Messages

1

General Mach Discussion / Re: Lathe motor question "Variable Speed"

« on: February 16, 2010, 03:43:19 AM »

Sounds pretty good to me - let us know how you go on.

2

General Mach Discussion / Re: Lathe motor question "Variable Speed"

« on: February 15, 2010, 09:00:04 AM »

The problems would appear to be with the motor then, which is normal. Torque is a function of the speed. DC motors tend to be higher torque at low speeds - e.g. railway traction motors, whereas I think most AC motors tend to produce their maximum torque at higher speeds.

I am not saying that your idea is necessarily bad, indeed for us it would be ideal - maximum torque over a whole range of speeds - and I am not in touch with the latest developments, it may have been that modern electronics had managed to produce more torque over a wider range of speeds, but as I say, I do not think it is necessarily achievable at the moment.

In the miniature railway scene, many years ago square wave was produced in a pulsed type of system, instead of merely increasing voltage, to produce more torque at lower speeds, and, indeed most traction motor controls use a similar system today, where full voltage in pulses is fed to the motor.

I don't think you can do that with AC yet, the speed controls using frequency control still have a sine wave type of output.

3

General Mach Discussion / Re: Lathe motor question "Variable Speed"

« on: February 15, 2010, 12:54:14 AM »

I think you will have to look at the torque figures produced over the range of sppeds you are talking about. As I say, I use a 2HP three phase motor in place of my 1HP single phase. My Omron inverter worls up to 60 HZ. Below 30Hz the torque drops off quite quickly, so if I want to turn 6 inch diameter wheels, which need a low speed,  I must gear down the motor to the spindle shaft to maintain the torque, (and therefore run the motor faster) to keep the torque, otherwise if I take anything of a reasonable cut, the motor says "I'm not playing", and stalls.

If you can maintain the rated torque over such a wide speed rahge, then fair enough - but if you manage it, patent it.

4

General Mach Discussion / Re: Keeping informed on Vis Basic

« on: November 16, 2009, 05:26:13 AM »

Thanks guys - My thanks message didn't register yesterday, or again today, so I have switched to "Opera".

Yes, I stumbled across "Message" in the wikki, I haven't tried it yet, but I will. I see Graham agrees I will have to use the "While Is Moving" line. I didn't really want to, but I can't see any alternative. At least I have got round to having my labels on the various DRO's changing according to their function in a particular program. Before I had to remember them all.

5

General Mach Discussion / Re: trouble with spindle speed

« on: November 16, 2009, 05:09:38 AM »

Barry -

The only experience I have is that I use an Omron VFD. This is a stand alone unit, with a touch panel on front to control speed manually. It can however be programmed to accept a signal from the computer. This is in the form of a voltage (0-12v) on a control wire. Reversal is a seperate couple of inputs - one on for forward, one on for reverse. If both are on together the thing blows up - no - an error message shows.

The forward / reverse is all controlled by Mach3, the speed is contolled by MachVFM output via a Digispeed, which converts the VFM output to a voltage the Omron can interpret.

1. What does your VFD require
2. Mach can output speed control signals in various ways - have you got Mach set correctly. There are instructions in the manual.

6

General Mach Discussion / Keeping informed on Vis Basic

« on: November 13, 2009, 04:10:54 AM »

I have written a program to re-profile railway wheels which involves a short G Code program and a Vis Basic macro. The program takes about half an hour or so to run.

I would like to be able to have an "indicator" to tell me where in the program the machine is.

I have tried using the message line - but I can't include variables in the text of the line - e.g.  Code "(Pass Number PassNum) to show on the message line. I have tried sending a number to a User DRO, but when I regen the display, or start the code, the Vis Basic executes right through and indicates the final position on the DRO - not really what I wanted.

I have a FOR/NEXT loop in the macro - and all I really wanted to do was it to indicate  which number loop it was actually cutting.

7

General Mach Discussion / Re: adding stop to all z movement

« on: November 13, 2009, 03:56:30 AM »

I am not quite sure what exactly you are wanting, here.

On Mach 3 you say you do not have the Z axis set up.  However, If you are worried about it moving, it implies that it is fitted and working ??

