Messages

301

General Mach Discussion / Re: No output from parallel port

« on: September 26, 2008, 12:40:48 PM »

No - you are confusing the question - is there any output from your parallel port socket. If your breakout board in defective, then you cannot test at the breaout board. What you need to do is disconnect your cable from the breakout board, and check the signals on the plug pins. See if there is any signal at these.

The easiest to check are the dir pins - which should change from 0v to 5v (or vica versa ) onchange of direction. There various output pins can be checked as well by putting out M3 M4 signals on the variou pins, and the input pins can be shorted to the 0v signal return lines - and will show up on the diagnostic page.

If you have signals on your plug, then you still have a fault on the breakout board.

302

General Mach Discussion / Re: Setup help much abliged!

« on: September 24, 2008, 07:50:07 AM »

As Hood said - change direction by using the active high/low facility on Config/Ports and Pins - dir pin.

If however, you have to set up your motors in a particular direction, butwith dir in the wrong active state for your drives, you can physically change the way the motors turn by reversing the wires to them - they are DC windings. Change either A with A+ OR B with B+ (but not both) and the motor will rotate the opposite way.

303

General Mach Discussion / Re: Turn Z part offset

« on: September 23, 2008, 06:13:18 AM »

As the last post said, it is all to do with offsets.

You do not mention a home position, and this is what you must establish first. You then home your lathe. Mach 3 then knows where it is and zero's the Machine Co-ordinates DRO's. Your home position should be established with switches (preferred) or a position to which you can return, time and time again, with absolute accuracy.

Using your selected method, create your tool table.

So you now have a home position, and the tool offset table. The tool offset table is an offset from an as yet unknown position of the lathe, and what remains to be done is  set that position.

If I want, therefore, to set an accurate offset, my X offset is 3.6267 to the lathe centre.  The Z offset varies as to how you write your program and where the Z position 0 is. It is usually, but not always, at the start face of the barstock.

If you were doing a large number of units, then I would use the HomeOff facility when homing, to zero the lathe at a position level with the face of the chuck. My offset would, therefore be how much the barstock stuck out of the chuck, or I would write my program so that it measured from the face of the chuck too, and there would not be an offset.

However you arrive at where to set the Z0 position, it depends on choice - your choice, and there are pro's and con's on either side.
Depending on the job it might vary. This is where the offset table comes in and you can enter the appropriate offset in the offset tables, using G55 to G58 and G59.7 to G59.255  - and use the offset for a particular program. Enter your x offset - usually to the centre of the lathe, then calculate your z offset from your home position.

Start up - home the table - and run the program. Provided you have accurately written the  tool changes, your machine will start up, and move to the correct position for that program and that tool.

It sounds a bit complicated but the rule is - the machine must always know where it is BEFORE you do anything.
1. Establsh a home position, either with switches (prefered) or a position to which you can return time and time again with accuracy.
2. Establish a 0,0 position from which all tools can be measured.
3. Calculate the correct offset for running the program - i.e. know the offsets from your "home" position to the 0.0 in your program

304

General Mach Discussion / Re: Problem with pp port ?

« on: September 23, 2008, 03:21:46 AM »

Mch controls spindle speed by two methods, one is step and direction - just like an axis.

The other is by Pulse Wave Modulation. In PWM, no direction information is given. The sole output is on the "Step" pin. This is in the form of a frequency output (which can be selected) of a 5 volt signal. This is then modulated (i.e. turned on and off) in proportion to the speed required. The result is a square wave signal which varies its ons and offs according to the speed. E.g. quarter speed - 25% on 75% off, half speed 50% on 50 % off. etc.

This resulting voltage can be read by a volt meter, but not very efficiently, and can be seen to vary as you increase the  speed of the spindle. To convert this into a voltage signal that can be read by an inverter, or control equipment, you need something like Digispeed, which converts the PWM signal into a varying voltage signal (0 - 10 volts) which controls your inverter.

Direction (on my machine) which has an Omron inverter is still controlled by M3 or M4 output. The outputs to these signals are on two seperate wires on the output set 1,14,16 or 17 (or actually I use pins 8,9 because I don't have fourth axis) with the PWM coming out on pin 17.

305

General Mach Discussion / Re: How to run Mach from a laptop

« on: September 20, 2008, 12:42:42 PM »

Jeff - I run Mach 3 from a laptop. I think the problem is the word - laptop.I am lucky, in that I got this laptop from my daughter, Jessica. She had bought it prior to going to Universirty, and it cost upwards of £1000 (plus £500 repair warranty) so it was not cheap. It is a full feature Toshiba.

The trouble with many laptops is that, to get the price down, the spec is cut, and many of the functions are shared. The memory is "borrowed" by whichever part of the machine needs it at the time, and the processors tend to be slower.

That being said, I think a laptop in the workshop is superb. It is compact, and at the end of the day you can close it up, so it is dust free. That being said, the screen just went on mine, so I have a spare thin screen attached to it.

By all means buy one and try it - by all means look at the spec. Put in an extra memory chip if possible. If it does not work, there is always Smmoth Stepper, which takes away from the computer a lot of the "donkey work" of running a CNC machine, and leaves the computer free for the real work.

306

General Mach Discussion / Re: Mach 3 runs on desktop, not laptop

« on: September 19, 2008, 05:43:14 AM »

You appear to say that you did have it running on the laptop, once.

If you have a printer - one with a 25 pin port - then (apart from saving it for posterity) check to see if the printer port still works. The trouble is with laptops is they do tend to share the memory about the various functions of the machine.

I run my system on a laptop, a full function Toshiba, but this appears to have no sharing whatsoever, and it works very well.

I would try to check the port - as Hood says, you can try it with a voltmeter - and you should detect the voltage changes, particularly on the step pins,(check the voltage between the step pins and the GND pins (18 - 25)) or try a printer on it. Another problem with laptops is that sometimes the output voltage is only 3.5 volts, not the full 5 volts, and this is not enough to drive some drivers.

307

General Mach Discussion / Re: Cutter comp, comps backwards

« on: September 17, 2008, 05:36:20 AM »

Search on the forum - Graham Waterworth gave a comprehensive explanation of tool cutter compensation no more than 1 month ago which explained which code to use depending on your direction and left or right compensation.

308

General Mach Discussion / Re: lpt problems

« on: September 17, 2008, 05:32:47 AM »

Pin 13 should be high when not connected to anything - Pin 11 was an inverted input so therefore may be low.

If you have to buy another card, you may consider then Smooth Stepper. This conncts to your USB input. It contains all the outputs for the axis, and also a large number of input and output lines for use with limit switches, rev counter etc.

It also has pulse generating in-built in the card, so the PC does not have to do it, meaning your PC can concentrate on the computing, leavng the Smooth Stepper to drive all the outputs.

I haven't got one myself (yet) but those who have them say the are excellent.

309

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

« on: September 17, 2008, 12:26:46 AM »

Kirsten -

To swing back onto the post, so to speak (although with that chimpanzee firing at me I am not so sure). I covered this  in an earlier reply.

If you have your homing switches fitted, and they are working, then to set your offsets up takes only a moment.

Home your machine. If you have set "Auto Zero" on Config/Homing Limits, then your machine should home, and all the DRO's should go to zero - when looking at Machine Co-ordinates (the machine co-ordinates button should be lit). You cannot zero machine co-ordinates any other way except by homing (now you have the switches set up and working).

If you press the Machine Co-ordinates button, the led will go out, and your DROs will now display Program Co-ordinates. This may or may not be the same display. If it is not displaying 0,0,0 like the Machine Co-ordinates, then zero them, using the buttons at the side of the display.

Type in your MDI line "G54". This is the default offset. Mach 3 (and all other machines) keep track of their position in Machine Co-ordinates, but to make the display more recognisable to we mere mortals, it adds an offset to the display so that we can associate it with the program we are using. G54 is the default offset, and should be selected at all times when not actually running a program.

Jog your machine to the start point or 0,0,0 of your program. The Machine Co-ordinates will change, and the Program Co-ordinates will follow, but when you get to the correct position, zero the Program Co-ordinates.

If you check the Machine Co-ordinates, you will see that they have not changed, and the difference between the two is the offset.
If you check in Config/Fixtures you will see that G54 has changed - and now reflects the offset.
You can do this with the other offsets G55 - G58, G59P7 to G59P255.

The idea is that you include the offset in your program, at the beginning, so that when you switch on, you "home" the machine - so it knows where it is. If you then run the program, the offset will be read in, and the machine will move to the correct position for that program. Each program might have it's own offset, or sevral programs might share the same offset, if they start at the same point - e.g. work is set in the same position each time.

DO NOT zero your  Program Co-ordinates while the program is running. It will automatically change the offsets. Only zero the Co-ordinates when setting up.

If you go to Config/General config - bottom right hand corner, you will see a box "Copy G54 from G59.253  on Startup"

If you want your machine to start in the same position on start up, then enter where you want the machine, and enter the offset in G59.253. This wil be copied into G54 and if you then go to 0,0,0 the machine will always move to the same place. If you are running a program, this does not matter, because once you run the program it will have it's own offset, which will over-ride G54.

Offsets do not accumulate, they are individual, and only one is in operation at one time. (However, Tool offsets then accumulate on machine offsets)

310

General Mach Discussion / Re: PLS HELP ME

« on: September 16, 2008, 11:48:20 PM »

Have you got a computer, and downloaded Mach 3 software. Have you bought a Mach 3 CD.

Mach 3  supports MaxNC machines. If you get Mach3 running on your computer, and then open up Config/Ports and Pins on the first page you will see that the right hand box has places for you to tick - Max NC is one of them.

Tick this, and then close down Mach 3 and open it again.

As far as I understand, if you do this, Mach 3 will be configured to drive Max NC machines - i.e. the Port and Pin numbers will be already allocated. You will need an interface between the computer and your machine.