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Losos
12-28-2004, 03:40 AM
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 (http://www.wetsand.com/resources/Mach_Nosecut450.jpg), just the cutter (http://www.wetsand.com/resources/Mach_bit225.jpg)), 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
12-28-2004, 07:44 AM
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
12-28-2004, 10:30 AM
Gerry,

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

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
12-28-2004, 10:41 AM
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
12-28-2004, 11:00 AM
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/Products.asp?catID=5493&pID=5075 $58.33 each

Good luck

buscht
12-28-2004, 11:01 AM
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
12-28-2004, 12:03 PM
Gerry,

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



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

Losos
12-28-2004, 04:33 PM
"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
12-28-2004, 04:44 PM
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
12-28-2004, 04:45 PM
"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
12-28-2004, 05:04 PM
"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
12-28-2004, 05:06 PM
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.

buscht
12-28-2004, 05:27 PM
A "Stanley knife" surface finish means that the surface finish is equivalant to what you could acheive with a manual hand plane. Stanley happens to be major name in hand planes.

"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"

Just guessing here, but that seems to mean to me that they are using a large diameter cutter (maybe 5"dia) with a 12,000 RPM and the high efficient and stress free possibly means that its a spiral cutter not a straight flute. This could be an aluminum body with carbide inserts to keep the weight down.

Again, thats just a guess.

From the photos, I can't see why you would need a 1/2" router bit. The bigger the better. You must have a limitation on your router motor, not the part geometry.

I thought that the French machine had an interesting part holding method. It looks like vacuum cups on adjustable bars.

Losos
12-28-2004, 05:38 PM
"From the photos, I can't see why you would need a 1/2" router bit. The bigger the better. You must have a limitation on your router motor, not the part geometry."

The 1/2" shank restriction is just due to the size limitations of the router I was looking at. What routers are out there that are capable of handling a 5" cutter like the one you described?


"I thought that the French machine had an interesting part holding method. It looks like vacuum cups on adjustable bars."

Yeah, that is one way of holding the foam blank and probably the way I will do it if I cannot find something better. The APS3000 guys apparently have figured out a method that is superior to this system, but provided limited descriptions (30 seconds to place and fully register the blank!) and zero pictures. They also claim to be able to cut 1# EPS foam without distortion, but I believe this is mainly due to their specialized no-load cutter rather than the support system.

Losos
12-28-2004, 05:47 PM
For those that are interested, here are a few post from Miki on the aps3000 machine

describing the cutting dilemma
http://www.swaylocks.com/forum/gforum.cgi?post=155693;#155693

and here are two others where he bashes router-based machines for surfboard manufacturing (I'm clueless on this one. What other types of machines are there that could cut something like a surfboard?)

http://www.swaylocks.com/forum/gforum.cgi?post=155683;#155683
http://www.swaylocks.com/forum/gforum.cgi?post=155430;#155430

Losos
12-28-2004, 07:18 PM
I've made a sketch to help people visualize the cutting problem. You can view it at http://mohrinnovations.com/tmp/short%20cutter%20problems.gif

buscht
12-29-2004, 09:21 AM
Losos, that picture actually clarifies what some others are saying. You don't need a 3" cutting length. You need 3" of router bit sticking out of the collet. A guess is that you only need 1-1/2" of cutting length (probably less).

That simplifies your search.

Also, that was very interesting reading about the pros and cons of machine styles.

HuFlungDung
12-29-2004, 10:37 AM
Losos,
Also, you would not be bound to plunging to full depth in one pass. We know you surfer guys are real men, but come on! :D

Ultimately, you will not want the cutter to be cutting deep into the blank as if cutting a slot. It creates unnecessary chip flow and heating problems, and there is potential for a plugged cutter to spoil the edge.

Instead, you will want to take a roughing pass, following the perimeter (but leaving a decent finish amount) with something like a 2" or 3" facemill. This will open up the stock so that you can then approach with a much shorter, stiffer endmill, and avoid drag of the toolholder. There is likely no reason to restrict yourself to 1/2" diameter either: its easier to get the circumferential velocity you want, with a larger diameter tool.

Losos
12-29-2004, 03:16 PM
Ha, yeah, we surfer guys are real men for sure! To tell you the truth, I hadn't even contemplated taking more than one pass to pierce off the shoulder of the blank... 3" deep cut at once... psshhhh, it's just foam! ;-)

I'm fine taking multiple passes at the shoulder, but I'd really prefer to do all my machining with one tool and with one pass. It's fine if there are a few ridges left, I'm planning on putting the finishing touches of the board on by hand.

huflung - you're the second or third person to tell me not to restrict myself to a 1/2"
diameter cutter. Are you talking about a 1/2" shank, or a 1/2" cutting width? The 1/2" limit I have is with my collet, I definitely was looking for a wider diameter cutting head (what's the tech. term for it?). Should I look for another router with a larger collet capacity? or will I be able to find a 1/2" shank, 3"-4" diameter cutter?

Thanks for all the advice!

buscht
12-29-2004, 03:53 PM
Here's an example
http://www.eagle-america.com/html/catalog/productGroup.asp/87710

The problem is not so much the diameter as your length. Most standard tools that are 4 or 5" long have a 3/4" or 1" shaft diameter.

