Reprap Software starts print in midair?

Hi,

I just recently got my Mendel up and running, and wanted to try some smaller calibration objects than the 4cm cube, purely so I don't waste filament while I tune the thing. Unfortunately, I've found that apart from that one cube, everything else seems to start printing in midair. I dug through the files, and have found that it just seems to start the gcode at a strange Z coordinate- see the following extracts from two objects, one which works perfectly and one which does not.

I'm using reprap-mendel-20110207 host software.

40mm cube

;#!LAYER: 1/133
G92 E0 ;zero the extruded length
G92 E0 ;zero the extruded length
G92 E0 ;zero the extruded length
T1; select new extruder
M113; set extruder to use pot for PWM
G92 E0 ;zero the extruded length
T0; select new extruder
M113; set extruder to use pot for PWM
G1 F50.0; feed for start of next move
G1 Z0.1 ;z move

Companion cube

;#!LAYER: 1/50
G92 E0 ;zero the extruded length
G92 E0 ;zero the extruded length
G92 E0 ;zero the extruded length
T1; select new extruder
M113; set extruder to use pot for PWM
G92 E0 ;zero the extruded length
T0; select new extruder
M113; set extruder to use pot for PWM
G1 F50.0; feed for start of next move
G1 Z6.2 ;z move

Why would it generate gcode starting in midair? Is it expecting a raft or something? I've not been able to find anything relevant thus far.

I can't attach the STLs, but Thingiverse links are below.

[www.thingiverse.com] - 40mm cube
[www.thingiverse.com] - Companion cube

Edited 1 time(s). Last edit at 03/17/2011 07:56PM by aref_naa.

look in your alterations/start.gcode and make sure it's not in there, if it is you can remove it, and re-skeinforge.

otherwise look at the raft settings and bottom settings.

@Anthong: He is using the RepRap Host to generate gcode, NOT Skeinforge!

---

Bob Morrison
Wörth am Rhein, Germany
"Luke, use the source!"
BLOG - PHOTOS - Thingiverse

LOL, oh... then use skeinforge

hah - I moved to Skeinforge after struggling with reprap host, but that in itself is a steep learning curve!!

The UI on Skeinforge makes me cringe, which is why I never tried it- will give that a shot, though, thanks for the tip ^^

If you're not feeling ready to learn Skeinforge yet, consider giving repsnapper a try. It doesn't render everything perfectly, but it has a tendency to get the height correct even on STL fils which are floating.

You might want to open your STL in replicatorG and see if it's floating there. If so, you can reposition it and re-save it using that.

Wouldn't a build file be better if you set z to zero position? or is that done in the main gcode elsewhere?

G92 sets xyze axis to whatever absolute position you tell it.

does any code following what you have there change z?


change this line in the companion cube to

G1 Z6.2 ;z move

to

G1 Z0.1 ;z move

If i understand it correct your code is before your gcode file starts. and it is possible the first regular line of gcode is G92 Z0
which sets whatever z axis height you start at to zero. in the first example z starts at.1, in the second example z is set to 6.2 then i think the following code starts at current position as zero, then continues to assume that through the build. IMHO.

can you list more of the gcode file?

or zip up the entire output file so someone here can take a look at it?

I think G92 would be undone if a home code, G28, is sent for that axis.

G28 would override the settings.

Edited 1 time(s). Last edit at 03/22/2011 02:29AM by jamesdanielv.

hey, i got one of my printers to do the same. skein forge assumes that you are starting at 6.2mm high. make sure your stl file object is level at zero, and on platform. use replicator-g to center and put your object on platform, then run skein forge to saved stl file.

Edited 1 time(s). Last edit at 04/04/2011 12:19AM by jamesdanielv.