Skeleton 3D -on steroids-

[Chriske]

3 years(or so) back my pal Marc has built a Skeleton-3D. It's a cute little printer that works very well. There was one major problem with that original concept, and that's the extruder, so I redesigned that extruder completely. That Skeleton has a capacity of just 100x100x100mm.
A few weeks back a fiend(Walter) asked me to help building a very small 3d-printer so I proposed him that Skeleton, only it's size is double that of the original Skeleton, 100x200x135. Walter is in modelling (trains) And said he only needed that printer for very small parts. And maybe he'll print some other larger parts with it. He's planning to use very small nozzles, depending on the size of the parts he'll be printing, he will use 0.3 or 0.25 or 0.20 or even 0.15 mm nozzles.?  That's a big difference compared to my own goals. I'm planning to use very big nozzles in my own printers, 2.0mm and beyond. My largest nozzle at the moment is 1.5mm and does a good job.

Anyway, this is how that little guy looks like.
There are only 2 parts I did copy from that original Skeleton on Thingiverse, the rest I needed to redesigned. I also integrated a fast interchangeable hotend, so he can swap hotend in a matter of seconds.
This printer almost fits on a sheet of paper A3. Normally I could have made it smaller but Walter wanted to use these big 2.2kg filament reels. That big reel is stored under the printer itself. The filament is guided upwards through a teflon tube. To be clear it is NOT a Bowden drive system. It's a direct drive. That big reel is mounted on two ball-bearings, so there's no friction at all. I use this system in all my printers.
He'll be printing on glass(not in the pictures yet)

And this bleu one is Marc's Skeleton. (with a completely redesigned extruder)

[Gina]

Very interesting ?  So that threaded rod framework is stiff enough then?  I guess being so small it can get away without needing a solid box.

[Chriske]

34 minutes ago, Gina said:

Very interesting ?  So that threaded rod framework is stiff enough then?  I guess being so small it can get away without needing a solid box.

It's surprisingly stiff, but I wouldn't make it much larger using threaded rods. There's no way it would work with longer rods.
I remember when I've built Prusa i2, years ago, I had to clamp these printers at 8 different point to it's cabinet. So doing I expected to stiffened these printers, still I ended up with very bad perimeters(mostly gosthing) We've made and tested about  20(probably more - I've lost count) different printers. It was only when I started building printers in sturdy wooden boxes, that's were the perimeters of my parts started to get far better. Not just these sturdy wooden boxes helped improving the quality of my prints. There are a few more items I've changed to improve that quality.

Still, after a few more tests, I'll decide whether there's need to reinforce that framework or not.

[Chriske]

Yesterday some more tests and seems that some reinforcements are needed. Printer must be stiffened a bit.
Prints are ok but there's some ghosting in the perimeters. So the new owner needs to print a few brackets and install some 45° angled threaded rods, connecting the most upper part of the printer with it's wooden box below.
This modification will be a good exercise for Walter because he's a novice at 3D-Printing.

[Chriske]

Meanwhile we've tested that partially heated beds I've installed in that Skeleton. I wanted to test if it would work, and it did...!
I've installed two small 100x100mm beds side by side under 3mm thick layer of carbon-fiber. One bed is directly connected to the RAMPS and the other is interrupted by a switch also connected to that RAMPS. There's only one thermistor. That thermistor is installed under the bed that's always 'ON'.
In case of very small parts Walter needs to place that object on top of the 'thermistor-side' when slicing. In case of larger parts he'll be using both parts of the heatbed.

This is in fact a first step to do just the same when I start building my large printer. I'll be using nine 100x100mm heatbeds side by side to cover the 300x300 buildsurface of my new printer. In the end saves lots of energy(at my rate of printing...). A large silicone bed 300x300mm consumes about 750w(230V)...
There's absolutely no reason why I should heat that large surface when printing only a very small part.

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In case of very small parts I only use part nr.5
Long and narrow parts I probably will be using 4+5+6 or another possibility is to use 2+5+8
In case of somewhat larger parts I'll be using 1+2+4+5 or maybe 5+6+8+9
etc....
Needless to say the thermistor sits under bed '5'