My custom D-Bot

Phaedrux

Over the past year I've been planning, building, and commissioning a custom D-Bot CoreXY I call the Z-Bot. I chose the D-Bot because it seemed fairly sturdy, was expandable to the size I wanted, and there seemed to be a decently sized community surrounding it. There's still a few things I'd like to do with it, but for the most part I consider it finished.

ZBot

Details:

300mm^3 D-Bot hardware kit from AliExpress
300x275x300 print volume
DuetWifi with 7" PanelDue
MeanWell SE-200-24V passively cooled PSU
13"x13"x1/4" MIC-6 aluminum build plate bonded to 12"x12" PEI
600w AC Silicone heater with Fotek SSR-40DA relay
0.9 steppers for A and B motors from SteppersOnline
1.8 stepper for the Z Axis
Three TR8*1mm lead screws connected with 1524mm GT2 continuous loop belt
Titan Aero extruder on custom carriage with BLTouch, belt tensioners and C shaped cooling shroud.
E3D pancake motor for extruder
Gates GT2 belts
Delrin V-Wheels
Aluminum spacers and precision shims.
Hardened steel 0.4 or 0.6 nozzle, 40w heater, PT100 sensor
Suited for high temp plastics
Sunon blower and Noctua fans for quiet printing
Z Max optical endstop for power failure recovery
PSU has integrated USB power ports and voltage display
Buck converter provides 12v for the fans
Raspberry Pi Zero W with camera module running MotionEye, powered by PSU USB ports.
Proper grounding throughout with a Ground Fault Circuit Interrupter plug
Aluminum plates and brackets in place of plastic where ever possible
Plastic parts printed in AMZ3D Red PLA and SpoolWorks Red PETG
Prints comfortably at 133mm/s with moderate acceleration and jerk settings.
Travel moved at 233mm/s 3000mm/min acceleration.

Here's a list of the key mods I used on this printer:

ZBot

The Z axis took the most time to finalize. The DBot's biggest weakness in the stock build is the bed. The stock build is only for 300x200 and uses a cantilevered bed supported at the back on V wheels and requires you to find the center of gravity for the bed assembly to position the lead screws. On a 300x300 build the amount of droop and bounce is unworkable. Furthermore, the stock build uses 2 Z motors which are problematic to keep in sync.

My solution was to add another beam and wheel assembly to the front so that it rides on all 4 corners. Then to balance the weight between 3 lead screws, one at the middle back, and two at the front left and right. This makes for a very solid bed that rides smoothly up and down the vslot.

ZBot

To keep the 3 screws in sync I used a single motor and a 1524mm continuous loop GT2 belt. Each screw is supported in it's own double bearing block. The motor mount also doubles as a slide tensioner for the belt. Both are existing mods from the community.

ZBot

In order to reduce the torque requirements for the single motor, and to prevent the likelihood of the heavy bed auto rotating downwards when power is removed, I chose 1mm lead screws and a 1.8 motor and a 2:1 gear ratio between motor and screws. (20T drive pulley, 40T screw pulley) It also allows for 0.0025 mm layer step intervals for high Z resolution.

ZBot

Originally I worried that the Z axis would be very slow in this arrangement, but it's actually turned out to be very stable, and quite fast. My only disappointment in the build is the aluminum plate has a slight bulge on one corner, likely from shipping damage. Mesh bed compensation to the rescue.

Where possible I switched to 3 wheel carriage mods with tensioners to help make getting the wheels aligned and equally tensioned a lot easier.

With the Titan Aero and a 40w heating cartridge I've managed PLA print speeds up to 200mm/s (0.4 width, 0.2 layers, 215c) on infill and perimeters with good quality. Overall I'm very pleased with the quality and speed of the printer, thanks in no small part to the Duet. The power and flexibility of RepRapFirmware cannot be understated. Being able to create and customize macros and live adjust values is a game changer. I can never go back to the way it once was.

