The past weeks (2021/02) I worked on various printhead designs, to summarize and provide an overview by mounting them on Ashtar K:
E3D V6 (bare without fans), 2019/09
Dual Independent Extruders (IDEX), 2020/12
Multiple Switching Extrusions (MSE), Rotary Y 2, 2021/02
Multiple Switching Extrusions (MSE), Rotary Z 4, 2021/01
4 Axis Rotating Tilted Nozzle (RTN), 2021/01
5 Axis Printhead (PAX), 2021/02
Also improved the display controller to simulate Marlin firmware and list heads and tool selection (MSE), coordinates (IDEX) or rotation angles (RTN & PAX).
So far all options are available for Ashtar C, D and M as well, but currently (2021/02) are just in draft and mostly untested.
RTN and PAX promise printable support-free overhangs, yet no public available slicing software exists to really take advantage of those two designs, as new algorithms of volume decomposition, sub-volume sequencing, collision detection are required and mostly debated in scientific papers as 2021/02 and only few companies, e.g. HAGE and VSHAPER, implemented new 5-axis 3D printing procedures, and DotXControl advertises a 5 Axis Slicer.
2021/01/18: added IDEX Features with Pros/Cons, Ashtar Series Genealogy, Comparison Dual Material approaches, and brief Hardware Requirements
2021/01/15: first version with overview side-by-side
Mid of January 2021 (01/12 – 01/14) I added IDEX (Independent Dual Extrusion) option to 4 designs, all still in early draft stage – here as a summary side-by-side:
Ashtar KAshtar K IDEXAshtar MAshtar M IDEXAshtar DAshtar D IDEXAshtar CAshtar C IDEX
Ashtar K IDEX has been fairly easy, as I was using an improved “old” design of the X motor mount for the 2nd motor and 2nd belt, and since Ashtar M IDEX is using the same XZ frame, it was a matter of a few minutes to port that option as well.
Ashtar D IDEX with Classic XY belt routing was more tricky as there was little space left to add another motor, so I realized I need to utilize what’s there and take advantage of it – result is a very space saving solution, but it needs to be verified in real life first.
Ashtar C IDEX with Core XY with an additional X motor was easy, I just reused a slightly altered X motor/pulley mount of Ashtar D, so that was done fairly quickly as well, yet the challenge will be the firmware support, as currently (2021/01) only Duet RepRap firmware supports the CoreXYU as my design falls under.
Features of IDEX
Pros:
double printing: duplicate or mirror mode
double printing volume at same duration
two materials with different melting points
two colors (non-mixing) with
more reliable than dual nozzle setups, as inactive nozzle does not run over existing printed piece often
in theory no purge block, but if ooze shields are shared among switching extrusions (more than 2 extrusions) there may be cross-contamination between colors/materials
the printheads individually are proven to be reliable
Hints:
single heatblock = same print temperature
dual heatblock = different print temperatures possible
dual nozzle = different nozzle sizes possible
Hardware Requirements
1x NEMA 17 42-45Nm with wire, extra stepper motor driver on motherboard
100-110cm long 6mm wide GT2 belt
1x pulley and 1x idler
1x hotend (nozzle, heatblock, heat cartridge, heatbreak, heatsink), extra heating connector on motherboard
Well, after the IDEX option designs – still as drafts – worked for Ashtar K (Prusa i3), Ashtar M (Moving Gantry) and Ashtar D (Classic XY), I thought, why not also target Ashtar C (Core XY).
Ashtar D IDEX is definitely a narrow design, so I thought to reuse two parts of it for Ashtar C as well, and hopefully the A and B belts route around – and well, it seems mechanically to work out.
On the firmware part it seems this CoreXY plus additional X motor is called CoreXYU and supported by Duet RepRap firmware – but details need to be researched in more depth. On the first glance the “traditional” CoreXYU setup routes the U belt off the X beam and not place a motor on it as I do, but routes at the end of the frames so the motor is stationary – definitely something also to look at.
Draft
The A/B belts route around the new X motor mount (borrowed from Ashtar D design)
. .. and also around the X idler holder.
Gallery
Issues to Resolve
Firmware supporting CoreXY IDEX:
E1: X & Y provided through CoreXY by motors A & B
E2: X provided by X motor, Y provided by CoreXY where X=0 remains (both motors A & B have to operate to provide X=0 while Y is moved)
Duet RepRap firmware provides CoreXYU support, and it seems it would cover my use case here
Marlin firmware as of 2.x does not support CoreXYU yet
Moving the X motor – or U motor as in CoreXYU context – off the X beam and route a much longer belt and place the motor stationary like the motors A & B of CoreXY
After just few hours working on IDEX option for Ashtar K and Ashtar M, I thought to try myself on doing IDEX on the very delicate Y carriage on Ashtar D – and after an hour roughly I realized, perhaps it is doable.
