Messages

271

General Mach Discussion / Re: Cutter Compensation

« on: October 15, 2008, 03:49:21 AM »

I don't know a great deal about cutter compensation, but, as far as I understand it, when cutter compensation is applied, you must then have a "run in" move for the tool - i.e. when you apply G41 or G42, the tool does not move to the new cutting position, but uses the next move to get into the right position. I assume it might take more than one move if the appropriate axis does not move (although thinking about it, that is doubtful, since, just moving one axis will get you into the right position)

If you are saying that, after you stop the program, for whatever reason, then restart, it says in the tutorials or the manual, that Mach 3 may take two or three moves to regain position.

I have recently been cutting some printed circuit boards, and I was having trouble with the Z axis not lifting properly, which caused the cutter to foul and then snap off (it is only 0.6mm). Stopping the machine had to be quick, but the point is, when restarting I had no idea where the tool was in comparrison to the program, particularly if I had jogged to change the tool.

I examined the GCode, and ran back to the last G0 movement, i.e. a move where the cutter was moving from one place to the other, without cutting. This would mean the cutter was well above the work, and the tool would move to the next cutting position accurately. This applied from whatever position I was at, whatever height the tool was at and whatever compensation I had on.

If you then looked at the code, the next move was "tool down", and the next move was "cut".

So, move back to a G0, click "set next line" and "run from here" and click "cycle start". The initial G0 move allows the cutter to move to the next position, apply the compensation, take a breath, and then get back to work again.

Restarting the program will obviously "start again" and if you look at the top of the 1024 Milling profile, you will see a list of the GCodes that are applied, and see that things are put back to a single profile, so that Mach kmows where to start from. If you look on General Config, left hand column, you will see a similar list of "tasks" when M30 is encountered.

We all have to, from time to time, stop in the middle of a run, but the thing is, after each stop, you must say to yourself "has the machine enough information to carry on from where it left off". This is particularly important if you use sub-routines and offsets, where information might be carried over. If the machine hasn't the right information, then performance is unpredictable.




 

272

General Mach Discussion / Re: Continuing a job after an event stops it

« on: October 12, 2008, 04:54:37 AM »

I think Ray has just about covered it all.

It all depends whether you have stopped the machine on the emergency reset button, or on the feed stop button. On the emergency reset, there is a good chance you will have lost position so the main thing is - are your DRO's accurate - in other words is the reading still refering to the present position of the cutter. It doesn't matter if you have moved it by jogging etc, while you clear the fault, but it does matter if it slipped when the fault occured.

If it slipped then you must , as Ray said, set them up again, including the Z height.
On most of my mill work. I have it drill a hole at the 0,0 position, so I can move back to this if I want to.I have home switches as well, but find this an easy way to re-locate in relation to the program I am running. Set all the DRO's to zero and that is it done. Set the Z at the work height and away you go.

Whilst many of the instructions to Mach 3 will remain, as you have found it will not switch the spindle on again, or the coolant, these are on/off applications and not remebered.

You can "step through" your program on the screen, by using the down arrow on the GCode window,  without setting the machine going, and if you watch the tool path display, especially on the big display on Page 3, it will show the current cut as a white line. If you compare this with your workpiece, you should be able to work out where the program had got to.

You must be sure that Mach has all the information it needs to continue, and this is where you need to be reasonably familiar with GCode, because you have to look at the code, and think - if I were the machine, would I know what to do. This is not difficult - look at the code and if you see for example a G0 movement, you can reasonable expect that the cutter was moving from a to b, and that it would be up out of the way to do so. If the next move is G0 Z -0.5 say, then that is the cutter going down, and if the next move is G1 X*y*, then that is the next cutting move, so - rewind your program back to the G0 move (up arrow on the GCode window). Click on "set next line" and "run from here". Start your spindle (and coolant) and click on cycle start.

Where ever your cutter was (and you needn't have tried to get it back to where you think it was) it will move to the next position on the G0 move, then pick up the Z down move, and carry on with the G1 cut.

The important bit, as Ray said - are the DRO's accurate.






