As someone who has printed almost 4 spools through his Rostock MAX, and the first to have a functional printer besides the prototypes (as far as i know!) i believe i can offer some input.
So i've noticed a few problems when trying to calibrate the bowden extruder. The real problem lies in finding the exact correct tension on the extruder bolts. If it is too tight, the filament gets squished to a very small diameter, and looses
strength in the bowden tube. This can cause the filament to BREAK OFF in the extruder gears during retraction.
On the other hand, if the extruder is too loose, it will just sit there and grind a flat spot in the filament.
The best way i've discovered to tune the tension on the extruder is to prepare a print, set your hotend to 230-240C (hotter is unnecessary) have your filament tension screws just snug enough to begin engagement with the filament.
You will also want to have plenty of light so that you can examine the knurled extruder gears.
Begin a print (does not matter what it is)
Slowly tighten each screw 1/4 to 1/2 a turn at a time (turn tension on both screws) untill you start to see extrusion out of the hot end. You are getting close.
Once the hot end begins to extrude, you will then want to clean off the filament shavings on the knurled extruder gears.
Once you clean them off, look to see if the filament is still being ground up. you will see evidence of this by small particles of plastic buildup in the knurled grooves. If this is the case, give both bolts another 1/4 to 1/2 turn, and clean
the gears.
I've had success cleaning the gears during a print by using a toothbrush to remove the plastic particles so i can re-examine the bolts for plastic grinding.
Ideally, your gears should not build up plastic in this area, plastic on the gears mean that the filament is not tight enough. The goal is to to get it tight enough, but NOT ANY TIGHTER. Otherwise, on retractions, the filament can easily
end up snapping or getting weak, or not extruding properly.
Now, the other problem i ran into after learning this tuning process, is that the geared assemblies inside the extruder were not tight enough, and it left the inner knurled gear assembly spinning, and not actually pushing on the filament.
im talking about the gears seen in the middle of this picture here:
[img]http://reprap.org/mediawiki/images/thumb/b/ba/ExtrudBottom_02.jpg/800px-ExtrudBottom_02.jpg[/img]
http://reprap.org/mediawiki/images/thum ... tom_02.jpg
this was MUCH harder to diagnose, because the filament will feed just dandy through the bowden tube, and then once it gets to the hot end it will not put force on the filament. I ended up taking my extruder back apart, and making
sure the internal two knurled roller assemblies were very tight so as to ensure ZERO slipping in this area. ---This had a monumental influence on print quality and consistency.
At this point, i now am getting fairly confident about leaving prints run. My longest successful print this far was a 20 HR print of an AR-15 Lower Receiver. Printed without serious issue in ABS (minor warping but thats another issue.)
I've attached a few photos of some recent prints to show you the part quality i am now getting with my Rostock MAX W/ 1.75 MM ABS Filament. @ .2MM Layers.
I Print on a GLASS Heated bed (Onyx) and i print on 3M PET TAPE (lulzbot) Prepped with an mild ABS/Acetone solution rubbed on it.
I slice all my parts with CURA 12.12A -- NOTE! Older versions of cura have problems with small or slow parts sometimes totally ruining prints. Use 12.12A or NEWER!
Another note, on your first time setup wizard, because the center of the bed is at 0,0 you must set your bed size to X 1MM Y1MM Z (Your Z Height) otherwise your prints will be messed up. also note, when adding files, you must manually set your SCALE to 1 (it will autoscale incorrectly because of the bed dimensions) It will however, slice just fine!
Another Note: I have a fan mounted to my rostock hot end. it helps a lot with small areas or small prints, etc.
Here are my settings:
Layer Height .2MM
Wall Thickness 1.0 MM
Bottom/Top Thickness 1 MM
Fill Density (Various)
Print Speed (20MM/sec - 75MM/Sec)
Printing Temp: 0 (Using Autotemp, set print temp to 0 then add this code in start [M109 S212 B255 F0.4] This is in my start code below)
Bed Temperature (At least 70 Degrees *C)
Filament Diameter 1.73
Packing Density .85
Nozzle Size .5MM
Line Count 1
Start Distance 1.5
Retraction:
Minimum Travel 5.0
Speed 68MM/Sec
Distance 11MM
Extra Length on Restart .6MM
Travel Speed 275MM/Sec
Max Z peed 275MM/Sec
Bottom Layer Speed 20MM/Sec
Minimal Layer time 13 Seconds
Cooling Fan Enabled
Initial Layer thickness .4MM
Duplicate Outlines <No>
Expert Settings:
Extra Wall Thickness 1.0MM
Minimum Feedrate 13MM/sec
Fan on layer 2
Fan Min Speed 15
Fan Max Speed 100
Raft:
Extra Margin 8MM
Base Material 100%
Interface material amount 100%
Support:
Material Amount 70%
Distance from object 1MM
Infil: Grid Hexagonal
Solid Infill Top <Yes>
Infil Overlap 38%
Bridge Speed 20%
Joris <no>
Retract on jumps only <yes>
Enable hop on Move <no> (only with prints with lots of tall, small separate areas)
My Start code:
Code: Select all
;Sliced {filename} at: {day} {date} {time}
;Basic settings: Layer height: {layer_height} Walls: {wall_thickness} Fill: {fill_density}
;Print time: {print_time}
;Filament used: {filament_amount}m {filament_weight}g
;Filament cost: {filament_cost}
G21 ;metric values
G90 ;absolute positioning
M106 100 ;Quickly Enable Fan, Then Turn it Down to Low Speed
M109 S212 B255 F0.4 ;AutoTemp Enabled
G28 X0 Y0 Z0 ;move X/Y/Z to min endstops
M106 16 ;Turn Fan to Lowest Moving Setting
;G92 X0 Y0 E0 ;reset software position to front/left/z=0.0
G1 Z15.0 F{max_z_speed} ;move the platform down 15mm
G92 E0 ;zero the extruded length
G1 F200 E7 ;extrude 3mm of feed stock
G92 E0 ;zero the extruded length again
G1 F{travel_speed}
My End Code
Code: Select all
;End GCode
M104 S200 ;extruder heater Low
M140 S60 ;heated bed heater Low (if you have it)
G91 ;relative positioning
G1 E-5 F4000 ;retract the filament a bit before lifting the nozzle, to release some of the pressure
G1 Z+2.5 E-12 X-20 Y-20 F{travel_speed} ;move Z up a bit and retract filament even more
G90 ;absolute positioning
G1 X0 Y0 Z352.0
G28
;M84 ;steppers off
This first item is something that is currently printing, its the reprap LCD case. it is shaping up very nice. i'll have to post some pictures of it here for reference of the quality you should be getting with a Rostock MAX
[img]http://imageshack.us/a/img824/9206/dscn0967d.jpg[/img]
[img]http://imageshack.us/a/img546/518/dscn0964f.jpg[/img]
[img]http://imageshack.us/a/img717/5295/dscn0962r.jpg[/img]
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