Zero shrink tooling resins

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#1

Hi all,

I’m planning on testing a few different tooling resins. Its an expensive test since none of the companies sell less than 25 liters (6 gallon or equiv) of resin. Thus, I want to do this systematically. Thats where I’ll appreciate your input.

The resins are all infusion resins (some are PE and some are VE), they are loaded with fillers that reduce shrinkage of the tooling after exotherm.

The mold will primarily be made with a surface layer consisting of 3-6 layers of VE resin + chopped strand mat, done one or two layers/day. Followed by a 12-18mm thick infusion with the zero-shrink resin, with the following structure:

From inside to outside–
a. Gelcoat
b. Surface layer (3-6 layers)
c. multimat (OCV 450/500/450)
d. Uniflow (OCV 450)
e. Multimat (OCF 450/500/450)
f. Soric XF-5
g. Multimat (OCV 450/500/450)
h. Uniflow (OCV 450)

My test requirements are to check the following:

  1. Mold stability
  2. Surface quality
  3. Cost
  4. Precision
  5. Ability to secondary bond a stabilizing structure.

The test will be done on a well polished new plug, that is treated with marbo-mold-sealer and waxed. The plug size is indicative of a regular structure that we have.

Any practical suggestions for enhancement?

Thanks,
N

#2

Which brands will you test? You do not consider hand laminating systems?

As for surface layers, do you feel that following the manufacturers recommendations is sufficient?

Suggestions:
post the recommendations/datasheets of all systems you will test. (before testing)

ability to bond a secondary structure: I am a fan of bonding with MS polymer instead of laminating, unless you laminate onto the flange, or a hard point in the mould.

Beware of bridging. Although all systems are low shrink, bridging WILL show.

#3

Herman,

I’ve taken your advice and am also investigating RM5000 and RM6000 along with another two similar resins.

Hand laminating systems: VOC, smell in the facility, not very clean for a facility such as mine etc. Once we finish lamination the whole plug with the mold (6mx1m) will be rolled into the clean room to have a temp controlled cure, and I don’t want to do that with a hand laminated setup. Although the cost is attractive. I actually have a hand laminating system which is from a company that went bust.

Lack of total confidence with the manufacturers recommendations is the reason to get input here on the forum.

The stack that I have suggested is an example of the manufacturers recommendation.

I have a lot of 400gm/sqm twill glass which I’ll like to use as the base layer in the infusion stack (After the skin coat of 3-6 layers of VE and glass. The innermost layer will be a glass veil of 80gm/sqm) and also at the outside most layer.

I know that bridging has to be avoided, so just to give you an idea: the laminate stack that I’ve shared will be on the entire mold without any bridging, then once the mold is cured (the zeroshrink part) then, on the flange I’ll add a stiffener grid that could use a welded steel frame as support. The steel frame will NOT be glued to the mold but the mold will be just supported on it and will be allowed to shift to take care of thermal expansion.

Of course the bondings will be at the flanges. We are looking for extremely high surface quality.

#4

Careful selection of the gelcoat, peroxide and VE brings more in terms of surface quality, than the zero shrink bit.

#5

Thats correct. Surface quality is one very important aspect. So what do you suggest, an unpromoted gelcoat? A VE gelcoat? What hardener? Which catalyst?

All the requirements as stated in the first post in this thread (including surface quality) are important. For instance, the dimensional tolerance is very important. The plugs are all machined to precision and then finished. A regular, non-zero-shrink, VE or PE will shrink enough to make a 6m mold go enough out of tolerance.

The challenge for me is to get the best “compromise” that today’s products will allow based on what my requirements are. Someone else may have different set of requirements and would need to optimize the process for those set.

#6

I suggest a VE tooling gelcoat. Ask your peroxide supplier to suit the best curing agent for you, and test it.

Curing rate is vital at preventing print. A barcol reading can help in determining curing rate.

