D-Bot 3D Printer

[tekkydave]

Further to adding the RPi3 to run the cameras I have designed and printed an enclosure for the Pi camera I have. It is designed to fit into the base I was already using for the webcam. The camera is one I bought on ebay a while back and comes with a removeable lens in a 12mm mounting.

The ribbon cable exits at the side to avoid the mounting so the camera is rotated 90 degrees. I have corrected for this by setting custom sizes and a rotation in the software

 

[Gina]

Excellent

[Dr_Ju_ju]

FYI, I came across this on the Duet3D forum https://forum.duet3d.com/topic/5263/grounding.

The recommendation is to have everything earthed, including the motors, but the printed parts means the motors are isolated, so I will have to re-visit the earth bonding of all parts.... 

 

[Gina]

That's interesting.  Hadn't thought of earthing stepper motors.  My XY motors are mounted on the frame but Z and extruder motors are insulated.  The extruder motor doesn't drive a belt but I think I'll earth it anyway.  I've been careful with earthing the frame and aluminium print bed on my Giant printer with a mains voltage bed heater as recommended.

[Dr_Ju_ju]

If the frame is anodised, as is mine, there is no guarantee that there is full earth continuity throughout.

In my BBC days, we spent ages adding bonding straps to everything on the racks etc. on every new installation, even if the equipment was housed in a wooden carcase, and not mains powered...

[Gina]

3 minutes ago, Dr_Ju_ju said:

If the frame is anodised, as is mine, there is no guarantee that there is full earth continuity throughout.

Ah, good point - I'll have to check.  May need yet more wiring...

[Gina]

Just checked continuity around the anodised aluminium frame and there is NO electrical continuity!  So all the stepper motors are unearthed as is the aluminium bed ATM.  More wiring is needed   On all three printers!!  But I shall be rebuilding my Titan printer so I can just incorporate extra wiring in that.  Not had any problem so far but better safe than sorry - particularly with the cost of Duet WiFi boards.

[Dr_Ju_ju]

I'm in the same boat, I already have Power Supply 0v rail and Bed ally plate bonded to earth, and most is relatively easy to do, XYZ motors, extrusion frame etc, if a little ugly with bonding straps everywhere. I could replace all the linking pieces & cut through the anodising, but that means buying more metal bits.

The only awkward one is the extruder as that will require a wire run up through the cable chains, which is a pity as I've only recently updated the wiring to cope with a change of bed sensor 

[Gina]

I find I get fed up with undoing cable spiral wrap, adding one wire, and winding it up again.  Then there's another etc.!!

[glennpierce]

I have recently finished my dbot and apart from a few things I am fairly happy.

However, I have noticed the top of the frame vibrating more than I expected when the xy gantry moves back and forth in the y direction.

I don't think it effects my prints but I thought it would be rock solid. Has anyone else experienced this ?

[Dr_Ju_ju]

Mine doesn't, so …  what extrusion are you using ?  2020 or 2040 ?  are your belts too slack so they are flapping about ? have you adjusted the running rollers so that there's no play ?  also have you fitted levelling feet to ensure that its down on the bench & solid ?

[glennpierce]

2040 . The 300mm Ooznest frame kit. 

I am using anti vibration feet and the belts seem tight enough and seems to be no play in the rollers.

It may well be the whole frame moving on the anti vibration feet as I can wobble the frame by pushing the frame at the top. 

In addition in is on carpet which probably doesn't help. I doesn't effect prints so maybe worrying about nothing. 

[Dr_Ju_ju]

If you have any, try sitting it on a square of 18mm ply, failing that, a solid table, that doesn't rock, or even flat flooring with no carpet\underlay etc. 

If it's wobbling, then prints will be affected, you may not see it unless your doing taller prints, but artefacts will be there.

