Messages

321

General Mach Discussion / Re: Home and/or limit switch

« on: September 12, 2008, 03:59:57 AM »

You have obviously been giving it a lot of thought and your last post was one where the light had switched on.

I'll dim it down (a bit) but it might help you even more.

The limit and home switches on Mach3 can all be daisy chained together and used through one input. Use them normally closed as you were going to do, but wire from the pin input through the first switch, then the second, third and so on and then to the supply. In this case ANY switch opening triggers a high input to the pin (i.e. the 0v wire is interrupted and the pull up resistor on the input takes the pin to 5v. (If you are going through a BOB, this might be the other way round).

Does this matter that all are on one wire!!
No - all limits and home switches are shown as using the same pin in your Config/Ports and Pins, and Mach 3 sorts out which one it needs at the time. Limit switches clearly don't matter - a limit is a limit, and should be obvious from the position of the table. The home switches are normally limit switches, BUT, when homing, Mach 3 changes the configuration  to suit homing. It knows which axis is homing, and when the signal is received, applies it to that axis.

Thus all your inputs are on one wire, meaning you have four other inputs. I know you said you had a spare port, but why use it if you don't have to - it is just something else to fiddle with. You will need other inputs for spindle control etc.

I think Hood said that the position of your home switches does not matter, my apologies if it was someone else.

The idea of Home switches is not for your benefit, it is for the machines benefit, so the machine knows where it is. It keeps track of all movement in "Machine Co-ordinates". When you home the axis, each axis moves to the switch in turn and zeros the machine code DRO (if you have auto zero turned on). Machine Co-ordinates are displayed when the machine code button light is lit.

Machine Code is of no use for work. The zero position could be anywhere and certainly not where your program starts. For this you need a convenient position on your table, many have a workpiece holder, or similar jig so the work is always in the same place. Milling programs normally have 0,0 on the bottom left of the table (but not always) and Z0 is with the cutter resting on the work.

If (in machine co-ordinates) you jog to this start location, when you get there, note the DRO's. Switch to "Program Co-ordinates" (Press the Machine Co-ords button and the light will go out). Zero the Program Co-ordinates DRO's (These will set to zero, Machine Co-ordinates will not, except when homing).

Your machine is now in a position to start work.
If you noted your Machine Co-ordinates, then this is the offset for that particular start point (or for that particular program), and if you check the Config/Fixtures table, you will find the co-ordinates have been entered in the G54 position (G54 being the default offset if no other is selected).

There are about 255 other offset slots - G55 G56 G57 G58 and G59P7 through to G59P255 or something. You can enter offsets into the table directly, or, if you select the offset first, when you zero the Program Co-ordinates it will be entered automatically. If you include that offset in your program, then the machine will automatically go to the correct position for that program. So all you do is home your machine and run the program.

A bit of a faf if you are doing a one off, but if you are doing a lot, or it is something you do a few of at different times, you can see the benefit. The only thing you must not do after you have entered an offset is zero the program co-ordinates (unless you mean to do so) because this changes the co-ordinates of the selected offset - and you will have to set up again (unless you have it written down).

Jim.

322

General Mach Discussion / Re: Need Help In Denver

« on: September 12, 2008, 03:16:43 AM »

Wish I was in Denver - some nice railways in Colarado.

323

General Mach Discussion / Re: CNC PEOPLE LOCATIONS

« on: September 12, 2008, 03:13:40 AM »

I thought half the people in Wisconsin were Scots anyway.

324

General Mach Discussion / Re: Invisible Mach-3

« on: September 10, 2008, 11:34:09 PM »

Yes - Easy peasey - BUT

someone will have to write the GCode.

There are several CAD/CAM programs on the market which will write these for you - I do not use them so I cannot advise.
There was a similar question on here a couple of weeks back if you look - he was engraving wooden signs, and had quite a collection. He might advise you what he used. I can't remember the name.

As far as an operator goes, a monkey could do it after that. Fit in the workpiece, select a title and press the cycle start button, in fact you can write an even better program which would just list the lines, and you just click on the one you want and the machine would cut it.

Mach 3 has an interface with Visual Basic - a computer language, and you can write "scripts" in that to "customiise" your machine.

325

General Mach Discussion / Re: homing accuracy

« on: September 10, 2008, 11:22:10 PM »

BEN

You still do not seem to be getting anywhere.

