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Topics - Kevin Steele

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1
General Mach Discussion / Using more than one cutter
« on: June 01, 2009, 05:31:57 PM »
I needed to drill some holes in a part after machining a form on to it.  I just wanted to centre drill the hole positions to pick them up for drilling later on.  Being lazy instead of working out how to use the tool table I just did two separate programs, one for the machining and one for the centre drilling.  It's a manual tool change, so no advantage in having it all in one program anyway.  I ran the machining, then when the program finished I changed the tool, reset the Z to suit the new tool, loaded the next program and ran the centre drilling program.  But the centre drill was out of position by about 1mm in X.  I've obviously missed a crucial step in the way I did this -can anyone tell me what that was?  I did notice that the original form was cut with tool 0, and the centre drill was tool 1 (they were programmed from one cam set up and it just incremented the tool number automatically), would this have made any difference.  I have had accuracy issues in the past, but I'm happy the machine is accurate now, as the form was cut in over 60 passes all of which lined up perfectly -I just centre drilled in the wrong place.  Obviously lost position somehow when changing tool and re-setting the Z.

Regards
Kevin

2
General Mach Discussion / Turning Syntax
« on: May 25, 2009, 09:25:04 PM »
I'm running a program to do some simple turning (shown below -just the bit with the arc move in) and all goes fine until it gets to the arc move.  I just end up with a straight line between atart point and end point.  is there something wrong with my code, or do I need to change some mach settings.

Also, if the software is configured in imperial (I have imperial leadscrews) can I get it to default to metric units or do i need to configure the machine in metric (which is dd figures with an imperial leadscrew, but possibe).

Regards
Kevin

N03190 Z-7.
N03200 X9.8
N03210 G00 Z-0.4
N03220 G01 X9.4
N03230 Z-7.
N03240 X9.6
N03250 G00 Z-0.4
N03260 G01 X9.2
N03270 Z-7.
N03280 X9.4
N03290 G00 Z-0.4
N03300 G01 X9.
N03310 Z-7.
N03320 X9.2
N03330 X19.8
N03340 G01 X21. Z-8.2 R1.2
N03350 G00 X25.8
N03360 X25.885 Z0.323
N03370 M30

3
General Mach Discussion / Accuracy Problem
« on: May 09, 2009, 12:52:32 AM »
I'm experiencing an accuracy problem, probably due to losing steps.  The machine is a Denford Triac.  I have replaced the original stepper drives and power supply with the 3A ones here http://www.arceurotrade.co.uk/Catalogue/Stepper-Motors/Stepper-Drivers and built the power supply to the plans on this site as well.  There is a cnc4pc C11 board in the base of the machine where the original controller used to be.  The original stepper motors have been left in place.  Everything seems fine, but I'm getting a positional accuracy problem.  If I run a program by the time it finishes the datum has moved.  Not by much, but it is obviously a problem.  I think it's missed steps as if I change the stepper drivers to half step or full step instead of microstepping the error increases.  I ran a small program to cut a square pocked leaving a circle in the middle.  It cut on two levels (1mm and 2mm deep) leaving a larger circle on the lower level.  As far as I could measure the circles were round, but they were about 0.05mm out of position to each other.  The larger the program the larger the error becomes.  I have the step pulse set to 5.  I tried the "sherline" setting, but this caused huge errors so was obviously not a good idea.  Increasing/decreasing speed doesn't seem to have any effect (I've never run the motor speed over 1000 mmpm).  I've tried reducing the speed and acceleration, but without success.  It was suggested that the PSU and stepper drivers were probably a bit on the small side for the motors (PSU running about 35V), but before spending a lot of money replacing everything I'd like to be sure. Given the sizes of error it's obviously only missing a few odd steps -but I can't work out where and why, any suggestions or thoughts?

Regards
Kevin

4
General Mach Discussion / Step Loss -help please
« on: March 19, 2009, 09:32:57 PM »
Hi everyone,

I converted a Denford Triac to Mach3 a while ago, but due to moving house have only just got round to serious use.  I'm having a problem with step loss in the Z axis.  It seemed fine on basic machining, but I've now tried some 3D engraving, and I'm loosing steps.  The program starts OK, but the Z axis runs up in Z so after a short while (actually about 10,000 lines of code -so quite a lot of movements) it's cutting in fresh air.  I thought I was trying to move it too quickly, but even dropping acceleration to 10 and speed to 500 it still does it (I'm in mm by the way).

I'm using the original stepper motors, with drives from Arc Euro (set to 8 microsteps) and they are run through a C11 board from CNC4PC.

I can't help thinking I'm missing something obvious, but don't know what.  Hopefully one of you will point me in the right direction.

Thanks

Kevin

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