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Retraction - Should it work? Does it work?


brictone

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Posted · Retraction - Should it work? Does it work?

I'm trying to use retraction and I can not seem to prevent strings from happening. I haven't been able to find concrete Cura settings for the Ultimaker 1.

This is what my settings are at.

layer height: 0.05 - 0.1

travel speed: 175-200

speed: 30-40

Temp: 220-225

retraction speed: 40

retraction distance: 4.5

I noticed the strings are less durable with retraction than without making it easier to clean up. I assumed they would be non-existent with retraction if it works.

Any advice? Are there better settings than what the defaults are set at in Cura?

 

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    Posted · Retraction - Should it work? Does it work?

    Make sure you are using a current firmware for the UM1, as that fixes things about retraction speeds. Then set your maximum e-speed to 35 (you can do this easily with the Ulticontroller if you have one, or via gcodes, if not). For actual Cura retraction settings, I recommend a retraction speed of 30 or maybe 35 mm/s.

    40 used to be the default, and because of a bug in the old firmware, it came out to be more like 20. If you have the new firmware, then that 40 setting is probably being limited by the max-e speed setting which might restrict it to 25 (which is a bit too slow, I find). On the other hand, if your max-e speed is actually allowing a 'real' 40 to happen, then that's probably too fast, and may cause skipping and or grinding, leading to bad results too.

     

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    Posted · Retraction - Should it work? Does it work?

    Everything above is the best advice. But here's also something to think about - temperature versus strings in pictures (which Daid mentions above):

    http://umforum.ultimaker.com/index.php?/topic/1872-some-calibration-photographs/

    I have the second shim robert mentions - the second link. The first one broke after a few hours of printing. The second one has lasted over a year.

    Also printing slower or thinner layers will help (you don't have to do both!). The slower you print the less pressure is in the head so that when it retracts (which takes time) there is less pressure to start with so less leaks out.

     

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    Posted · Retraction - Should it work? Does it work?

    Awesome, I'll be going through this list of advice and see what works best for me.

    Thanks!

     

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    Posted · Retraction - Should it work? Does it work?

    Everything above is the best advice. But here's also something to think about - temperature versus strings in pictures (which Daid mentions above):

    http://umforum.ultimaker.com/index.php?/topic/1872-some-calibration-photographs/

    I have the second shim robert mentions - the second link. The first one broke after a few hours of printing. The second one has lasted over a year.

    Also printing slower or thinner layers will help (you don't have to do both!). The slower you print the less pressure is in the head so that when it retracts (which takes time) there is less pressure to start with so less leaks out.

     

    The issue I found is that running at a low enough temperature to get absolutely no stringing also reduces the layer adhesion. To get the strongest parts, I have to run above 220 C. Is there something to be done about that? Maybe printing really slow?

     

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    Posted · Retraction - Should it work? Does it work?

    Alright so I made some small progress. very small. Here's what I changed.

     

    M203 E4000 in the start Gcode

    Retraction speed: 50 (I haven't noticed skipping or grinding but that thing whips back and forth pretty quick.)

    Temperature: 210

     

    I have a shim that came with the v2 extruder drive kit. The whole thing still seems to move a bit.

    I did mess with a retraction distance of 5.5 and it seemed worse.

     

    Other notes about my printer:

    I have purchased in the past the Knurled drive bolt v3, extruder drive upgrade, hot end upgrade v2 (which came with a little blue shim)

    Firmware 13.12

     

    Here are photosIMAG0054-1024x577.jpg

    IMAG0056-577x1024.jpg

    Any other ideas?

    I'm not exactly thrilled with the surface quality at 210 degrees either like aviphysics mentioned. 220 seems much nicer.

     

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    Posted · Retraction - Should it work? Does it work?

    It's impossible to retract at 50mm/s. The firmware is limited to 40,000 steps per second on any one axis, which comes out to about 48mm/s. So if you set retractions faster than that, you're the firmware will slow them down. There's also a good chance of getting motor stalling at very high speeds too, which can make a real mess of a print - if it fails to fully de-retract, or de-retracts a retraction that never happened.

    Is it even trying to retract when moving between the upper parts of those two pillars? Because it doesn't really look like it. What speed and layer height were you printing at? Was a minimum layer time set? It's possible that the plastic was staying molten and just getting dragged around, due to too little cooling time on small parts - but it's almost like there is no retraction.

    Are you using the most recent Cura?

    Is retraction turned on? What do you have as the retraction settings in 'expert settings'?

     

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    Posted · Retraction - Should it work? Does it work?

    It's impossible to retract at 50mm/s. The firmware is limited to 40,000 steps per second on any one axis, which comes out to about 48mm/s.

