Bamboo Printer

Hi,

[reprap.org]

I have added my ideas for a compliant linkeage printer onto the RepRap wiki. Have a look if interested and let me know if there is any future in it.

I like to think that it replaces a lot of mechanical vitamins with natural or consumer suplements instead. Not sure if it is possible but I have mentioned it on the facebook reprap group and there has been no comment so trying the more formal approach here.

Could it work and what are the biggest barriers to making it viable?

Kalle
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Johannesburg, South Africa

A flexible mechanics is an interesting idea. I think you have already hit on the main obstacle. Either you have to redo the firmware to account for non linear motion of each axis, or you have to try to adjust for it with complex linkages. The other thought I had was that in order to have precision it seems you would need some stiffness but that would also load your steppers more. I think the firmware issue would likely be the most difficult depending on the design.

I actually designed a Bamboo Mendel based machine almost two years ago that used cables even before I built Tantillus. [github.com] I never actually made it but one of the goals was as few unique parts as possible and to have them all cast-able as to make quick reproduction possible from a limited set of moulds.

It has three different Y axis including a conveyor style.

W/ Capstan Y axis


W/ Cable Y axis similar to a belt drive


W/ Conveyor style Y axis

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Hi Kalle, I like it! Compliant linkages are discussed occasionally around here.

VDX pointed us to some really cool work over in this thread - basically a 3-axis cartesian manipulator that folds up from a sheet of material. I wrote up a simple (1-axis) proof-of-principle experiment here. There are a lot of interesting devices in the See Also section of that writeup. See in particular the 2-axis stage by Hoover, which probably has a lot of potential. Imagine sliced up plastic soda bottles held together with glue or something, I don't know.

Also, bamboo comes up from time to time. It seems to be one of Vik's favorite building materials . See here and here.

Hi Kalle,

this 5 years old thread could be of some interest too: [forums.reprap.org]

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Viktor
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Aufruf zum Projekt "Müll-freie Meere" - [reprap.org] -- Deutsche Facebook-Gruppe - [www.facebook.com]

Call for the project "garbage-free seas" - [reprap.org]

Thank you all for those links.

I will read them more carefully again but some of the stuff is not relevant thought the compliant link details are the sort of thing I was alluding to that would allow for making the setup more compact using more industrialised designs. Those 'See Also' links have some very good stuff. I had never stumbled on this on the RepRap wiki before, it is not on any of the main development trees as far as I have noticed. I have looked at the Sarrus links before (and for other project) but they add complexity just to use more plastic and this is only valid on a space station. I still believe using natural supplements to replace vitamins is better than trying to print all the parts just for the sake of printing.

What seems to have been missed is the feedback mechanism that I proposed that would make non linearity and drive errors irrelevant. A lot of the more elaborate compliant links are more complex than required because they are usually trying to gain close to linear motion. In my design the sine/cosine (and slightly worse) error is not important. Parallelism at a low complexity has been my goal but just now while writing this I realised 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 in line 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. The dual bamboo sticks could then be replaced with a single stick and allowing the build platform to rotate as it wants to. The forearm would amplify the rotational error of the upper arm so I would still use a dual stick 'parallel' arrangement for that I think.

The spectra line or similar should be fine as the feedback will compensate for errors there as well.

Remember software replication cost is free and the slicers and firmware are doing things these days that we would have thought impossible just 5 years ago.

Getting the firmware to handle the camera feedback would be hard for me but easy for some hacker out there. Having the camera/motor 'servo' controller respond to standard step/dir signals would compartmentalise the problem completely.

The sine/cosine error in the z-axis will be sorted out by the Wally project so I'm not worried about that.

The use of bamboo is obviously not because it is a specific material just to replace the current rigid structures of the frames but because it is a natural 'bendy' material, tent sticks or ski poles would also work . The bottle plastic compliant links are the closest common ground to found items (bamboo sticks) used for replacing the linear or angular bearings of the current generation machines.

The reason I also like this optical feedback on a lever design is that it lends itself to simple scaling by just lengthening the bamboo sticks (within limits) at almost no cost up to the limit of buld time for any given nozzle.

Thanks for reading

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Kalle
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Lahti, Finland
The only stable form of government is Open Source Government. - Kalle Pihlajasaari 2013