Mendel design (an idea)

I've been wondering the mendel designs based on movies i saw on how it works.
And i came to wonder, and so (without having actually buid one) i'd like to give a sugestion.

The up and down movements are based on long screw threaded axles (sorry dont know the right english word for that)
Two of those upwards axle's are rotated trough a band system at the bottem.
The printer head itself moves left right on a rail system with the left right engine on the print head.
It seams pretty complex to me, although ingenious too some technical minds make wonderfull complex things

The idea i have is a bit simpler:
Make only 2 threaded verticle axle's static (not rotatable)
have two horizontal screw threaded axles; on each end side place an electric stepper motor to be able to rotate them.
One can be used for up down, the other one for left right; so the printhead would becomme smaller.
Which would improve stability and accuracy as the moving printhead becomes lighter in weight
Instead of accuracy it might also allow for faster printing. ( faster vs accuracy )
The printhead would use the updown axle only as glyder rail. and the other rail for its left right movement.
For up down moving a normal screw should have a cap so it could be driven by the threaded axle
Since the updown driven axle is only using threading at the ends it might be a normal axleo too and only use a plastic cap part to create a worm axle to drive that updown screw.

I think this requires the same amount of axle's but removes need for bottom rubberband system.
A solid main structure would also strengthen more (the top ends could be soldered as well
maybe fused to printboards, as soldering is maybe a more simple construction too
Maybe also the electric up/down engines would require less power this way (but i'm not deeply into such knowledge)


Well its an idea i have not build one, cannt make enough time free for it currently

Edited 2 time(s). Last edit at 09/28/2011 06:03PM by PeterArt.

Maybe at least post a drawing? I don't quite follow what you are saying there. And as for simpler bots, take a look a the Prusa variant of the Mendel printer.

see attached pen sketch

On the left top i detailed the "screw gear cap" the left engine drives them on each side by a worm axle to allow for up down.
The right engine drives a worm axle on which the printhead platform get its left / right (the platform is fixed to it by 2 screws (maybe one will do too).. that same platform uses a holow pipe glider around the other worm axle that is for up/down so the platform stays horizontal.

Well one could get the idea from this i believe, i hope its clear

Different from prusa only 1 engine for up/down.
Different from prusa and from the original mendel, no ruber / chain bands at all (a less complex design ?)


Note the horizontal axle that drives the updown part doesnt need to be a complete worm axle from begin to end, if only the ends have a worm part thats enough. (one could print them so they can be larger)

Edited 4 time(s). Last edit at 10/02/2011 03:26PM by PeterArt.

I think a belt/pulley would still be less complicated than custom machined steel rods.

The belts work really really well and are quite simple in my opinion.

Seems vaguely similar to the ultimaker approach, but with gears instead of belts. Could certainly work, but would be hard to implement (for me, at least)

Just to explain further the difference between a threaded shaft and a belt... a belt is very fast, simple but low torque. In other words you wouldn't be able to drive a CNC wood router with a belt hooked directly up to a small stepper like in the case of 3D printers. The screw can be fast but you need to go to custom designs or acme threads with multiple starts. Either way you loose speed with a screw unless you are willing to pay for something custom. Screws are solid and accurate as long as you don't make them too long.

On your design the platform seems to be where the extruder mounts, correct? So your right left is the X axis. I'm assuming the in-out or Y axis which is not shown. The confusing part is the origin of the z axis screws seem to be mounted on the same platform assembly that holds the extruder. If that is the case how can you mount the elevation mechanism on the same platfor that it is suppost to elevate?

Try sketching ideas in isometric form. Or try cutting and gluing up your idea in something like cardboard, wood or foam. Or learn a cad program. there are a number that are free.

the lower part of the picture is a top view, so the two axles you see there are horizontal in the same plane.
The right stepper motor controls left right.
The left stepper motor controls updown.

(both stepper motors could be placed on one side too, but i think this is better balanced this way)

Left/right speed might be a problem..although worm axles, require little force to move something while they are strong to move a screw; maybe a lighter faster stepper motor could be used here.


For the updown one think of this image and put a fixed screw in its center (then it can climb an axle)
almost like this