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VIDEO TUTORIAL

How to Make Complex Split/Multi-Part Mould for Composites

Follow this step by step guide to take a composite pattern and create a precise, multi-part split-mould for fibreglass/GRP/FRP/composites.

If you want to make a copy of an existing part (or original design pattern) in a composite material such as fibreglass or carbon fibre then you will need to take moulds from the original part or pattern.

Sometimes, the shape of the part that you want to copy means that you can't make a simple one-piece mould and in this case you will need to make a multi-part 'split mould' which can be bolted together to lay-up the part and then unbolted and split apart to remove the part.

If you're not familiar with the techniques for making a multi-part mould then this process can be quite daunting but in this professional video tutorial we take you through the complete process, from start to finish, demonstrating the best practices for producing a multi-part split mould. In this video we create a 3-part split-mould for the airbox pattern that we made in our Composite Pattern Making Tutorial.

TUTORIAL BREAKDOWN

1. Mould release agents

Throughout the mould making process, there are many times when you will need to prepare your original parts or pattern with a 'release agent' to prevent the new mould materials from sticking to your part or indeed to the new flanges of other parts of the split-mould. Throughout this tutorial we use Easy-Lease Chemical Release Agent to ensure a reliable, easy release.

INTRODUCTION

1. Working with temporary barriers

At various points during the mould making process we need to position temporary barriers around our pattern or part to create flanges on the mould sections and create any split-lines we need. Temporary barriers can be made using Fluted Sign Board (such as we did in Part 1 of our Carbon Fibre Bonnet Making Tutorial), or using a smoother, sturdier material such as the polypropylene sheet that we use throughout this tutorial.

Generally, when making split-moulds, temporary barriers are used to make the flanges for one part of the mould but are then removed once that part of the mould is cured so that the next part of the split-mould can utilise the new flange of the first part of the mould as a barrier to make its own flange. Doing so ensures that the different sections of the mould come together perfectly. When using the flange of a prior mould section as the barrier to make the flange of a new section it is of course very important to apply several applications of release agent (as though it were a new mould) to the flanges.

TUTORIAL BREAKDOWN

1. Using filleting wax

Filleting wax is used throughout the process to fill gaps between barriers and the part and to create softer radiuses where required. Filleting wax is also used to create 'registration dots' that are positions on barriers or flanges to create matching male and female lugs which will help to accurately locate different parts of the mould, ensuring they are perfectly aligned.

2. Uni-Mould mould making materials

In this tutorial, all three sections of the multi-part mould are made using our Uni-Mould Universal Mould Making System. Uni-Mould is a special tooling system that is compatible with the widest possible range of processes, will release reliably off most materials including polyester, vinylester and epoxy patterns and can then be used to produce parts using any of these resin systems.

We sell the Uni-Mould system in a complete starter kit including all the resins, catalyst, chopped strand glass and laminating tools or any of the individual parts can be purchased separately. For detailed information on using the Uni-Mould system please see our Uni-Mould Advantages and Laminating Guide PDF.

3. Use with prepregs

Although it is possible to use Uni-Mould moulds with out-of-autoclave (oven cure) prepregs (such as XPREG® XC110) we no longer recommend Uni-Mould moulds for this purpose.

Instead – for prepreg use – better results will be achieved using high temperature epoxy moulds made using our EG160 / EMP160 tooling system or XPREG® XT135 Tooling Prepreg. These high temperature epoxy tooling systems allow the prepreg to be cured at the optimum 120°C which reduces the cure time and improves the mechanical properties of the component. Additionally, epoxy tools have been found to result in a better surface finish with prepregs such as XPREG® XC110.

DISCUSSION (18)

Please share any questions or comments you may have about this video tutorial.

Blender Physics29/7/2022

Are plies always hand drawn and hand cut like this? Or would you normally use CAD drawings and laser cutters produce these stencils of carbon fibre?

Easy Composites› Matt

That really depends on the production volumes. For relatively low production volumes, for example if you're making a few of these parts at a time or make them infrequently then you probably wouldn't go to the trouble of CNC cutting the plies, however, for larger volumes, if you have the equipment (a CNC cutter using a drag knife, not a laser cutter) then it's quite common to CNC cut the plies (which can also be numbered by the CNC at the same time). Often, these pre-cut 'kits' of all the different plies required for a component are bagged together and re-frozen ready for future use.

