I think the updates that would allow an enclosure and to beef up and make the frame more sturdier would be awesome.
The other upgrades sounds good to me I have not built it yet so I'm not sure but would be relying on what other people say and what you think would be the best route to go to make this printer the best that it can be.
I guess I will wait before I print se parts for my printer. Maybe after all the other input and the decisions are made exactly what you're going to upgrade, would it be possible if you could let me know what parts would still be original and that way I could start printing them right away.

I also like the option to be able to move the lead screws to the middle front and middle back for the z-axis. I guess that is what AKEric did..

 

Two motors on a cross beam is what I went for, Carl mentioned the front back motor arrangement which is what Eric did. They seem to have about the same mechanical stability, both require an extra piece of extrusion. Either way, I think 3 lead screws is only necessary with a very large or very heavy bed.

Side by side of the D-bot and the 'E'-Bot.

 

@Carl Feniak : I've found one specific 'issue' of the front\back leadscrew\stepper arrangement, really just realized last night: I turned on the 'lower platform on retraction' option, and... it did a lot of 'squeaking' during the retractions as it lowered and raised the bed (specifically on the 'raise' part): Previous, with both leadscrews in the back and I enabled this option, there was really no noticeable sound. But on the front leadscrew, where it goes through the acme block, it 'squeaks' now: If I shove a bunch of grease in there it cuts down on the sound.

I've not noticed anything bad happen because of this, print quality doesn't suffer (and again, the build platform is far more stable overall), stepper temp seems normal. Note that when the bed lowers between layers, there is no noticeable sound. Even when the bed raises after a print it doesn't sound out of the ordinary either, until it gets to the veeery top, and it squeaks a bit. Which now makes me wonder if my squeaking is isolated to the first few inches of print, (and my print last night was only a few inches tall...).

Just tossin' it out there. This isn't to discourage anyone from trying, and I have a feeling if anyone went the ballscrew rout this sound would probably just 'go away'. I'm thinking it's the added friction of that front leadscrew on the acme block lifting the weight of the platform, since grease seems to help.

 

I had squeaking with my screws too. A drop of light mineral oil killed that mouse and haven't had a squeak since. Also using the delrin block.

 

Wanted to share my new Duet case for my C-Bot...



Now I just need to get it all wired back up.

 

A few random thoughts:
3-point mounting for the bed might be an improvement. It was certainly an improvement on my Ultimaker when I changed from 4-point to 3-point leveling. 3 points always form a plane and made leveling the bed much easier.

Any thoughts on moving the Z-axis ends & motors to diagonal corners, e.g. the front-left and rear-right? mount for the screw nuts could be made part of the axis ends. It seems like that would help with the cantilever effect, but I'm no engineer.
Would a belt-drive Z axis like this design be workable / an improvement / cheaper : Axe Z pour smartrapCore (alternative Z axis) by andreasL ? With the Z-ends on diagonal corners a continuous belt wouldn't be needed, unless the Z axis height is greater than sqrt(X^2+Y^2) or a bit less than 17 inches for a 12x12 machine, as a cut belt could be joined along the bottom horizontal section.
Speaking of cheaper, would 3 v-slot wheels per axis end be rigid enough? 2 on one side - guessing top for XY ends/carriage and outside for Z, a single centered on the other side w/ eccentric nuts to tighten it down.

I got a spool of carbon-fiber filament (XT-CF20 from Colorfabb) as an early Christmas present, but no time to start printing C-Bot parts until after the new year...


Edit: Also - 1 more idea - attached is a frame corner concept I was working on for 2020 misumi profile. The idea was to tap two of the extrusion ends and bolt to the 3rd extrusion. I designed it corner-up to minimize interlayer stress, and to be printable without bridging or overhangs. I never finished the design and some small corners on the inside around the bolt clearance holes are unsupported, but that's fixable. I could do a redesign for 2040 v-slot with side-mount screw holes like the openbuilds corner plates if anyone's interested.

 

These look like good improvements. I had thought that the front XY motor brackets needed a brace between the motor mount plate and the extrusion corner bracket. Do they flex much without it?

I especially like the 90degree corner brackets. They look very solid. Possibly a bit of a waste of material in the diagonal braces? I'd imagine a right angled triangle cutout in the centre of the brace wouldn't reduce the strength that much?

Talking about braces...
Coming from a wanhao i3, there is a popular set of brackets that brace the Z to the Y with threaded rod, and printed adjustable nut covers.
Here's a link: Z braces for Wanhao Duplicator i3 by AzzA
Idea being that you lock one end, and then adjust the other to set the ZY in place.

I was thinking of using the same idea with threaded rod between diagonal corners on a side of the printer (then duplicating on other sides where required), with a modified 90degree bracket at each end. The bracket on one end (smaller) has a pair of nuts locking the threaded rod from rotating or moving up and down its own axis. The other end of the rod has another 90degree bracket (larger to allow for movement) with a captured nut that will move the 90degree bracket along the axis of the rod, allowing you to tension the diagonal.

I'll have a go at modelling something tonight as I've been mulling this over for a week or so now, and should really get working with it.

I'm nearly ready to assemble my solidworks re-modelled c-bot. It's 500mm extrusion on almost all edges and stiffness of the frame concerned me when a few mentioned it a few weeks ago.

Few cheeky photos to boot!

 

Would it be easier to put an enclosure plate on the very bottom of the printer so you don't need cutouts for the motors etc?

 

Is your cold end fan connected directly to the 12v power supply?

Some slicing programs specify retraction distance and the retraction re-feed distance seperately, I had that problem where it would print something, retract, then not refeed the same distance before continuing to print.

 

Are you cooling your stepper driver chips?

Is it the extruder motor that stops turning or does the filament keep feeding and disappearing? Are you fan cooling your stepper motor driver chips?

 

Have you done PID tuning of the hot end thermistor? If you are running from a program like Repetier Host, command the hot end temperature to various levels and look at the temperature graph to make sure the temperatures are going to the levels commanded.

It seems like a wrong setting in the slicer, my first print came out wrong because the default filament width was 3mm so it did not extrude enough. Go through all of the settings menus and submenus in your slicer to verify everything matches your setup.

You don't have to fan cool your motor driver chips, but they should at least have heatsinks. I like to fan cool my electronics to be sure everything runs well, I say better safe than sorry.

 

PID tuning the hot end thermistor is critical for proper operation.
@AK Eric did a good walkthrough on his blog Building the C-Bot 3D printer: Part 21 : Software Day 4: PID Autotune & start/end G-Code

 

How would you enclose the top where the flex tube has to feed the moving hot end?

 

It came standard on my Printrbot Simple Metal and I really like it. I was planning on using an optical device on the C-bot. Haven't decided on auto leveling or just stick with manual.