Here are some example prints.

lawn darts

Lawn Darts printed at 0.3 layer height @ 100mm/s

benchy

boaty

alt text

For anyone building a DBot and wanting to see my configs, you can find the original config files here: DBot Config Files

More modern example config file sets for RRF2 and RRF3 can be found here: https://github.com/Duet3D/RRF-machine-config-files/tree/master/DBotCoreXY

More photos of the printer and example prints can be found here: Photo Album

Thanks for taking a look.

Coffee

NICELY DONE !!! I dig the red printed parts!!

Phaedrux

@coffee Thanks. AMZ3D Red PLA and SpoolWorks Phonebox Red EDGE (PETG). It looks a lot redder in person.

jackatom74

AWESOME!!!!

Dr_Ju_Ju

Well done , similar to my DBot, but i've gone for the dual z motors. I like your print carriage \ cooling fan parts, have you published them anywhere ?

I tried a Titan Aero, but just couldn't get it to print nicely, so I've reverted to a normal Titan, combined with a Precision Piezo, which gives great prints.

Phaedrux

@dr_ju_ju Here you go, https://www.thingiverse.com/thing:2849355

It's not my design but I've made a few variants of it to fit more stepper sizes.

Dr_Ju_Ju

Thank You

AS-3D Druck

You're D-Bot looks way cleaner than my.
Is the 3 Leadscrew System woth it?
I got 2 with a BLTouch as a probe and i'am not shure if the 2 Leadscrews are not good enough or the Z Probe is crap.

T3P3Tony

great looking printer, I like the cable management!

Dougal1957

@as-3d-druck said in My custom D-Bot:

You're D-Bot looks way cleaner than my.
Is the 3 Leadscrew System woth it?
I got 2 with a BLTouch as a probe and i'am not shure if the 2 Leadscrews are not good enough or the Z Probe is crap.

the advantage with 3 is that then defines a plane so when setup correctly the bed must always be level when you have just 2 then that is a pivot point.

Doug

Phaedrux,

Are you planning on releasing any of those custom files for the z carriage?

Paul

Phaedrux

@as-3d-druck I would say that using 3 lead screws is worth it. It's far easier to get them leveled and lined up. I just lower the bed as far as I can, loosen off the bolts for the mounts of on the frame and the bed and let everything relax and align, then retighten and raise the bed. I run the z motor at 80% of rated current (~1500) and I get no binding or skipped steps top to bottom.

I've seen people use 2 screws belted together to keep them in sync, but then you still have to find the balance spot. At the very least adding the front cross bar and wheels keep the bed from bouncing and should help make the sweet spot for balancing the bed a little more forgiving.

You could also go another step further and use 3 or 4 independent motors and do auto leveling. But the extra cost and complexity didn't make sense to me.

@t3p3tony Thanks, it wasn't always so tidy. A few of the pictures in the gallery show the work in progress wiring and there were times when it looks more like a pile of wires than a printer.

@hozza I updated the first post with a list of mods used with links.

Phaedrux

This post is deleted!

Phaedrux

This post is deleted!

@hozza I updated the first post with a list of mods used with links.

Brilliant thank you...

Saltypetz

https://forum.duet3d.com/topic/5280/need-help-with-x-stop-and-bltouch
You were great help and you almost have me there.

Thank you so much for your help

Ak Eric

Looks great. I have a heavily modified C-Bot (D-Bot wasn't around when I made it) and I really dig your z-axis leadscrew setup. Nicely done!

Phaedrux

@ak-eric Thanks a lot. I read through your build logs while I was planning out the build. Definitely learned a lot.

Stealthy_TT

Love the build. This is my next build, But I wont be ordering the kit, I cant seem to find a D-bot thing on Thingiverse, I did see your Thing on there and will be using it. Is there a thing with all the files that need to be printed? My plan is something like a 22x22x24 build index, don't need it but why not haha.

