Monthly Archives: August 2018

3D Printing: Ashtar K: It’s Alive ;-)

Well, after merely 3 months (2018/06/06) when I started to code the first lines of OpenSCAD to develop a series of parametric Prusa i3-like designs, and few weeks ago decided to go with the “K” series with 2020 alu profiles: simple 11x 500mm beam T slot (B-Type) alu profiles – the 1st prototype happen to print the 20mm XYZ Calibration Cube as of 2018/08/27:

The bed is very temporarly fasten with tape, as I haven’t decided on the actual details of the bed mounting yet and leveling details – but I wanted to see how well the mechanics already works – and it performed quite well so far.

1st print came out mediocre, when I realized I had to tighten X and Y belts more, 2nd print came out much better; 0.5mm nozzle with 0.4mm layer height, merely printed in 8mins with 60mm/s print speed and 80mm/s 20% infill:

And just for the fun of it, 0.2mm layer height with 0.5mm nozzle, at 70mm/s:

Incredible quality: X and Y surface very good, some inconsistency at “X”, on the “Y” side some slight ghosting; but most surprising is the edges on the Z axis – I operate with a simple M6 threaded rod and M6 nut – that’s all – moving nylon wheel-based carriage up and down – sure, I require to print more tests, in particular larger prints to really see how well all axis print up to 300mm.

I had to use blue tape on the mirror otherwise PLA would not stick – eventually I will use the black sticker as I used for the CTC DIY printer which worked quite well.

Nylon Wheels vs Sliders

The past 2-3 weeks, while waiting the nylon wheels to arrive, I decided to check alternatives such as sliders with PTFE tubes – and this paid off: the nylon wheels 23.0mm OD with 7.3mm width sit quite nicely into the T slot (B-type) but when used in real life, like with X carriage, I had some sinus wobble in the vertical – apprx. 0.5mm to 1mm – way too much. So, I exchanged the wheel-based X carriage with the slider-based carriage, remounted the hotend with Bowden setup, and after 5mins the exchange was done:

Current setup:

  • X axis: slider-based carriage, holding on top and bottom side with 2 tightening screws
  • Y axis: simple sliders (just sitting on the groove)
  • Z axis: nylon wheel (23.0/7.3mm) based carriage

The next days and weeks I will review my options:

  • slider-based carriage with
    • 1 axis support or
    • 2 axis support
  • wheel-based carriage with
    • nylon wheels 23.0/7.3 and 23.0/7.0
    • double V wheels

both on T slot alu extrusion – I know ideally would be proper V slot alu extrusions, but I like to find out how good it works with the easily available T slot extrusions. Worst case is, I have to use on X and perhaps Z axis proper V slot alu extrusions, on the Y axis it seems the simple sliders (just a block) work fine.

0.5mm Nozzle

Since I deal with nearly 3x the bed surface compared to 200×200 I thought I have to use a bigger nozzle as well, as a bigger build volume would imply larger objects to be printed. The increase from 0.4mm to 0.5mm diameter also implies 1.5x or +50% more material being extruded and I still desire to print with 60mm/s average with 80mm/s infill – this means I have to test well the hotend performs with that speed and higher throughput of material.

Specifications

Current specifications of Ashtar K 3d printer:

  • 380 x 300 x 320 mm build volume (400 x 300 bed)
  • E3D V6 clone hotend
  • 0.5mm nozzle
  • Anet 1.0 controller board
  • 210 x 210mm 12V heatbed

TODO

  • bed mounting & leveling
  • 300×300 or 400×300 220V heatbed
  • proper print surface (likely black sticker 300×300 or 400×300)
  • improving cable management:
    • Y carriage and heatbed with proper cable chain
    • deciding on position of LCD display
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3D Printing: Ashtar K Printer: Motor & Belts

Brief update of motors, belts, threaded rods and end stops mounted:

X Axis

I switched from slider based carriage to the nylon wheel (23.0mm OD, 7.3mm width) based carriage (X and Z axis), apprx. 120cm belt length.

 

Y Axis Belt

Apprx. 90cm belt length – with some considered cutting X + Y ~ 2m belt length.

This part was tricky – the parts are glued to bottom of the wooden carriage:

  1. mark the positions of the sliders (left: 65mm distance from top and bottom, left: center of top/bottom)
  2. glue 2x sliders on the left (where the Y motor is mounted)
  3. glue 1 slider on the right side
  4. put carriage on the rails, avoid any horizontal movement, push it slightly down (a slight snapping you sense from the sliders)
  5. let it rest (don’t touch or move it) for 30min – glue must dry
  6. move Y carriage gently forward & backward; if there is slight resistance then
    1. loosen all screws of the right 2020 beam so you can move it sideways
    2. then move carriage forward and backward and let the beam slightly find its new position
    3. when the carriage moves gently without resistance
    4. fasten the screws gently
    5. retest and if it’s still resitance, repeat procedure
    6. this is a bit tedious work, but worth it

This part is to do next (once I concluded those PTFE pipe chunk based sliders do their job well):

  1. drill holes and use Zip ties to fasten sliders
  2. glue Y carriage belt mount, let it dry
  3. mount GT2 belt to carriage belt mount
  4. fasten Y carriage belt mount with screws: drill holes from the bottom side

 

I will make some short videos of putting the carriage together and mounting it – it’s quite fast to attach and detach with those sliders (no screws to unfasten).

Z Axis

I extended the corner brackets so the Z stepper motors can be inserted, this weakens the part but saves quite a lot of space and hides the threaded rods nicely behind the 2020 Z beams. I might work on those brackets later to increase rigidity again.

