Messages

461

General Mach Discussion / Re: Mach3 rouns corner when running fast X,Y feeds

« on: July 01, 2008, 12:57:58 PM »

Mach 3 runs in two ways - either Absolute Stop, or Constant Velocity.

To get a precise right angle on a cut, then the x axis must cut - to above the line (to allow for tool clearance) then stop. The Y axis must then start. This happens when you jave the machine set to Absolute Stop - see General Configuration - second column.

In Constant Velocity - which is designed to smooth out changes between multiple straight lines, - the computer  calculates the acceleration of the next line, and as the last line slows down, to a stop, it feeds in the acceleration of the next - i.e. it never stops - constant velocity.

You can never, however , get rid of the rounding on an inside angle, because of the tool diameter.

462

General Mach Discussion / Re: Hot Stepper Motor

« on: July 01, 2008, 12:13:22 PM »

If you have the Arc Euro Trade motors wired in parrallel as your diagram, then I have llimited miine to 4 amps - running off 24 volts. Use a 60K resistor or the nearest preferred

As long as you have current resisting at 4 amps, the voltage you are putting to them - in your case 38 volts should make not difference.

I am just thinking of upping mine to 36 volts - so let me know how it goes, please.

463

General Mach Discussion / Re: Limit Switch Problems

« on: July 01, 2008, 12:02:26 PM »

Innovator -

It is more than likely that the position that you machine stands at 0.0.0 is useless for normal macining.
There are two positions for a machine - one is machine co-ordinates - the other is program co-ordinates.

Machine Co-ordinates - This shows on the DRO's when your Machine Co-ordinayes button is lit. It is the position that the machine knows it is at. When you "Ref All Home" the machine moves to the switches in turn, each zero, and then the DRO's all change to zero in turn. You cannot change these DRO's. This position is probably usless for any general purpose machining.

If you than move the machine to where you wish to begin a program, the DRO's will move. If you then note that position, then this is an offset. It can be entered into a table using codes G54 to 58 then G59p7 to G59p255 so there are planty to go at.

If you then press the Machine C0-ordinate button, the light goes out - and the DRO's are now displaying Program Co-ordinates These are the co-ordinates that you use to run your program - and these you can set to zero.

Let us say you wish to use G56 in your program., so enter these co-ordinates in the table.

You "Ref All Home" - this sets your Machine Co-ordinates to zero - You then enter your offset - G56. If you now check your Program Co-ordinates by pressing the Machine Co-ordinates button, the numbers will not be 0.0.0 but will be your program co-ordinates. If you then do G0X0Y0Z0 your axis will automatically move to the place to start your program.

I hope that is clear - if not come back.

464

General Mach Discussion / Re: output question

« on: July 01, 2008, 11:23:21 AM »

To follow on from Hood - I would say yes -

write the Macro - if you name it M300 - so it is easy to remember (as opposed to M30) and then make the first line of the script set your output pin, and make the second line call M30.

465

General Mach Discussion / Re: Zero plate problem

« on: June 30, 2008, 04:13:54 AM »

The input wires on the LPT1 pins are normally kept high by internal pull up resistors in the computer.

It may be there is an internal fault on your LPT1 port. Disconnect you cable and test the port, check with a voltmeter whether the pin is high or low. Make sure (as Hood says) you have not inadvertantly also applied it to some other function before you test it.

The settings on Mach 3 make no difference to the actual voltage on the pin, only if that pin is recognised as active or not.

Lastly - try another pin, if you have one spare.

466

General Mach Discussion / Re: X and Y Axis Ball Screw pitch

« on: June 30, 2008, 04:05:23 AM »

I would agree with Chip - every axis can be individually set, but  a 1 inch pitch is very high.

1. You will need a very big motor (out of proportion with the others) to drive the axis.
2. Stepper motors normally have 200 steps per rev, the drives contribute 10 microsteps so if you fastened this up directly, you only have 2000 steps per inch, so your accuracy can only be 1/2 a thou - and even that cannot be guaranteed, becasue you shouod not rely on microsteps for accuracy.
3. My steppers are 60,000 per inch, and I can get 40 ins per minute so I cannot see that speed is going to be a factor, so I would seriously think of gearing that axis down, so you can use a smaller motor, and gain accuracy.

I appreciate that you may be using servo motors - but the arguments are the same.

467

General Mach Discussion / Re: Why did this bad cut happen??

« on: June 30, 2008, 03:52:28 AM »

But then where did you resume from

Yes, the fact that you were cutting a circle may have something to do with it. You cannot just resume in the middle of a cut, having just hit Stop, becasue there is no telling what information has been lost.

You need to rewind you GCode at least a line, so that Mach 3 knows where it was at the end of the last line, and then processes the line again to recut it. If, unfortunately this means moving the cutter back manually to where it was at the end of the line, I am afraid that is what you have to do.

I usually lift the cutter with the jogg, then use the MDI line to get the cutter back to the co-ordinates it was at at the end of the last line, then use the MDI line to drop the cutter back down to it's correct depth. Wind the GCode back, make sure the correct line number appears in the window, then run from here and Cycle Start.

468

General Mach Discussion / Re: Stepper motor size

« on: June 29, 2008, 02:16:05 PM »

If you are in UK then try ArcEuroTrade for their selection of motors.

As I say I use the 220Ncm motors  - and I think there is an offer on them at the moment - my last ones were only £21. They are certainly powerful when wired in series.

Gecko drives you can get direct from the US - but watch dear Alistair Darlings import tax. If you have a friend in the states can post you one, that would be a lot cheaper - my worked out about £70.

469

General Mach Discussion / Re: Progressive Move Error with X and Y

« on: June 29, 2008, 02:04:08 PM »

If you have a progressive error, your steps per unit will probably wrong.

You do not say what machine you are using, or how you have set it up.
We will assume it is up and working.
You now must calibrate it accurately, and then first thing to do is set the steps per unit - see Config/Motor tuning, bottom left hand corner. Whatever your units are, inches or millimeters, you must calculate how many steps your motors need to move your axis I inch (or mm)
This is a round figure. My Gecko drives have 10 microsteps, my motors requie 200 steps per rev, I have a 3 to 1 step down gear to my leadscrew, and my leadscrew turns 10 times per inch. My steps per unit is therefore 10 x 200 x 3 x 10 = 60,000 steps per inch.

Art included a system for the machine to calculate this, but it involved measuring, so it is flawed, since you cannot measure accurately. It is alright to check your figure with this and see that you are not out by some rediculous amount, but the steps per unit is the calculated figure, not the measured one.

You can then run your machine to 1 inch, 2 inches, 3 inches - in fact as far as you can measure. I am not saying you will get a precisely accurate 1 inch measurement - it might be 0.998 or 1.001 - but over the rest of the measurements the accuracy will stay within these limits, because the errors on the system are not repeatable.

Always remember when taking measurements to move the table right, stop, zero everything, then carry on moving right. Or the other way, move left, stop, zero everything, then start measuring. This will get rid of backlash.

Once you have you steps per unit set, then you can configure backlash.

470

General Mach Discussion / Re: New 6 Axis dual closed loop Motion board "CNC Brain""

« on: June 29, 2008, 01:45:12 PM »

Anybody got much idea of the cost - there are no prices on his website.