 

273

General Mach Discussion / Re: help Me

« on: October 11, 2008, 03:56:05 AM »

Rich - I got the same picture, and the program seems to repeat 4 or 5 times. The maximum cut is 25 mm, and the size is 130mm by 160 so it would appear to be wood (if that is english)

It must be a tool diaameter compensation query

Djjroo -

If you have your cutter tools entered in the tool table, with all the radius/diameters, them

G40 - Cancels compensation
G41 - Compensation left
G42 - Compensation right

Enter the code where you want the machine to apply compensation. The machine must be away from the job, and, after you have applied the compensation, the tool must move to the work, to allow compensation to be added.

274

General Mach Discussion / Re: VFD Forward/Reverse Relay Control in Mach3

« on: October 11, 2008, 03:26:26 AM »

The way I interpret your start and reverse functions is "start" on gives you a forward rotation, and "start" and "reverse" together gives you the reverse direction - I may be wrong, but this is fundamental to your wiring, and you must be certain.

Mach 3 puts out signals on seperate pins for forward and reverse.
I take it that you will be driving relays from these pins and the easiest way to me, is to drive the two relays via diodes. I do not know what pins are available on a smooth stepper, they have more outputs  and inputs than the 25 pin lead, but if I stick to the 25 pin output, someone will enlighten us ( probably Hood) when it comes to Smooth Stepper.

I take it that pins 2,3  4,5  and 6,7 are taken up with the axis drives. You therefore have 8,9, 1,14,16,and 17 left. (As I say with Smooth Stepper you may have more)

On the spindle page allocate M3 and M4 to outputs 1 and 2,  and uncheck disable relays. The PWM base should be 5, not 1000. It sounds daft, but the slower the PWM base is, the more control you have over the speed - since Mach has greater time to split the PWM base signals into a greater number of segments). Tick Use Spindle motor output and PWM control.

The PWM signal is allocated to the step pin of the spindle motor (on the Motor Outputs page) so put that out on whatever pin you want.
The outputs 1 and 2 are allocated to pins on the Output Signals page ( I have mine on 8 and 9, but you can put them on whatever you like.

If you then drive your "Start" relay say from pin x via a diode, and wire your "Reverse" relay from pin y with a diode across to pin y to the "Start" relay, then you will get the effect that pin x will fire up the start relay only, but pin y will fire up the start and the reverse relays.

I think everything is covered there, and it seems like you have 90% of it anyway. The bit you need seems to be in bold type.
If you find that your start and reverse "switches" are indeed seperate, then it seems alright as you were doing it - forgive the ramblings of an old man, especially so early on a Saturday morning.
 

275

General Mach Discussion / Re: High Voltage Unipolar Stepper Driver

« on: October 09, 2008, 03:05:21 PM »

It will need it

276

General Mach Discussion / Re: Alarm/buzzer when cutting is finished

« on: October 09, 2008, 02:58:58 PM »

Yes - Hood beat me to it.

I have looked at the cnc4pc site, and the C11, but I can't seem to access the technical files.

If you are using  a powered breakout board, you would be better to contact cnc4pc, and ask them how to power the buzzer you have from their board - given that you can get the signal to an output pin. I see there are two solid state relay so they might suggest using one of those (if you haven't already used both)

As far as mach 3 is concerned, on the standard 25 pin LPT1 socket, 12 outputs are provided. You normally use 6 of these for the three axis, which leaves you 6 to go at. These can be allocated on Ports and Pins, as you probably know.

From a Gcode point of view, it would be clearly simpler to use an unused Gcode command to activate the output pin - hence I said coolant -  there is M3 M4 which you probably also use, but as you say the mist output is available - you could use that. Allocate this to an unused pin and an M7 command with activate it. M9 would switch it off.

However, as Hood said, you can make up your own range of M*** commands in Mach 3 using Visual Basic script.  They are not difficult to write and there is a tutorial video to watch which will show you how. Hood has given you the relevant line (probably the only line in your script) and as he has put it - turn on output 4. Allocate output 4 in your Ports and Pins to an unused output pin - and wire to your buzzer as instructed.

