update 2 22-12-18 I have tried adding a 10mm linear shaft to each leadscrew in the hopes that that would fix the z-wobble, it did not. I have now abandoned leadscrews and am going back to one of my previous attemps: a belt driven bed. I am leaving this thing up for anyone who wants to experiment with this themselves.
update 1 A weakness of the current design is that the leadscrews are relied upon for keeping the build platform steady in the xy plane, which they are not meant for. The new design will incorporate 3 10mm linear shafts to adress this.
I wanted to completely eliminate the z-banding/noise caused by stiction in the lineair bearings/bushings on the z-axis guides. I did this improving rigidity in the z-direction with a belt driven triple leadscrew build platform.
The end result is an absolutely rock-solid build platform. No give whatsoever. You also get about about 220mm build height out of this configuration.
This conversion requires about $15 in parts in addition to the printed parts.
so how do I do this?
The frame needs to be modified to accomodate the new triple leadscew setup because the leadscrews have to be secured at both ends. The distance between the top and bottom extrusions of the frame needs to be 30cm for this purpose.
This leaves no room for the coreXY part of the printer so that has to be moved above the top 2020 extrusions. If the CoreXY part remained in the same orientation as in the stock hypercube the nozzle wouldn't be able to reach the print bed. So all the CoreXY parts (belt idlers, left/right motor brackets and shaft clamps) have to be flipped upside down.
The original hypercube was designed in such a way that if the CoreXY parts butted up against the top 2020 extrusion they would be alligned correctly. To achieve the correct allignment with the flipped CoreXY assembly, whilst still having enough room for the XY joiners to move along the shaft, there needs to be 17.9 mm between the top 2020 extrusion and the CoreXY assembly. I've made a simple spacer for this purpose.
To couple the three leadscrews I've spliced my own looped belt by cutting away teeth from one side and material from the other and fusing them with CA superglue. You can buy a looped belt if you don't want to do this.
The build platform is attached to the leadscrews via two parts: t8 adapter & bed to t8.
These parts are separate to allow for precise allignment of the build platform to the leadscrews and frame before fusing both parts together with CA glue.
- two additional t8x8 mm leadscrews (or three t8x2 leadscrews for more accuracy)
- one gt2 belt idler
- one small looped belt to connect the z-stepper to a leadscrew.
- five 20 tooth gt2 pulleys
- one 30cm 2020 extrusion (for the build platform)
- a small scrap piece of 2020 extrusion to connect the belt tightener to (8cm in my case)
- six KFL08 bearings
- a 100cm to 110cm looped belt or 130cm of belt to splice yourself
please share if you make a leadscrew driven platform yourself!
don't forget to reverse all motor directions in marlin since all motors are upside down from the original configuration