BenTV7/9/2020

Hi what's your opinion on PVA release agent? I like to spray it on my bucks & moulds & haven't found anything else you can put through a gun.

Easy Composites› Matt

For the transition from a pattern to a mould PVA can sometimes be the right choice, particularly on a pattern or mould with a dubious surface where getting a good release is in doubt. Personally I'm not a fan of the finish that PVA leaves on the pattern, resulting in too much work to restore a good finish. Our approach would be to use a reliable coating material on the pattern, so that the release is assured, and then use a release agent such as wax or chemical release agent (such as Easy-Lease) which will leave a better finish on the mould.

Louvin Rivard

Why don't you degas the gelcoat?

Easy Composites› Matt

There's no need to degas the gelcoat when applied carefully in this way. Also, because the gelcoat is vinylester it has a styrene solvent content, this solvent content will boil off under vacuum and so the gelcoat would appear to bubble indefinitely, all the while the gel would be becoming thicker as the styrene boiled off.

Sharoan Thomas

Can you make carbon fibre parts in a fibreglass mould?

Easy Composites› Matt

So, by 'Fibreglass' mould I'm going to assume you mean a conventional polyester resin, polyester gelcoat and chopped strand mat. If you're going to use epoxy resin to make your carbon fibre parts (which is the most suitable resin system for carbon fibre) then it has a nasty habit of 'sticking' in polyester gelcoated moulds, even when they've been prepared with a release agent. If possible, it's far better to make the moulds using a vinylester gelcoat or an epoxy gelcoat which epoxy resin will release from very reliably.

Uriah Siner

Could this process be used to make my own carbon wheels?

Easy Composites› Matt

Out-of-autoclave prepreg carbon fibre could, in theory, be used to produce carbon fibre wheels however, as components go, this is not really an appropriate starting point for a number of (hopefully) obvious reasons. If you do gain skills and experience making more straightforward components first then you would be in a better position to know whether wheels would be a suitable project.

Wajdi Rebei

Is it possible to make carbon fibre parts using moulds made from Styrofoam?

Easy Composites› Matt

Is possible to use Styrofoam to create your pattern but you need to be aware the polyester and vinylester resins will attack (and melt) Styrofoam so, if you're going to use either of these resin systems for your mould, you will need to protect the Styrofoam from them. To do this, you can 'scrim' your Styrofoam pattern using epoxy resin (which won't attack Styrofoam) and a lightweight woven glass cloth. This can then be flatted and polished ready to take your mould off.

neibedepil

Did you apply release agent on the polypropylene form part before gelcoating ? I didn't see it in the video.

Easy Composites› Matt

No, no release agent is needed on the polypropylene - it's totally non-stick to resins like polyester, vinylester and epoxy.

spiritual cramp

can i use the original metal air box as a pattern to make the mould? Any suggestion about particular release agent to use on it?

Easy Composites› Matt

Yes you can use the original airbox as long as it is in good enough condition. You would follow the same process just skipping the carving of the foam, as you already have the basic shape. Use the same Easy Lease release agent as you see used in the tutorial.

Setoain20

How many times will the mold last, in other words, how many pieces can you make with a mold before it starts to have surface imperfections??

Easy Composites› Matt

Treated sensibly you would get hundreds of releases from the mould before it started to show scratches or other signs of damage and deterioration. We use this exact mould system for most of the 'Carbon Mods' brand products that we sell meaning that we have daily production experience going back 7 years. Some moulds we made 7 years ago are still in use today. The great thing about Uni-Mould is that you can flat and polish the surface if it gets stretched or faded and it will be like new. That's why we normally 'double gelcoat' to give ourselves extra repairability.

Spencer Edwards

Hi, I'm using a fairly thin poly tooling gelcoat. Is there a filler that's safe to use for thickening a tooling Gel? I have your fumed silica.

Easy Composites› Matt

Fumed Silica is normally the filler powder of choice when it comes to thickening resins and gels. Start with only a very small percentage as the fumed silica is quite effective but takes a little while to 'develop'.