[tekkydave]

It's been a while since I posted anything so here's an update on changes I've made to the D-Bot over the last few months:

1. I've changed the way the z-axis screws are driven. Previously I had a single motor driving all 3 screws via a belt & pulley arrangement. It worked ok but I wanted to try driving each screw with it's own motor. So I purchased another 2 motors and also a Duet 3D Duex2 expansion board. This gives me the additional 2 motor channels I need plus a whole load of extra input/output options for future projects. It also gives me an on-board 12V supply so I can use that for 12V fans without needing the buck converter I was using before.

Having 3 independently driven screws means that the firmware (RepRapFirmware) on the Duet can automatically level the bed. Once you set up the exact positions of the screws, and the nearest point on the bed to probe it just does it by issuing a G32 command. You just need to set up the following

config.g

M584 X0 Y1 Z2:5:6 			  ; Drive Mappings: setup 3 Z motors connected to driver outputs 2, 5 and 6
M671 X-37:337:148 Y50:48:354 S3.0         ; leadscrews at front-left, front-right and rear-centre

bed.g

G28					; home all axes
G30 P0 X10  Y50  Z-99999		; probe near LH Front leadscrew
G30 P1 X290 Y48  Z-99999		; probe near RH Front leadscrew
G30 P2 X148 Y284 Z-99999 S3		; probe near Rear Centre leadscrew and calibrate 3 motors

; re-home z axis in case it has shifted
G28 Z

You also need to ensure any Z values in commands like M92, M350, M566, M203, M201, M906 have extra values for the 3 motors

e.g

M92 X100 Y100 Z3200 E419        ; Set steps per mm

becomes

M92 X100 Y100 Z3200:3200:3200 E419        ; Set steps per mm

2. I also wanted to upgrade my E3D Titan to be an Aero model. I bought the Aero conversion kit but this meant I wouldn't be able to continue using the Orion Piezo module as it is not physically compatible with the Aero. I decided to switch to the Re-X Carriage as there is also a Piezo Mount option for it. This also needs a different  electronic module from Precision Piezo - the Universal Piezo Z-probe PCB which has up to 3 inputs for piezo devices. I fitted a 27mm piezo sensor in the mount and it works extremely well. Much better than the groove-mount mounted Orion.

3. I have decided to switch from 3mm to 1.75mm filament. I'm finding the Titan can be a bit of a struggle to load 3mm filament, especially PLA which is often quite brittle.

I have some 3mm to use up so I decided to build a 1.75mm Aero front that can easily be swapped in & out for different filament sizes.

The Aero heatsinks are different for 3mm & 1.75mm - the 3mm has an M6 thread whereas the 1.75mm has an M7 thread. Obviously I would need to replace that. I also purchased a 1.75mm heatbreak, V6 heatblock and 24V 40W heater cartridge. I already had a spare nozzle and cartridge thermistor to use. With inline connectors on the heater and thermistor circuits it should be simple enough to unplug & unscrew the 3mm Aero Front and plug & screw in the 1.75mm version. I have some 1.75mm filament on order so we'll see how things go.

I'll post some photos later.

 

[Gina]

Very interesting, Dave ?  I'm using 4 threaded rods and just one motor on my Giant printer and it does struggle a bit.  I need supports on all four corners because I'm moving a frame up and down with the XY axes on it rather than the bed.  This frame is not rigid enough to work with 3 rods.  It would be interesting to try 4 independent motors but I haven't investigated if the Duet could handle this.  I would need 3 extra motors which would mean the Duex5.

Edited September 26, 2018 by Gina

[tekkydave]

4 motors is possible but you would need the Duex2 or 5. If you are not using the E1 stepper that could be used with a Duex2 to give 4 channels (Z, E1, 5, 6).

The current Duex2 version 0.8a is identical to the Duex5 except 3 of the stepper channels are not populated with driver chips. Earlier Duex2 models only had 2 of everything.

The other thing with 4 motors is you need a bed/frame that will flex - the G32 process will try to remove any twist in the bed/frame. Mine is 6mm cast Ali so 3 motors is more appropriate - it adjusts each motor to put the bed in a horizontal plane. It's quite amazing to see it working. I deliberately wound one of the screws a few turns and ran G32. After probing in 3 places the screw got turned back to where it should be

 

[tekkydave]

Pics as promised. First the new leadscrew arrangement - one motor per screw. I have some better oldham-style motor/leadscrew linkages on order.

