Tag Archives: Cantilever

3D Printer Ashtar B: Cantilever, First Draft

It has been on my mind for quite a while to do a 2020 alu extrusion based Cantilever 3D printer, and so I started in December 2020 with a rough design, starting from the existing Ashtar K design and cut away parts:

  • using Head XZ and Bed Y
  • aiming common build volume (e.g. easy to source print bed)
    • 140mm to 190mm each axis
  • tried 6, 7 and 9 beams options, settling with 6 beams for now
  • aiming for uni-length 2020 alu extrusions, T-slot and V-slot where a carriage rides (X & Z axis) with V wheels.
  • trying to keep as simple as possible

Frame: 6 vs 7 vs 9 beams

The 9 beams give an overall better sturdiness, but not sure how essential at small building volume (less than 220mm each axis). I might be able to remove beam, the last beam at the back at the bottom reducing to only 6 beams, in that case the Y motor is mounted on the remaining beam in the back.

Z Carriage: 3 vs 4 wheels module

The 4 wheels looks best but it also sacrifices some of the X range by apprx. 10mm, the obvious choice is 3-wide mount – actual tests will tell if the X & Z axis are solid enough.

Different Sizes

The 200mm build axis length would be good, but I’m not sure if the XZ carriage will allow it as the max margin or tolerance would be half of a layer-height, e.g. 1mm layer height ⇒ 0.05mm tolerance, at X = 0 .. max the head should not flex more than 0.05mm. At this this early draft stage I don’t know which size is most suitable, I focus on 180mm build axis.

The project page on Ashtar B summarizes the current state.

3D Printer Ashtar B (Draft)

Status: just a draft

Ashtar B (Cantilever)

Updates:

  • 2020/12/23: added more details on Y bed, and size comparison, blog post published.
  • 2020/12/17: X motor mount done, X belt pulley holder, XZ cantilever x-offset 10mm.
  • 2020/12/12: just the basic idea, an early draft with a few options (extra foot, 3/4 wheels for Z carriage), 6 vs 7 vs 9 beams.

Introduction

Ashtar K was the first design with 2020 T-slot alu extrusions, and I used 11 beams of 500mm length to make up the entire frame. In the back of my mind I thought also doing a Cantilever 3D printer with 2020 T- or V-slot, like the Prusa Mini or Printrbot Simple Metal, and as before I like to reuse the frame as rails directly and not use any smooth rods or alike, which means X beam as V-slot, and optionally Z beam as well as V-slot, Ashtar B:

Draft

A build-volume of 140mm to 190mm each axis is targeted in order to keep the X axis short – also, likely using a Bowden extruder setup where just a hotend resides on the X carriage.

Specifications

  • Build Volume: ~180x180x180mm
  • Frame: 6x 340mm 2020 alu profiles
    • 2x V-Slot (X and Z axis)
    • 4x T-Slot (Y axis with simple sliders where T-Slot are sufficient)

Issues to Resolve

  • X belt routing: outside of 2020 extrusion or inside
  • X motor mount: rather simple, perhaps combine with xcarriage_short_hmount_2020(), done
  • Y motor mount position: will determine overall build volume
  • Y bed slider: perhaps like Ashtar K final version
  • testing overall stability: 6, 7 or 9 beams
  • 3 vs 4 wheels on Z carriage, 4 wheels (see below why)
  • positioning: extruder, controller, display, power supply, optional filament holder
  • positions of X, Y and Z endswitches
  • tune to a common build volume while having uni-length beams/extrusions
    • 150mm, 200mm, 215mm for X & Y build axis length

Frame: 6 vs 7 vs 9 beams

The 9 beams give an overall better sturdiness, but not sure how essential at small building volume (less than 220mm each axis). I might be able to remove beam, the last beam at the back at the bottom reducing to only 6 beams, in that case the Y motor is mounted on the remaining beam in the back.

Z Carriage: 3 vs 4 wheels module

The 4 wheels looks better also because it allows to add another 2020 horizontal mount or wider mount, some X range is sacrificed (10-20mm).

Different Sizes

The build volume from 150mm to 200mm for each axis, I like to have 200mm but not sure if the X axis can maintain linearity fully (e.g. half of a layer-height such as 0.1mm ⇒ 0.05mm linearity for head X = 0 .. max), I might to have to settle for 180mm or even 150mm. Actual tests and fine tuning of the Z axis (4 wheels V carriage) and X axis (3 wheels V carriage) will tell.

Comparison

Build Axis: 150mm (83%)
Area: 225cm2 (69%)
Volume: 3.4Kcm3 (58%)

Build Axis: 180mm (100%)
Area: 324cm2 (100%)
Volume: 5.8Kcm3 (100%)

Build Axis: 200mm (111%)
Area: 400cm2 (123%)
Volume: 8Kcm3 (137%)

IdeaFormer Magnetic Sticker
(Aliexpress, 2020/12)

Common quadratic bed-sizes are 150mm, 200mm, 214mm, 220mm and 235mm e.g. for magnetic beds. A 200mm bed can be used but only 180mm be printed, as I have sufficient margin on the XZ cantilever side.

Y Bed

I gonna use the simple slider riding on T-slot (derived from an existing nylon slider) for the Y bed, 3 sliders in total:

The sliders are glued beneath the Y carriage, then the Y bed snaps into the T-slots easily. I have printed on these sliders with two Ashtar K‘s (K1 = 380×400, K2 = 300×300) for about 1+ years successful. This simple approach requires gravity, and the bed needs its own weight to stay in place (cannot be up-side-down or in no-gravity environment like International Space Station ISS).

Back & Bottom View

Ashtar B (back view)

Ashtar B (bottom view)

References