Matthew Ault

Is it possible to make a rough carbon fibre surface (e.g. from wrapping) glossy, by sanding and adding more resin, or is having a smooth mould the only way to get that smooth shiny glossy surface finish?

Easy Composites› Matt

Ideally a smooth mould will be the quickest way, however you can use the skinning method by coating layers of resin on top of raw cloth. You will need to spend considerable time sanding and smoothing the resin but great results can be achieved with patience.

For the love of life

Can you resin infuse a multi-piece mold? Not a tube like this but for say a lip for a car. I could make it 1pc but the angles of the front are too great to get my hand in there to try and make it look right.

Easy Composites› Matt

Yes you can. By the far the easiest method is to use "envelope bagging" i.e. putting the entire mould into a single bag (like in this video) as it solves issues with trying to seal the join lines on a multi-part mould.

DjCasonDrift

Is there a product that I can use to make high temp parts like exhaust manifold or even turbo down pipe I see a lot of intake manifolds and carbon mufflers any info would be appreciated thanks for an intuitive program keep it coming please

Easy Composites› Matt

We have a high temperature epoxy resin that will, with a post cure, go up to 180°C. That is not massively high but for some exhaust trims can be ok. You will need to measure the actual temperature the part will likely experience to decide if it is a suitable resin for you.

IrishPalestinian

Is it possible to combine a mold similar to this, maybe two-part, with vacuum resin infusion? I haven't done prepreg and have done infusion. I want to end up with a hollow part (an intake primary plenum) with a slot like yours but narrower.

Easy Composites› Matt

In theory yes it is. However it will be difficult to ensure the fabric is tightly against the mould surface, and you will have to take plenty of extra care during the vacuum pulling and infusion to ensure you get a good result. Would definitely be a challenge and take some skill!

Jente Ameye

Is there a reason for the use of PP sheet to make the split line of the mould? I want to make one for my master thesis as well and have a lot of PVC sheets here, should it be feasible with PVC or does it react with the gel coat or other coatings?

Easy Composites› Matt

Hi Jente, we use polypropylene sheet because it has great self-release properties (doesn't need any release agent) PVC will also work in a similar way (it shouldn't react with the gel-coat) but I would advise a coat of release agent to ensure easy removal.

JerseyMikeP

What's the purpose of the 'coupling coat'; why can't you just use regular resin? I would like the least amount of different materials, this allows (me/us low production guys) to by a greater quantity (at a cheaper cost) of the most useful materials?

Easy Composites› Matt

We use a coupling coat because of the high temperature use. For ambient temperature, you wouldn't necessarily need the coupling coat but for high temp you do. The reason is because when laminating the main reinforcement layer, because the resin is filled you can't see through it. If you can't see through it then you can't spot any small pockets of trapped air. If these air pockets are directly against the gel then when the mould is used at temperature the gel will blister. When you use the clear coupling coat and a thin skin of lightweight glass you can ensure that there are no such pockets which means you won't get blisters when the mould hits temperature. There's other reasons too such as the way the coupling coat helps to interface between the VE gel and the filled PY resin but the main reason is to eliminate blisters.

J Dana Clark

How is your tooling gel not absolutely full of porosity, we normally get lots when we spray gelcoat. We also switch colours of tooling gel 1/2 way through the application so that in the future what doing mold repairs we know when we are sanding too far through the gel.

Easy Composites› Matt

I've never experienced the issue with porosity that you're describing. We have a number of tooling gelcoats and I've never encountered this - it might be time to consider changing your tooling gelcoat. It's an option to give yourself more than one gelcoat colour so that you can tell when you've gone down fully through one layer but at the same time it can be visually quite distracting when you're trying to check the perfection of the mould surface after repair or restoration. Personal choice I guess.

Gabriel Morales

At 13:08 you mention that you must make this a 3-piece mold because of 2 parallel sides. Is that because it would be really difficult to remove the master plug if you don't make this mold as 3 parts? Could you install a nipple and use compressed air to remove it from the mould?

Easy Composites› Matt

If you have parallel sides on a mould then it will be almost impossible to remove parts from it, even with the use of compressed air. If you do manage to remove the part then it's likely there will be damage to the part and the stress on the mould will reduce its life. It's a much better idea to design a split into the mould for sides even approaching parallel.