Use "Tn S1" to change tools without moving

[thinkyhead]

Reference: #4000

Background: In some cases, users need to change tools and have the coordinates updated, but not have the tool automatically move to realign itself to the same position.

This PR adds allows you to add S1 to the tool-change command, and it will switch tools without doing the automated move.

[ZetaPhoenix]

Why not use a G53 G91 move?

On Jun 11, 2016, at 3:38 PM, Scott Lahteine [email protected] wrote:

Reference: #4000

Background: In some cases, users need to change tools and have the coordinates updated, but not have the tool automatically move to realign itself to the same position.

This PR adds allows you to add S1 to the tool-change command, and it will switch tools without doing the automated move.

You can view, comment on, or merge this pull request online at:

#4013

Commit Summary

Use "Tn S1" to change tools without moving
File Changes

M Marlin/Marlin_main.cpp (6)
Patch Links:

https://github.com/MarlinFirmware/Marlin/pull/4013.patch
https://github.com/MarlinFirmware/Marlin/pull/4013.diff
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[thinkyhead]

@ZetaPhoenix I don't follow. What can G53 G91 do to change the behavior of the tool-change command so it doesn't move the carriage?

[ZetaPhoenix]

In theory, a G53 would switch to the machine coordinate system and then do an incremental move. A G54 command would be used to switch back to work coordinate system 1.

Does Marlin support multiple work coordinate systems?

I.E., G53: location on the limit switches
G54: print bed (M206 offset from G53)

On Jun 11, 2016, at 4:00 PM, Scott Lahteine [email protected] wrote:

@ZetaPhoenix I don't follow. What can G53 G91 do to change the behavior of the tool-change command so it doesn't move the carriage?

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[thinkyhead]

@ZetaPhoenix No, Marlin supports only a single coordinate space. This is adequate for your average printing-only RepRap machine. With recent changes, the "entire coordinate space" is altered by commands like G92 and M206, which apply offsets to the current position and the software endstops.

[ZetaPhoenix]

Scott,

I understand, I has been one of my nitpicks of Marlin that the original
coordinate system is lost whenever a G92 is used. M216 above was supposed
to be M206.

The question I have now with the pull request is when is the offset
applied? In true (CNC) Gcode the Tool offset is only applied when a G43 Hx
is called. On the next motion move (ie G0 X0), the offset would be
corrected.

You would see:

;code with tool 1;

Move to tool change position
G6 T2 (Change to tool 2)
G43 H2 G0 Xxx Yyyy Z10 (Move and apply new offset along the move so T2
arrives at xxx yyy 10mm above the part)

;T2 code;

On Sat, Jun 11, 2016 at 4:22 PM, Scott Lahteine [email protected]
wrote:

@ZetaPhoenix https://github.com/ZetaPhoenix No, Marlin supports only a
single coordinate space. This is adequate for your average printing-only
RepRap machine. With recent changes, the "entire coordinate space" is
altered by commands like G92 and M206, which apply offsets to the current
position and the software endstops.

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[thinkyhead]

Unfortunately we don't have the luxury of using the CNC methodology in this case. Slicer software, host software, and the RepRap community expect a tool-change command to "just do the right thing" all by itself for their given machine, and not to require any extra commands or modes. CNC machines, by contrast, may expect to be able to pick up tools from a rack, and will need more complex handling.