Messages

561

Feature Requests / Re: Rotational offset on Z plane

« on: December 02, 2010, 11:26:13 AM »

I've seen a couple of past posts discussing it, so he probably already knows.

562

Feature Requests / Re: Rotational offset on Z plane

« on: December 02, 2010, 09:38:00 AM »

Yes, I can, but I'm told that R has some accuracy issues at certain angles.

563

Feature Requests / Re: Rotational offset on Z plane

« on: December 01, 2010, 09:07:17 PM »

I've got it working great.  The only problem is that Mach doesn't play well with IJ arcs and circles after a G68.  I found a post that said that R mode arcs work fine.  Just don't know if it's worth all that just to rotate the part.  Most, if not all of my part files have IJ arcs.

564

Feature Requests / Re: Rotational offset on Z plane

« on: December 01, 2010, 03:11:09 PM »

Exactly what I was looking for.  Thank very much.

Is there a way to get the X an Y bounds of a part file so you could rotate on the center of the part?

565

Feature Requests / Re: Rotational offset on Z plane

« on: December 01, 2010, 01:20:46 PM »

Now that I think of it, I'm not sure there is even a way to read a file line by line in VB Script.  Is there a way?

EDIT:  Looks like you can use regular VB Script in Mach.  Don;t know why, but I was thinking mach used it's own limited subset of the language. 

566

Feature Requests / Rotational offset on Z plane

« on: December 01, 2010, 01:18:57 PM »

I've always thought that it would be handy to have a button on screen that would rotate the part in Mach.  That way if it doesn't fit in the space intended on the sheet it could be rotated on the shop floor to match the material without generating a new g-code file.  Is this possible?  I know you can do work offsets, but I'm not sure about setting offsets that would effectively rotate the part on the Z plane.  A quick test shows that simply swapping x of y and y for x in the code effectively rotates the part 90 degrees, so one not so elegant solution would be to go through the loaded g-code file, swap it's contents over to a teach file swapping x or y and y for x, then loading the teach file.

Offsets would be so much cooler.

567

General Mach Discussion / Re: macropump does not work

« on: December 01, 2010, 09:59:42 AM »

I've found that I have to enable the macro pump twice to get it to stick.  First time I enable it, exit Mach then restart, I find that the macro pump in general config is still disabled.  If I enable it again, exit and restart, it stays enabled and the macro pump works.

568

General Mach Discussion / Re: PLC With Analog Input

« on: November 30, 2010, 03:41:30 PM »

I wouldn't need floating point math to compare two voltages?  The voltage readings should be doubles.  Not sue how many decimal places there would be but it won't be an integer.  When I compare, am I actually comparing the numbers or an I comparing the hex equivalent of the number or the 16 bit word sitting in the analog input register? 

569

General Mach Discussion / Re: PLC With Analog Input

« on: November 29, 2010, 02:39:58 PM »

I agree completely but look at it this way.  Most, if not all of these low cost THC's use a pic or some other programmable microcontroller.  It their simplest form, they read an analog voltage, compare it to a set analog voltage and set the Mach THC UP/DN pin accordingly.  What makes a good THC is the programmed logic, and I agree, there is a lot to consider.  I have to believe that the programming capacity of a good PLC at least equal that of a micrcontroller, which means that the same even more complex logic could be done with a PLC.

The other end of this is the voltage divider.  A stable analog voltage to the THC is pretty important.  This is a bigger deal for me than programming the PLC.  My electronics background is minimal.   

570

General Mach Discussion / Re: PLC With Analog Input

« on: November 29, 2010, 01:51:13 PM »

You should be able to control the THC with just the PLC. Yiou would need some communication between MACH and the THC so it would know when initial height has been set.

Mach has an input for ArcOK.  You would just need to provide a signal on that pin so Mach knows that it's OK to start movement.  If ArcOK is lost, then Mach automatically pauses the program until ArcOK is restored.

Initial height can be set with just a timer, go down until the switch contact opens, raise for some amount of time, stop motion and tell MACH that the torch is in position. Another timer can be used to raise the torch when the THC run is turned off by MACH.

I hadn't thought of just using a standard DC motor.  That would work as long as the PLC can reverse the motor direction.  A better solution might be to just use a simple DC motor control that way you can control speed...Unless the PLC can send a DC pulse similar to a motor speed control.

The PLC will work for a THC with just about any type of motor - you could use a reversible AC motor, or a DC motor - you would have to use relays to control either

Ah yes...I've done that before.  Used a DPDT relay to reverse a DC motor.  If you fed the relay through a speed control and used the PLC to switch the relay, that should work.  CNC control over Z feed rate wouldn't be needed but a way to adjust the speed would be.

I would think that it would be easier to treat the THC as a separate component and not try to control the height with MACH because the  height doesn't have a good number as it is relative to what is happening between the torch and the plate.

My reasoning there was that the PLC would handle all of the logic.  ArcOK is just a low current voltage or a relay contact coming from the Plasma unit.  The PLC can monitor that and apply 5V to Mach's ArcOK input.  Mach Also has inputs for THC UP and DOWN.  If I used a stepper and stepper driver connected to Mach, the PLC could just control Mach through the UP/DOWN inputs, although that may be slower than a DC motor.  The other advantage to letting Mach control motion is that I would retain the ability to attach a router, drill, engraver, etc. to the same machine, all of which do require Mach control of the Z axis. 

This is how the Sound Logic THC works.  Not sure, but my guess is that Toms unit works the same way. It controls Mach through the THC UP/DOWN inputs.  The above idea would basically just replace the sound logic or CandCNC board with a PLC.  All that would be required is a PLC with analog input.  Not sure if this is possible, but instead of setting a PP pin high for torch UP/DN and ArcOK, just signal Mach through the serial interface without using any inputs or outputs.  If you can programatically control an input on the PLC, you should be able to signal Mach from software just as if a physical input were applied to the PLC.