BIG router bit for foam

[benergy]

Hello everyone....
im trying to find out about home made or custom made cutters for BIG fast foam block machining. I have seen 400mm long router cutters described as hollow alloy tube with sand/diamond grit or something similar bonded to the outside and perforations so foam debris can be vacumed through the inside and out through a manifold near the router motor as the foam is sanded rather than milled. Another was an alloy tube with a piano wire wound around the ouside, this one worries me if the wire snapped, but if it works and the machine is shrouded.......what the heck...
another was 3 electirc planer spindles with disposable blades, all bolted together on a shaft as axle and fitted to a router, the max speed and balancing would seem critical to me, how would this be calculated?

Any knowlege of any form would be amazing!

regards
Benergy

[svenakela]

Actually, I have never seen a similar mill but I'm shure there are people with knowledge about it here.
There shouldn't be much precision work in those cutters, so why don't just glue a really heavy duty sand paper to a tube and make a test run?..

Regards,
Sven

[braidmeister]

What do you mean by 'BIG' ??? Do you mean LONG or large diameter? Is this going to be for profile and pocketing 2D cutting or for 3D relief cutting?

As for long bits, you will have to think about how much Z travel you have, how thick the material is, and a little extra room for safe Z clearance. You can get SXL end mills (and ball end) in 1/2" shank, 6" OAL and 3" CL. As for bits larger than that, it depends on what you collet/spindle/router can hold. You can use a large (up to 2") corebox (like a 1/2 ball) router bit, but you have to keep the RPM down...it just isn't safe going larger than 2" in diameter on most tools...the outside of these large cutters approach the speed of sound!

As far as a DIY el cheapo solution, you can use a drill bit with a flat or ball ground on the end of it if you are ONLY cutting low density polystyrene.

-B

[ger21]

http://www.3dcutting.com/products_FROGTOOLS.php

[svenakela]

Originally Posted by braidmeister What do you mean by 'BIG' ??? Do you mean LONG or large diameter? Is this going to be for profile and pocketing 2D cutting or for 3D relief cutting? ... -B

I think both are correct. There are extremely long cutters (see Ger's post) but if it's going to be a hollow mill it must be pretty big to take take the load, and if it's going to be used to vacuum away the dust it gotta be big too.
The length is interesting, how deep would it cut really? Even though you're modeling something in foam the first layers are cut just a centimeter or two (that would be an inch... ).

[benergy]

Have a look at http://www.bornemann-werkzeugtechnik...sch/frame.html
By big i mean coke can sized but a few inch longer possibly, in between the two styles at the bornemann site.
Im going to try alloy tube with sandpaper stuck to outside. I think this tool style is interesting.
x
benergy

[smoker]

Hi Benergy, any luck/progress?

[benergy]

At the moment im trying the grinding large drill bits down to ballnose. Ill play with the tube method in a month or so, ill post any results too.

Benergy

[eoinie]

Hi folks
I'm new to the list and hope I am posting this query in the right section - if not my apologies. I see that ger21 has posted alink to the Frogmill site. I am researching a CNC foam carving setup and was drawn to the Frogmill range. It seems ideal. However it also seems very expensive. I should say that I have very little experience in this area and realise that the Frogmill range might be very good value. I am interested in the sculpture modelling side of the business where accuracy and fine finish would be considered important. I currently use a manual hot wire carver on EPS foam but don't think this would machine well using cutters. Can anyone advise me on 1) whether the Frogmill system is the most appropriate (or are there there other systems which are cheaper but of comparable quality?) and 2) waht type and density of foam do I need to look at for crisp edges etc.?

Thanks in advance for any help

Eoin

[eoinie]

Am I in the right forum or is this info just not out there?

[svenakela]

Originally Posted by eoinie Am I in the right forum or is this info just not out there?

Let me put it this way; you asked more questions than you think you did...
And besides that, some of the words in your post are contradicting.

First of all, what is accuracy for you? For me, sculpturing with smooth surfaces is not the same thing as accuracy. For me, 0.01 mm is accurate.
Do you aim for one roughing cycle and a fine cycle for the smoothness? When I was making moulds for the big companies, maybe three fine cycles in a heavy duty production machine (accurate enough for me, that is) gave a smooth surface that didn't need polishing.
What are you going to do with the foam, lost foam moulding, let it be as it is or just for prototyping? There are hundreds of different foams and they all have their purpose.

The Frogmill is for sure a great machine that probably will be bad ass overkill if you only want to cut foam. I've seen machines less sturdy than Frog's making outstanding work in hard wood and aluminium. I can guarantee that if there are tenths of a millimeter in tolerance difference on two foam copies you still wouldn't see it. So yes, the Frog is overkill if you only have foam in your mind.

My suggestion is to look around in the Router and machine forums to see what type of machines other people uses. There are probably people that can point out what type of foam and density they use.

And if you're unsure, just make another thread or post!

Regards,
Sven

[eoinie]

Hi
Thanks for the reply - I see what you mean about the questions. I'll search the other forums as you suggest.

Regards