Diylilcnc

[Joe Hillmann]

My thought is to use 3/16 or 1/4 cutters hoping that I can then cut through 1/4 plywood in a single pass. I pretty much assumed that the designs that I use on the laser will have to be completely redone to work with cnc.


What do you mean, faster than a router? Are you referring to using a router bit with a guide on it an hardboard patterns?

[Michael Simpson Virgina]

The general rule of thumb is half the diameter of the bit for depth. There are other factors as well. Generaly a $2500 or $3000 DIY machine is not going to be as ridgid as a $5000 DIY machine.

[Gerry Grzadzinski]

The general rule of thumb is half the diameter of the bit for depth.

I don't know who created that rule, but Imo, it only applies to bits smaller than 1/8". With the right bits, you can probably cut through 1/4" ply in 1 pass with a 1/8" bit. No problem at all with a 1/4" bit. Not a carbide tipped bit, but a solid carbide spiral compression bit. With a rigid enough machine, you can do it at 400ipm, too.

At my day job we cut through 3/4" plywood in a single pass with a 3/8" compression bit at 800-900ipm. So throw that rule out the window when unless you're using very small bits.

[Michael Simpson Virgina]

What kind of CNC are you using at your day job? Probably not a $3000 DIY machine.

[Gerry Grzadzinski]

Morbidelli 636

Here's a used one for $98K
http://www.exfactory.com/Detail.aspx?recnum=FT-010061

[Michael Simpson Virgina]

My point exactly.

[Ross Moshinsky]

The truth is somewhere in the middle. Even with my small engraver we do passes at more than 1/2 the thickness of the cutter.

It comes down to the router/spindle having enough power. The machine being rigid. The piece being secured properly. The quality of the bit. The actual material.

As for the original question, you aren't going to be happy with belts and chains. R&P is the safest way to go. It's fast, relatively cheap, and hard to get wrong.

[Gerry Grzadzinski]

My point exactly.

I cut more than half the diameter with my home built machine, with skate bearings on pipe for linear bearings. I can also do 3D carving at 175ipm with a 1/16" ballnose bit.

You can remove a lot of material with a 2HP router. Rigidity is the key factor in exactly what the machine can do.

[Joe Hillmann]

Gerry,
Am I understanding you correctly, you are using pipe as the rails on your machine? What type of accuracy does that allow? And how big is your machine?

[Gerry Grzadzinski]

It's actually 2" EMT. There weren't a lot of inexpensive options when I started building it 8 years ago.
It's got a cutting area of 30"x45". And it's extremely accurate. Just not as rigid as I'd like.

So I'm currently building a new one, that will be bigger, faster, and stronger. I'm using HiWin rails this time, and they'll cost more than the entire first machine.

[William Adams]

FWIW, I wound up getting a ShapeOko (then a ShapeOko 2 so I could write up the assembly instructions). Very happy w/ it, even w/ the belts, which are a nice compromise on speed and affordability.