Jovian published a new build:

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while building up the case for this build I was looking around for what extruders and electronics I wanted to use and think I will settle on E3D 1.75 Direct Drive for flexible filaments, their Kraken extruder for a multi-material/color extruder and likely the Duet for electronics as its the only one that I know of atm that has enough connections to run all the kraken extruders

The Duet gives you a WEB interface this is the Open way to go for interface control.
Would be nice in HTML5 & CSS3 so all browser platforms would work over your private LAN.

Or, plug a RaspberryPI with OctoPrint installed into the board's USB, and run it wirelessly in any browser from any computer, tablet or phone allowed on your wireless network. And using Splashtop security to access the home network from outside you can not only manage the printer but watch it with Raspberry's built-in support for camera, from the beach if you want to. One Raspberry/OctoPI can handle as many printers as you can plug into the Raspberry's usb hub and will work with any controller board. And if it matters - OctoPrint is HTML5 & CSS3 running through Python, with source code freely available with Apache License.

As for E3D. Finally! Truly awesome extruder. Filastruder.com has USA inventory for quick (reasonable) stateside shipping.

I just got a Megatronics board in today. Looks like it has more features than Duet for a lot less money but single card design. I'm hoping to replace RAMPS 1.4 with it.

Does the top wobble back and forth?

Jovian

Even if two motors at the top of the Z axis posts do not cause "wobble", they will likely cause vibration that will show up in perimeters. The skp was saved sketchup v13 so I couldn't view it with my v7, but from the snapshot it looks like maybe small 34mm length nema 17 or lighter nema 14s could be mounted down on the bottoms of the posts for threaded rods. Or, put an idler at the post top and run belts instead of threaded rods.

That said, I've shied away from designing with "belt in pinion" for a printer. That concept seems suited for slower moving axises such as engraving, routing, laser cut, etc, but not plastic printing. Consider on your design that the weight and inertia of 3 nema 17s (excluding extruder motor) will all be moving on a rectilinear 45 degree infill. Consider infill for a 2.5 mm wall. The inertia will have to be stopped, reversed and accelerated for strokes that are less than 1mm in length. Even at a snail's crawl of only 10mm per sec that reversal will be happening 10 times per second. I'm thinking that lock-tight on all your frame nuts might not hold it all together.

I see you are using MXL belts and pulleys. MXL are perfect timing belts for one-direction travel. The GT2 is designed for two-direction without backlash. Considering the inertia powered backlash you'll have to deal with you may want to try GT2 belts. Even in the tight confines of a "belt in pinion" I think you're still going to have considerable backlash reversing that inertia.

I'm developing 3 printers with mini v wheels on the X axis using the E3D extruder. Originally I had the motor above the plane of the two top wheels. By moving it down so the center of the motor's weight was also center between the top and bottom sets of v wheels (and center to the v-slot bar) I picked up more than 40mm/sec speed on infill and 20 on perimeters. That single motor's inertia vibration was that pronounced (another good argument for bowden extruders).

But, I'd certainly love to see you prove me wrong on the inertia problem. That way I could spend another two months tearing my design apart !AGAIN! to try something different (next week's venture - fishing line). Keep us up-to-date on your progress!

Keith
I have thought about octoprint but my hesitation is with it is that its yet another board to setup and maintain where as the duet is all contained.

Just got my first e3d running today and gotta say Absolutely LOVE it. Zero issue with a couple hour print in pla ootb.

I will have to look at the megatronics boards. thanx for letting me know about them.

As for the shaking, vibration, and inertia. I am very worried about those things myself as you pointed out. But I am curious enough about to see how bad it really is with this setup. If it works we have a incredibly scalable printer. If not well back to the drawing board.

Thanks for the tip about the belts as well. I hadn't known that and was using the ones I have since I had them around. Guess I will try with the ones I got if they don't work or have too much backlash I will look at the GT2s

I think a threaded rod would have a lot of inertia. The only way to reduce the inertia is to put the motor in a fixed mount at the end of the axis and run a belt loop like repraps do. I think you could also do what locomotives do for braking - transfer the inertia from stopping into compressing air, and then release the compressed air back to the wheels to accelerate. You could probably get away with using an electric clutch in reverse and have it charge/discharge capacitors. I dunno. It would be like the v-slot power-assist technology, haha.

Dude you could put anti-wobble technology at the top like they do in skyscrapers. I bet you could even 3d print a part and stick ball bearings in it and then glue it on top of the machine and it would probably work.