I think your problem is that you have no idea what the problem is - and this makes it difficult to find a solution.
1 - The problem appears intermittent.
2 - As far as you can see, where is the problem - is it always on one axis, or does this affect both ??
3 - Your set up appears compact so it seems unlikely that any stray signals are getting in there.
4 - From what you describe, the problem is the axis ( or both) suddenly seem to do their own thing.

Try and narrow down the problem - BUT - if you have a spare drive I would change it - if this means just switching the four wires and reconfiguring ports and pins, all well and good.

The problem when you are starting up is different, and Hood has already mentioned this. You must, when starting, take some action to "zero" the machine - so it knows where it is. This does not mean that physically it is in the same position as when you left it, it means that all the counters and DRO's have reset on start-up to the correct settings. I am not talking about configuration - since this does stay set. I am thinking of offsets and such, which can easily become altered.

You should really "home" your machine when starting. You do not need switches on it, but you need to put the machine at the same position everytime, on start-up. If you can attach a couple of blocks on the bed, so you can jog the tool holder up to these blocks (slowly) until the motors miss, and then stop, you can then "RefAll Home" or if you are using the lathe screens, "Set Home x" and "Set Home z". This position can be anywhere on the lathe bed, and might be better at the tailstock end, so they do not get in the way of normal operations.

If you check the DRO's, the Machine Co-ordinates should now be 0,0. ( The machine co-ordinates button should be lit  - or on the lathe screens - selected) The machine always keeps track of it's position in  machine co-ordinates

I must assume that your work is always in exactly the same position - and your tools fit in the toolpost in exactly the same position. If so, then jog to your position  0,0 on your program. This takes a bit of doing on a lathe, particularly finding the lathe centre for the X axis. Press the machine co-ordinates button and the light will go out. The machine is now displaying "program co-ordinates" (Or on the lathe screens these are selectable on their own).

Type in the MDI line G54 ( The default offset ) and zero both DRO's

You will see the display got to zero, but if you have a quick look back at the machine co-ordinates, they will not have changed. This is the "offset" for your program. If you look in the  Config/Fixtures you will see that G54 contains these figures. The other offsets should all be zero - if they are not, then clear them all.

Copy the figures from G54 to say G55, or any of the other slots. G54 is prone to change if you are not careful (indeed they all are) so do not zero the program co-ordinates again, or it will change the offset.

You can either add the G55 offset to your program, or type it in manually when you start the day or indeed, at any time after you have homed your machine. It is more professional if you add it to your program. Make a note of it somewhere, because, providing the stop blocks stay in the same place, that is always the offset for that program.

And This is Why.
At the beginning of the day, run your table up to the blocks, and zero the "Machine Co-ordinates" That is the job done - your machine knows exactly where it is.

If you have added the offset to the beginning of the program, there is nothing else to do, when you press cycle start, the offset is entered and the machine then moves to the correct position for that program. You must make sure, of course, that there is a path for the table, and tool to the start point, without hitting anything else.

If you have not added the offset to the program, type it in on the MDI line. The program co-ordinates will change to take account of this, and if you were to type in the MDI line G0X0Z0 then the machine would move to the 0,0 position of your program. As it is you can just jog roughly up to the start position, it doesn't matter exactly where, press the cycle start and the machine will go to the correct start position anyway.

Note: Once you have zeroed the "Program Co-ordinates" when setting up the offsets, you do not need to zero them again at all. You must not zero them while the program is running, or the offset table will alter.
On a lathe the x offset is usually always the same, so only need be fiddled with once. The Z offset might need altering for different program.


Thats a bit of a diatribe - but I hope it helps.

326

General Mach Discussion / Re: Trying to understand offsets

« on: September 10, 2008, 09:49:46 PM »

This has been known about for some time.

I suppose the problem is one of compromise.

The pattern is shown correctly at the start, because Mach runs through the full program, and then displays it, all from Machine Co-ordinates. The yellow line display of the cutter runs from program co-ordinates.

To have the display show all the offsets, all the time, would mean that the display would have to run from the Machine Co-ordinates, not the program co-ordinates. This means for those with home switches and such, the whole area of movement of the table would be shown, when all you are really interested in is the actual bit where the cutter is, and I can't really see a simple way of "focusing" on the bit you are interested in and leaving the rest out.

327

General Mach Discussion / Re: can not calibrate axis

« on: September 06, 2008, 03:57:18 AM »

My mother was Scottish - I might come home


Have we lost the thread of this post ?

