Noob question about speed

[rlrhett]

Well I'm getting closer to having my new hobby workshop, and when that comes I can start my first build. Looking at the plans and kits that are available, I'm confused about the speed people are reporting.

Specifically, everybody talks about the speed of the machine during rapids. For me it would seem that the speed of the machine cutting would be more relevant. I was on David Solsylva's site and saw for the first time mention of how fast and deep the machine can cut. He demonstrates his belt driven machine cutting at 100ipm and 1/4" deep. He claims to be using the same 200oz motors from Xylotex that everyone seems to use. He also is using a standard Hitachi router. I don't know what bout using belts allows him to cut deeper and faster, but I'll leave that to another post.

The projects I have in mind involve a lot of surface carving, where the bit will likely touch the whole surface of the project. I'm looking to turn flat stock into flowing organic surfaces. Knowing that a design can hog out 1/4" at a time dragging a bit across the surface at 100ipm seems much more useful that knowing how quickly it will reset back to home on a rapid.

Is there something I'm missing?

[ger21]

Originally Posted by rlrhett Is there something I'm missing?

Being able to cut as fast as possible should probably be your main goal. The reason you hear about fast rapids is that waiting up to a minute for you're machine to move from one end to the other gets old very fast. Just a few years ago, 60ipm was considered fast.

[wcarrothers1]

Also consider what he was cutting.. isn't SPF frame board most like pine? Quite soft.

I do mostly ply wood with my machine and I go maybe 80ipm and take passes in and around .2" or so if I'm going to cut all the way through. How ever I've not pushed my machine to the point of chatter to know a limit.

Rapids are important. I like the fact that I can rapid my 8' length at 400-600ipm. Course my 4' direction is screw based and limited to ~180-190ipm before the geckos will fault thinking the servo isn't keeping up. If I boosted my voltage a bit I'd be able to go a little faster.. I'm using 1100oz servo motors so I have quite a bit of power but don't like to overload my router either.

Also mach will only rapid in a direction as fast as the slower axis max if both axis are involved with the rapid move. so keep that in mind I suppose to.

[rlrhett]

So is the speed that a machine can cut limited more by "chatter" of the bit than the speed of the motors/rails? In other words, is the bit and material going to be more of a limiting factor than the speed of the machine?

[ger21]

The limit may be one (or more) of several things.

1) Motors power or gearing.
2) Your motors might have enough power to reach a certain speed, but your machine might not be strong enough to handle it. If the machine is too flexible, or has a lot of vibration, that could limit your speed.
3) Spindle power.Your spindle may not have enough power to go as fast as you like, causing it to bog down and possibly break bits. One workaround would be to take several light passes. You can also use tools designed to use less power, such as chip breakers or roughing bits.

Your PC and/or control software might also be a limiting factor, and there are probably several others.