     

    I must not understand how a travel speed can run at 175mm/s if the steps are limited to 48mm/s in the firmware on any one axis. Is this just for the extruder? Does the M203 E4000 override that? is the 40,000 step limitation a different scale than the E4000?

     

    Is it even trying to retract when moving between the upper parts of those two pillars? Because it doesn't really look like it. What speed and layer height were you printing at? Was a minimum layer time set? It's possible that the plastic was staying molten and just getting dragged around, due to too little cooling time on small parts - but it's almost like there is no retraction.

     

    I walked away while it was in the upper section. sorry I just don't know if it was failing to retract at all.

    Infill speed 40mm/s

    Inner shell speed 30mm/s

    Outer shell speed 25mm/s

    Minimal layer time 7.5

    Layer height 0.05mm

     

    Are you using the most recent Cura?

    Is retraction turned on? What do you have as the retraction settings in 'expert settings'?

     

    I think I see what was happening. Since I made a small part to test it may not have met these minimums. Now that I'm printing a bigger part It's looking like a success.

    IMAG0057_1.jpg

    Here's the settings.

    Retraction

    Minimum Travel(mm): 2

    Enable combing On

    Minimal extrusion before rtracting: 0.04

    Zhop: 0

    Here is my Ini fiile

    I'm open to any suggestions anywhere else.

     

    
    

    [profile]

    layer_height = .05

    wall_thickness = 0.8

    retraction_enable = True

    solid_layer_thickness = .8

    fill_density = 10

    nozzle_size = 0.4

    print_speed = 70

    print_temperature = 220

    print_temperature2 = 0

    print_temperature3 = 0

    print_temperature4 = 0

    print_bed_temperature = 70

    support = Everywhere

    platform_adhesion = Brim

    support_dual_extrusion = Both

    wipe_tower = False

    wipe_tower_volume = 15

    ooze_shield = False

    filament_diameter = 2.85

    filament_diameter2 = 0

    filament_diameter3 = 0

    filament_diameter4 = 0

    filament_flow = 100

    retraction_speed = 50

    retraction_amount = 4.5

    retraction_dual_amount = 16.5

    retraction_min_travel = 2

    retraction_combing = True

    retraction_minimal_extrusion = 0.04

    retraction_hop = 0.0

    bottom_thickness = 0.0

    object_sink = 0.0

    overlap_dual = 0.15

    travel_speed = 175

    bottom_layer_speed = 25

    infill_speed = 40

    inset0_speed = 25

    insetx_speed = 30

    cool_min_layer_time = 7.5

    fan_enabled = True

    skirt_line_count = 1

    skirt_gap = 3.0

    skirt_minimal_length = 150.0

    fan_full_height = 2

    fan_speed = 100

    fan_speed_max = 100

    cool_min_feedrate = 7.5

    cool_head_lift = False

    solid_top = True

    solid_bottom = True

    fill_overlap = 15

    support_type = Grid

    support_angle = 40

    support_fill_rate = 0

    support_xy_distance = 0.7

    support_z_distance = 0.15

    spiralize = False

    brim_line_count = 10

    raft_margin = 5

    raft_line_spacing = 1.0

    raft_base_thickness = 0.3

    raft_base_linewidth = 0.7

    raft_interface_thickness = 0.2

    raft_interface_linewidth = 0.2

    fix_horrible_union_all_type_a = True

    fix_horrible_union_all_type_b = False

    fix_horrible_use_open_bits = False

    fix_horrible_extensive_stitching = False

    plugin_config = (lp1

    .

    object_center_x = -1

    object_center_y = -1

    [alterations]

    start.gcode =

    G21 ;metric values

    G90 ;absolute positioning

    M107 ;start with the fan off

    M203 E4000 ;change retraction limit

    M104 S{print_temperature}

    G28 X0 Y0 ;move X/Y to min endstops

    G28 Z0 ;move Z to min endstops

    ; if your prints start too high, try changing the Z0.0 below

    ; to Z1.0 - the number after the Z is the actual, physical

    ; height of the nozzle in mm. This can take some messing around

    ; with to get just right...

    G92 X0 Y0 Z0 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 E5 ;extrude 5mm of feed stock

    ;G1 F200 E3.5 ;reverse feed stock by 1.5mm

    ;G92 X-90 Y-100 Z0 E0

    M106

    ;G1 X60 Y20 F10000

    G1 X0 Y0 Z10 F5000

    M109 S{print_temperature}

    G1 X0 Y0 Z0 F5000

    G1 F100 E15 ;extrude some

    G92 E0 ;zero the extruded length again

    ;go to the middle of the platform, and move to Z=0 before starting the print.