Including M100 (say) in your programs at the end before the M30 would turn on the output.
Although the GCode program would then finish, the output would remain on until cancelled.
To cancel it, add a button to your screen labelled Alarm Cancel or similar and add a script to the button which reads "DeActivateSignal(Output4)". If you clicked the button, this would turn off the signal.

We have given you a bit of food for thought - and you thought it was going to be a simple job 

It is really, when you get down to it. The hardest bit will be fathoming out the cnc4pc board.


 

277

General Mach Discussion / Re: PCB Isolation Milling using LazyCam

« on: October 09, 2008, 02:07:58 PM »

You can download the PCB Gcode from the following link :

http://www.brusselsprout.org/PCB-Routing/

Unzip what you download into the ULP folder and away you go.

To call the program use run pcg-gocode.

Its as simple as that.

I have just finished a board yesterday - I had a bit of trouble getting the settings right. I can only seem to get a 0.6mm (24 thou) or a 0.8mm (32 thou) for my Dremel machine, and I am not sure how to utilise this in the PCB GCode. I got a good image with Eagle, and the last try with PCB gave me a 2500 line program for top cut and bottom cut. The top drill program I have siorted into a more logical sequence, and by putting bracketed comments in, I can keep track of where Mach is in relation to the program.

The program in pcb gcode ran well, but in my latest attempt surrounded all the "electrical islands" with a border, using another 7 or 800 lines of code - and took quite some time.

I snapped my milling bit on the next attempt ( I had removed the border with manual editing) - so it will have to wait until I get some more bits.

The fault lies with my machine, in that sometimes it doesn't retrat properly and hence plunges too deeply on the next cut, then snaps.
I need another Gecko for the Z axis

278

General Mach Discussion / Re: speeding up my 4th axis rotary table?

« on: October 09, 2008, 01:43:26 PM »

Lets just get the right angle on this ( couldn't resist that)

From what you are saying you have your step per degree set correctly and your velocity set at 2000 degrees per minute - so, if you do a G0 on your A axis - does the thing turn at 5.5 revs per minute - or 11 seconds per rev (approx)

If it does then Mach is working correctly and the problem obviously lies in your program.

When using two axis (or more) at once, Mach moves the slowest axis at its fastest speed, all other axis are slowed to start and stop at the same time. I don't know whether this could affect it.

I see you have said that your program is limiting the axis to 6 - the program says inches per  minutes - and the machine is using the 6 and converting it to degrees per minute. You might be better to alter the A axis to linear motion, and alter your steps per to the correct number to move the cylinder round one inch ( and this will clearly depend on the diameter of the cylinder). If it is something you do a lot of, then it is worth caculating it.

If it is a one off job, then keep on rotary but use your speed in inches multiplied by 33.3/D ( to convert to speed by degrees) to get the correct speed. Check the maths, I think it is right, I am a bit off song tonight.

279

General Mach Discussion / Re: High Voltage Unipolar Stepper Driver

« on: October 09, 2008, 01:00:30 PM »

Going to 160 volts is way over the top. Steppers motors start and stop each step, and there are (usually) 200 steps per revolution. To get better performance out of them it is normal to use about 5 times the rated voltage - which "encourages" them to accelerate faster, without burning them out.

I misread your first post, and you do not say what voltage the 0.83 amps is applicable to - there must be one.

Try testing across one of your coils and see what resistance the coil is. This will give you some idea. E = IR and all that. I would use about 5 times the rated voltage - any more and you then stand the risk of burning out the motor - not when it is moving - but when it is stood, because unless you build into the circuit some sort of current limiter, since steppers still have current going through their coils when stood, this is when melt down will occur. At 160 volts I would have thought that to be fairly soon.

280

General Mach Discussion / Re: Alarm/buzzer when cutting is finished

« on: October 09, 2008, 12:51:09 PM »

If you drive the alarm from a relay or a darlington array this is quite easy.

I don't know what outputs you already use from mach 3 - but, for instance, do you use the coolant.

If not that is one signal that is already programmed in Gcode you could use. Include an M7 or M8 at the end of the code, and switch the appropriate output on  - which triggers your relay. The same applies to any of the readily available out puts, which can be quickly programmed in Ports and Pins.