You can try two ways -  On config/ports and pins - turn the z axis off. I haven't tried this - the Z axis will not work, but whether Mach says - "You are trying to move the Z axis and have it turned off so I will not play" I don't know.

The other way is disconnect the step and direction wires to your stepper driver or whatever, and turn the power off to the drive. The Z axis will definitely not work, and since you are not affecting the "computer" side of the set-up, Mach will be unaware that any thing is wrong.

You MUST make sure, however, that the X,Y movements you make do not depend on a particular height of Z, e.g. to miss a clamp of anything - make sure z is fully up and out of the way.

8

General Mach Discussion / Re: softlimit problems

« on: July 21, 2009, 03:35:58 AM »

The problem is that you are looking at the wrong set of DRO's.

Soft limits work on Machine Co-ordinates, not Program Co-ordinates.

I have just run a test on the Mach3 on this computer, which is not connected to a machine. I set the machine co-ordinates to +70 in X,Y and Z, the set the soft limits to + and - 20 in x,y and z. True enough, when I pressed the soft limits button, I got the same warning that you did.

You need to zero your Machine Co-ordinates. Press the machine co-ordinates button on Mach (the surround lights up) and this will alter the DRO's to display machine co-ordinates. The only way to zero these is to press the "Ref All Home" button. If you have no home switches, this should zero them - if you have the auto zero box ticked on your homing page..

Once you have Machine Co-ordinates zeroed, then press the Machine Co-ordinates button again, the DRO's will now display Program Co-ordinates. You can zero these manually  by pressing the zero x, zero y and zero z buttons. Your machine and program co-ordinates now have no offset. Go back to the machine co-ordinates.

If you had started this with your cutter in  say the bottom left hand corner of the table, then this is your soft limit poition for  minus  x and minus Y. If z is fully home then you can enter 0 in the z minus box as well.

If you jog to the other extremeties of the table, this is your soft limits + position.

If you switch on soft limits now, it should be OK.

Remeber this is working on Machine Co-ordinates.  The program can follow program co-ordinates just the same, but if it approaches the extremities defined by Machine Co-ords, the soft limits will kick in and stop the table, regardless of what is displayed in the Program Co-ords DRO's.

I must admit I have amended some screens on my displays to show just Machine Co-ords in small DROs under the main display. The main display I can leave on program Co-ords. I find this very easy to use as a quick check.

9

General Mach Discussion / Re: Mach3Turn - dimension troubles

« on: July 20, 2009, 03:39:23 AM »

The problem in X is always the same - where is the lathe centreline - which most people have as their X axis.

Unfortunately, unless you spend a lot of time (and a little money) setting up home swithches, accurate quickchange tool posts, and then set up an accurate tool table, then everytime you start up, or change tools, you will have to find X0  again.

I have tried all sorts of things, but the only way I have found to do this accurately is to put a peice of old bar in the lathe, and take a cut along it. Measure this diameter accurately with calipers or micrometer, and then enter that diameter in your X DRO (or half that if you are in radius mode). As a check then move x in by 10 or 20 thou, take another cut, and see if the DRO and the actual diameter correspond.

I have been turning a lot over the weekend (locomotive axles) and once I had set this up, I run through the first axle and check the next to last cut and see if the DRO's are still accurate - and then finish. Once I was satisfied with the first one, the rest were turning to within 0.02 mm, which according to me is less than 1 thou.

I do have home switches fitted, and a quick change toolpost, and a tooltable, but I still take a cut and check the diameter before I sart a days work.

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General Mach Discussion / Re: PC Lockup with Mach3

« on: July 20, 2009, 03:16:38 AM »

When you say the "computer" locks up - do you mean the computer, or is it Mach that locks up.

Check your GCode - or try running something so simple that you can see it is right.

I have been writing GCode over the last week, and the favorite thing that locks up Mach is silly errors in the code.
This is particularly apparent when using subroutines, if you have misnamed it, or not put in a  return command.

Errors usually get picked up as you enter the program. Mach runs through the entire program and gives you the tool path pciture. Do you get as far as that, without anything appearing in the comments window.
 
I take it, other than this, everything else works fine, like jogging, accuracy etc etc.