Messages

431

General Mach Discussion / Re: Perfect circle--I wish

« on: July 12, 2008, 03:32:57 AM »

I am on my soapbox again - The steps per inch checkout pretty close. What does this mean

Either they are correct - to the number you have calculated , or they are wrong. Please yourself. Your steps per inch will be a simple round number e.g. mine is 60,000 - not 60023 or 59395. Claculate your steps per unit and put them in.

Motor - probably 200 steps, microsteps - depending on drive - 4,8,10 or 16. gearing down motor to leadscrew 1 (straight drive), 2,3, etc and finally leadscrew pitch - mine is 10 to 1 inch - multiply together and get a round number. Do not measure, jog up and down or anything else. The calculated number is your steps per unit and cannot be altered.

If you are to do "perfect" circles then you will need backlash compensation engaged. You may have none - lucky you - but there is some there, otherwise your machine would seize up. In describing a circle, all axis change direction once and probably twice - depending where on the circle you start, and if you have not compensated for backlash, however small, you will not get a "perfect" circle.

Check your machine over by making sure there is no obvious slop and then simply zero the DRO and type in the MDI line  GOX1 to get rid of backlash.Make sure backlash compensation is not on Set up a DTI or a pair of digital calipers - I use digital calipers - take a reading and zero them. In the MDI line type G0X2 then G0X1. The axis should move an inch and move back. Measure with the digital caliper again - this should be zero, but it will not be - and the figure shown is the backlash - that amount of the inch the axis did not move, whilst the gears and everything were swapping round to push the other way.
You can repeat it if you wish and take an average, but I normally put the backlash in the computer and turn it on and repeat what I have done, and see if I get to zero.

Now the backlash figure is one you can mess about with until you get it right. My lathe is cheap, and the backlash is quite large (I shall fit ball screws when the pocket and inclination decide) but Mach 3 deals with it very well and I get acceptable results. I must admit I have not done what Rich says and tried to machine a hole into which I press a bearing - I might try that with the milling head.

Perfection - Ah Well !!!

432

General Mach Discussion / Re: printer port vs controller card ?

« on: July 11, 2008, 06:40:12 AM »

If you have settled on the Gecko's - and they are first class - then all I have as a breakout board is a non-powered Routout CNC board, which gives me the pins and the 0v from the LPT1.

I use Gecko 201's. These are internally opto isolated, so you don't need opto isolation again. The only thing you will have to provide is a 5V power feed to run the low voltage side of the Gecko's. I did this with a small phone charger type power unit, and a 5 volt regulator.

It will also provide any 5 volt feed you might need for your switches or relays for the spindle drive, limit switches etc,

433

General Mach Discussion / Re: No stepper motor movement?

« on: July 10, 2008, 12:03:34 PM »

I better introduce myself - since Hood has mentioned it.

Jim PInder 01924 264385 I live in Wakefield, West Yorshire junction M1 and M62 - if you want to pop over , you are more than welcome.

For the information of the masses - I only set up my machine in imperial, becasue it was an imperial machine - i.e. the dials and lead screw were in inches. I actually use mm probably more that inches - but what the hell, they are only numbers !!!

You were asking about your home switches - well you are getting into a whole new ball game there.

434

General Mach Discussion / Re: printer port vs controller card ?

« on: July 10, 2008, 11:50:56 AM »

I find that LPY1 is more than adequate for my machine - although my requirements are relatively modest. I want to control spindle speed, which takes up two inputs (Ihave two spindles) and three outputs M3 M4 and my PWM. I want to control coolant, which takes up one more output, and I have three homing/positional switches. I might add a forth axis (rotary table)

My problem is that if I wanted anything else, the the LPT1 port cannot provide it.

I think therefore, if I was starting again from scratch, and had a modest budget, the the smooth stepper would be my choice a) for ease of connection - USB is the way ahead - and 2) it has more input and output capacity than I would think I would ever need - and 3)from what I understand it produces it's own stepper driver signals and therefore takes pressure off the computer, allowing it to do the computing - or allowing me to use a more modest computer - saving me some cash in the long term.

435

General Mach Discussion / Re: my DRO' s don't go to zero

« on: July 10, 2008, 11:38:54 AM »

Your machine displays two forms of DRO. One is Machine Co-ordinates the other is Program Co-ordinates.

Machine Co-ordinates are the machines own reference by which it regulates all it's movements. This is displayed when the machine co-ordinates button is pressed (red surround is lit). It can only be zeroed by the "RefAllHome" button. If you press this button, your machine should visit the three "home" switches and stop there, and zero all it's references. It now knows where it is.

It is unlikely that this position will be much good for general machining work and will certainly not be the place from which most of your GCode programs start - which on a mill is usually (although not always) at the bottom left hand corner of the workpiece, with the cutter resting on the top of the workpiece.

If you zero your machine co-ordinates then change your display to program co-ordinates, by pressing the machine co-ordinates button so the light goes out, you can zero this display (if not already at zero) by typing in zero at each one.If you then jog your machine to it's working position - say - where the program starts, and then note the display - this is the offset from your machine co-ordinate zero. If you now zero this DRO's again, the program will run from this new position. (but if you check machine co-ordinates, it still has these in it's memory)

If you now look at your offsets - in Config/Fixtures - you will see that G54 now has the offsets that you just noted entered into it.
G54 is the default offset. You also have g55 to g58 and g59p7 to g59p255 (I think) - anyway, plenty to go at.

