long cutter options

[Losos]

Let me give you some background on my project first. I'm hoping to make a cnc surfboard shaping machine for my senior project (at Cal Poly SLO, for any alumni out there!). I have most of the machine drawn out but I'm kind of stuck on my cutting options. This is my first post here at the forum, but I'm sure I'll have many more as I dive deeper into the details of the machine.

I'm looking for a ballnose cutter (up to 1/2" shank) will a full 4" cutting flute. At first I had planned to use a grit/sanding cutter similar to this one (cutter with board as reference, just the cutter), but unfortunately that will not work.

The cutter must be capable of cutting balsa & basswood, polyeurethane foam, and also 1# EPS. The EPS is what is limiting me from using a grit cutter -- the grit cutters require too much force for the limited support provided to the foam blank, causing inaccuracies as the foam bends slightly out of the way of the cutter.

Any ideas?

[ger21]

I'm pretty sure these guys can make some for you, but they won't be cheap. Probably $2-300 each. I've had some custom spiral bits made by them before. Outstanding quality tooling.

http://www.vortextool.com

[HuFlungDung]

Gerry,

There's a name for a 1/2" dia, 4" long flute, 1/4" radius ballnose: its called a screamer

I'm just picturing what I think a surfboard looks like and I can't visualize why you'd need a cutter that long. I'd do everything I could to reduce its use to a minimum.

However, I'm looking in the KBC tools catalogue at a Niagara four flute extra long reach ball endmill with a 1/2" diameter, 4" length below shank, 1.25" flute length. This tool is a little bit stiffer than one that is fluted the whole length. If you can hold your depths of cut to 1.25" per pass, it would work.

Another option might be to use a larger diameter cutter with 1/4" radius tip (bullnose form) in order to improve the stiffness of the tool.

[chuckknigh]

For EPS, you could always use a hot wire for cutting. It'd necessitate a "changable head" design, though.

I wonder if you could get away with a small loop of wire as a hot cutter...something along the same lines as a router bit?

Alternately, can't you support the foam blank somehow, to make it more rigid?

-- Chuck Knight

[buscht]

Here's the best that I could find
3" flute length with a 6" overall long 1/2" dia ball nose end mill.

http://www.cetdirect.com/pub/Product...=5493&pID=5075 $58.33 each

Good luck

[buscht]

Here's another. At the bottom of the PDF file you'll find a 4-1/8" long spiral foam cutter, but its not a ball nose.

http://www.hartlauer-bits.com/HartlauerBitsList.pdf

Maybe they will make you one as a custom.

[ger21]

Originally Posted by HuFlungDung Gerry, There's a name for a 1/2" dia, 4" long flute, 1/4" radius ballnose: its called a screamer

I wasn't advocating it's use. Just trying to help the guy out.

[Losos]

"For EPS, you could always use a hot wire for cutting. It'd necessitate a "changable head" design, though."

This is true, and I am planning on having a swapable hot wire for cutting the rocker and deck profile out of the eps blocks. However, I also need to cut pe foam (I heard doing so with a hot wire cutter was toxic) and with the pe foam comes a wooden stringer down the middle of the blank.

"Alternately, can't you support the foam blank somehow, to make it more rigid?"

Tha blank support system is the one other aspect of the machine design that I don't really have a good design for. I'll probably throw this out there as it's own post in a few days. The problem is that the blanks come in all kinds of shapes and sizes so there is no way (that I can think of) to get continuous support of the blank while still maintaining the ability to pierce all the way through when finishing off the rails.

[buscht]

Here are some websites that already have some CNC surfboard machinery. Maybe they will spark some ideas.

http://www.aps3000.com/index.html
http://www.shape3d.com/3dmotion.htm
http://www.shape3d.com/frame_us.htm

[Losos]

"I'm just picturing what I think a surfboard looks like and I can't visualize why you'd need a cutter that long. I'd do everything I could to reduce its use to a minimum."

Ignoring rails, I could easily get away with something as small as a 1/2" flute. The rails are by far the most demanding as far as cutting. Some blanks are over 3" thick and there is often an inch or two of excess foam remaining outside of the rails that needs to be sliced off. I could go to a slightly smaller flute length if I decided to machine this excess foam off as usual but, since it's just foam, I'd prefer to pierce (maybe someone can provide a better term for this operation?) it off in a single pass around the outline of the board. I'll try to sketch out a cross section of the rail being cut to help explain my dilemma.

[Losos]

"Here are some websites that already have some CNC surfboard machinery. Maybe they will spark some ideas."

Thanks buscht. I've actually been talking a lot with the machine designer (Miki) and the software designer (Jimmy), but I can't get much out of them in terms of machine design. Miki claims to have a number of pending patents tied up in the machine (22 of them to be exact), but, because they are pending, I can't access the details of them.

But, here is what I have got out of him... maybe some of you can interpret it better: "Stanley knife" surface finish, ultra high efficient and stress free cutting, the cutter runs at a circumference speed of 400km/h and that is only possible because of its very different design.

The gallery on the aps3000 website shows examples of the surface finish. Amazing if you ask me. Maybe looking at the finish would spark some ideas on the type of cutter to use.

[Losos]

I just want to take a post to thank all of you for your responses. I never expected so many responses in such a short amount of time. Thanks again, this forum is great.