McWire RepStrap Z-Stage System

I posted on my blog about a z-stage system that I got from these Universal Stereoplotters I tore down. The basic idea is that you use a couple of magnets to hold the extruder head and mount plate with its bearings to a plate that is attached to the cartesian bot frame. The pictures on the blog make it more clear what I'm talking about.

[the1001opinions.blogspot.com]

Obviously the part with the roller bearings on it doesn't have to be so complex and you would also want the mount plate to be longer to allow for more travel but it seems to be a good idea overall and much better than using bolts, springs, etc to tension another couple bearings to keep the two pieces together.

Demented

Hi Demented,

... for this ready-to-use part it's a good idea, but if you have to build it from scratch, then it would have some problems with accuracy and weight (iron/steel for the magnets) or you have to apply a iron-sheet for the magnetic fixing ...

The idea with magnets as 1-dimensional fixing is good, but the possible holding-force is depending of the iron-sheet-thickness, so the weight of the traveling part is essential - better apply the magnets on the travelling part and the iron on the basis, so you can make it light by building from aluminium or even reprapping ...

Viktor

Viktor,

Sorry I wasn't clear but the magnets are on the traveling base and the steel is fixed. I also figured that one could use sliding bearing tracks to handle the slop and accuracy of the system. Making it adjustable allows people to mess with it until it gets to the desired level of accuracy.

Demented

Hi Demented,

... as you know, i'm a big fan of magnets as assisting elements

It's dependant of the involved forces, what you can make with them - for a leightweight extruder- or a laser-head it's no problem, when i have more or heavier toolheads, then the magnets and bearings have to be bigger or in another arrangement.

When you manage to balance the masses, so the feeding is vertically symmetrical or you have only a horizontal feeding, then i can help you with some hints for very accurate and friction- and stick'n'slip-free feedings where i use magnets, plane surfaces and some ferrofluid ...

Viktor

Viktor,

I see what you are saying. For this application I think the magnets don't need to be that strong. The extruder heads are very light and as long as the feed line comes in vertically symmetric. I can make it do that so it isn't a problem. I haven't seen what other options there are and how they work so I'll be watching for better ways to do this in Zach's design and others.

Demented

Zach,

You asked for some more detailed pictures of this device. I took a bunch from all different angles and have posted them on Picasa

[picasaweb.google.com]

Hope that helps.

Demented