Which Post And How to Configure

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cire
Posts: 4
Joined: Sat Jul 15, 2017 6:01 pm

Which Post And How to Configure

Post by cire »

Hello all,

Let me preface this with I am new to the CNC world and I've hit a brick wall with getting my machine to operate smoothly. I believe the issue resides within the post configuration, but hopefully you guys can point me in the right direction.

Issue #1

My floating head does not retract far enough to prevent it from dragging on the material. The torch head goes down until the switch is closed, then it retracts just enough for the switch to open and then proceeds to cut.

Question:


1) How or where do I configure an offset to allow my floating head torch to retract far enough to not drag on the material, then position itself for the pierce? I suspect this is done within the post processor, but that leads me to another question:
2) Which post processor do I use with my setup below? Are there any specific configurations required for my setup?

Issue #2

The MiniTHC test works great through the controller. The Z axis works fine through Mach3 jog mode. It goes up/down/torch on etc as intended. There aren't any errors noted. I assumed during the actual operation of the unit that the THC would take control and prevent dragging, regardless of the post processor offset, but that did not happen. The THC just let it drag. Once I fix issue #1 I believe I can run another test to gather more information as to why the MiniTHC did not react.

In short, everything appears to work other than the MiniTHC taking control or the floating head offset. The Z axis does move up/down during the cut, but only when moving to the next pierce. It's the initial pierce and during each cut is where I'm facing the dragging issues.

Setup:

DIY water table with floating head torch setup.
- BOB, drivers, NEMA23 steppers are all from Stepper Online. They all communicate through LPT card 1
- MiniTHC controller. This communicate through LPT card 2
- Software is Mach3 and Sheetcam
- Plasma is Hypertherm PM45XP

Any help is greatly appreciated!

Thanks,
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Les Newell
Site Admin
Posts: 3661
Joined: Thu May 11, 2006 8:12 pm

Post by Les Newell »

First of all, disable THC and use the 'Mach3 plasma' post processor. You will need to manually jog the torch down to the work and zero the Z axis. With this setup you aren't using any THC functionality. If this cuts successfully try enabling the THC. At this stage you still need to manually zero the Z axis at the top of the work but you should see the Z axis moving a little as it cuts. If it dives straight into the work the THC is not working correctly. In Mach3's diagnostics page check the THC up and down inputs are triggering. Make very sure up and down are the right way around. If they are you may have the wrong THC voltage set.

Once you have it cutting correctly measure your switch offset. Put a piece of metal on the table then place a sheet of paper on it. Jog the Z axis down until the touch-off switch operates. Now slowly jog up until the touch off-switch releases. Zero the Z axis and slowly jog up while gently pulling on the paper. Stop when the paper slides out. Make a note of the Z axis position. This is your switch offset. It may help to repeat this a couple of times and take an average.

In SheetCam select the 'Mach3 THC with scriber' post. After selecting the post click on the 'Edit post' button. Near the start of the file are a number of options. Most can be left as-is but you do need to set the switch offset. Use the value you worked out earlier. Note this must be in metric. If your value is in inches multiply it by 25.4. Hopefully now it should all work correctly including the auto touch-off.
cire
Posts: 4
Joined: Sat Jul 15, 2017 6:01 pm

Post by cire »

You are AWESOME, Les! Thank you!

Your directions helped me with every aspect and now everything works as it should. The issue with the THC was exactly what you thought, wrong THC voltage setting. The issue with the retracting head was also due to lack of offset within the post.

Thanks again!
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