Sequential printing ignores heights when homing on complete, causes collision issues

[andyc]

I've just had an issue when sequential printing objects of different heights - the shorter object was completed last and on completion it homed the print head at its current z height and crashed straight into the taller object leaving a mark on the print and almost breaking the printer's fan shroud.

When sequential printing finishes it should raise the print head to the highest point before homing to avoid this kind of issue.

[S3D-Jake]

Hi Andy,

Which version of the software are you running currently?
If version 4.0.1, Can you please attach your factory file that shows this issue?

[andyc]

Yes we're running version 4.0.1

I've created a factory file that reliably reproduces the issue by placing the first part at the origin, in fact the preview clearly shows the nozzle embedded in the first part on completion

Obviously we've not actually been placing tall parts right at the origin, however the way the printer is laid out there is more clearance in front of the nozzle than behind (see https://i.ytimg.com/vi/S9eWP_NJIF0/maxresdefault.jpg) so we would order parts to print from front (Y 0) to back.

However this means once finished the head will travel back across all the parts (and it homes Y first before X) so if I didn't place the tallest print last there is a good chance of a collision.

Attached are the factory file and a screenshot showing the gcode preview.

[S3D-Jake]

Andy,

Thanks for your factory file. The sequence if you walk through the preview seems to only collide with the part when the ending script is executed. You can eliminate the collision by instead of homing X0 Y0 in the ending script, add a vertical move to the maximum Z then homing X and Y.

Thanks,

[andyc]

Thanks for the suggestion, however our printer's maximum Z height is 1800mm so sending the head all the way up and back down takes a very long time!

At any rate it seems like the kind of thing that Simplify3D should add to the generated gcode (or at least warned about in the Multi-Part Printing guide) as anyone not aware of the issue will not know to do that and could end up with a damaged printer.