Grasping WCS

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Bkamplain
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Grasping WCS

Post by Bkamplain » Sun Sep 04, 2016 9:07 pm

I'm having a hard time getting my head around setting up WCS. I have limit switches and use them to home the machine but i start getting lost after that. I would like to be able to set the front left corner as a starting point and type a command to send the machine there without having to manually do it with the arrow keys. Also want a repeatable zero on a specific project so I can run different bits on different files and avoid trying to wrestle the bit change in the middle of a cut.

I have read the wiki but does anyone have a link to a video tutorial of the WCS process? Not finding much on youtube. Maybe I am overthinking this and a visual of it happening should clear it up for me.


side note- is there a way to have the machine home for bit changes pre programmed from say carbide create? Otherwise the spindle only lifts slightly and it makes it difficult to change bits.

WillAdams
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Re: Grasping WCS

Post by WillAdams » Sun Sep 04, 2016 9:36 pm

http://www.shapeoko.com/wiki/index.php/ ... ow_is_this:
Simplest workflow is this:[edit]
First time:
Home the machine.
Jog to where you want your WCS 0, 0, 0 to be.
Say G10 L20 P1 X0 Y0 Z0.
GRBL calculates the offsets from machine origin and stores them in non-volatile memory (EEPROM).
Every other time:
Home the machine. Done.
c.f. http://www.shapeoko.com/forum/viewtopic ... 76&p=41406
Shapeoko 3XL #0006 w/ Carbide Compact Router w/0.125″ and ¼″ Carbide 3D precision collets

Picengraver
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Re: Grasping WCS

Post by Picengraver » Mon Sep 05, 2016 12:50 pm

I have my SO2 machine set up to home to the front left. Just change GRBL's setting from $23=0 to $23=3 to home to X=left/Y=front/Z=top.
John
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WillAdams
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Re: Grasping WCS

Post by WillAdams » Mon Sep 05, 2016 2:45 pm

There are good reasons and long-standing traditions for homing being in a safe direction.
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Bkamplain
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Re: Grasping WCS

Post by Bkamplain » Mon Sep 05, 2016 4:37 pm

I am okay with the default homing position. I just wish the machine would automatically return to home for a tool change rather than just lifting off the workpiece by the designated height. Depending on the size of the workpiece it makes it difficult to change bits...my solution I guess is to run different bits on different jobs. The issue with this is accurately returning to the same zero point. It seems setting up wcs is the answer to this?

Sorry, I know I'm a noob and this was probably discussed and solved many moons ago. Thanks for the help though.

WillAdams
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Re: Grasping WCS

Post by WillAdams » Mon Sep 05, 2016 8:10 pm

Behaviour at tool change is a function of CAM programming or Comm/Control app functionality.

You can achieve the behaviour you describe by editing the G-code to move so before each toolc change.
Shapeoko 3XL #0006 w/ Carbide Compact Router w/0.125″ and ¼″ Carbide 3D precision collets

cvoinescu
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Re: Grasping WCS

Post by cvoinescu » Tue Sep 06, 2016 12:49 pm

You can configure your CAM to emit G-code at the end of each job that takes the machine where you want it, or even to emit specific G-code for tool changes.

The best way to get to the same physical position, regardless of WCS and G92 offsets, is to use G53 (machine coordinates): for instance, G53 G0 Z-1 to lift Z to 1 mm below the top (lifting it to Z0 would activate the top Z limit switch), followed by, for example, G53 G0 X-210 Y-420 to bring the machine forward (this assumes metric mode, and traditional homing at the positive end of the X, Y and Z axes, that is, to the right, toward the back, and all the way up). The beauty of this is that G53 is not modal, so the machine remains in the same WCS and with the same offsets; the command on the same line as the G53 just ignores those temporarily to move the machine to an absolute position, you then change the tool, and the next command resumes using the current WCS to continue the job.
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Bkamplain
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Re: Grasping WCS

Post by Bkamplain » Thu Sep 08, 2016 6:26 pm

I will have to try this. Thank you.

fredfow3
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Re: Grasping WCS

Post by fredfow3 » Thu Sep 15, 2016 2:30 pm

Hey all,

Good information here. Where do G28 or G30 setups fit in? can they be used for manual tool change positioning?

Thanks,

Fred
Shapeoko 3 XL - Dewalt 611 Router
PreciseBits Collet Set
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WillAdams
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Re: Grasping WCS

Post by WillAdams » Thu Sep 15, 2016 2:38 pm

We have a bit on the wiki: http://www.shapeoko.com/wiki/index.php/G-Code
G28: Takes an argument of an X Y Z coordinate for the intermediate point that the tool tip will pass through on its way home to machine zero.... Usually used to park the machine.
That last links to an excellent discussion on this: http://www.shapeoko.com/forum/viewtopic ... 95&p=51581

G30 seems a variant which allows one to set a different position (in case one has different fixturing? Perhaps one could be used if the machine is to the left of center, the other if it's to the right?)
Shapeoko 3XL #0006 w/ Carbide Compact Router w/0.125″ and ¼″ Carbide 3D precision collets

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