presence of undercuts leads to non-uniform shrinkage. Furthermore, resin compositions can affect how much a part shrinks; hence, it is important to consult with your manufacturer regarding material choices. Given these factors, and by delineating explicit tolerances that have been set, one ensures that part dimensions are maintained according to specifications. Always reconfirm how shrinkage is handled with your manufacturer beforehand.
    • J

      Hi,  I am concerned about shrinkage in polyurethane vacuum-cast parts during the curing process. These parts have tight tolerances, such as ±0.2 mm, and some features are designed carefully to fit together, such as snap joints or press-fit inserts. Should I make adjustments to my CAD model sizes to account for shrinkage, or is this something that the mold manufacturer automatically takes care of?  

      0
    • D

      Shrinkage occurs frequently in vacuum casting, but that is not your problem as a designer—rather, it’s something for manufacturers to deal with. Your CAD model should be submitted at nominal dimensions when you send it to the manufacturers. They will then adjust the mold-making process to compensate for any shrinkage that may occur during the curing cycle of the urethane resin. This adjustment is typically built into the mold itself, so your CAD model needs no changes whatsoever. You should only need to indicate clearly defined tolerances within your model. If you’re concerned, you could always ask the manufacturer how they deal with shrinkage compensation in their system before finalizing anything.

      0
      Reply
      • D
        Dimitris

        Jumping in to add that the manufacturer makes adjustments for shrinkage based on material properties, thermal expansion effects, and moisture sensitivity. Shrinkage also depends on the geometric shape of a particular part: thin-walled sections usually shrink more than thick ones, and the presence of undercuts leads to non-uniform shrinkage. Furthermore, resin compositions can affect how much a part shrinks; hence, it is important to consult with your manufacturer regarding material choices. Given these factors, and by delineating explicit tolerances that have been set, one ensures that part dimensions are maintained according to specifications. Always reconfirm how shrinkage is handled with your manufacturer beforehand.

        0
        Reply
How to deal with shrinkage issues in polyurethane resin parts during vacuum casting
Your information:




Suggested Topics

Topic
Replies
Views
Activity
Mesh accuracy concerns with FDM
I'm working on a small gear-driven mechanism for a camera panning rig and considering printing the 45° bevel gears in PETG (FDM). Tooth pitch is 1.5 mm, and the gears will be rotating slowly... read more
M
n
3
28
Apr 29
OD and ID vs OD and Wall Thickness – which is the best method of dimensioning?
Hello All, I am designing a conical-shaped plastic bushing and am confused if specifying the OD and the wall thickness is better for controlling the manufacturing process, or OD and ID separately, with their tolerance... read more
1
59
Apr 23
Metal 3D printing for watertight watch cases
Hi! I'm prototyping a watch case and considering metal laser sintering (DMLS or SLM) due to cost constraints—CNC machining is out of budget. My main concern is whether an as-printed sintered metal part will... read more
H
R
2
149
Mar 25
99 model kia sephia kontak termiği yapabilir misiniz
99 model kia sephia kontak termiği yapabilir misiniz kontak anahtarının girdiği yerde 3 tane kırık var onun için anahtarı tam olarak kavramıyor ve motoru çalıştırmıyor bu kırığın yapılması gerekiyor veya değişmesi gerekiyor fakat piyasa... read more
S
1
108
Mar 19
Moulding of a Concave Disk
Hello everyone, I want to make a disk of 203 mm in diameter, 25 mm in height with a concave curvature of 3.22 mm.Will this precision be respected knowing that I am not a... read more
1
112
Mar 17