    G1 X{machine_center_x} Y{machine_center_y} F{travel_speed}

    G1 Z0.0 F{max_z_speed}

    M117 Printing...

    end.gcode = ;End GCode

    M104 S0 ;extruder heater off

    M140 S0 ;heated bed heater off (if you have it)

    G91 ;relative positioning

    G1 E-1 ;retract the filament a bit before lifting the nozzle, to release some of the pressure

    G1 Z+0.5 E-10 X-20 Y-20 F{travel_speed} ;move Z up a bit and retract filament even more

    M84 ;steppers off

    G90 ;absolute positioning

    G28 X0 Y0 F{travel_speed} ;move X/Y to min endstops, so the head is out of the way

    start2.gcode = ;Sliced 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

    M107 ;start with the fan off

    G28 X0 Y0 ;move X/Y to min endstops

    G28 Z0 ;move Z to min endstops

    G1 Z15.0 F{travel_speed} ;move the platform down 15mm

    T1

    G92 E0 ;zero the extruded length

    G1 F200 E10 ;extrude 10mm of feed stock

    G92 E0 ;zero the extruded length again

    G1 F200 E-{retraction_dual_amount}

    T0

    G92 E0 ;zero the extruded length

    G1 F200 E10 ;extrude 10mm of feed stock

    G92 E0 ;zero the extruded length again

    G1 F{travel_speed}

    M117 Printing...

    end2.gcode = ;End GCode

    M104 T0 S0 ;extruder heater off

    M104 T1 S0 ;extruder heater off

    M140 S0 ;heated bed heater off (if you have it)

    G91 ;relative positioning

    G1 E-1 F300 ;retract the filament a bit before lifting the nozzle, to release some of the pressure

    G1 Z+0.5 E-5 X-20 Y-20 F{travel_speed} ;move Z up a bit and retract filament even more

    G28 X0 Y0 ;move X/Y to min endstops, so the head is out of the way

    M84 ;steppers off

    G90 ;absolute positioning

    support_start.gcode =

    support_end.gcode =

    cool_start.gcode =

    cool_end.gcode =

    replace.csv =

    switchextruder.gcode = ;Switch between the current extruder and the next extruder, when printing with multiple extruders.

    G92 E0

    G1 E-36 F5000

    G92 E0

    T{extruder}

    G1 X{new_x} Y{new_y} Z{new_z} F{travel_speed}

    G1 E36 F5000

    G92 E0

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    Posted · Retraction - Should it work? Does it work?

    The limit is in steps per second. It applies to all axes.

    The speeds in the gcode are in mm per minute.

    Since the x,y axes have roughly 80 steps per mm, the speed limit on those is 40000/80 = 500 mm/s. The extruder axis has roughly 830 steps per mm, so the fastest it can feed is a bit less than 50mm/s. You can't override it without changing the firmware source code and recompiling.

    Also bear in mind that during normal printing, the extruder is turning at less than 2mm/s. Each mm fed in provides a bit over 6 cubic mm of plastic. And the standard printer can't extrude more than about 10 cubic mm per second - often less, depending on temp etc. So the feeder has to turn at less than 2mm per second to keep the printer supplied with all the plastic it could possibly need.

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    Posted · Retraction - Should it work? Does it work?

    Minimum Travel(mm): 2

    Enable combing On

    Minimal extrusion before rtracting: 0.04

     

    Pictures are very valuable. I didn't realize your test piece had columns so close together!! If you had looked at the part in cura layer view you probably could have seen it wasn't retracting without even printing anything. Blue lines in "layer view" are non-printing moves. If the blue line has a little vertical section then that doesn't mean the head moves up - it is a symbolic representation indicating retraction for that move. So look for those vertical blue lines.\

    Regarding the settings above - they might have prevented retraction as those 2 cylinders were so small and close together. "minimal extrusion .04" refers to mm of filament. There is (I believe) a 120X multiplier at .1mm layers so that would be 4.8mm of laid filament. Or maybe I'm wrong - maybe there *was* retraction. Those tiny things between the towers aren't exactly "stringing" but they are caused by tiny tiny amounts of leaking filament - they are easy to cut off with a razor. If the towers were farther apart it wouldn't look so messy as they wouldn't go all the way across.

    Some filaments (particularly white I have found is bad) string worse than others.

    The "bonding" issue at 220C is different for each type of filament so I can't comment other than to say if it looks better or feels stronger at 220 then use 220.

     

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    Posted · Retraction - Should it work? Does it work?

    Thanks for the tip on the little blue vertical line on the path preview in Cura. I didn't know about that. I've already moved on to another model I need to print but I'll keep an eye out for that.

     

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