Mendel90

mendel90Mendel90

The printer is a mendel90 from a kit from nophead. It is working nice and easy but the frame is somewhat flexible. So try not to move the printer as the base might bend and cause the bed to be unlevel. The printer is equipped with Melzi electronics and Marlin firmware. In the printer there is also Octoprint running on the adjacent raspberry pi. Octoprint can be reached at http://mendel90

The known settings at the moment are

  • print area, x=0-200, y=0-200, z=something similar. Eg. 0,0 is in the corner
  • Good temperatures are 65-70 for the bed and 170-185 for the hot end
  • With Printbite surface the temperatures seem to be around 100 for the bed and 172-180 for the hod end when printing PLA
  • hotend is a 0.4mm version as standard

There are no limit switches in the printer as there usually are not. Instead there are home switches. The printer needs to be homed before any movements for the printer to “calibrate” itself and thus prevent hitting walls. This is done automatically in the sliced gcode with default settings. One pain is the z-calibration as the home switch is all the way up and the Z=0 level is at the bed height. The home position is set in firmware and thus not really easy (almost “impossible) to adjust. There should not be need to adjust the Z but if the hot end is removed or other similar maintenance done it might affect the Z.

The firmare is somewhat standard as per nophead except the 0,0 is not bed center but in the corner.

Slicer

Cura with proper settings for slicing is available on tunkki5, the “olmari” desktop computer. It also works together with Octoprint.

Cura is known to be ok. Slic3r is also in use and Skeinforge has been used. The ease of use goes in the same order. When using any slicer note the needed calibration on z axis. In Cura it is done with start.gcode where the head is run to Z5 and then next line tells printer that it is now at Z(something else). In Slic3r there is z-adjustment in the settings.

Usage

Do not put any adhesives or other chemicals (pvac, hairspray, abs-juice) on the white PrintBite printbed. If cleaning is required use acetone, IPA or window cleaner to the bed. The first layer is the most critical. If it sticks the print will most probably stay fixed on the bed for the rest of the print.

Start Gcode

Some start gcode for the printer as of 2014-06-12 (note the 0.8mm calibration with G92)

G21
G90        ;absolute positioning
G28 ; home all axes
G92 E0 ; reset extruder
G1 Z1
G92 Z1.8
G1 Z0.3 ; move z to 0.3mm to avoid scraping bed
G1 X100 Y5 F4000 ; move half way along the front edge
G1 Z0.05 ; move nozzle close to bed
M140 S70.000000
M109 T0 S185.000000
G1 E5 ; extrude 5 mm of filament
G1 X10 F12000 ; move 50 mm towards the origin as fast as firmware permits
G1 Z1 ; lift nozzle to 1 mm ready to begin main sequence
G92 E0 ; reset extruder
;G1 Z15.0 F{travel_speed} ;move the platform down 15mm
;G92 E0                  ;zero the extruded length
;G1 F200 E3              ;extrude 3mm of feed stock
;G92 E0                  ;zero the extruded length again
G1 F{travel_speed}
;Put printing message on LCD screen
M117 Printing…