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Topics - steve_p

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1
General Mach Discussion / CV not working
« on: December 04, 2011, 03:01:20 PM »
I have a problem with cutting detailed 3D reliefs, in that I can't seem to get mach to do any CV blending of moves- the workpiece I'm currently doing is 2m x 1m and I'm rastering (in the Y axis) a relief 18mm deep, with a 0.35mm stepover.. the code is not far off a million lines long  :o

The machine is acting as if it's in G61 regardless of whether it's in G61 or G64, and whatever the CV settings are at- it does a move then pauses for a fraction of a second, then does the next move. This happens whether the angle between moves is shallow or steep. I've been pulling my hair out trying every combination of motor tuning and mach configs, but I can't get it to do anything different. Even if I could stop it pausing between moves (the pause seems roughly 0.2s), I'd save days on the machining!

normal profiling stuff seems fine. Also, I recently did a bunch of vacuum-forming moulds in MDF that were done in slices and built up to a foot or so thick, and these ran smoothly, but they were less detailed, so I guess my problems have something to do with the smallness of the moves. I can do very fine V bit engraving of serif text on the machine with no problems.

The machine itself is a large woodworking machine, I'm running a PCI Galil 1860 with approx 1kw AC servos in torque mode, and it's capable of 60m rapids (2300ipm), so I'm sure it's not a machine limitation. My problem might possibly be Galil related, but I thought I'd ask in the general forum in case it's a CV issue.

I'm a bit confused about the X-Y, Y-Z etc settings in the general config, they sound like what I'm after, but they have no effect with my code. Is there any detailed documentation on these?

Can anyone tell me whether mach actually does CV when the main axes of motion are X-Z or Y-Z?

Thanks for any info


2
Galil / toolpath drifting during cut
« on: March 22, 2011, 10:50:50 PM »
hi, i'm running a 2160 on a large woodworking machine with 10hp atc spindle.

i'm having a problem when cutting 3D relief files, in that the axis doing the large number of 'raster' passes slowly drifts, so the relief ends up slightly trapezoidal. The machine isn't out of square, it's just that each pass shifts a small amount from the previous one.

The overall length of each pass is correct, it's only the start and end positions that vary. I have tried generating the toolpath so that it rasters in the other direction, so the other axis is doing all the passes, and the problem occurs in the same way. The drift is always towards the 0 end of the axis.

The error seems to be consistent and linear and always in the same direction, so I'm guessing it can't be random noise. The enoders are A/A- B/B- Z/Z-, I've tried running them single ended but it made no difference. I've also tried powering them from the Galil 5V line rather than the servo amps' own supply. The fact that the same happens in both the main axes seems to suggest it's not an encoder/cable /drive problem.

If I look at the live data record in smarterm or galiltools, with the motor energised the encoder position is perfectly static- if I push against the machine as hard as I can it resists the movement, and I can see the (small) position error appear then disappear as the error is corrected, and the encoder returns to exactly the original position.

I've attached a picture- the inner rectangle is a relief cut with 0.5mm stepover, rastering in the Y axis (up/down in the picture). I also did a larger file as an 'air cut' with the spindle off (to eliminate noise from that source), and you can see the larger rectangle where the extractor brush cleared a path in the dust, showing the angle again.

[by the way, the 'choppy' edge you can see is mostly because it's a ballnose doing a relief, so it's at varying heights when it reached the end of each pass, which makes it look uneven.]

Any ideas?... I'm running out!

3
General Mach Discussion / minimum spec for pc with galil
« on: November 28, 2009, 09:21:18 AM »
Hi, I'm in the planning stage of building a 3 axis router with brushless servos which I plan to run with mach

I was thinking it might be a good idea to take the strain off mach by using a hardware motion board, so I bought quite cheaply an advantech mini industrial pc with a galil 1750 card already installed (and a few galil servo drives included too..) It all appears really clean, like new (the drives are new in their boxes, so it may well all be unused.)

I see from the forum that the mach drivers for galil seem to work well now, which is great (well done everyone who puts their time into this stuff!), so I think I will end up using the card, but the pc is only 233mhz. It's a socket7 board, and it has jumpers to change the core/bus voltages and clock speed, so I think I could get away with swapping the cpu for at most a 550mhz pentium (the fastest cpu supported on a standard socket7 it appears.)

I know 1ghz is the recommended minimum for mach3, but since it won't be actually running the drives directly, is it possible to get away with a slower machine? It won't be running any CAM software, it'll just be in the machine.

It's no big deal if I can't use it, it's just a nice compact chassis to fit into a machine, with filtered fans etc. If I don't use it, I'd need to find a faster motherboard with an ISA slot for the galil (chucked plenty of those out over the years!)

thanks


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