Tool pathing trick

[gabepari]

Thought I'd pass along a little trick that utilizes the "built-in" flex of the gantry and all things attached.

First cut I made on the shopbot was a square, cut full depth single pass in conventional direction; the part was undersized. So I cut it in climb; part was oversized. Next I try two passes, second pass removing .050" thickness. In conventional, I've got a .020" or so step all the way around my part, and the majority of the cut is still undersized; But AHA! I notice that on the waste side, the cut is beatiful. Hmm, so I try climb cut. The step moves to the waste, and the good side is on the part, but some of the wood I cut doesn't like climb cut.

So my solution, cut climb to about .050" above the table, then cut conventional full depth plus whatever you dive into your spoiler, I go .005". Since doing this, I've never had to fight with the allowances. The cutter and gantry flex force the bit away from the part on the first go round (experience shows about .020") then the second cut in the conventional direction cleans it up right to spec.

Tool pathing in Insignia is easy, after the climb cut, just type in a new name at the bottom, change to conventional and increase the depth accordingly.

Of course, YMMV, yada yada. Works for me though.

Gabe Pari
www.socalteardrops.com (http://www.socalteardrops.com)

[harryball]

Are you running an alpha? I'm running a PRT Alpha 96

Maybe my setup changes the dynamics. My Z axis is on one side, not the middle. It had 2 Z's when I bought and one was removed. I've never relocated it to the middle holes. The downside is I can only effectively cut to 96.5" with my current layout. But I have not noticed any difference in part sizes or shapes when running at various speeds. Perhaps the Z location makes it more ridgid?

I have noticed edges not clean, I think everyone calls it chatter. I don't know what to do about that except slow down on the final cut pass.

Robert

[gabepari]

running a 5x10 Alpha. The z is located in the holes nearest the y motor (should be lowest torque moment in this position). I get the chatter as well, building a set of gearboxes soon to eliminate that. If you run a small enough chip load (with high cutting edge speed) you probably won't have the flex. But my bits burn up too quickly that way. When cutting where the bits are happy, the machine flexes.

Just my $0.02


Do what works for you, I mentioned this technique to Mike Richards and he said it worked great for him.

Later,

Gabe Pari
www.socalteardrops.com (http://www.socalteardrops.com)

[richards]

Gabe,
I use your cutting method on almost every cut. It is probably the single most effective thing that I've done to speed up production and improve quality at the same time. Before talking to you, I had to offset the cut so that I could make a finish cut, now I just climb cut most of the way through the material and then conventional cut it to final depth. Since the gearbox had already eliminated 'chatter', all that was left was to simplify my technique. Your cutting method took care of that!

[scottcox]

Robert,

Check the location of your proximity switches. You may be able to squeeze that extra 1.5 inches in there by moving your stop blocks and proximity tabs outward. 2 minutes just bought me 2 inches!

[harryball]

In about another half an inch, if that far, the wheel of the gantry will go over the edge. I've moved the stops as far out as possible. This bot was a show bot with twin Z's and I guess in the rush the table top is shifted further toward the far X end than it should be. On my next spoil board I plan to move it back at least an inch once I see the vac plenum underneath.

Right now I'm concentrating on using it and I've only run into the limit once.

Robert

[pete]

Gabe, what size and style bits are you using in your method pls. Thanks, Pete