Fibreglass Milling,Can anyone help?

[ml_batt@yahoo.c]

Hi All,
I am embarking on the whole CNC thing for the first time and very interested to learn if there is anyone out there with experience in milling fibreglass laminates (Epoxy/Fibreglass) and plastics such as HDPE and Nylon,
Can I use a bench top style of Router or do I need a full blown workshop with 3 phase power and a mill that will tackle metal? I am mostly working on Fins and Rudders for water sports craft such as surfboards and sailing craft. so I don't necessarily need much Z axis but I do need enought o make moulds.
Blueline

[mxtras]

You can cut what you are talking about with a router spindle, but I don't think you will be too happy with something like a handheld router motor. I think you might be more interested in a larger spindle with more tooling capacity.

The advantage to using a router spindle is the higher RPM which is essential. Router spindles are available from companies like Perske and Columbo - to name a few.

You can run these higher end spindles with a VFD - in fact, many are installed in commercial equipment through a VFD. The VFD will likely allow you to run from single phase power source.

Scott

[Thinwater]

How are you going to cut a mold in fiberglass? I make boat molds and other fiberglass tooling and have never seen it done this way. Normally you make a master "Plug" and treat it with one or two of many release agents and lay up the gel coat and fiberglass mold on it. The mold is opened and the master removed.

I am also a home shop machinist. I bought a milling machine from a shop that used it to mill fiberglass ijected plastic parts. I got worse fiberglass itch in my hands every time I used the mill than I ever did cutting, grinding or laying up boats or boat molds. Once I completely degreased the mill and re lubed it it cured this problem.

Good luck with your project.

JIM

[Unabiker]

Originally Posted by ml_batt@yahoo.c Hi All, I am embarking on the whole CNC thing for the first time and very interested to learn if there is anyone out there with experience in milling fibreglass laminates (Epoxy/Fibreglass) and plastics such as HDPE and Nylon, Can I use a bench top style of Router or do I need a full blown workshop with 3 phase power and a mill that will tackle metal? I am mostly working on Fins and Rudders for water sports craft such as surfboards and sailing craft. so I don't necessarily need much Z axis but I do need enought o make moulds. Blueline

Assuming you are planning on vacuum bagging your parts, there are a lot of different materials that you can use to cut molds depending on how many parts you plan on pulling out of said molds.
For very low numbers of parts (1-10), you could cut a mold from a tooling foam, seal the surface with epoxy, sand it smooth, wax it up and pull parts.
For a larger quantity of parts, there are several varietys of Renshape that would be a better material. That would involve cutting the mold, sanding to an appropiate finish, waxing/ mold releasing, then pulling parts.
As far as using the CNC to trim the part, it is do-able. You will need to make a fixture to hold your part while the machine does it's thing. The propper tool bit is crucial for good results and they are not cheap. Personaly, I would not go through the trouble and expense unless I was planning on running over 100 of the same part.
You can cut foam on a fairly simple machine with a fairly basic spindle. Harder materials will require a more robust setup. Using foam molds, it is possible to make parts with a reasonable amount of detail and accuracy (+/- .010".) Rensape wiill hold much more detail with acrruarcy >.005". You should decide what sort of accuracy you will need and build towards that. Of course, more accurate = more $$$.
You will find that a good CAD program and CAM software and the knowledge/skill to use them will be crucial in order to have any success with this sort of process. After all, you gotta be able to draw the parts and molds before you can cut 'em.

[juzwuz]

Would a mold made out of delrin or similar plastic work with vacuum bagging?

[Thinwater]

Originally Posted by juzwuz Would a mold made out of delrin or similar plastic work with vacuum bagging?

You would have to check your mold material and make sure your resin would not melt into it. Epoxy is not likely to react to most things but gel coat (It is polyester resin based) Polyester resin, polyvynil resin and anything with MEKp hardner may eat up the mold.

Cut the mold of aluminum and polish it well and you will have no issues. The above post about cutting a part in foam (mold tooling foam, not cooler material) then laying up a mold on it with tooling gelcoat followed by several layers of fiberglass mat is the industry standard. When you have it thick enough just remove the master and polish the mold. Then it is ready to vacuum bag.

Here is a thread where i made a RC boat mold. It came out OK for a homemade mold. http://www.modelpowerboat.com/forum/...read.php?t=186

JIM

[Unabiker]

Originally Posted by juzwuz Would a mold made out of delrin or similar plastic work with vacuum bagging?

In theory, you could pull a part off of a mold made of delrin.
That being said, I don't think delrin is a very good material to make molds out of. First and foremost is cost. Delrin is a pretty expensive material. A quick look at McMaster-Carr shows delrin in the neighborhood of $80 a board/ft. Ouch! It's also a fairly soft material. Normaly when you clean up a mold after pulling a part, you'll scrape the leftover resin away with a putty knife. I can see where it would be easy to gouge up your mold. Being such a soft material also makes it difficult to get a nice shiny surface from it.
For inexpensive, low heat, vac-bag molds, you can get very nice results using quality hardwoods like maple, mahogany, or walnut. They machine well and can be sealed with epoxy or polyester resin. Either of those surface coats can be sanded out to 800 or 1000 grit. Follow that up with several coats of carnuba wax and some buffing, and you can get parts with a very high quality finish. With propper maintence, these kinds of molds will be good for lots and lots of parts.

[Unabiker]

A good source of mold making material and information is http://www.freemansupply.com/

As mentioned, when I say foam a few posts up, I'm referring to tooling foam, not styrofoam. It is possible to make plugs and molds using styrofoam as your base, but you have to becareful and use a resin system that will not eat styrofoam.

[juzwuz]

Thanks for the link. I'll take a look at tooling foam. I have some scrap pieces of Delrin to play with but I thought I'd check to see if anybody has tried a Delrin mold before. I'm curious to see if epoxy resin will stick to Delrin.

[Unabiker]

Give it a quick coat of carnuba wax and it won't stick for sure.