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Z lift on extruder change

Posted by triplanedave 
Z lift on extruder change
November 24, 2015 01:03PM
Have a Kossel Mini with RAMPS 1.4 and Marlin; printing via Repetier host. I have successfully printed 2-color prints, but at the time the color change occurs (switch from E0 to E1) the printer Z lifts up about 5mm.

Here is the GCode at the time of the transition:

G1 X13.581 Y11.119 E12.71375
G1 X13.546 Y11.085 E12.71949
G1 F1800.000 E7.71949
G92 E0
G92 E0
G1 F1800.000 E-4.00000
G92 E0
G1 X-33.273 Y5.294 F7800.000
G1 E4.00000 F1800.000
G1 X-34.953 Y4.136 E4.24239 F540.000
G1 X-35.626 Y3.807 E4.33135
G1 X-36.822 Y3.450 E4.47958
G1 X-37.373 Y3.390 E4.54540

My guess is that it's a firmware setting that's forcing the hop - it happens slicing with either Slic3r or Cura. Here's a video of the print - up to and including the lift. [1drv.ms]

Suggestions on what to check/change/etc to prevent this?


Re: Z lift on extruder change
November 26, 2015 02:48AM
The gcode shows no z hop in any case. It also does not explain why extruder takes so long to switch so I guess you have somehow compiled in a temperature change and also the z hop.

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Re: Z lift on extruder change
November 26, 2015 11:23AM
I can reproduce it manually by doing a tool change (T1) and then a move operation.

If I use Repetier host, and type in the following, it'll do the lift:

M104 T0 S195
M104 T1 S195
G92 E0 ; Reset extruder position
M109 T0 S195
M109 T1 S195
G0 F6000 X2.68 Y-2.96 Z10
G1 X0.16 Y-5.40

So, it's in firmware. And, so far, I've spent 2 days searching the code trying to find the issue. No luck.

I'm using a FSR branch of Marlin V1.0 firmware.
Re: Z lift on extruder change
October 31, 2018 03:42PM
Hey Trip, you ever get a fix for this. Currently I am using 2 extruders. When switching to what ever other extruder during printing I can see a 3mm or so z hop up n back down. When manually toggling extruders with my lap top software it will also perform this hop.
Re: Z lift on extruder change
April 09, 2019 08:37AM
Hey @Wilner, @triplanedave,

You guys may be looking for the TOOLCHANGE_ZRAISE setting, in Configuration_adv.h:

 * Universal tool change settings.
 * Applies to all types of extruders except where explicitly noted.
  // Z raise distance for tool-change, as needed for some extruders
  #define TOOLCHANGE_ZRAISE     2  // (mm)
// ...

In configuration_store.cpp this gets copied into toolchange_settings.z_raise which then gets used by some of the methods in tool_change.cpp.

I've tried using this setting because Cura seems really bad at swapping extruders. Without firmware retracts enabled Cura leaves the nozzle sitting on the current layer while it retracts, changes extruder, reheats and primes - resulting in ugly blobs on the surface of the print if the nozzle was positioned anywhere near the outer walls... which it usually is, of course.

Hope this helps.
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