#7

Herman,

This is what one of the manufacturers recommends:

The gelcoat should be VE as I’ve been informed. The tooling gelcoat and the VE based skin on the top layers have a normal peroxide butanox50.

The infusion resin in this case is PE and the peroxide is very slow: called LPT here.

All the tooling materials are low profile.

#8

Yes, I see. However, with slightly different peroxides you can achieve a better final cure. Like MEC from Syrgis.

#9

I had an interesting discussion on tooling resins the other day with a local moulder & supplier. He reckoned that the proprietory tooling resins (expensive) are basically DCPD resins heavily loaded with Aluminium tryhydrate filler. With this a mould with zero shrink was possible.
Problems he mentioned were that with the high loading of ATH you have to lay the mould up in one go as it is dependent on a good exotherm for proper cure, also once gone off bonding of subsequent layers was poor. Also that once the ATH is added you have to use the stuff within a day or so.
I have just built a plug for an interior moulding for a 5.5m rowing boat & am curious if it would be worth going down the above route as i am concerned about distortion.
I would be interested to hear any thoughts on this!

#10

The moulds I made with RM2000 and RM3000 all came out beautifully.

Indeed the tooling resin can be DCPD, but mostly is ISO or VE. The loading of ATH can be done onsite, as the old Polylite system did, or can come pre-loaded. Also present is a polymer which expands as the polyester shrinks. This only happens at higher temperatures, hence the relatively high exotherm needed.

Keith: I would see no problems in using a rapid tooling system with your mould.

#11

Thanks for the explanation & advice, having now googled the RM series they are available here & prices are a fair bit cheaper than i was quoted for an alternative system. Bonus!
Let you know how i get on.

#12

Hi there,
With 20 years of experience (and test) I can say the cheapest way is VE with glass fiber and lowest resin ratio. But if you need high precision mold I suggest the LV10 carbon past/fiber from Hutsman with HY 98 or HY06 hardener. You can get a 10 to 18 mm thick mold, massive and rigid. A 225 gr carbon 12K with epoxy resin directly on the SV18 epoxy GC give you a perfect finish.This technic require a post curing… You can get info on Hutsman website for further info.
For more technic tip with this product you can let a post here…
KR
Steph

#13

Steph,

I’ve investigated the huntsman material, but its way too expensive. What I’m looking for is precision at low cost. The zero shrink resins are pretty good in that.

Current status: I’ve tested one product and it seems to work. Today I’m setting a small test piece for infusion, which has the following stack:

0-90 Twill 400gm E-Glass
±45 Twill 400gm
0-90 Twill 400gm
Soric XF5
±45 Twill 400gm
-----------sym------------

So there are 8 layers of glass in total and two layers of Soric XF5

The real stack for the mold is the following:

Outside
0-90 Twill 400gm
±45 Twill 400gm
Soric XF5
±45 Twill 400gm
0-90 Twill 400gm
Multimat 450-500-450
Unifilo 850-450
Uniconform 600

Barrier layer is with VE tooling resin
450gm CSM
225gm CSM

VE Tooling Gelcoat 800microns

Inside

All the layers above VE Barrier coat will get infused in one shot using a zero shrink tooling resin.

The outermost layers will give a very tough and stiff structure which is light and conforming. I’ve got to see if the approximately 2400gm of CSM between the the fully cured VE barrier coat and soric will be able to prevent the print through and will be able to handle the exotherm of the zero-shrink resin.

BTW this is our first excursion into VE and PE world, having used and worked with epoxy till now, VE and PE is new learning experience.

Thanks for your responses.
N

#14

I am curious to see whether the 3x400 gr woven will impregnate well. The tooling resins are all highly filled with solids, and will filter out quite quickly.

As you can see in your first post, there are only little amounts of fabric which can have a filtering effect.

