Hello friends,

I intend to make a medium-sized piece (1.35mx 0.30m) with polyester resin, but I saw that it corrodes the potential risk of shrinkage during resin curing.

- The resin has the gel time of: 30 minutes and the manufacturing process would be by Hand Layup + vacuum bag or Resin nfusion.

The doubts are as follows:

"What do I have to do to stop this from slowing down?"
Because I can not have dimensional changes due to the product accessories.

Desmoulding after 4 hours of lamination cause me problems?

We have a small production line and we need to be quick in our process.

Thanks,
Dezer

i disagree with hanaldo in the point of doing oh in multiple steps, only a few layers each time. in my understanding of physics, this is the best way to get a warped part. polyester resin shrinks a lot during the curing, and most of the shrinkage happens during a stage, where it is already solid. so if you laminate a few layers and let them cure, the layup will shrink a bit, but consistently over the cross section. than you add more layers and let them cure. they will shrink, too, but the will be bonded to the layers wich are already cured. so the inner side of your part shrinks, while the outer side doesn't (any more). this leads th warping.
My recommendations are:
-do everything in one pour, and as quick as possible
- keep the gelcoat as thin as possible (same reason as explained above)
- keep the fibre content as high as possible (fibres resist the shrinkage). therefore infusion might be the better way
- keep the temperature low during the cure (room temperature) and try to avoid, that some parts of the mold get hotter than others (sunlight though the windows, deep sections, in wich the polyester pools  and heats up)
-use filled non-shrinkage resin, like the unimold tooling resin
-use epoxy resin (most likely no option cost wise)
last but not least I would like to say, that shrinkage is not avoidable, at least to a certain degree. so keep your ambitions realistic. even companies like koenigsegg spent hours on a jig, fitting their body parts, to get a perfect look. panel work will never be 100 percent plug and play, unless you really know you tolerances and include them into you calculations.