If you are a professional machine shop, then, then first thing that happens in the morning is that the machines are zero'd - i.e. all are set "RefAllHome". The fixtures table is filled in with offsets for all the various programs, and so the program will start with say - G56,G0X0Y0. The machine will then pick out the offset for G56, and move to the new 0.0 position ready to start work.

You don't necesarily need to work with offsets - but if your are wiring up your home switches, I would think you will

436

General Mach Discussion / Re: Viz Basic Interpreter gone funny.

« on: July 09, 2008, 10:02:14 AM »

 Scott -

I don't have any files in Mach 3/Macro folder other than Mill, Plasma and Turn sub folders.  These just contain Vis Basic files that I have written (or other people). There are no basic.exe files or interpreters or anything.

The drivers are still working on the workshop lathe, in fact everything is fine, the machine is running well, apart from this inability to write, or edit, Vis Basic files. as I say - if I do them on this computer in the office everything is fine. I must have corrupted something - but I don't know what.

Jim.

437

General Mach Discussion / Re: X,Y,Z display 0.000 at start up. How to?

« on: July 09, 2008, 05:41:33 AM »

Kerry - That is a bit of a simplistic question.

Mach 3 keeps many values of DRO's in it's memory.

There are two you need to be concerned with - one is Machine Co-ordinates - the other is Program Co-ordinates.

Machine Co-ordinates  are kept by Mach3 so it knows where the machine is. Machine Co-ordinates can only be zeroed by clicking the "Ref All Home" button. If you have home switches fitted and activated the machine then moves to these switches, and when it touches them it stops and zeros the DRO. If you do not have home switches activated, then clicking the "Ref All Home" button will zero the DROs wherever the machine happens to be.

Machine Co-ordinates are displayed when the Machine Co-ordinates button is lit (red ring round). If you press the button, the led goes out and the DRO displays Program Co-ordinates.

It is unlikely that machine co-ordinates provide a suitable location from which to start a program, and therefore offsets are provided G54 to G59 to "relocate" the 0.0.0 position from that used by Machine Co-ordinates to that used by your program. You can set these up if you wish, and include them in the program -

e.g. Ref All Home then in the program G54, G0X0Y0 would ref you machine to its Machine Co-ordinates, then change to the G54 offset, then move the table to the new 0.0 This is the way the professional machine shops start the day.

You can ignore that and jog you machine to a suitable 0.0.0. position, then manually zero all the axis for the start of your program.
Be aware, however, that the machine always operates in Machine Co-ordinates so this a) does not alter the Machine Co-ordinates position and b) it changes the G54 offset in the fixtures table to compensate.

I assume all you are wanting to do is start your machine up - presumably with the table in the correct position and have the DRO's zero themselves - ready to run the program. This is not good practice, although I can understand it.

For the moment I would (assuming you have no home switches operative), jog to your start position if needed, then click "RefAllHome" which will zero the Machine Co-ordinates. If you look at Program Co-ordinates make sure they are all zero as well (if not zero them). Your machine is then all zero with no offsets. I would then run in machine co-ordinates. If you keep "Persistant DRO's" on, this position will not change and if you go back to 0.0.0 the machine will always return to the same psoition.

I hope this is clear - it is a bit to get your head round at first. There is a video tutorial about offsets and things which is quite good.

If there is anything else - come back.

438

General Mach Discussion / Viz Basic Interpreter gone funny.

« on: July 08, 2008, 06:05:33 AM »

I had a hiccup on my workshop lathe, whilst doing a Viz Basic macro, but the trouble is something has gone funny now.

Anything I write (macro wise) will not run, and the interpreter will not recognise the syntax, even if it is correct - e.g. a line with more than one & in.

If I write it on my "office" computer - and then transfer it across to the workshop, it runs fine.

Can anybody tell me where the Viz Basic exe file(s)  is/are  in Mach 3 so I can copy a decent file across, I can't find them

439

General Mach Discussion / Re: Connectivity Issues

« on: July 08, 2008, 05:59:23 AM »

Have you installed the Mach 3 drivers and then restarted your computer

440

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

« on: July 08, 2008, 04:09:13 AM »

Thank you for such a clear explanation of your steps per. Your calculations are spot on, and should therefore produce accurate results. Errors are non-repetative so you are looking for a single error that causes this.

I look at your steps per inch and I would point out that with such a screw (5 tpi) and only 1000 steps per inch, a loss of a single motor step will cause a thousanth error. Yes - the Geckos do 10 microsteps - but this is an artificially held position for the motor, and amounts to one tenth of 1.8 degrees - and cannot be relied upon to be accurate. I have a 10tpi leadscrew and a 3 to 1 reduction, and therefore have 6 steps to the inch (or 60 with the Geckos) which is much more accurate. It also allows much more tolerance when rounding up or down in tangent calculations.

Your print out for your driver seems very good - probably better than mine - so I don't see that as a problem.

If you are in touch with Brett, I will leave it there. I would also try the Geckos wired directly to your LPT1 port - mine are, since my breakout board is non-powered, and this will eliminate any error on the board. The only problem will be that the Geckos require a +5volts feed - since they are opto isolated as well.  If you have twin opto-isolation this might be where the steps are going.