#15

Herman,

Actually, that first post was based on a stack that was suggested by one of the potential vendors. I decided against using the biaxial+soric since when I saw the resin. The resin does not have any additives in suspension and the resin is crystal clear. Since the additives (basically poly vinyl acetate) were dissolved very uniformly, it doesn’t get filtered out. Its viscosity is also suited for infusion with a tight stack. It has half the viscosity of the epoxy resins that I usually use.

Therefore, the test stack was set. I did the test yesterday with the first set of resin system. The 3x400 wet up very well. Actually the laminate was:

[0/90, -45/+45, 0/90, XF5, 90/0, +45/-45, 90/0]_sym

Or:

3x400
Soric XF5
2x400
Soric XF5
3x400

The exotherm was around 50degC and the laminate turned a nice white.

The problem though is controlling the exotherm if I vary the accelerator and catalyst ratios. Today, one part went for a toss when, based on the suggestion of the technical expert of the resin manufacturer and in his presence, I had to increase both the accelerator and the catalyst, which gave an exotherm that reached 150degC, very scary! I have a feeling that my plug could have got fried by the exotherm.

N

#16

OK, it is an unfilled resin. That is good. Much easier to work with.

Sorry to hear about the fry-up. I once infused a VE sheet 23mm thick, with 3 layers of 6mm Soric, and the temperature was such that I dared not touching it or the glass sheet that I used as a mould. It was tempered glass, and I am totally impressed by the amount of heat it can take.

All you can do at that point is spray water.

#17

You know had I stayed with the amount of catalyst and accelerator that I’d used in the test and not gone with the advice of the technician, I’d not be as sorry as I’m now!

Still have to de-mold the mold from the plug, I’ll do that tomorrow. But something I’ve realized, that the low profile resin takes its time to harden unless there is a noticeable exotherm. So all the areas where the resin film is less than normal, think of edges of the part or between the release film and flow medium etc, its not exothermed enough and one can see the resin as transparent. This is also in the test piece.

I’m having second thoughts to use the zeroshrink method and perhaps may rethink and make the molds out of epoxy. I wonder if there is an epoxy gelcoat that can give me a high quality part (with lots of gloss) and if I need to repolish the molds after 50-100 pulls, would permit me to refinish it. Molds of the size that I use are expensive and future refinishing is an important criteria.

What are your thoughts?

N

#18

Make sure your mould is smaller than the laminate, so you can cut off the sides, which indeed can be less than sufficiently cured. Should be just a cm or so.

The rest should be gone off properly.

Another route which can be tempting is using VE tooling gelcoat, with a VE skin coat, peelply used, and infuse epoxy behind that. (with lots of Soric). This is what we did when making a 15 meter mould for a boat, and that mould is still in great shape.

#19

What was your laminate schedule on the skin coat? I have VE tooling gelcoat as well as VE tooling resin at hand. The only thing I’ve been advised is to not have more than 3 layers on skin coat (wet on wet), perhaps I can go upto 4 layers. I can then peelply the area or even sand it after the skin coat.

Well, just after I shot that response on the site, the technical folks called me again and said that perhaps the accelerator and catalyst ratios were not correct!!!:mad:!!! So they’re going to send me some trial resin (the initial batch was purchased by me), so I can redo the test with different laminate.

I’ll try this after de-molding the current plug. I do hope that its still intact.

Another question: Since this is my first excursion in the world of Polyester/VE world, I wonder if I use the stack that I’ve used in the test, and go with that behind the skin coat of VE tooling resin. The resultant laminate is very strong and stiff. I tried to break it with a hammer and after 3-4 hard hits, nothing happened, and AFTER that I cut it and measured it and took the photos below. So suppose I do this 8 layer sandwich behind the skin coat. Do you think that it will not print through?

#20

For the curious cookies there: Here are some photographs of one of the test infusions (75% vacuum) the laminate schedule here is:
[0/90, ±45, 0/90, SoricXF5, ±45]_sym

The total thickness: 12.2mm

Hope this helps you to choose your own laminate better.

PS: Sorry, but I cannot divulge the name of the potential vendor.

N