[damae]

I just saw your 1500ipm at 200lbf figure. There is NO, I repeat, NO, way that you'll be able to do this with a homeade gantry style machine using extrusion. It simply isn't rigid enough. The extrusion will definitely flex a good deal with these kind of speeds. Heck, even my machine that was made entirely out of solid square stock flexed a little. When that flex does happen, it's going to eat your cutters alive. Your chiprate could jump from .001 to .1 in a matter of milliseconds.

I don't mean to discourage you, this is just a little reality check. High speed DIY routers are very possible, but not in the ballpark of 1500ipm.

I really appreciate your cautions and advice, since I lack practical experience. I'm learning a lot about why machines are built heavy and why good parts cost so much. (I'm already in for $2400 for just a handfull of components). What I need is some rule-of-thumb, to figure out where to start for framing.

You make good points about the flex. Your machine made from solid square stock -- is it solid aluminum or solid steel? What dimensions? Or are you refering to your Series II? I would love to see what a commercially available machine of similar specs looks like (with similar cutting area, power, speed). Or perhaps I should say, I would love to see what a commecial machine with similar 2hp servos looks like. It may help set my expecations of what is within reach.

Ultimately, my goal is to build the strongest and fastest machine I can, without breaking the bank. I am beginning to consider building the frame from steel beams instead of aluminum framing. I had budgeted about $1000 for the frame using aluminum framing. Steel is a lot cheaper, but I worry about how to keep the frame straight, especially if it is welded.

Aside from the flex problem, I also have a spindle speed problem. Cutting at 1500 (or 750) IPM reqiures a FAST spindle, which *sigh* means more $$.

[damae]

Would you ever consider selling the Emerson system if you found out that smaller servos would work? I'm retrofitting a Bridgeport and need beefy motors like these.

I recently came across some 316 series Emerson motors, which may be more appropriate for my application. They're .75hp. The only problem is that I could only buy two of them. Perhaps I will get these smaller motors to work if I can find a suitable Z axis motor.

[Cold Fusion]

I was referring to my DIY cnc router. It was solid Aluminum square stock. It was 30"x30" with 17"x17" travel.

I have since aqquired some large servos of my own, which I'm struggling to make work. I bought two 1.5hp servos, and it turns out that they are brushless. Now I'm struggling to find a brushless drive within my budget.

The Z axis motor doesn't need to be near as powerful as the X and Y axis. I used to run a Z axis stepper that was 1/3 the power of my X and Y motors and it worked fine.

[damae]

I was referring to my DIY cnc router. It was solid Aluminum square stock. It was 30"x30" with 17"x17" travel.

I have since aqquired some large servos of my own, which I'm struggling to make work. I bought two 1.5hp servos, and it turns out that they are brushless. Now I'm struggling to find a brushless drive within my budget.

The Z axis motor doesn't need to be near as powerful as the X and Y axis. I used to run a Z axis stepper that was 1/3 the power of my X and Y motors and it worked fine.

Cold Fusion, can you tell me what the cross-section dimensions of your frame are? For instance, were the solid square bars 3" x 3" solid?

Glad to hear you found some big servos! I looked at your project page and they look great! When I bought my motors, I was given the caution that they really would not work with any other controller than the same brand, Emerson. After reading the documentation for a few weeks, I agree that there are a lot of details about the motor (especially the resolver) that would be hard to match to another controller.

I hope you find one that makes it work for you!