Enclosed delta 3D printer 'D-Box'
- see [
rouzeau.net]
The printer is enclosed with air recycling through activated carbon filter
This printer does have a particularity: its angles are not equal (120°) as on usual deltas
This prototype have angles 135°, 90°, 135° but this will be modified, see below.
It started from the idea of a 'square' delta by Ryan Carlyle (90°,90°,180°), but following his comments of lack of stability, I have choosen this compromise.
It is an entirely new design, as no parts from another printer were reused.
It is working but not finished yet (Oct 2015) as there is no heatbed neither chamber heater, nor a second hotend.
Complete test shall be carried out.
Really usable area diam 286mm x height 400mm
Overall size : Width 570 x Depth 420 x height 840 mm.
Box is made of 10mm thickness plywood but could be more easily built at lower cost and less paint work in melaminated chipboard 18mm (but that will be heavier and a bit larger).
Control board
Control board is the 32bit arm-processor new Duet 0.8.5 [
blog.think3dprint3d.com]. There is one stepper driver more for a second extruder on this Duet version.
Printing is done from an SD card. Files are transfered to the SD-card via an ethernet link at an amazing speed (I got 400kb/sec with a high-end SD card). There is an incorporated web server in the board, which is used to control the printer through any browser. If there is Wifi on your network, you can control or check the printer through a smartphone or tablet.
I started it without difficulties as this is nearly the same as used on the Fisher delta.
Carriages and columns
The carriages are rolling on ball bearings on galvanised steel angle. This is a bit more noisy than other system, but the rolling noise is not the dominating noise of this printer, which is more the belt/motor humming.
There is no endstop switches, the carriages are stalled on the roof at low current. This is noisy and not precise, but calibration will further correct the position. The angle used are 35mm x thickness 1.5mm and lack a bit torsional stifness.
Arms
The arms in aluminium are ended with 8mm balls [
www.animationarmatures.com] , which articulate in printed cups on carriage and effector. They are maintained in contact with high tensile polyethylene wire (Dyneema/Spectra) and a spring. The aluminium does not give the lightest arms, but this is easy to supply in any DIY store.
Hotend
The hotend is a Prometheus [
www.dta-labs.com] by Distech, which have the particularity to be fully adjustable→[
www.dta-labs.com] . Its stainless steel nozzle is integral and does not need any re-torquing when hot. Fan is a bit noisy, which is limited by the enclosure. The hotend is delivered with 1m cables, which fits perfectly this setup. So, there is no local plugs, but this is not a problem with the magnetic effector mount.
Hotend positioning
The hotend is positioned on the effector with a kinematic coupling [
pergatory.mit.edu] maintained in place with magnets. This system is also used as a calibration sensor.
This is very practical for hotend maintenance or exchange.
The idea is taken from the Fisher, but set on the effector instead of the bed, which makes the calibration much easier to adjust (there is only one offset) and is more efficient for mechanic protection as the inertia is lower.
Idlers
Belts are twisted to have their back rolling on the idlers (flanged bearings F623).
Motors
Motors are 0.9° Wantai motors 42BYGHM809 torque 4.8daN.cm (also for extruder motor)
They are installed with cork dampeners
Power supply
Power supply voltage is 24V, which allow higher speed and is required notably due to the use of 0.9° motors.
The heated bed will be installed on the mains, so the power supply will not be used for the heatbed. Its rating is 350W, which offer a huge margin, but the extra-cost over a 150W power supply was low and this kind of power supply is not of good quality so a good margin may help to improve reliability.
To allow the use of old 12V computer fans (recycling and board cooling fan), I installed an adjustable buck converter->[
www.ebay.com], set at 10V to reduce fan noise.
Extruder
Extruder is direct drive.
The extruder is positioned to have the minimum bowden tube length,which is 640mm.
Filament is maintained very close to the hobbed insert.
Pressure is adjustable and cleaning is easy.
Bowden is screwed in an ordinary M4 nut, which was chosen after tests of other solutions.
A manual thumbwheel allow easy manual feeding.
Air recycling
An air recycling system flow through activated carbon for removal of pollutants and odors.
Activated carbon filters are easy to supply as they are used in kitchen hood fans.
Delta kinematics
The unequal angles is not optimal. The best stability of an effector is obtained with the largest arm space with the smallest offset. Having irregular angles limit the possible arm space and oblige to increase offset. The actual arm spacing value (60mm) is correct in comparison with similar deltas, because of the compacity of the articulation system, but could be improved.
Design will be modified to have more regular angles 125°, 110°, 125°. However that will make the geometry control more difficult. With the present right angles, geometry checking is very easy.
Noise
Before starting the machine, I was quite afraid to have resonances on the box panels, as others experienced. Hopefully, this was not the case except for some retract speed on the extruder, which was easily solved.
The box significantly reduce the fan noise, but the overall noise is not reduced a lot and this machine is not very silent. The noise is relatively deep, so this is less aggressive than other printers.
Documents
Simulation on OpenScad, plans and details will be released under OHL V1.2 licence, when ready.
I was intending to have a dual extruder with a tool changer, possible easily with the magnetic system but the crossing of the bowden tube may not be easy to manage. Such system may neeed to have an extruder on each side of the printer, which will take a lot of space on a printer already quite large.
Credits :
- Ryan Carlyle, for the idea that a delta does not need to be equilateral
- Tim Jacobsen, for the rod system with wire tensioning system.
- RepRapPro company, for the idea of kinematic positioning system used as a sensor, but here I set it on the effector instead of the bed.
Edited 1 time(s). Last edit at 10/06/2015 10:47PM by PRZ.