HuFlungDung
12-29-2004, 03:55 PM
I've looked through a few catalogues for reduced shank tools, and not had much luck. You might find 1/2" shank 3/4" dia router bits, but they are not very long.

You might well be able to be quite aggressive in cutting foam, but less so in wood, I suspect.

When you say you want to cut "in one cut" you realize that forming the rounded edge of a board is not going to happen in one cut? Its going to take several cuts to approximate anything like a rounded edge, even for hand finishing purposes. So by the time you work your way down to the "parting line" of the board, you're not going to have a tremendously deep cut to make, unless you intend to suddenly plunge right through. Most likely instead, you will want to turn the board over, and cut again from the other side to complete the contours. The final "break through cut" will not be a major event requiring a deep slot at all.

Losos
01-03-2005, 02:27 AM
huflung - you're right, the actual amount of foam to cut through on the shoulder removal pass is not much. The problem is that you still have the ~3" thick shoulder to the outside of the cutter to worry about. By "in one cut" I mean I don't want to have to work down the shoulder pass by pass... I'd like to finish the rails (top first then bottom as you had said) and then do a single run around the outline to shear off the remaining shoulder.

HuFlungDung
01-03-2005, 12:32 PM
Losos, that's why I recommended a roughing procedure around the perimeter, to open up the area enough to allow the nose of the toolholder to get in deep enough.

Heck, just acquire a face mill and bore it out to fit over the snout of your toolholder. That way, it'll demolish anything that gets in its way :D

Losos
01-03-2005, 02:34 PM
It's looking like I may just have to do that.

I've never heard of a face mill before. They sound fairly suitable to my needs -- high cutting speeds, low cutting forces -- and the larger diameter would explain how Miki is able to run his cutter at such a high circumference velocity. I also read that they can be used for finishing as well as roughing. The problem is that they only seem to be used for flat faces. Could a face mill be used to mill out such a curvy surface as a surfboard? If not, is there a hybrid cutter that joins the benefits of a face mill with the benefits of an end mill?

Losos
01-03-2005, 03:09 PM
What router options do I have if I want to use a cutter like the ones below. The second one as a 1.5 dia shank!

http://www.stellram.com/Milling/contour.htm
http://www.stellram.com/Milling/Contour/MI5515VS12ENI.PDF

HuFlungDung
01-03-2005, 03:12 PM
For your task, you may want to use a shaper cutter, rather than a face mill. We metalworkers use facemills and woodworkers use shaper cutters. They are both toothed wheels, but a shaper cutter usually has a large chip gullet, high rake angles, large keenly sharpened inserts etc, which make them better for cutting wood and light materials.

Face mills are built heavier, and use relatively small inserts for metal cutting.

There are maximum recommended speeds for all these types of tools which you will want to observe for safety sake, and the cutter needs to work inside a safety enclosure. If an insert comes loose while the tool is cutting, it needs to be stopped.

As far as 3d milling using a large diameter cutter goes, you might get away with it. You'd want to use radius corner cutting inserts of course, that would put the cutter into the class of a what we call a bullnose cutter. For intricate contours, you can end up with unintentional toolmarks (small gouges) on the surface, because the position of this tool is not so well controlled as a simple ballnose tool, which is considered the best all around 3d shaping tool.

ger21
01-03-2005, 05:27 PM
What router options do I have if I want to use a cutter like the ones below. The second one as a 1.5 dia shank!



Something most likely WAY out of your price range. I'd guess about $2500 for a spindle that will take a 1" shank tool. That's all our 10HP spindle at work will hold ($8000-$9000).

I also doubt you'll get a good finish with metal cutting tools, like HU says. The geometries of wood and metal tools are very different. If you can get away with a square end tool, Onsrud makes a 3/8" shank foam bit, 5" OA with 3 1/2" cutting length that might work for you. It would probably break if you tried to cut wood with it, though. 52-574 at http://www.onsrud.com .

If you really need the ballnose, I'd have a 3/4" diameter spiral made with a 1/2" shank. And if your using a standard handheld router motor, make sure it's variable speed. You don't want to spin something like that at 25,000 rpm. And if you plan on cutting wood (even basswood), your depth of cut will be limited by the routers power (or lack of :) ) Just get your wallet ready. You can get custom insert cutters made, too, if that's what you want.

PS. are you aware of the prices of those cutters you linked to?

Losos
01-03-2005, 09:29 PM
Something most likely WAY out of your price range. I'd guess about $2500 for a spindle that will take a 1" shank tool. That's all our 10HP spindle at work will hold ($8000-$9000). Yeah, that's way out of my price range. I'm looking in the $200-$300 router range.


If you really need the ballnose, I'd have a 3/4" diameter spiral made with a 1/2" shank. And if your using a standard handheld router motor, make sure it's variable speed. You don't want to spin something like that at 25,000 rpm. That could work. I'm thinking now that I'll just start with a fairly standard (and safe!) cutter and then work up from there, rather than trying to pick the optimum bit on the first bite.


PS. are you aware of the prices of those cutters you linked to? Nope... humor me

xshaper
06-28-2007, 02:19 AM
Did you get your machine going? If so what bit did you go with?
Mark