It’s been a while since we blogged about something that’s just pure, unabashed, experimental geekery. As proud as we are of our products and as much as we love sharing them with you, we’re also tinkerers at heart. With this in mind, this blog post is about taking one of our established products (Scaffold) and pushing it to see what it’s capable of.
You may be asking why are E3D playing are messing around with composites - they’re not our usual area of expertise. There are multiple reasons, aside from the obvious facts that composite parts are incredibly cool and we’re insatiably curious:
We tried several different methods for making carbon fibre parts from printed scaffold molds. For those wanting to give this a go, there is some advice and links to helpful stuff at the end. But it’s important to note that this is very much a work in progress proof of concept, and we are far from composite experts. The following is our exploratory research and should by no means be considered the last word in this technique - in fact we hope that we inspire others to take this further!
Starting simply, we made positive moulds consisting of just a Scaffold core, over which we laid 2 layers of carbon fiber pre-impregnated with resin. We chose a a wing section for our first tests to make the printing and layup process as simple as possible. We followed the basic lay-up for vacuum bagging: prepreg, release ply, breather, vac bag (essentially this kit). As compositing was something that was new to us we followed a tutorial, and the whole process was honestly pretty straightforward.
The mould before layup
We did diverge slightly from the instructions (we’re engineers, we have trouble following manuals) and used a small 12V piston pump which we got for less than £15 from Amazon, rather than buying an expensive composites vacuum pump. We also didn’t pull vacuum while oven-curing the part as this would have required a vac oven and we wanted to see what was possible from a process that most people could do at home.
We cured the part at 60°C for 10 hours as we were worried about the Scaffold mold softening with higher temperatures and compressing due to the vacuum. After curing we simply removed all the bagging materials and left the part sitting in warm water overnight to remove the Scaffold, with a light scrubbing the next morning to remove any remaining bits of support filament.
The part after demoulding
As you can see the results were fairly good, with the geometry coming out accurately. The surface finish left a little to be desired, but on the other hand this is what the part looked like straight after cleaning, as with any composite part you would need to sand it down and apply a layer of epoxy to get an nice gloss finish.
Obviously we are not the first to have done something like this and certainly not the best, however we wanted to see for ourselves what you could achieve with essentially no prior experience with composites. It’s pretty clear that you should be able to get good results for simple things such as wings for RC planes using this method and with a bit of sanding and epoxy they should look fairly nice as well.
Realizing our lack of experience in composites and knowing some people who have both 3D printers and excellent composites skills we sent some Scaffold over to them, and what we got back was pretty impressive.
Serious vacuum wrapping
They sent us back images of a twisted vase-like object as a capability demonstrator piece. Producing it would have normally have required a 6-part machined mold. Our sources estimated that the mold would have cost thousands and taken weeks to be made.
They also mentioned that being able to use simple tap water instead of aggressive and potentially nasty solvents to dissolve the material was a big bonus. While it is possible to make cores by hand by carving and sanding polymer foams, the results are not only less accurate than printed parts, but also have to be dissolved away using nasty solvents that require industrial disposal.
Back at E3D headquarters, we were really excited by the success we had had with the simple wing part, especially because it was essentially done with a standard printer and a normal oven, meaning that pretty much anyone with a bog standard printer could have done it.
So following on from this we decided to try something insane, awesome, and in hindsight a little bit overly complex. The part we decided to make was actually comprised of 3 parts in 1:
The pipe mould
We decided to print a Y-branched pipe with a valve (because it was looked like a cool test piece). The body of the pipe was printed in Scaffold and the valve was pre-assembled and embedded from carbon nylon.
Printed and ready for layup.
So far so good! As you can see it printed out rather nicely. We decided to try out a different composite technique, using dry fabric and separate resin as we thought this would get around the tight curves more easily. As an added bonus, it also wouldn’t require an oven cure.
Somewhat less professional vacuum-bagging
We vacuum-bagged it the same as before and left it to cure at room temperature for 24hrs. We then demolded and removed the Scaffold in the same way as well.
The "part" after demoulding
Oh dear. As you can see the results weren’t quite as good, to put it kindly. To put it less kindly, it looked like children’s papier maché done in carbon fiber. It did, however, provide a lot of useful insights which we’re happy to pass on:
We decided to tone it down a bit and go for something simpler, going back to printing wing sections but this time gluing in additional solid prints to be embedded in the carbon fiber part. The rationale being that this would only require a single material printer, that the prints are less challenging, that the total size of the component could be bigger than the printer's build volume, and that you could still have embedded functional elements like the dual extrusion method above.
A pre-layup wing
In this test we made some ribs for the wings out of PC-ABS and glued them together with the Scaffold parts using PVA glue, which should also dissolve away during clean up along with the Scaffold. As with the first wing section we used pre-preg, vac bagging and oven curing.
This had good success, with the PC-ABS parts bonding really well to the carbon fiber, there were also some further learnings:
As you can see we tried several different things, for those ambitious souls thinking of giving this type of composite manufacture a crack, here is some advice and links to other resources. We’re excited to see what you create: