Messages

251

General Mach Discussion / Re: Control the Z axis when a program is running.

« on: November 08, 2008, 04:40:00 AM »

What control are you wanting - height and on/off - or is the "target" undulating.

You can search the forum - this question has come up before - and, I think, been answered.

If you look in Config/Ports and Pins/Mill Options you will see a box refering to THC which I think is Torch Height Control. THis allows you (I think) to alter the height of the Z axis whilst "on the move".

I don't know for sure, becasue I don't use the feature.

252

General Mach Discussion / Re: I'm lost

« on: November 01, 2008, 05:58:54 AM »

Has this fault just occured since you installed a new Gecko driver ?? ( I have no explanation - but just need to understand the problem)

Was the machine working correctly before.

I had a problem with my miller, becasue the Z axis was sprung upwards, and my motor was not powerful enough to force it down against the spring. I reworked the spring and put in a more powerful motor - it's fine now, but I need a new driver.

The other thing that has been mentioned in this forum is that Geckos have optical isolation on the inputs, If your Bob board also has optical isolation, the first pulses of each move were lost, resulting in "creep" on the axis in one direction. This fault was retified by feeding the Gecko directly from the LPT1 output and avoiding the Bob on the drive pins.

253

General Mach Discussion / Re: Backlash Compensation question...

« on: November 01, 2008, 05:46:00 AM »

Lets just study what happens, because if you have backlash on your system, you have it, whether or not you have backlash compensation turned on.

Mach seems to do three things if backlash is turned on. The pulses go to the axis (which may or may not move, depending on the amount of backlash you have. Mach then seems to realise that you have reversed direction, and stops. It then applies the amount of backlash compensation you have asked for (at the speed you have set it at) and then carries on with the move

For the first x number of pulses, the axis will not move, becasue of backlash, then it will and your encoder will start to move - but surely will always be the x number of pulses behind Mach. If compensation is NOT turned on, then Mach will stop and the encoder will stop, still behind - but seeing Mach has finished the move, then obviously does not register it. If compensation is turned ON, both will stop (in theory together)  - but this time registers a fault.

I think the only explanation is that you have a little too much backlash compensation on - and so when backlash is applied the encoder gets in front of Mach 3. This clearly does not matter when moving, the encoder is happy to be in advance, but if Mach stops the move and the encoder is still in front - then it must register a fault.
I can't see any other explanation.

254

General Mach Discussion / Re: M-command speed and delays

« on: October 30, 2008, 06:54:00 AM »

I was speaking to Brian Barker about this at the UK Model Exhibition. I understand that the disproportionate delay on M3 has been fixed.

If you are wanting a faster response that the activate/deactivate, then are the step and dir controls any faster - and use the A axis as a driver for the laser - using a G0 command. The difficulty would be in the time "on" since this would have to be equated to the distance the A axis supposedly moved - but it seems this could be relatively easily calculated. If the "step" pin was used (to fire a retriggerable monostable) the "distance" travelled could be gradually reduced to give the minimum "fire" time - or indeed the monostable could be hardwired to give the time directly.

255

General Mach Discussion / Re: Connecting spindle to breakout board

« on: October 27, 2008, 12:55:26 PM »

If you are connecting up seperate electrical systems - which you are, then you only need one reference point - 0volts.

Let us go through the Inputs to your inverter first.

The inverter will require 3 inputs. Forward signal, Reverse signal and a speed voltage signal. Looking at it , your Denford may require a spindle on signal as well.

Mach 3 puts out two signals for M3 and M4 - spindle forward and spindle reverse. There is no spindle on signal. This will have to be generated from the M3 and M4 signals that Mach 3 provides.

As you are probably aware, Mach 3 can be configured to put out these signals on any wire, but if the cnc4pc has a predetermined wiring plan then follow theirs. Connect your PC to the BOB board, and configure Ports and Pins/Spindle Setup.
Untick "disable spindle relays" and assign M3 and M4 to an output - say 1 and 2.
Then go to Ports and Pins and assign Outputs 1 and 2 to a pin number on your output. If this is done for you on the Bob then make sure they are allocated to the right pins.

On you Bob board, you can now check the M3 and M4 output by typing in the command on the MDI line and checking the pins outputs on your Bob board. See if they change from +5 to 0v, or 0v to +5 when they are set.(The problem is that some Bob boards invert the outputs) Check now what your Inverter input requires - does it require an 5v+ signal, or a 0v signal to drive it. IF the wrong signal is being output, then go to Ports and Pins, Output signals, and tick Active Low, and this should change the output. Check it again.

Once you have the right output for the M3 (forward) and M4 (reverse) signals, then to generate a Spindle "on" signal you connect a diode between the M3 and "Spindle on" and another diode between M4 and "spindle on" and this will provide the spindle on signal, whether M3 or M4 is active. The direction of the diode depends on whether a negative or a positive signal is required - but you can't do any harm by connecting it the wrong way, it just won't work.

