Need adjustments to improve print quality

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Re: Need adjustments to improve print quality

Postby flurin » Wed Mar 13, 2013 6:19 am

It looks much better!

1. #define DEFAULT_MAX_FEEDRATE {500, 500, 5, 45} // (mm/sec)

I've posted it again, see brnrd comment and your reply. Later on you may increase this value, my setting is 10 (= 600 mm/min).

2. #define DEFAULT_AXIS_STEPS_PER_UNIT {78.7402,78.7402,200*16/1.5875,115.3507}

Are your settings for your threaded rod and your extruder?

3. Did you change anything in the Configurations_adv.h?

4. It would be helpful if you would post the head comments (starting with ";") of your Gcode-File, just to verify your latest settings.

Here is a photo of the blue cube surface I've posted before:
CubeMC5.jpg
Last edited by flurin on Wed Mar 13, 2013 11:58 am, edited 1 time in total.
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Re: Need adjustments to improve print quality

Postby flurin » Wed Mar 13, 2013 10:15 am

tmccafferty wrote:The gcode is moving the z axis at 7200mm/min. I can't find where this speed is set in slicr3 or marlin. Anyone know?


I didn't remember how it works but I've found a note in my old documentation:

Slic3r uses the "Speed for non-printing moves -> Travel" for the Z-speed.
However this is a theoratical value because the Z-speed is limited by the firmware setting (marlin default = 5 mm/sec => 300 mm/min).
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Re: Need adjustments to improve print quality

Postby cozmicray » Wed Mar 13, 2013 4:37 pm

Check your z-axis settings

#define DEFAULT_AXIS_STEPS_PER_UNIT {78.7402,78.7402,200*16/1.5875,115.3507}
X, Y, Z, extruder steps per mm

200*16/1.5875 = 2015.75

The wiki has the settings and calculations here.

http://www.buildlog.net/wiki/doku.php?i ... resolution

Code: Select all
Resolution = s * m / p
Stepper Resolution (s) = 200 steps/rev
Driver microstepping (m) = 16 microsteps/motor step

!!! For 1/4-20 Threaded Rod !!!
Lead Screw pitch (p) = #1/4-20 = 20 threads/in = 0.05 inch = 1.27 mm
Resolution = 200steps/rev * 16microsteps / 1.27mm/thread = 2519.68

!!! For 8mm x 1.25mm Threaded Rod !!!
Resolution = 200step/rev * 16microsteps / 1.25mm/thread = 2560 steps/mm


I am using 2570 for ATI M8 z-axis
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Re: Need adjustments to improve print quality

Postby tmccafferty » Wed Mar 13, 2013 5:02 pm

Wow, the layers of the blue cube are amazing!

Yes, sorry I didn't mention the settings are for my z rod and extruder. I am using 3/8" x 16 Acme threaded rod. Also, since the layer height doesn't work out even for mm, if I want close to 2.5mm height, I would actually use 2.49125 layer height.

Here is the header portion of my gcode file.
Header.txt
gcode header file
(450 Bytes) Downloaded 848 times


The only thing I changed in config_adv was to enable Z_LATE_ENABLE by removing the comments.

I have now changed the Z_MAX_FEEDRATE to 5
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Re: Need adjustments to improve print quality

Postby flurin » Wed Mar 13, 2013 5:55 pm

I spent sleepless nights to achieve that results including the techniques to take macro photos. :)

1. You can easily round the layer height to 0.249 mm.
2. I didn't set a different first layer height, but you can if you like.
3. The next step will be to fine tuning the extruder setting and/or the extrusion multiplier.
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Re: Need adjustments to improve print quality

Postby tmccafferty » Wed Mar 13, 2013 11:51 pm

What does the extrusion multiplier do?
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Re: Need adjustments to improve print quality

Postby brnrd » Thu Mar 14, 2013 12:10 am

It's basically a fudge factor to the E steps per mm. In theory, it accounts for how deep the filament gear digs into the feed. It would be expected to be larger for PLA than ABS since PLA is harder.
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Re: Need adjustments to improve print quality

Postby tmccafferty » Thu Mar 14, 2013 1:53 am

Thanks brnrd.

For ABS, is everything pretty much the same except the temperature?
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Re: Need adjustments to improve print quality

Postby fma » Thu Mar 14, 2013 6:18 am

For the theory, yes. Practicaly, ABS does not behave the same as PLA does... First, ABS always remains viscous; it never becomes liquid. So, you can push the temperature as high as you can, without having it burn (turning yellow).

Second, ABS retracts a lot when cooling down, so warps a lot. You need a hot bed to avoid that.

For small parts with thin details, you need to cool it down, but not the entire part, or you will unstick it! That's why I'm working an a design to have a little air flow only near the nozzle, very close to it.

It looks like it it harder to extrude ABS; on some points, yes, but the good point is the hot-end won't jam easily, because of its viscousity.

I sold my olrd Prusa to a friend. I only extruded ABS; just after it switched to PLA, the hot-end had a leak! We changed the internal PTFE part and all went back OK (the higher temperature of the ABS destroyed it quicker).

All that said, I'm only extruded ABS, and I like it :)
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Re: Need adjustments to improve print quality

Postby flurin » Thu Mar 14, 2013 9:41 am

tmccafferty wrote:What does the extrusion multiplier do?

Slic3r Definition for the Extrusion multiplier:
Change this to alter the amount of plastic extruded. There should be very little need to change this value, which is only useful to compensate for filament packing (default: 1)

There is a documentaion how to use this setting:
https://github.com/alexrj/Slic3r/wiki/Calibration

Extrusion.jpg

The image (click on the image to see the original) shows 3 different layer height settings and the theoretical extrusion areas. The layer height is what you set in Slic3r and the extrusion width is calculated by Slic3r.

This is the theory, however there are a few parameters that affect the amount of plastic extruded (firmware configuration, speed, temperature, filament, inaccuracy etc.). To correct this deviation Slic3r has added the extrusion multiplier:

How to use (let's take the cube above as a sample):

Slic3r Settings:
Perimeters = 2
Nozzle diameter: 0.35
Layer height: 0.25
Extrusion Multiplier: 0.95

Slic3r calculates the extrusion width = 0.39 => wall= 2 * 0.39 = 0.78mm

1. Print the cube.
2. Measure the wall thickness = 0.9mm (sample).
3. Calculate the new Extrusion multiplier = 0.78/0.9 * 0.95 = 0.85.
4. Set the new value for the Extrusion multiplier to 0.85 in Slic3r and slice the cube again.
5. Repeat step 1 to 4.
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