The new x carriage including a piezo sensor embedded in the motor holder. The piezo electronics is hidden in the lid on top of the carriage. The Re-X carriage also has tension adjusters for the v-wheels and tensioners for the belts on the rear.

The Duex2 expansion board connected to the Duet WiFi via a 50-way ribbon cable. I had to print a bigger enclosure. The boards mount back to back and hinge out of the enclosure for easy access. I have replaced the 80mm fan in the lid with two 60mm fans in the bottom of the enclosure.

Finally my 1.75mm Aero Front ready for when the 1.75mm filament arrives

 

[Gina]

2 hours ago, tekkydave said:

4 motors is possible but you would need the Duex2 or 5. If you are not using the E1 stepper that could be used with a Duex2 to give 4 channels (Z, E1, 5, 6).

The current Duex2 version 0.8a is identical to the Duex5 except 3 of the stepper channels are not populated with driver chips. Earlier Duex2 models only had 2 of everything.

The other thing with 4 motors is you need a bed/frame that will flex - the G32 process will try to remove any twist in the bed/frame. Mine is 6mm cast Ali so 3 motors is more appropriate - it adjusts each motor to put the bed in a horizontal plane. It's quite amazing to see it working. I deliberately wound one of the screws a few turns and ran G32. After probing in 3 places the screw got turned back to where it should be

Thanks Dave.  I'd forgotten about the E1 driver so yes the Duex2 will do.  The frame does flex which is why 4 mount points are required.

[Dr_Ju_ju]

Good luck with the Aero, I had one of the bad batch, where the bearing would seize (rectified by E3D). But I also found I could easily clog the filament path, as the cooler is so efficient that even moderate retractions had the potential for congealing forming a clog (even after tuning the fan).

In the end I reverted back to a Titan with no issues...

[tekkydave]

Are you bowden or direct & what length retraction. I generally use 1mm for PLA and 2.5mm for PETG.

[Dr_Ju_ju]

It was direct drive, & trying to print Rigid Ink's  PetG & ASA with a 2~3 mm retraction, it would also happen when moving between multiple parts on the bed.... 

Other than the Aero, everything was working great, its just that I had to re-set & clean a few times, which is very annoying, & wasteful of time & failed prints.

If I was 'lucky' & it seized early in the print run, I wasn't wasting too much filament, otherwise it starts to get expensive....

[Stub Mandrel]

36 minutes ago, Dr_Ju_ju said:

I wasn't wasting too much filament, otherwise it starts to get expensive....

I'm about to print a Mk VIII airsoft gun magazine adaptor. Versions II to VII and this one have all been in PETG and take about 4 1/2 hours to print at ~60g a time.

The last one was perfect but I had moved a clip to incerase the pressure and when I did so this I thickened it by about 40%. This made it too stiff and it snapped off ?

Thoroughly fed up of printing these now!

I shoudl have done each test in PLA and just used PETG for the final one. At least I have improved my PETG prints to the point where they are as good as my PLA aside from the odd blemish.

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

[tekkydave]

The Aero has performed ok so far <touches wood> but I haven't done any particularly long prints. Are you using 1.75 or 3mm filament?

[Dr_Ju_ju]

I only use 1.75

[tekkydave]

I have swapped the flexible couplers on my three z axis steppers for these plum (or spider) couplings

The motors are a lot quieter now and I can achieve a much higher speed on the z axis. Previously I couldnt get above about 5mm/s without binding & stalling. Now I can get 10mm/s and more. I have set the max speed at 10mm/s (600mm/min) as any faster is probably putting undue stress on the steppers. I have 1mm pitch leadscrews so 600mm/min is equivalent to 600RPM.

Edited October 1, 2018 by tekkydave