The Ov connection on your Bob should be connected to the 0v on the Inverter - which I feel will be the spindle common or the spindle on common.

Inverters, unfortunately are fickle beings, and on some, the higher voltages are not necessarily tied to Ov earth potential.

Inverters normally provide a Ov and 12v supply, which goes to a converter - which in my case converts the PWM output from Mach 3 to a 0 to 10v signal - my board is a Digispeed.

The "high" voltage side of a Digispeed is electrocally isolated from the "low" voltage (computer) side, and so you connect the 0 and 12v supply to the "high" side of the Digispeed - and it returns a 0 - 10v signal back to the inverter to control the speed.

I would ring up cnc4pc and ask if this is what they have done - I think it may be- in which case you can connect the 12 volt supply from your inverter - and the associated 0v supply - to the appropriate Bob board input and you will get back from the Bob a 0 - 10v motor control voltage.

This is the best I think we can do on this forum - because every Bob board is different - but I seem to remeber that this was the case when I studied their circuit diagrams. I feel, however, that you must ask the supplier.

By all means come back if you are having any more difficulty.

256

General Mach Discussion / Re: Flame Cutting

« on: October 26, 2008, 03:18:25 AM »

The flame cutting I have seen at my local profiler is a relatively simple job. His machine worked on paper diagrams, which the machine then followed. He has probably stepped up to CNC since the last time I was there.

Mach 3 can control the X and Y axis quite easily, whilst the Z axis will take care of the torch height.

There are plenty of otputs for ignition either an M3 (which is ispindle motor "on" - but you can use as a torch control) or you can adapt one of the other outputs quite simply.

257

General Mach Discussion / Re: Visual Mill Z Axis

« on: October 24, 2008, 08:32:32 AM »

I do not know how you have set up your machine before trying this program. What should the program do ??

If this is at the beginning of the program, then look at the G Code and try and trace the Z axis movement. I assume your program is written for the z axis to start at 0 or a plus value - say +10 (I assume this is mm). If you ignore this glitch, does the z axis then perform properly.

Two things to look at first. The z axis is plus going up and minus going down. Try this on jogging, and if the jog is correct then that is fine. If your z axis is indeed moving the wrong way. You can alter this by changing the dir pulse to active low (or active high if it is low) - see Ports and Pins/Motor Outputs - or you can reverse the direction of your motor by swapping the leads in either A with A+ or B with B+ coming out of your driver.

The other thing to look for is that you do not, inadvertantly, have an offset programmed into the machine.

If you do not have home switches fitted, or they are not switched on, then set the machine to the position where the program says 0,0,0 is. This, for a mill is normally (but not necessarily) at the bottom left hand corner of the table, with the cutter resting on the work.

Then press the "RefAllHome" button. Check the machine co-ordinates - they should all now be zero. Change to program co-ordinates and change all the DRO's to zero also. Check the offsets by looking at Config/Fixtures ad all the offsets should now be zero.

Move you z axis up to a safe position,  (you can take out the tool while you check) and run your program again. See if it now runs correctly. If it does, try it with the tool in.

If it still goes to -10 and back to 0, look at the GCode program and see if you can identify where it is doing it (or even better - why). It may be that you CAM program  starts with the cutter in a position of say +10 - which it calls 0 - but this should be made clear somewhere in the instructions.

258

General Mach Discussion / Re: feedrate & units per min are different

« on: October 24, 2008, 07:23:47 AM »

This is the problem with what I call "short" programming.

When writing my code, I always put in the complete line e.g. G0 X0 Y0, not just the co-ordinates I want to move to. Similar when I want a cutting move, G1 F4 X3 Y3. It makes it a lot easier to check the code when something like this happens, because you don't have to trace back to see what the machine is actually doing..

Unfortunately if you use a CAM program, you are stuck with what it gives you.

259

General Mach Discussion / Re: motor should stop exactly when limit/home interrupt

« on: October 19, 2008, 02:21:18 AM »

I don't know enough about Galil systems - but there are many on the forum that use them.

Search the forum for GALIL - and rename your post and include the word Galil - something like Need Help with GALIL 2123 and I am sure someone will reply.

260

General Mach Discussion / Re: Gross loss of position

« on: October 19, 2008, 02:03:08 AM »

What fires up the torch.

1. Has this ever worked correctly - i.e. are we looking for a fault that has developed, or one that is occuring from the start.
2. You say that Mach will describe the pattern correctly every time, unless the torch is firing up during the run.

It would seem to me that there are some spikes, or something in the supply lines that is badly affecting one (or both) of your drives to the X and Y axis, as the torch starts up - you have probably thought of that.

Are the power supplies for the torch and the motors completely seperate, and are they all correctly earthed.

Check the return path for plasma cutter starter circuit, particularly if it is a high voltage starter.

I would also check to see that the  ground connection from the computer or BoB IS NOT connected to the ground connection on the high voltage side of the driver cards.