Roman

Fibreglass, Carbon Fibre, Paper Mache - The composites chat thread

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ADH26

I've previously been in a panic about trying to get stuff sorted before my pot goes off. 

But I also figure I dont actually need a few hours worth of pot life either.

35 mins at 20deg is a lifetime compared to what I was using before haha!

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4 hours ago, Roman said:

ADH26

I've previously been in a panic about trying to get stuff sorted before my pot goes off. 

But I also figure I dont actually need a few hours worth of pot life either.

35 mins at 20deg is a lifetime compared to what I was using before haha!

West system? I rate how the slow hardener is still mega fast with that stuff, exotherms without hesitation! AT products are so much nicer to use.

Be careful with chilling the 243, much below 10deg and there is a slight risk of crystal growth, from memory the datasheet lists min storage temp of 15deg.

Have you got your head around the post cure?

 

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Just now, flyingbrick said:

@Roman can also sit your bowl of resin in an ice bath if ya worry

Previously I found that keeping the pot cold was good, but the epoxy geys way thicker and doesnt want to flow into the part.

So I needed to heat the part up which was then the catch 22 of making it set faster (although as it turns out, not really an issue once out of the pot)

So it will be awesome to use stuff thats just way thinner and lasts longer in the pot without tricks.

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Just now, NickJ said:

West system? I rate how the slow hardener is still mega fast with that stuff, exotherms without hesitation! AT products are so much nicer to use.

Be careful with chilling the 243, much below 10deg and there is a slight risk of crystal growth, from memory the datasheet lists min storage temp of 15deg.

Have you got your head around the post cure?

 

I had some random boat building stuff, was yellowy rather than clear like west system.

But tried that too.

It was ok but just not the right stuff for what i wanted to do. And no data sheet for the boat stuff so unsure how it deals with temps. Seems most "normal" epoxy seems to have issue above 60deg.

And yeah post cure process makes sense from what I can gather but always happy to hear some advice.

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I've found the west system a little too high viscosity to get reliable results with vacuum impregnation, probably just an ID10T error though

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@Roman please DIY some superaccurate thermostat controlled oven that has ramp control.

Post PowerPoint slideshow displaying results pls.

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Just now, Evan said:

@Roman please DIY some superaccurate thermostat controlled oven that has ramp control.

Post PowerPoint slideshow displaying results pls.

@dave My DIY suisvide setup would actually work perfect for this (I'd have to check on sensor range first). All you'd do is plug in between the wall and whichevever device you are using to provide heat.

hmmn, although oven plug is too big and currents probably too high in total.

If you ever need it you are welcome to borrow it - easy accessible quick option. 

Have seen post cure ovens on youtube made using plywood so temps cant be that high?!

Edit, its a PID setup, so very accurate control. Autotunes pretty well for whatever application.

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My 3d printer uses a solid state relay to control a 510x510mm 240v heater pad with pid. Works quite good. For parts not too huge I could just add an air temp sensor to a sealed box over my printer and add some code and a menu to add a ramp rate. As the heated pad has no problem going over 100deg which is the max cure temp needed for this resin.

But come to think of it I might just buy another heat pad and SSR and make a dedicated box thats a bit bigger.

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Resin cold, part warm is standard logic, just a pain with de-gassing in the middle, gotta watch resin bulk so the temperature doesn't get away on ya. If feasible, take lots of temperature readings for future reference.

With post cure, the part needs to be fully supported, in the mould is best. The theory is to ramp up just behind the advancing HDT so that the part never suffers any major loss in rigidity.

Very simply, the higher HDT is from increasing cross linking, if the part is ramped too fast, the cross linking can occur in a distorted part, never to return to planned dimensions.

From a similar viewpoint, uneven heating can do the same, either ramp real slow or get a big fan in the box to ensure low temperature gradients.

Mould choice is very limited if you want to post cure to 120C, MDF shouldn't go past 60 (bad smells...) Normal resin moulds tend to turn rubbery but with some experimenting and cunning it can be done.

 

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16 hours ago, Roman said:

Soo.... Measure all the things. 

