Bamboo Printer

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Revision as of 22:59, 19 August 2013 by KalleP (talk | contribs) (name possiblility)
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Bamboo Documentation
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Bamboo-Printer

Release status: concept

Bamboo printer.JPG
Description
A compliant link mechanism, no bearings
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Based-on
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CAD Models
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This will eventually become a development page. Please comment on the discussion page if you have any thoughts on the ideas here.

Introduction

At the moment it is just to store a couple of ideas that I have that may allow the use of natural herbal supplements instead of vitamins. Basically I am thinking of using cheaper mechanical components to allow for building in less industrialised regions by making use of more parts from nature or the hardware shop. A couple of the other components may need to be less standard but may become cheap if there is a little development added to them. Parallelism at a low complexity has been my goal. However it is also of no consequence if the rotational error is measurable (then it can be calculated away) or the optical centre of the absolute position detection camera is positioned with the extruder nozzle (it does not matter if the part rotates slightly under a point source dispenser) but this configuration cannot use the simple double wishbone Z-axis with the Z dependent X error.

A specific drawback to this idea is that it is likely to have a larger in footprint than an industrialised RepRap but there is room to make modifications especially if some of the parts are printed (or laser cut) instead of found in the back yard.

This project cannot work yet as some of the ideas have never been tested and I do not have the personal skills to do the development. I hope to develop it to a point where just one or two people/teams might be able to complete the missing bits of this idea at which point it could become a viable development path.

Compliant linkeages

I have decided to call this the Bamboo Printer not because it prints in bamboo but because of the innovative use of bamboo (or other flexible material like glass fibre reinforced tent frames or ski poles) skewers is used to replace much of the linear and rotary bearings of the present RepRap variants. The compliant nature of the mechanics may result in various non linear and other geometry issues but is ignored due to the position feedback system described below. Compliant links

This design will not have a large portion of printed parts though the 'bamboo' bits could be partially printed I expect, though at a higher cost. Possible compact versions It will however have a much reduced vitamin cost (or that is my thinking).

The bamboo sticks will supply a restoring force if only flexed in one direction from rest. Over a certain range they have a reasonably long linear operation region but with a additional spring tension they would have a movement range of double if they were to move both sides of the rest position. If always under simple tension the motor arrangement may be simplified.

Software issues

Optical 2D feedback

The second part of the project that needs new development and is a bit beyond me personally at this time is the optical camera mouse position feedback system (servo control). It is possible that the software could be simplified in part if one were to replace the mouse cameras with a more expensive USB camera (especially for proof of concept testing) but the idea is to make use of the ubiquitous optical mice to do the tricky part of the project. In short one places one mouse guts upside down looking up at a printed high contrast graphical pattern on the underside of the build platform with that is sliding on a sheet of plate glass. The camera observes the motion and sending incremental signals back to the controller to position the platform as per host commands. Absolute position can be established by having a second mouse camera (certain debug modes allow picture taking) looking at the pseudo random pattern. No limit or home switches will be needed, mechanical end stops can be driven against and used to check motion function and build limits.

Here is the start of the feedback controller, it is single axis but with more horsepower if should be able to do two and read the camera/s. Microstepping with optical feedback.

X correction

Finally similar to the ideas of the parallelogram idea for the Z-axis that is also proposed for the 5 link SCARA design that is being developed the Z axis would also be a compliant bamboo double wishbone and the sine/cosine error affecting the X offset would have to be corrected for. This arrangement is used in the Z mechanism in the print bed on the Wally [1] in the thread on the forum. On the Bamboo printer the head will move with the Z axis as the bed translates in both directions. On the whole I like most of the Wally ideas but it is still a industrialised platform and suffers from expensive vitamins.

Consumer grade motors

The position feedback arrangement will allow for use of salvaged or consumer motors; DC, brush-less, stepper, pneumatic, linear motor or what have you as long as the controllers can be found or developed.

String drive

A number of delta-bots have tested the use of 'Spectra' line instead of timing belts and this would be the preferred mechanical transfer medium. Again the feedback will allow for simple coupling using variable diameter capstans (like on a sailing boat) pulley that may or may not slip a bit as this will be corrected automatically.

Other links

  • [2] Discussion forum thread
  • If this ever gets made it could get renamed to the Kelchner printer after the Scot Kelchner and his team that studied genetics