328

General Mach Discussion / Re: Something looks different about the home page tonight

« on: September 06, 2008, 03:49:07 AM »

No rewards needed - but if anybody across the pond is coming to the UK for the  show, and can bring me a Gecko drive (for which I will gladly pay) that will be fine. Over here the price in dollars ends up as the price in pounds, by the time you've paid postage, import duty and any other tax this Government can think of.

So much for free trade.

Mind you, if the pound slips any further, it will be pound for dollar.

Not suprised those north of the border are seeking independance - and flying the flag.  Still, we can get all our european workers to rebuild Hadrians wall 

329

General Mach Discussion / Re: Trying to understand offsets

« on: September 06, 2008, 03:34:38 AM »

There is no bug.

Mach3 keeps track of its position in Machine Co-ordinates. These are only changable by homing. If homing switches are fitted, then the machine homes and stops and the machine co-ordinates go to zero. You cannot change these co-ordinates. (Yes, If your home switches are disabled, then pressing the Ref All Home button turns all three axis to 0 at any position - but you would normally use the switches)

It is doubtful that the home switches will be in a position where any useful work can be done, and certainly not in a position where the program was written from, so offsets are used. Each program should have the offset from the home position written in at the beginning of the program. In other words you jog your machine to the position where your program starts and then zero the program co-ordinates (displayed if you click the machine co-ordinates button and the led surround goes off). Program co-ordinates can be zeroed at any position.

So you now have you machine at the start point of your program. If you look at the program co-ordinates it will show 0,0. but if you look at the machine co-ordinates it will still show the position of the table as offset from the home position. If you have no offset selected then G54 is the default offset, and if you look in Config/Fixtures, you will see that g54 has these co-ordinates entered in automatically. If you transfer these co-ordinates, say to G55 (or any of the other 255 slots), then if you amend your Gcode program and include g55 at the begining, then the machine knows where to start, and if you were in a professional machine shop, you would home you machine and then when you run the program, the machine automatically moves to the correct position for the start of that program.

For us mere mortals, however, following the position in Machine Co-ordinates is confusing, because the figures refer to some obscure position that the machine knows, but we don't, so we follow the proceedings in program co-ordinates, because they also relate to the program we have written, and we can check it as we go along.

The toolpath window only displays Program Co-ordinates so where you are doing the same pattern at different offsets it seems to repeat over itself.

What you are doing is setting the machine up so that your Machine Co-ordinate position co-incides with your first program co-ordinate position (G54 is 0,0) so as far as the machine is concerned, that is it's home position. It ignores g54 since it is no offset.
It runs the program  from 0,0 and if you look at program and machine co-ordinates you will see they co-incide.
When you feed in g55, the 0,0 position for the program moves to machine co-ordinates 1,1. The program runs from 0.0 again, but it starts at machine position 1,1, and so on. The toolpath window just displays the program, not the machine co-ordinates.

I see in the program you have g54 and then put the comment "reset offsets". g54 does not reset the offsets, it is an offset in it's own right, it is just that you have set it to 0,0. and therefore it is using the machine co-ordinate position.

There is nothing wrong with what you are doing, providing you remember to RefAllHome at your 0,0 point. Indeed if you had some sort of switches you could set to home to this position it would be most convenient. Mine are lasers shining on detectors so I could possible do it, but with mechanical switches it is difficult.

But that it the explanation. If you think about it, if you home you table somewhere out of the way, and RefAllHome, (to zero your machine-co-ordinates) then jog to your starting position and then zero your program co-ordinates - check g54 - it might read 5,4 (for simplicity).
If you now alter g55 to read 6,5 and g56 to 7,6 you will get the same effect. Jog your table anywhere and set it running.

The machine will pick up G54 and run to the first start positiom, then g55 and run to the second start position and g56 and run to the third position.

Offsets are all calculated from the 0,0 machine co-ordinates 0,0 position

330

General Mach Discussion / Re: Need relay setup help

« on: September 06, 2008, 02:33:39 AM »

As Hood says, it is as simple as that.

Are you asking how to wire up the relay as well ?

I wired up four relays on my machine to turn on the motor and coolant (still to do the coolant, but the relays are there)

The easiest way is to drive the relays via a Darlington array, direct from your LPT1 port (or from your breakout board). A Darlington array is  a power amplifier, and all the circuitry is contained in a 16 or 18 pin chip, which contains 7 or 8 seperate circuits. The cost less that £1 in UK from Maplin.

The circuits can each sink 1/2 amp and can be wired in parrallel to increase that. They take in a GND wire from your computer and a positive supply to drive your relays (whatever voltage you need). They are simple and easy to use, and do not need any additional diodes, etc.