New boxed delta 'D-Box'

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.

I am very impressed by your design. It could be really nice to see / hear some videos of it printing and some high-res pictures of prints and some comments about obtained speed.

The setup in general does not seem so rigid to me (but that is always hard to judge from photos). I am interested in how perfect your walls becomes on complicated objects with sharp angles and printed in high speed. Do you have problems with waves and changes in wall thickness?

Looks good! I have been trying to work out how to enclose my delta, and yours looks like a neat solution.

How regular is the size and shape of the galvanised steel angle? How do you attach to to the base so as to ensure it is perpendicular to it?

Is the additional board with the 3-digit LED display a temperature controller for the enclosure? If so, an alternative would have been to connect an SSR and thermistor to the third heater channel on the Duet 0.8.5, because RepRapFirmware supports control of a chamber heater using M141. Or if you want to keep the 3rd heater channel free for dual extrusion, you could connect the SSR and thermistor to the expansion connector instead, along with one resistor and one capacitor.

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Large delta printer [miscsolutions.wordpress.com], E3D tool changer, Robotdigg SCARA printer, Crane Quad and Ormerod

Disclosure: I design Duet electronics and work on RepRapFirmware, [duet3d.com].

I will try to build some test parts. I have done a test with a vase double twist in spiral vase mode, which looks not bad, but since, I've seen there was some play in my carriages (not sufficiently tightened).
It is only three days that the machine is working, so that is quite preliminary.
I made the mistake of not removing the spool while making new holes in my wood plate, that polluted the filament and while I tried to clean up it, I got a severe jam that I did not yet succed to remove.

As for the stiffness, the box is very stiff, the angles are relatively stiff in bending, but quite weak in torsion.
You can't consider that the foot and top supports give any stiffness to maintain the angle perpendicular to the plate. This is not possible with plastic parts. So, it is reasonnable to consider the angle as a beam articulated on both end. Compared to beams maintained in 3 points, this is more flexible, but the bending stiffness of this steel angle is better than aluminium profile 20x20.

I was afraid of the poor quality of steel folded angle, so I initially started with steel rolled angle, but while I had thorougly brushed them, the rolling was very irregular with hard points and while improving with time, I abandoned that solution.
I bought these folded angle and they were of much better quality than I expected and the rolling is quite smooth. That may be because of the galvanisation.

The small board is just the buck DC-DC converter for the fans, the display is for in/out voltage. I get it for 4 euros, shipping included !

As per your advice in dedicated topic [forums.reprap.org], SSR and thermistor are ordered, but I have yet to find an enclosure heater. 230V Industrial heaters are quite costly and I did not found any low cost controllable dimmer to heat with lights, so yet I am bending in favor of a small toaster (750W) . I prefer to have a static heater (no fan). Another solution is to use a silicon pad installed on a wall with a space (10~15mm).

Quote
PRZ
As per your advice in dedicated topic [forums.reprap.org], SSR and thermistor are ordered, but I have yet to find an enclosure heater. 230V Industrial heaters are quite costly and I did not found any low cost controllable dimmer to heat with lights, so yet I am bending in favor of a small toaster (750W) . I prefer to have a static heater (no fan). Another solution is to use a silicon pad installed on a wall with a space (10~15mm).

Have you considered using a small mains voltage halogen lamp? Or a large cartridge heater clamped to an aluminium heat spreader? If you want more than about 100W heating power, then I think you will need a fan in order to keep the heating element cool.

Depending on how well insulated the sides and top are, you may find the bed heat is sufficient to keep the chamber warm, although you may still want a heater and fan to get it up to temperature initially.

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Large delta printer [miscsolutions.wordpress.com], E3D tool changer, Robotdigg SCARA printer, Crane Quad and Ormerod

Disclosure: I design Duet electronics and work on RepRapFirmware, [duet3d.com].

Using a halogen lamp on mains was my first idea, but for control you need a fast on/off switching that I am not sure you can get from a SSR. In principle, halogen lamp are controlled with angle phase dimmers, and I was searching one that I can control with a PWM output. It seems it does exist, but not as low cost parts. Maybe the use of angle phase dimmers is only to limit EMF emissions ?
I have yet a light spot 40W power, and it maintains the chamber 10°C above ambient, so for a chamber temp 40~50°C, the power requirement will not be that high, maybe 200W.

Manual manipulation shows that the stability of the effector is irregular. The flexibility around y axis is more than twice that around X axis. While near the right column, the flexibility is much higher than near other columns. And that show in prints, where it is near perfect on left side and with irregularities on right side.
So, unequal angles will be abandoned and I will go back to equilateral angles (120°), with a small usable diameter loss (280mm instead of 286mm), which will allow an arm spacing of 84mm for an offset of 30mm and a much better stability.

Tests with the unequal angles shows that the quality of the print varies depending the position.
Good on the left, but bad on the right.

I have done a first test with this double twisted vase [www.thingiverse.com], but the model is full of artifacts, which show in prints, especially with some extrusion parameters.

Test was then done with this pentagonal twisted vase [www.thingiverse.com] scale up 4 times.
It is an interesting model because it does not have artifacts, it does have flat inlined areas, sharp corners and as a pentagon, you will escape from regular printer angles.

It have been printed in spiral mode, 0.25 mm layers, in RepRapper PETG at 275°.
One layer is deposited in just above 10seconds, which makes a real average speed of 50mm/s. Acceleration 8000.

A small film here [rouzeau.net]
You hear neatly the drumming noise inside the printer. Hopefully, this is less marked outside the printer. If no sound (Firefox), try another browser.

On the left of the print





On the right of the print

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Pierre

- Safety [reprap.org]
- Embedded help system for Duet and RepRap Firmware [forums.reprap.org]
- Enclosed delta printers Lily [rouzeau.net] and Lily Big [rouzeau.net]
- OpenScad delta printer simulator [github.com]
- 3D printing on my site [www.rouzeau.net]

Here you will find a small video of how the kinematic positioning system works.
The part inserted for the hotend to 'jump over' is 0.85mm thickness.
Look the top of the hotend support behaviour.
You see on the right of the part that the realignment is perfect.

[rouzeau.net]

I no sound on Firefox, try another browser (video converted with VLC)

Edited 2 time(s). Last edit at 10/08/2015 12:32PM by PRZ.