Im loving this already 

you must be near the only one on this planet who manages to capture all the right things when for the rest of us, the one bit of information that would be useful is the one that we didn't.

 

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It's been great learning to program Arduino.
Like there are just so many situations where it can be useful. 
I mean sure I havent done any of them yet. But I could. haha

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So new epoxy turned up, and mixed up a small batch to see what it's like. 
I'm surprised that it's actually rediculously gluggy!
I thought it would be thin and watery but it isnt.
Like the other stuff, the key to this must be getting the temperature of the part up, to get it flowing. 
It's cold-ish here today (13deg) so that wont be helping. 
Definitely wont be able to do any big parts over winter without a scheme for heating.
 

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warm some in a cup with a heat gun to 20-25C and you'll find another world

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So I've had this 3d printed gearbox crossmember in the car for a while (not running, its PLA) 
DSC06280.jpg.65938a4089bd1e0f5db54673e1d393a7.jpg.52dd8776ea81cb9df17657632187292f.jpg

It managed to hold the motor up for maybe 6 months or so before it broke for whatever reason. 

So thought it might be an easyish item to learn some more CF stuff, so printed a mould for the outer shape.
I've found that with 3d printed moulds there are peaks and troughs from the layer lines, and its really easy to skim off the peaks to flatten it out. But the troughs you'd have to sand it forever to get them out. So this time just going straight to filler primer and just try fill it up. So far results are good, got it smoooooottthhhhh with first sand then I've just put second layer of primer on. 


102323751_540736760142843_5100391543672406016_n.thumb.jpg.2b30d160d0d57eb1e5069f7b3e63bd51.jpg

So will hopefully only need 2-3 runs of filler primer then some glossy finish on it. 

Is there any reccomendation on a certain type of paint to use/not use, to minimize chance of the epoxy sticking to it? 
I've heard black shoe polish is a good thing to use, or any other suggestions? 
Or should the waxing just take care of that and so whatever is underneath shouldnt be an issue.

This time I'm trying not to repeat stupid mistakes so I've added 3deg draft angle, and I'm going to make some templates for cutting the sheets so I've got a good plan miles ahead of anything to do with epoxy. Not sure if I'll try infuse it or wet layup as of yet.

Although it sounds stupid this wont actually be a usable part that will do anything apart from hold the gearbox in place while my car isnt going. 
As I want to push my motor further back, but I'm stuck unable to do that for a while yet.
It's on the learning budget I guess you could say. I dont think I could actually cert a crossmember like this / not worth the hassle for something structural I dont think.

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You may struggle to get it airtight without a solid gelcoat if vac infusion is the path you want.

Any release film will do the trick on a good gloss paint finish, providing the paint has bonded well to the mould. I do wonder if the cheaper rattle can paints will soften under the epoxy, is that what you were thinking? No harm in running a test panel on some scrap.

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Well I wont be doing much any time soon as found my vac pumps oil full of epoxy.

Not too sure how as ive got a vacuum chamber in line with the parts. Maybe it creeped across the top of the lid.

Bugger haha. Looks like might be rebuildable okay.

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27 minutes ago, Roman said:

Well I wont be doing much any time soon as found my vac pumps oil full of epoxy.

Not too sure how as ive got a vacuum chamber in line with the parts. Maybe it creeped across the top of the lid.

Bugger haha. Looks like might be rebuildable okay.

Thats well lame! Do the in lines project into the chamber? I run them down into the bucket cos I hate cleaning the inside of vac chambers

I have wondered about putting a clear inline fuel filter by the pump, if resin made it to there it would wet out the filter element and cause massive flow restriction slowing further migration.

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Yeah I havent looked yet but I think the pipes dont extend downwards at all, so if any resin makes it into the pot it would just as likely creep across the top lid as it would drip down. 

Last time I used it, I had super super short pipes on it because it was in lockdown and wanted to test it out. 

So that's probably part of it, previously I've always had the pump and the pot way uphill of the part to minimize the issue. 

I've pulled the pump a bit further apart, I think so long as I can get the resin out of the pump housing without scratching it I'll get away with it. 

The mix of vac oil and the resin is super grotty stuff haha.

Live and learn! 

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