Creating Moulds - Hands Off !

[AppleNation]

Hi,
I'm new here and don't know a lot. So please bear with me.

I am looking at creating female moulds to build boats.

The question i have is what advantage is there to create a mould by hand than by some automatic process.

As far as I know you can create a mould using Styrofoam and then laminating it.

What are the problems with this, surely this saves a lot of time and money?

Forgive my stupidity if that is what it is.

Thanks.

[Fanie]

Moulds can be made 'hands off'

The problem is the size machine required to do this and the costs involved.

If there was this easy (and cheap) way of doing it, everyone would have a mould or two in their back yard.

Mould making is a big job. It has to be strong and stiff enough to carry it's own weight as well as the boat you make in it. You must also be able to get the actual boat out of the mould, sounds easy but some prep required.

It is usually easier to work inside a mould than on it's outside.

Some foams are attacked by the resins and have to be specially prepared for something like this. It is not going to be durable and strong enough for ie production.

[AppleNation]

Anyone have any ideas what sort of machinery would be required?

Just thinking with so many companies going under whether some cheap CNC machinery is available.

[marshmat]

A 5-axis CNC router that can handle, say, 4 x 10 metres, starts at around $300k (USD) for a nearly dead one that needs a complete overhaul, and runs up to the $1m plus mark for a nice German or American millimetre-precision machine in ready-to-run condition. Don't forget that it needs its own enclosed space, and they need clean, high quality industrial space, a sketchy warehouse won't cut it. The software and computer to run it are relatively cheap (a couple thousand $). But you also need a machinist trained to program the thing (takes a while to learn) and maintain it, and he'll cost you $50 or so an hour (burdened- incl. taxes, benefits, payroll overhead, etc). The machine needs overhauls periodically, putting it out of commission for a few weeks and sucking back a few tens of thousands in cash. If you're cutting foam, you still need manual labour to finish it; if you're cutting materials that can be used directly as tooling, cutting will take forever and you'll burn through $200 cutterheads at an insane rate.

And therein lies the problem. Low-skill manual labour can be had for $20 a man-hour (burdened). Unless the 5-axis router is going to be perpetually busy, with jobs that need its capabilities and can't be done more cheaply by hand, it's a difficult investment to justify.

I have worked on moulds built of Styrofoam, and given a strong wood or aluminum truss structure to hold the shape, it can work. Once you have the shape, the surface needs to be glassed (using epoxy, polyester eats the foam), faired and sanded, then coated with a tooling gel of some kind to get a smooth, polishable surface. It's labour intensive, but with sufficient care to get a good finish, it works.

[AppleNation]

Thanks MarshMat.

Brilliant reply for a newbie like me...

How good a quality mould was achieved in your experience? What sort of life did it have... and what sort of temperatures could it tolerate?

Thanks again.

[marshmat]

Hi AppleNation,

If you are patient with sanding and fairing, the finish on a glass-faced styrofoam mould/plug can be as good as any other method. It can't be used at high temperatures or for autoclave curing; above 90 C it can't hold its shape, and it weakens substantially above 60-70 C. For room temperature curing you could probably re-use such a mould a few times, but it won't last as long as a real fibreglass one.

If you want a long-lived, durable, hi-temp mould, you can either carve it directly from a high temperature tooling material like Renshape or TEPIC (you end up with a bulky, heavy mould) or you can laminate a mould by hand from a cheap foam plug with the glass finish described earlier.

[AppleNation]

Thanks again.

Looks like it is manual labour all the way after all.

[marshmat]

There are also a large number of one-off or short-production-run mould making systems that work well for specific applications- some for chine hulls, some for round bilge, some for developable shapes only. It's worth browsing the 'Net (and this forum) for ideas, there are a lot of weird systems out there that actually work (and that I wish I had known about a few years ago).

[Fanie]

I am looking at creating female moulds to build boats.

There is a reason for moulds to be made as they are. As I've said before, if there was this easy (and cheap) way of making a mould, everyone would jump for it and use that method instead.

The fastest way to make a boat is probably roto moulding but the cost of it... which is always the problem with hi-tech stuff.

If you want to make boats (like in more than one up to many) I suggest you invest in a good mould that would pay for itself. For the most part, a cheap and inconsistent mould will require maintenance and in my opinion end up costing more in the long run.

[grob]

The question about the best way to build moulds very much depends on factors like size and how many you are looking to build. If the boats are fairly small you can have a CNC hot wire cutter create some quite clever shapes from foam, which you then laminate by hand, and hand finish. If the boats are large this may become uneconomical.

High quality moulds for long production runs are most econonomical made out of metal. You can make sheet metal moulds much cheaper than using a CNC router and or casting.

You will need to provide some more information to get the best answer, such as size and type of boats.

Where are you in the UK as there are a number of UK people who can help you.

Gareth

[AppleNation]

Originally Posted by marshmat

Hi AppleNation,
or you can laminate a mould by hand from a cheap foam plug with the glass finish described earlier.

Hmm.. i think i erad over this comment before...

This would be a good idea i think...

So if a get a foam plug made cheaply i can then make a really decent mould from it?

Cheers.

[AppleNation]

How much for a foam pluag do you think?

[rwatson]

Hi AN. I would advise not getting too caught up in cheap moulds as yet. Best tack is to build a high precision hull first, using more traditional techniques. My current project is using female stations because the external dimensions are critical. Working over male stations is a lot easier.

If the hull is a success (financially or whatever), you can use it as a 'plug' for a proper female mould.

Most new ventures will build a number of hulls (then one high precision one after all the practise) before investing in a full scale mould. You will find building a male hull is a lot easier (quicker, cheaper) than starting a female mould. Working on concave surface, and getting it all fair and straight is really hard.

The first hull is a complete project ready to test or sell, where all you have after builiding a mould is .... a mould. All that time and money and still no product.

[marshmat]

Rwatson has it right here.
It's hard to justify the investment in a high-quality female mould until you know you have the hull just right. It's a lot of time, a lot of money, and you don't really know if it'll work just right.
Using a decent tooling foam, or XPS with a lot of hand finishing, you can make a very good male plug that can be used to produce a top-quality female mould. But that's only useful if you know the design is right, and you know you can build and sell enough to pay off the investment.
Building the prototype using a one-off technique, testing it, making modifications, and then pulling a mould from it once you're happy, seems a prudent way to go....

[AppleNation]

Thanks for the advice rwatson and matt.