Easy to build linear stages

Hi Viktor,

When you say "soft-pressing" about your ferro-fluid peristaltic pump does that mean low pressure, or "soft," but possibly high pressure? i.e. not "harsh," so that the blood cells get to flow out of the way before being crushed?

Also, Why can't you design a tripod that can be stiff? It seems to me that triangles are considered more stiff than squares, but that may only be ture if they don't move. People have built buildings out of triangles to take advantage of the structural features. The darwin itself takes advantage of triangles to reinforce it's cube shape. Of course, maybe all this only applies to the frame, which is closely related to the positioning system in a tripod.

How hard do you think it would be to make a scissor-jack style tripod that could collapse and expand in the z direction, allowing it to allocate workspace, either wide and short, or thin and long? This could also enable the device to get longer then it's longest tube, allowing it to make all of its own pieces. You don't really have to make the collapsible reprap to meet that design constraint, but it might still be useful. Just wondering.

-Samuel

Hi Samuel,

... 'soft' mean, that the ferrofluid in the magnetic field can perform only weak pressure forces - dependant of the size and strength of the magnets, the amount of feerofluid and the gap-width i achieved some Newtons as pressure on the complete surface, what mean, that the compressing force on the tube is a bit lower.

Normally a wall of ferrofluid can withstand a pressue of 0,3 to 0,5 bar, what should be the pressure on the tube too ...

To the tripods: i can make a stiff tripod for milling, but with my 'self-joining' magnetic hinges there is the possibility, the speres displace a bit, when i apply high foces and vibrate the structure through the stepper-motors ...

When designing a 'milling'-tripod, i use massive ball-hinges, were the gliders are from sintered metall or plastic, so they aren't so precise in translating micro-moving, as the not gliding but rolling magnet-ball-hinges.

Look at the second image - 'CA-Tripod.jpg' - here normal ball-hinges are used, so the system ist stiff, can perform high dynamic movement for milling or so, but isn't able to move precisely in the sub-micron-range, as my Mini-Tripod ...

Viktor

... i'm nearly ready with the mechanics of my vertically aligned Tripod: [forums.reprap.org] (from here: [forums.reprap.org] )

Viktor

Viktor,

Looks good. I would be interested in seeing some video of it running through some test movements when you get it up and running. Looks like a really solid design that does not suffer from too much "part bloat" as other designs tend to.

Keep up the good work!

Demented

Hi Demented,

... i'll post the next steps of progress in the builders blog - when the software/drivers will work, then some videos too ...

Viktor

My attempts to build a simple linear stage have been hampered by the screwed rod bought from several local suppliers not being straight. Is it possible to buy threaded material on a RepRap budget that will rotate without a millimetre wobble?

Farnell do M8 1M threaded rods for about £2. I haven't bought any M8 but I have found their M6 and M5 perfectly straight.

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[www.hydraraptor.blogspot.com]