28 avril 2016

Continuing the search for good print

So, I ws not happy with this horizontal banding and very small waves on sides. so I went through a systematic and  looooooong test processing,  changing parameters and  hardware configuration one by one.  Now I have got more than 30 samples....
There is a good test on thingiverse for that : http://www.thingiverse.com/thing:277394
Most  samples are printer at  70mm/sec minimum

To summarize all changes I did:

  • marlin parameters tuning, especially "Accelerations" and "Jerk"
  • bed and Heater temperature
  • filament flow extrusion rate  (80-120%)
  • extrusion speed, retract speed
  • infill 0 or 25%
  • infill overlap
  • perimeter after infill
  • two types of motor controller (DRV8825, A4988)
  • 2, 8, 16 or 32 bits motor substepping
  • install the print on dampers to avoid vibration resonnance from the table
  • belt tensioning
  • install motors on antivibration support
  • print on various places on the bed
  • reinstall bowden vertically inside a cable chain
  • add some grease to Z axis
  • check all screws
  • reinforce bed structure
  • check and reduce extruder filament compression
and finally:

  • replace sliders with bronze bearing tube by new slider with linear bearing LM8LUU
  • replace Z axis leadscrew TR8x8 by TR8x2 

See pictures below, the black one has been printer with a small compact printer (minifabrikator)

01 avril 2016

Horizontal banding

I just spent lot of time trying to understand why I got horizontal banding on new parts with oboXL3D printer. Initially it looks like this:
 To compare with another print coming from Kossel printer (the orange part)

After many tests and assumptions like bad threaded rod on Z or not aligned, accuracy of XY, bad filament, bad heater, etc... I finally found the solution, thanks to a post found on a forum.
That post explains that this type of banding may come from the regulation of head bed temperature.

So, I followed the instructions and did this:
1/ uncomment #PIDTEMP Bed in Marlin configuration.h, to activate true PID regulation of the bad, instead of basic regulation (as defined by default)
2/ add correct values Kp,Ki,Kd (as computed automatically by Marlin). 

And it gave this, (on the left before tuning, on the right after tuning):

Thanks to those posts:

22 mars 2016

Progresses on OboXL3D

The two heat beds are working ok.
Both are driven by their own electronic switch and power supply.
The electronic switches are  driven by the Rumba main board.
Only one temperature sensor is used as current Marlin firmware does not seems to allow more than one bed temperature sensor.
Below the bed, I have added some thin aluminium to enhance thermal isolation.
Bed comes to temperature pretty quickly, so far so good :)

10 mars 2016

Hot bed for OboXL3D

Given the large size of the printer (600mm), for the heat bed  I decided to use two pad (from china), with dimensions each 300x300mm.

The problem is that each pad requires roughly 300w power supply.
So instead of a *big* power supply of more than 600w,  I decided to use 2*350w power supply at a reasonable cost (35€) each.
To control these power supply, instead of using SSD relay with doubts about the end of life, I use two electronic boards with  mosfet.
That works perfectly already on my other printer 3D, and it decouple the electronic+heat head+motors+fans from the Bed power supply.  More than 10A is used by bed, reste of electronic requires only 1A. A large current consomption from BED does not impact the rest of the printer.

The Bed regulator control board schematic comes from here:
and I adapted in on prototype PCB with strips.
*Be careful to NOT link both GND , or you may damage all*

Each power supply is 350W, model meanwell  LRS-350. I printed the protection case and adapt plusgs and swtich.  See http://www.thingiverse.com/thing:1221600

Orange power supply is 12V, for electronic board, motors, heat head, fans.
Black power supply is 24V and for each PAD of the heat bed.

28 février 2016

Larger test part

First print test video


Designed for a geared motor. Easy to change filament by pushing on the spring