A clean cut on melemime with a v bit?

[knight_toolworks]

got some mdf core melemime today and did some v cuts and the plastic top has some ragget chuncks hanging from it. normal or am I doing something wrong? using the 60 degree v that I bought with the bot. I dont' think the bit is dull yet but who knows?

[elcruisr]

V bits and melamine tend to be a bad combination, the cutting geometry is wrong. Melamine is very hard and brittle, not to mention hard on cutters. There is tooling designed with melamine in mind but none in v bit that I know of.

[ed_lang]

I do not have any melamine in the shop right now but if I did, I would try using the new solid carbide V bits from Centuriontools.com At least give them a call and talk to them. I have three of them and have found them to give me a super clean edge on everything I have tried them on. Sans melamine.

[cnc_works]

What were your speeds & feeds, Steve? Any chance your hold down allowed vibration of the material?

I've v grooved quite a bit of melamine and seldom have problems with ragged edges. Of course, I seldom use a 60deg bit, mostly 90deg, but I would be a little surprised if the 60deg bit were any more prone to ragged edges than the 90. And just standard carbide bladed bits.

Most of the what I have done is v carved lettering using my PC router in my small CNC, so speed maybe 20K and feed maybe 90ipm, though because of the nature of v carving, it probably seldom really gets up to 90ipm.

Donn

[knight_toolworks]

it's not so much the cuts are ragged as the melemime is not cut smooth. it's liek when I used a mask and the mask has pieces hanging over the cut that weere nto cut clean. it may be the cut speed rpms are around 14000 but the cut speed is 200 ipm as that was wokring in the materials I had been cutting.

[richards]

Steve,
I think that Eric's answer is the key. The configuration of the cutter is the issue. All of my V-cutters act like straight cutters in that they DON'T shear the melamine like a down-cut spiral cutter.

I use down-cut spirals exclusively with Melamine. If I were to cut all the way through in one pass, I would use an Up/Down spiral cutter (compression type).

[bleeth]

Steve: Just for the heck of it try lowering your router speed to around 10,000 RPM. Verify your bit is still sharp and does not have any build up on it. The Melamine is extremely hard and the underlying mdf is quite soft. You need to base your chip load on the hard plastic.

[doug]

I have Vcarved 50 or 60 plaques in Melamine with a 60 degree bit at 9000 rpm, 4IPS,with>5 stepdown withou seeing a ragged edge. I've also used this same bit in MDF and hardwoods.

[knight_toolworks]

I think the problem is the melemime. it does not have the hard surface I am used to it has more of a vinyl surface on the soft side.so it leave pieces hanging on after it is cut.
it was labled mdl so maybe it is a different type. I play with feed speed I lowered it from 300im to 100 no change then changed the rpms and going to my top spindle speed made it better but not perfect 9000 rpms was the worst. I sharped the bit so I don't think that was it

[bleeth]

Sounds more like pvc or something typically used for thermoforming. I tried to v-carve that when I first got my bot and learned quickly that you can't.