Messages

1171

General Mach Discussion / Re: loosing steps in one direction

« on: August 06, 2007, 02:00:29 PM »

I am trying to envisage what a "small" mill is that needs 320 oz motor to drive it. You do not say what your maximum travel is, therefore I cannot work out the accuracy. There would appear to be no benefit in moving the axis 50 times, because that confuses the issue.

If it is a problem with backlash, depending on where you start, (say the centre) then loving left, moving right and back to centre should get rid of backlash and be accurate. Doing it 50 times would make no difference. So you can eliminate backlash (and do not need to compensate for it)  by doing this. DO NOT start at one end and go up and down, because you only get one set of backlash.

You seem to be saying that you inaccuracy is 0.150 inches which seems to be a fair bit if you have ball screws etc. but test for back lash  - move in one direction then the other an equal distance and see if you have any back lash. Only do it once.

If you have rid of back lash then the other problem is you travel is not correct. Test your travel (in one direction only) and see if your table moves say 1 inch at a time, using your digital calipers. You may have to adjust your number of pulses per inch on your motor configuration to get this accurate, particularly if you axis thread is metric and you are working in inches or vica versa. Having said that, if it is wrong in both directions, it cancels itself out when you do it twice, let alone fifty times.

There really is not other reason I can think of, other than then, you are missing steps driving your stepper motors, but if you are saying this 0.150 is common to all axis, it is difficult to envisage each axis missing a similar number of steps and all in one direction (because if they missed steps in both directions you could not see anything wrong.

I have a feeling it is backlash - but it seems rather a large figure to me.

1172

General Mach Discussion / Re: Max distance parallel printer cable

« on: August 06, 2007, 01:18:20 PM »

I think I woud keep the printer port cable as short as is reasonably possible. You are dependent on the power supply from the computer to keep the signals in this cable sweet. I would make sure that each application (or siganl) has it's own earth wire, and not try and run the whole thing through one earth ( there are eight, pins 18 - 25). I have mione mounted by the computer with a short lead to it, and the long leads are the power supplies to the motors, plus the leads (shielded) from the limit switches.

The power supply to my spindle motor is also mounted qute close and feed from relays driven by the 25 pin port.

1173

General Mach Discussion / Re: Z axis design and Mach3 control

« on: August 06, 2007, 01:11:28 PM »

I have absolutely no idea, becasue I have no idea what you are trying to do.

My own set-up is just a lathe with a milling head for steel, with only 9 inches by 18 inches movement, if that. My milling head only moves up and down about 1 3/4 inches. I have no idea what you mean by a tangential knife.

I am pretty good with logic, once I get the idea what you are trying to do.

1174

General Mach Discussion / Re: HELP pleeeeeese Z axis problem !!!!

« on: August 06, 2007, 12:52:08 PM »

what are you using for a power supply for your motors.  Used together, the motors can take 7.5 amps, and if you are putting bigger ones on, then even more. A power unit to supply 24 volts at 7.5 amps is quite a big ****, and after a while, if it is not up to the job it will give in, or the voltage outpput will fall and cause you steppers to miss.

To try it out  get the machine up and running a test the voltage out of the power supply when running a G0 x1 y1 z1 or something similar that tests all three motors running at once.

1175

General Mach Discussion / Re: G100 a/d d/a

« on: August 06, 2007, 12:43:05 PM »

what for ??

1176

General Mach Discussion / Re: spindle encoder?/

« on: August 06, 2007, 12:40:32 PM »

don't keep us in suspense - who did you find

1177

General Mach Discussion / Re: Question around operation and parameters

« on: August 06, 2007, 06:42:07 AM »

During your downtime, have a look at the instructional videos. One includes a complete piece on changing the M6 macro to suit individual requirements. I have done this myself, and now when I include an M6 instruction the lathe moves to a convenient position for me to change the tool.
I can change the tool, and if I include the T(?) instruction just after the M6, in puts up the number of the tool on the screen to remind me, and no doubt I can include the new tool offsets there.
I hit the resume button and off I go again.

Jim

1178

General Mach Discussion / Re: Max distance parallel printer cable

« on: August 04, 2007, 04:19:00 PM »

I think you are asking a question that no one can answer, since it depends on just what your own personal set up is - i.e. what other things is the cable going to passs that might interfere with the signals on it. You can run printers at quite some distance - but the trouble caused when a printer misses a beat is nothing compared to some instruction to your lathe/milling machine - or more so the signals to you computer from the lathe/miller.

How far do you want the computer away from the machine - it doesn't want to be too far and any commercial cable of reasonable length should give reliable service.

Mine is a couple of metres, but that is just what I had. Bear in mind it is only running at 5 volts. The other wires to your steppers could be extended because they run at 24 volts and are less prone to interference. The other inputs could be lengthened because they do not carry large amounts of info, and are generally on or off.

Jim

1179

General Mach Discussion / Re: spindle encoder?/

« on: August 04, 2007, 04:06:36 PM »

Could you send me a schematic of your set up, it sounds to be just what I want. I take it when you say you did a little work with the soldering iron, it was some sort of transistor circuit to link into the 25 pin parrallel port ??

From that I assume I can make two, one for my milling spindle and one for my lathe spindle (they both work from the same motor, but the gearing is different.)

jimpinder@tiscali.co.uk or post it on here and we can all download it.

Jim

1180

General Mach Discussion / Re: pulse frequency and stepper tuning

« on: August 04, 2007, 01:55:26 PM »

Try it this way -
If your stepper motors require 200 pulses per revolution and your have the driver card set to 8 pulses per step, then Mach3 must put out 1,600 pulses per revolution of the motor. If you have say a five to one step down on your stepper motor to axis drive, then Mach3 has to put out 8,000 pulses to drive the axis screw round once, and if your screw moves the axis 1/10 inch per rev, then your need to put out 80,000 pulses to move your axis one inch.

In the stepper motor settings if you are trying to make the axis move at too fast a rate, the required pulse rate will exceed the rate at which Mach3 can output pulses to drive them - so you need to move up a stage from 25 kHz. Mach 3 can be set at different speeds, but it is advisable to use the lowest speed for your requirements.