Messages

641

General Mach Discussion / G code to generate a mathematical profile

« on: August 12, 2014, 04:43:09 PM »

Ok, thanks for that Ray.  I'll follow the G1 route then and see how it goes.

642

General Mach Discussion / G code to generate a mathematical profile

« on: August 12, 2014, 10:56:55 AM »

Hi all, I have a question about the best way to accurately mill a defined profile on the edge of a plate.  The plate will be mounted flat on the mill table on a sacrificial spacer, and the edge milled using just X and Y moves.  The curve I want to generate will be generated by a simple mathematical formula, and with care I can avoid the necessity of cutter radius compensation.

Ideally I would like a G code instruction of the form "Gxy X1 Y1 X2 Z2...Xn Yn" where the Xs and Ys are a series of coordinates of points along the desired profile; and the controller would use a suitable interpolator to smooth between the points.  However, as far as I can see there is no such Gxy instruction in Mach 3!

The obvious alternative is to use a (long) series of small line increments and a G01 move:
G01 X1 Y1
G01 X2 Y2
....
G01 Xn Yn

but this could be a large program (but no matter, I can generate it from a simple Excel spreadsheet). 

My question is, am I missing something?  Is there a better / well known way to do this please?

643

General Mach Discussion / running 2 CNC machines from 1 pc

« on: July 31, 2014, 06:14:54 PM »

Me too.  Have a converted Myford S7 and a Denford Novamill, separate profiles called Myford and Denford, and a switch box I bought from an online computer supples place.  Works fine as long as I remember to set the switch properly!

644

General Mach Discussion / Is this a suitable power supply

« on: April 21, 2014, 03:54:37 PM »

That's the one I use for my Denford Novamill conversion.  Works well.


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645

General Mach Discussion / Re: Is this a suitable power supply

« on: April 21, 2014, 04:43:32 AM »

That looks like a useful driver.  Set the current pot to the rated current for your motors before powering up.

It goes without saying I guess, but mount the board in the vertical plane so that air can convect past the heatsink.

646

General Mach Discussion / Is this a suitable power supply

« on: April 20, 2014, 06:15:42 PM »

It's the current that fries the motors not the voltage.  Do the drivers have provision to set the motor current?  Can you provide a link to the driver details?


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647

General Mach Discussion / When is a circle not a circle? When it's 4 arcs!

« on: April 15, 2014, 05:12:52 PM »

Even cutting a full circle the screws have to reverse at some point and backlash will come in then.


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648

General Mach Discussion / Need help with lathe ,

« on: March 31, 2014, 03:37:11 AM »

You seem to be feeding at 0.8mm/min so no wonder things are slow!


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649

General Mach Discussion / Probing around a pin to find center

« on: March 24, 2014, 03:52:55 PM »

Pete, you can make an isolated probe of a known diameter that fits your spindle and use the probing input on Mach, just as I assume you are doing for height.  I use this all the time and the machine stops virtually instantly when the probe touches the work, no apparent problem with "microcrashing".  I must say that I haven't tried Lautard's manoeuvre because up to now I haven't had the need to centre on a disc.  It would also be possible to touch at 3 or more points round the pin, but the maths looks trickier.  I'll try to get a pick of my probe later.


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650

General Mach Discussion / Re: Probing around a pin to find center

« on: March 24, 2014, 12:05:20 PM »

If you have a circular probe, you can use "Lautard's Maneuver".  I haven't programmed this but it would be easy enough to do.  Steps are as follows.

1.  Set the probe approximately in line with but at the left of the pin at a Z level where it can contact the pin.  Make an X probing move until the probe contacts the pin. Lift the probe above the pin keeping X and Y fixed.

2.  Move the probe to the right by half the sum of the probe diameter and the pin diameter, and record the "X" value.

3.  Move the probe in the negative Y direction until it clears the pin, and lower it.  Make a probing move until it contacts the pin.  Lift the probe above the pin keeping X and Y fixed.

4.  Move the probe in the positive Y direction by half the sum of the probe and pin diameters and record the "Y" value.

Go to step (1), and repeat the process 2 or 3 times until the values of X and Y make no significant change.