Motorsport Composite Fundamentals: Finishing

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Finishing

07.03

00:00	We're now most of the way through our mould making process, and our fiberglass laminated mould is fully cured.
00:06	We still need to release some mould from the pattern, but there's a few finishing touches required, not only to make the mould functional, but also as good as possible.
00:15	We'll start with a quick denib of the backing surface to remove any potentially sharp areas, and make the mould easier to handle.
00:23	You might be thinking from the previous module that, because we used our unwaxed resin, the backside surface that was open to the air won't ever cure fully, and will remain tacky.
00:34	In practice it will eventually cure, or pick up a bit of dust so that it loses its tack, which isn't going to do any harm since it's not the mould surface we're talking about anyway.
00:44	To speed up this process, we could throw a bit of talcum powder on it and rub it in, or alternatively, brush a coat of waxed resin over the back and let it cure.
00:53	Before doing anything that will possibly shift the position of the mould sections relative to each other, we'll drill the holes in the flanges that will be used to hold the mould sections together when it comes time to lay up the parts.
01:06	We need to exercise caution during cutting, drilling and general material removal with fiberglass, and always wear suitable PPE.
01:14	That means eye and hearing protection, as well as a respirator, coveralls and latex or nitrile gloves.
01:20	The dust is extremely irritating and it's also very messy, so we recommend doing it outside if possible.
01:27	We want the holes to be about an inch from the edge of the part to avoid damaging the mould surface while also leaving room for tools to tighten the hardware.
01:35	Having the bolts in from the outer edges also means if we ever vacuum bag the mould, we could use foam pipe guards or pull noodles cut down their length to pad the edges and not puncture the bag, while still clearing the hardware.
01:48	We'll roughly mark out the spacing of these holes at about 150mm and then use a simple twist drill bit to drill the holes, which easily cuts through fiberglass.
01:58	To save time we can drill straight to 8.5mm for the M8 hardware.
02:03	This isn't going to make the most perfect hole, but we're not relying on them for our locations.
02:08	We've used our furniture feet locator keys for this.
02:11	Another important step to make the mould easier to handle is trimming the edges.
02:16	This can be done with an angle or die grinder.
02:18	A general inox cutting disc you'd use for cutting steel will make short work of the fiberglass laminate.
02:24	In this particular case we want to keep most of the flange and just trim away enough around the edge so we're into solid laminate.
02:31	We're finally ready to release the mould from the pattern and see our mould surface for the first time.
02:36	It's a major step in the process where we get to see if we've done a great job, if the results are salvageable, or if worst case we'll be starting again.
02:45	Knocking the edges of the flanges with a rubber mallet will help to free up the parts, and then it's really just a matter of starting to split them apart.
02:53	Don't knock the backside of the mould surface though, as this can cause star cracks in the laminate and the surface which we want to keep in as good condition as possible.
03:01	We can use our hands or the help of specialised tools like wedges to pry the mould sections apart and off the pattern.
03:08	In some cases these can be stubborn and require quite a bit of force.
03:12	Certain mould designs also lend themselves to blowing compressed air down the gap to help with the release.
03:18	The mould should be stiff and strong, but we still need to be very careful we don't break it and undo all of the hard work we've done.
03:25	If we're using tools to aid the release, just be sure not to slip and drive them into the mould surface.
03:30	Since we used PVA parting film, our release was fairly easy, and after release we can see the mould surfaces look really good.
03:38	We've had a small amount of reinforcement break away around the mounting tab that bolts into the door jamb.
03:44	This was likely caused by lack of reinforcement behind the surface as it was quite a difficult to laminate section.
03:51	However, it's an easy repair job or we can just use some plasticine to build up this area before making our parts.
03:58	The PVA film remains on the surface so the first step towards surface finishing is to wash this off with some water and a cloth.
04:05	Then we use wax and grease remover again to get rid of any leftover plasticine or other residue.
04:11	With the pattern out of the way, we can see how the parts snap together very positively with the locating features which have nicely defined edges and should work much better than the bolt holes, especially as we continue to use the mould.
04:24	The area that needs our attention is the all important mould surface.
04:28	Because we primed, sanded and polished the original fenders, the surface straight after release is relatively smooth but there's no sense in leaving it as good enough since we've put so much time and effort in to get to this stage.
04:41	Our tooling gel coat gives us some material that we can sand, cut and polish for a much smoother and more glossy finish that'll be transferred over to our final parts.
04:50	Again, it's already relatively smooth so we can jump straight into wet sanding.
04:54	We'll start with 800 grit and work up to at least 1200 grit or 2000 grit ideally.
05:00	Our cutting compound will be our gel to remove the scratches from here.
05:03	What's important to keep in mind when sanding the surface like this is the thickness of the gel coat.
05:09	We only have half a millimetre or so to work with so we don't want to work too hard on one spot and wear through it.
05:15	Long even motions and the use of a sanding block will help distribute the effort for a more even surface.
05:22	After wet sanding we're ready to move to our cutting compound.
05:25	You can buy composite specific compounds and polishes but generally the same products we use on our cars work well on our gel coats.
05:33	We're using an orbital polishing machine with a foam pad to apply the compound.
05:38	Again, being careful to move around the surface evenly and not burn through a certain area.
05:43	This can be done by hand with an applicator pad if we don't have a polisher, it's just going to take a bit longer.
05:49	The compound can then be wiped off the surface with a microfibre cloth ensuring we get into all the corners and details.
05:56	We'll then follow this up with a less abrasive polish for a high gloss finish.
06:01	At this point any remaining scratches in the surface will be minor and we'll still be able to surface finish our final parts anyway so we'll leave it there for now.
06:10	We'll be applying release agents based on the materials used to make the composite parts from these moulds so we'll carry on with this in the next practical section of the course.
06:19	In summary we started our process of finishing the moulds by denibbing the surface and an optional coat of wax resin.
06:27	With suitable PPE and in an area that we can get messy, we then drilled the holes in the flanges for bolting the mould sections together and trimmed the excess off the edges of the flanges to make the moulds easy to handle.
06:40	Then it's time to carefully release the mould from the pattern using our hands or some demoulding wedges.
06:46	We removed the remaining PVA film with water on a rag and then removed the plaster seam with the help of some wax and grease remover.
06:53	The mould surface was wet sanded up to 2000 grit and then cut and polished for a smooth glossy finish.