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Messages - rabphxaz

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General Mach Discussion / Re: Inaccurate routing
« on: January 19, 2009, 08:07:55 PM »
Thanks, Bill. I really appreciate your consideration.
All the best, Bob

General Mach Discussion / Re: Inaccurate routing
« on: January 19, 2009, 01:27:26 PM »
I don't feel confident using something I didn't generate myself using VCarvePro -- I'm still too new at this to read Gcode, and I'm afraid that if I don't enter things like Z zero or cut depth through the procedures that I already am familiar with then I may screw something up that will damage my machine. I have both profiled  and pocketed circles and squares now, and that has convinced me that my machine is within the accuracy tolerances that I need. But I appreciate your effort and help, and I cut both those square and circles because of your suggestion.
Thanks again, Bob

General Mach Discussion / Re: Inaccurate routing
« on: January 18, 2009, 09:16:59 PM »
OK, I've been working hard on this, following everyone's advice and ideas, and here's what I have learned: First, bolting a 3/8 steel plate to the gantry has helped immensely. You can't get any flex out of it now with a crowbar. Secondly, I cut circles (as per Bill's suggestion), squares, pockets and profiles, and I tried all kinds of different offsets. What I discovered is this -- when you do an offset, you are left with the original vector and the new one, and unless you magnify the area, you can't see that there are two vectors there. You need to delete the outside one. This, of course, doesn't explain why the profile is still coming out bigger than the pocket, but I have used all the slightly oversized veneers I made by making them smaller on the spindle sander. Tomorrow I will generate a new design and, starting from ground zero, see if the same thing happens. BTW, all the circles and squares measured out exactly as they should have. I am sure that the machine is cutting accurately.
Rich, I am not aware of the compensation technique you mentioned -- how do I do it?
Thanks again, Bob

General Mach Discussion / Re: Tool Offset and Home Z questions
« on: January 17, 2009, 10:26:16 AM »
Thanks again, Hood.

General Mach Discussion / Tool Offset and Home Z questions
« on: January 16, 2009, 07:37:08 PM »
Hi Everybody,
2 questions:
1.) When I press Go To Z, the first thing that happens is that the Z axis drops down, and then the x and y run. This means that if I have made some change to the z height during a project, the tool bit gets dragged across the material, or worse. Is there any way to have the Z axis operate after the machine gets to x and y zero?
2.) Is x and y zero at the edge of the tool bit, or the center. In other words, when I specify 000 Home, should the bit's center be pointing at the cross hairs of x and y, or should I allow for the bit radius?
Thanks again, Bob

General Mach Discussion / Re: Inaccurate routing
« on: January 16, 2009, 03:00:48 PM »
OK, I've spent the last several days trouble shooting this, and I think I found the problem: My gantry had flex to it. This explains why all my measurement tests came out good, and I was always pretty sure my pulleys, bearings, etc. were tight. I bolted a 3/8" x 8" steel plate to it, and it's doing a lot better. I do think there might be a software problem with the profile/pocket application: When I profile a shape and then try to fit it into a pocket made from the same shape, it's always too big. At least now it's too big the same amount all the way around the shape, and I'm playing with the offset tool in order to dial that difference in.
At any rate, again, thanks to everyone who helped me with this. For me, doing cnc would be impossible without this forum.
All the best, Bob

General Mach Discussion / Re: Inaccurate routing
« on: January 12, 2009, 10:19:52 AM »
Thanks, Bill, I will do it. However, I may have figured out what the problem is -- my gantry has some flex to it along the x axis. I'm going to weld some 3/8 plate to it and see if that fixes it. Then I will retest.
Thanks again, bob

General Mach Discussion / Inaccurate routing
« on: January 11, 2009, 10:37:27 PM »
Man, is there anybody who has as much trouble as I do? I spend more time on the forum that I do cutting. Here's my latest issue: I ran a test cut on 2 identical ovals, doing a profile on one and a pocket on the other. I wanted to see how closely the profile piece would fit into the pocket. The answer was, not very well. The profile fit into the pocket with about 1/8th inch of gap on one end, and the gap was not symmetrical. In other words, both cuts were not perfect ovals, even though they were designed in VCarvePro, not some design I imported into VCP, and one was an exact copy of the other. The ovals were only 3" x 4", so an 1/8th inch gap is huge for that size job.
My machine is tight and there are no loose screws, bearings, etc. I have anti-backlash lead nuts, and I was running very slow and cutting not very deep into soft material. To retest, I cut a 2" square and got similar poor results. Anybody have any ideas of what it could be?
Thanks again, Bob

General Mach Discussion / Re: Screen question
« on: January 10, 2009, 12:55:59 PM »
Hi Chip,
That's the right screen....how do I move/resize it?
Thanks, Bob

General Mach Discussion / Screen question
« on: January 09, 2009, 11:50:54 PM »
Hi all,
Hope everyone had a great holiday, but it's time to get back to the grind stone and answer some more dumb questions! Here's my latest: When I activate the little jog screen, its left side covers the last 2 numbers of the DROs that are shown in the middle of the work screen. All other pages fit fine. Anyone?
Thanks, Bob

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