Phaedrux

@stealthy_tt here's the stock DBot thing https://www.thingiverse.com/thing:1001065

And here is the thing with all the mod files for the z-axis setup I used. https://www.thingiverse.com/thing:2651649

Stealthy_TT

@phaedrux Thank you, I couldn’t find it to save my life.

uncreative1

Thanks for posting this. I am in the process of ordering parts for a new D-Bot build pretty much identical to yours. I have a quick noob question; On the 3-lead screw mod, what GT2 pulleys do I need to achieve the 1:1 ratio for screws and motor? I've ordered these 8/2 lead screws: https://www.amazon.com/gp/product/B017AR5QBS/ref=od_aui_detailpages01?ie=UTF8&psc=1 and these stepper motors: https://www.amazon.com/gp/product/B06ZY9SPWL/ref=od_aui_detailpages01?ie=UTF8&psc=1. Im just new at this and am unsure about the pulleys as there are so many choices.

Phaedrux

@uncreative1 Are you planning on using a single motor to turn 3 screws, or one motor for each screw?

The screws you linked appear to have 8mm of travel per revolution which would be fairly steep in my arrangement and might require more torque to lift a heavy build platform than a single motor can reliably provide. This wouldn't be as much of an issue with one motor for each screw though.

For the pulleys I just chose 40 tooth GT2 pulleys to give the belt ample surface to grip. They are the same tooth count between the motor and the lead screws, which gives 1:1 ratio. 5mm bore for the motor and 8mm bore for the screws. The triangle arrangement ensures that the belt gets good contact and reduces the chance of slippage.

Here's a link to the pulleys I used. https://www.aliexpress.com/item/10pcs-New-GT2-Timing-Pulley-30-36-40-60-Tooth-Wheel-Bore-5mm-8mm-Aluminum-Gear/32822906054.html

In your case, you may want to change up your gear ratio between the motor and the screws to gain more torque. For instance, a 60 tooth pulley at the motor and 40 at the screws.

ntgorilla

This is a really pretty build, and it's made me pull the thread on building one. I just bought a kit and am looking at what other parts I'm going to need to buy. I definitely like some of the changes you've made and used, and plan to use some myself. Looking through your pictures and this thingiverse file you used (https://www.thingiverse.com/thing:2401504), and I'm not getting how the lead screws stay secure in the flange bearings. He said something about using 8mm clamping collars, but I'm not seeing how that would keep it any more secure than the toothed gear. Am I missing something? I looked through your pictures, but couldn't from the angles. Thanks for sharing your build!

Phaedrux

@ntgorilla Thanks for the compliment. I think you'll enjoy the build, it's a challenge, but pretty satisfying when it all comes together. Spauda01 did well on the design.

I took some more pictures of the lead screw mounts that show how I have used them. I didn't follow exactly the description from that original thingiverse mod. The pulleys I used have a body small enough to sit comfortably on the bearing, so the weight of the bed assembly holds it down onto the bearing. The lead screw protrudes from the bottom just enough for a lock collar to clamp on and keep the lead screw in place against any lifting forces. It doesn't do anything else other than let you clamp the lead screw into the bearing sandwich.

During installation I slide the lead screws into the bearing blocks and put the collar on so that the end of the lead screw is flush with the collar. Then I push down on the pulley and up on the collar and secure the set screws of the pulleys. That keeps the lead screws quite secure in the mounting block.

Before putting the belt on I rotate the lead screws so the tops are flush with the top of the nuts in the bed mount. Then carefully wrap the belt around the back pulley and then side pulleys without making them rotate to keep the in sync. Then into the tensioner. It really helps to have a second set of hands for this step. I try not to tension the belt too much or else it deflects the lead screws a bit which can cause binding when the bed is at the lowest extent.

Speaking of binding, it's also critical to get the lead screw bed mounts perfectly lined up with the screw mounts. The bed frame needs to be tightened in stages to allow for some wiggle room in the X or Y. The Z wheels need to be aligned on the V slots before being tightened. Everything needs to be done in stages otherwise you will run into binding.