Mould tool reinforcement

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#21

ideas: create spars on the finished mold. if the PU tool IS IN GOOD SPEC, then reform the carbon mold back, adding very very specific spars to strenghten it.

When making the mold, create spars at that point, deviating away from the normal layup. if you have too, make tooling supports, and add them in WITH the original cure of the tooling prepreg.

Create solid spars and supports, glue them in after you somehow get the mold back into spec in the tool master.

Make a skin layer of the mold, cure it, and then add your reinforcements later. This way, you won’t get print through and deviations in your tool surface.

Things change. The tooling prepreg might have changed as it ages, along with the PU master. CTE is an issue always, and even luck plays a deal with things.

#22

I am thinking a mechanical correction of some sort? Aluminum/steel with fasteners?

#23

I have already tried to bond spars under the mould surface to facilitate flatness without success due to excessive undulation of the surface but i do like the idea of adding extra spars for support during the lay-up of a new one, thanks. Just the small matter of the two cured moulds I need to reinforce so flatness is achieved ?

#24

Typically you want to do everything is one curing operation if possible. When you move to multiple curing operations then you starting bonding laminates that will shrink to laminates that have already shrink. This can make things go ugly.

Trying to fix the mold will be difficult especially if the mold has to undergo a heat treatment. Molds for room temp curing can often be repaired with steel frames. The CTE of the carbon mold and the steel at elevated temps will cause problems.

In the future you might consider creating the mold with a sandwich structure. Something that will get the mold to 1" thick or more can really bring a lot of stability to a mold.

Slow, slow, slow, slow, slow curing also helps. I often do 2* per hour.

#25

I hear what you are saying. Very frustrating not knowing what the cause is for definite though as all five were done pretty much the same way but still the last two were bowed. The PU pattern has been sitting under ambient temp between cures unsealed for more or less six years so I am convinced there is something happening under heat to it even though it is flat at ambient. Maybe moisture or something else going on I am just unaware of.

#26

If you are sure that the PU master is correct at RT, you can can make a new composite plug from it with RT gelcoated carbon laminations. (female and male)
Anyway I doubt that the PU one couldn’t whithstand 50°C.

#27

You might have something there mate, I may be able to take a splash off one of the good tools even though they are used.:slight_smile:

#28

Does your curing oven have hot or cool spots? This could induce warping to the panel since some parts will have undergone more shrinkage than other parts. Something you might want to check anyway.

#29

Interesting point, willl check mate. Thanks.