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Author Topic: THC 300 and Sheet Cam... Touch off question.  (Read 7146 times)

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Offline Shuey

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THC 300 and Sheet Cam... Touch off question.
« on: June 08, 2008, 10:15:21 PM »
Hey Guys,

New to the forum and new to SheetCAM.

Question:

I've have my table running for a little while now using a Hypertherm 1000 and everything is great except one thing... the torch is not touching off on each cut. Is there a way to get it to touch off and trigger the Z-Home switch at the start of each cut?

It seems to touch off the first cut, then attempt to touch off on the second and subsequent cuts, but doesn't quite get all the way down, then travel back up the switch travel (pierce height and cut height) amount before firing the torch.

As each piece is cut the amount the torch travels down seems to get less and less, does not trigger the Z-home switch, travels back up the amount of the switch travel (pierce height) then fires the torch... eventually, it fires the torch to high from the Job for it to pierce, then the THC has to adjust down to cut.

Hope some can give me some assitance.

Regards,
Marcus

Offline da21

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Re: THC 300 and Sheet Cam... Touch off question.
« Reply #1 on: June 09, 2008, 03:01:42 AM »
i'd check the calibration of your stepper / servo and backlash if any , if you move the axis say 1" how far does the axis actualy move
and is it repeatable every time , if your using steppers it could be loosing steps , so giving you this problem , you may in that case have the tuning too high .

so check for repeatability of axis movment and motor tuning
and any backlash etc
Dave   

Offline Shuey

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Re: THC 300 and Sheet Cam... Touch off question.
« Reply #2 on: June 09, 2008, 03:36:28 AM »
I have the axis set up perfectly. zero backlash ballscrew and its running through a 5:1 gear head... plenty of torque... good thnking though!

I have found the issue... I think... G28.1 Z3.0

I run my system in Metric Units just in case Z3.0 seemed strange.

I have manually adjusted some G-Code and set it to G28.1 Z0.00 and run the G-Code. It all seems to have worked.

So, how do I adjust the G28.1 setting?

Regards,
Marcus

Offline da21

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Re: THC 300 and Sheet Cam... Touch off question.
« Reply #3 on: June 09, 2008, 03:59:26 AM »
G28.1 is reference axis ,
G28.1  is set in mach3 under  Configure .. config referencing

Dave 

Offline Shuey

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Re: THC 300 and Sheet Cam... Touch off question.
« Reply #4 on: June 09, 2008, 04:42:22 AM »
THanks.

I have looked at Mach 3 Config drop down menu, and I don't have a Referencing option in my list.

As a side note, when I open the G-Code once generated by SheetCAM the g28.1 Z3.00 is already in there... eg.

N0080 (Process: Plasma,  D22_PARTS, Plasma, 0.7 mm kerf)
N0090 M06 T2  (Plasma, 0.7 mm kerf)
N0100 G00 Z30.0000
N0110 X1655.8700 Y371.2800
N0120 Z13.7500
N0130 G28.1 Z3.00
N0140 G92 Z0.0
N0150 G00 Z0.0000
N0160 G92 Z0.0
N0170 G00 X1655.8700 Y371.2800 Z13.7500

Must be something in SheetCAM to adjust it... your thoughts?

Regards,

Marcus

Offline da21

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Re: THC 300 and Sheet Cam... Touch off question.
« Reply #5 on: June 09, 2008, 04:59:23 AM »
take a look at the sheetcam  post file

under pendown macro
it appears by my understanding it multiplys x 3 ? , i may be wrong , as i dont use sheetcam often
sorry i cant be more specific

Dave

Offline Shuey

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Re: THC 300 and Sheet Cam... Touch off question.
« Reply #6 on: June 10, 2008, 08:16:57 AM »
Hmm...

I read up more on G28.1 z3.0 and it appears that the Z3.0 is to slow the decent of the axis down when it thinks it is getting close to the home switch. I thought it had some other effect.

I set up my milling machine about 18months ago and kinda had a average/good understanding of code back then. Since setting it up initially i've just been machining stuff up and forgotten setting up a machine correctly. I'll go back and do a refresher before asking silly questions.

Thanks for your input in any case.

Regards,

Shuey

Offline Shuey

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Re: THC 300 and Sheet Cam... Touch off question.
« Reply #7 on: August 11, 2008, 09:09:12 AM »
Hey Guys,
My plasma table is working great, except for one painfull issue... Seems as though Mach3 is ignoring the G28.1 command. I see it in the code as Mach reads/runs the code. I watch for the Z switch to be triggered in the Diagnostic screen, but sometimes the torch travels down and doesn't quite reach the torch switch before it stops, then travels back up the correct peirce height setting... then fires the torch (too far above the workpiece to pierce and cut initially).

I don't see the Z LED light up as I would when it does travel all the way to the switch... i could be wrong... but could it be that I have noise my system (I'm running a normally closed limit switch arrangement, through a Transistor relay setup... in an effort to remove noise from my limit switches) and the noise is causing a Z switch trigger???

This issue has me stumped!

Interested to hear the thoughts of any and all.

Cheers,

Shuey
Perth, Australia