The Impression Is Stuck or Tore on Extraction
An impression tears or stays stuck when the removal constraint is higher than the product accepts. It also happens if you pull it the wrong way. Do not measure a torn impression. Change one of the points below and take a new one.
Check the Removal Constraint Again
Recalculate C = (1 − Dmin / Dmax) × 100. Here, Dmin is the smallest section the impression passes on its way out, which is not always the diameter of the bore.
You can use the product only if its maximum removal constraint is strictly higher than C. If it is not, take a more flexible product: F20 accepts 30%, F40 accepts 35%, and F30 Max accepts 40%.
Check How You Pull
Always pull in a straight line. Never rotate or unscrew the impression, because a rotation destroys a replicated thread.
To give yourself a grip, use a demolding ring and leave a surplus of about 1 cm. On a through part, extract the impression from the side with the larger exit diameter.
Check the Surface
An impression that sticks to the part often points to a greasy surface. Degrease the part with DN1, and never with acetone.
When No Product Is Flexible Enough
If you do not need a diameter, take a partial impression, as the removal constraint drops to almost zero. If a complete impression is mandatory, use the temporary void and reinjection technique.