Currently I use M6 threaded rods for the Z axis, one cycle gives 1mm height change.

X, Y, Z Motion & Homing

Flashing the Anet 1.0 board (which I currently use) with latest Marlin, this was required:

  • using Arduino Uno R3 (clone), installing Arduino ISP on it
  • cabling Uno R3 with Anet board (Uno powers Anet board with 5V, all stepper motors or power detached)
  • installing Bootloader (“Burning Bootloader”) with “Arduino as ISP” as writer
  • downloading latest Marlin, copying Anet Configuration.h and starting to change it

Finally, after hours fiddling around (bad install of Arduino failed to compile and/or upload anything to my Uno R3) the LCD display greeted with “Marlin 1.1.8” 🙂

Moving X, Y and Z axis briefly, 380 x 300 x 320 build volume with the current V carriage with 23mm OD, 7.3mm width nylon wheels – no extruder and no bed heating and leveling yet.

3D Printing: Ashtar K Printer: Carriages (X, Y, Z)

State: Work in progress

As I finished the frame, I focused on the carriages:

  • X carriage: moving left to right with the hotend with Bowden setup to keep it light: Wheel-based Carriage
  • Y carriage: moving bed forward and backward, relatively heavy with 400×300 bed with a mirror to ensure flatness: leaning toward Sliding Carriage
  • Z carriage: moving up and down with X carriage: Wheel-based Carriage

XZ Frame with X- and Z-Carriages

I made some tests with sliding carriage (composed with PTFE tubes), and finally the Nylon wheels arrived and I began to review two kinds of wheels:

  • 23mm OD, 7.3mm width: even it’s wider it sits better in the T slot 2020 alu extrusion
  • 23mm OD, 7.0mm width: is bit more narrow, but doesn’t sit well on the extrusion

So, I put the 23/7.3 nylon wheel on the V plate to compose a V carriage, and applied to X and Z axis:

Y Carriage

The nylon wheels work very well, given the fine-tuning capability, whereas the sliding approach with 2 axis support (PTFE tubes in sliding direction plus vertical to stay in line) doesn’t give tuning capability.

Currently I lean toward the more simple slider (white PLA) with 2 axis stabilization, as with the wheel-based carriage too much vertical force will be applied to the wheel in a perpendicular manner and wear the wheels rather fast.

One of the challenges is to mount three such sliders on the bed – two can mounted quite freely (with margin of 1-2mm) whereas the 3rd slider needs to be mounted very precise.

I update this post as I progress.

3D Printing: Ashtar K Printer: Frame

State: Work in progress

Building 3D Printer Ashtar K starting with the frame using 2020 T slot 6 alu extrusions, changing design slightly from 9x 500mm to 11x 500mm as early tests showed the XZ frame wasn’t stable enough toward Y bed – so two additional beams (later photos in the series) to make XZ frame sturdy toward the bed.

and the current state more or less:

20180811_152129

While waiting for wheels to arrive I thought to make some tests with sliders composed with PTFE tubes (4mm and 3mm in diameter) – I might actually use them in the X axis and Y axis:

The building volume with the 500mm beams can be stretched to 380 x 300 x 360mm, if the X carriage is short(er) – this means, the bed can be 400 x 300.

3D Printing: Sliding on Alu Extrusions

State: Early draft, work in progress and likely will receive updates.

Updates

  • 2018/08/15: Added Slider with PTFE tube inlets with 1 and 2 axis support with photos and brief test video
  • 2018/08/05: First overview with a 3 approaches

While waiting for the shipment to arrive, I thought to study some of the alternatives to wheels on alu extrusions, such as sliders.

2020 Nut 6 B - 999991_1

Nylon 2020 Slider

gleiter-glatt-b-typ-nut-6_3Commercially manufactured, apprx. cost EUR 2.50 per piece, sold in 10 pieces bag.

 

 

 

 

 

3D Printed Sliders

Simple Slider

A simple replicate of one of the simple 2020 sliders:

The sliding nose is 5.8mm wide. Ideally this would be printed in nylon; PLA might work as well but tends to stick more and grease or oil is required therefore.

TODO

  • print samples and measure friction with PLA
  • publish model

Slider (2 Sides) with PTFE tubes

Improving the simple slider with 10mm long 4mm PTFE chunks to decrease surface and use proper material for sliding:

screenshot-from-2018-08-15-06-21-23.png

and in use for the Y axis of a Prusa i3 like style:

20180813_084627

and a small improvement to take care of the 2nd axis as well (reducing 2nd axis wiggle):

Screenshot from 2018-08-15 06-21-15

20180817_102329

and then mounting them with a carriage together with M3 screws to control tightness:

and a brief test:

Slider (4 Sides) Carriage with PTFE tubes

A bit more complex using PTFE tubes on all 4 sides:

each inner side has 8 tube chunk insets, which gives you the variable option:

  • 4 chunks (a 10mm) x 4 sides = 160mm total
  • 8 chunks (a 10mm) x 4 sides = 320mm total
  • 12 chunks (a 10mm) x 4 sides = 480mm total
  • 16 chunks (a 10mm) x 4 sides = 640mm total

The OpenSCAD module takes parameters such as length of the carriage and the diameter of the PTFE tube (e.g. 3mm or 4mm), default length 60mm.

And the adjustable version with 75mm width looks like this:

which breaks the one surface apart with the mounting hole; if a plate would use all 4 holes that side would become non-adjustable that way – so this isn’t ideal, but perhaps work for single side use.

A possible application as X carriage and two Z carriages in a Prusa i3 use case:

printer-ak-with-sliders

TODO

  • print model and make actual physical tests, measure friction of the possible options
  • publish model

 

 

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