The main idea is to reuse the NEMA17 shaft as axis for the idler of the 2nd belt, and use 3mm diameter shaft with 5-10mm length as extension, and stabilize the extension in the idler itself likely the shaft seems long enough by itself – the most space saving option:
Reusing NEMA 17 shaft as axis for idler
Reusing NEMA 17 shaft as axis for idler (see through)
If possible, rotate entire X motor mount / carriage and mount it on the other X side.
Draft
I had to color the belts and V modules, as I otherwise get confused while fine-tuning the design within such narrow margins:
X1/E1 in green
X2/E2 in red
I just love symmetry! I just love symmetry!
Gallery
Issues to Resolve
X motor-mount isn’t fully Y symmetric yet, it’s off by a few mm; needs some further fine-tuning until X2 motor-mount mounting holes align with V module, resolved
V module belt mount for X2 needs be adapted, as I can’t mirror it as that “back” mirrored is the “front” side where the printhead is mounted and occupied already, a new piece is required which mounts within the V module
2021/01/14: Ashtar M (Moving Gantry – Draft) also with IDEX option now
2021/01/13: ooze prevention at rest position added, mechanical conflict resolved
2021/01/12: starting with a first draft, one mechanical conflict to be resolved
Introduction
I have been pondering on a dual independent X axis upgrade or option for a while, but the other designs of the Ashtar Series I wanted to do first (Ashtar D and Ashtar M) those matured by now (2021/01), so I decided to get back to IDEX upgrade for Ashtar K:
Ashtar K
Ashtar K IDEX
For now I like to keep single 2020 V slot alu extrusion for the X beam where the X carriage rides, and route the2nd beltabove for the 2nd X carriage – and this was a quick solution as earlier version of Ashtar K had the belt routed above the alu profile so I just reused the old pieces again.
“Above routed belt” option with its pieces are weaker and possibly need enforcement improved the strength, so it’s a fast start – just took me 2 hours – but needs definitely some fine-tuning. Alternatively the 2nd belt could be routed at the back of the X carriages, but fastening the 2nd X motor would be challenging.
Old “above routed” X motor mount
New stronger “above routed” X motor mount
For now I use the same code base of Ashtar K and introduce IDEX = true flag, and enhance a few existing pieces in parts.scad and optionally add those new pieces when rendering printer-ak.scad.
As I progress with this option or upgrade I update this blog-post.
Draft
X motor #1 routed within
X motor #2 routed above
Ooze prevention in rest position
Ooze prevention in rest position
Both heads in rest position
Issues to Resolve
X carriage #1 belt mount conflicts mechanical with belt 2: redesign xcarriage_beltmount_2020 piece, make it shorted in Z or fasten it inside V module: resolved, shifted 2nd belt a bit Y off, and shorten xcarriage_beltmount_2020(idex=true) by 2mm.
2nd belt slight Y offset so X belt mount #1 doesn’t touch belt #2
xcarriage_short_hmount_motor_2020 which is the base piece which routes the belt within the 2020, with idex=true option provides idler holder on top
X motor #2 is mounted on a x-mirrored version of xcarriage_hmount_motor(20,"left",idex=true) but definitely needs reinforcement, added ooze prevention in case of idex set
Nozzle drip prevention:
using a piece of sheet metal which the nozzle moves over when in rest position left or right, first attempt done (see below)
and/or use purge box with brush to clean nozzle after and before use
make extending “nose” detachable/replaceable as it’s expected to break or overheat otherwise entire X motors mount needs replacement, resolved
xcarriage_nose-idex-left and xcarriage_nose-idex-right with 10mm wide sheet metal insert
how dealing with long resting hot nozzle?
drop temperature by 5-10°C in rest position, and heat up when in use again
heat creep possible weakening extending printed nose – heat insulation required attaching sheet metal
Inside and Above 2020 belt routed X motor mount, w/ removable nose with ooze prevention
Nozzle at resting position, a sheet metal preventing oozing
Right-hand side ooze prevention
Gallery
Ashtar M IDEX
And since Ashtar M (Prusa i3 Moving Gantry – Draft) shares much of the Ashtar K design it took me a few mins to add the IDEX upgrade option as well:
