Electronics > Open Source Hardware

The TangiBot 3D Printer, a clone of Makerbot Replicator

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Makerbot should make something that looks like this:



--- Quote from: ivan747 on August 15, 2012, 09:02:25 pm ---
--- Quote from: robrenz on August 15, 2012, 01:55:56 pm ---
--- Quote from: joseph.anand on August 15, 2012, 07:05:08 am ---The only thing keeping me from buying any of the existing 3D printers or CNC milling machines is the absence of a feedback mechanism. For the same price, I reckon I should be able to make one with a feedback mechanism. For the time being, I am stuck with deciding on a rotary encoder with suitable gear ratio or a linear encoder for feedback. Any pointers anyone?

--- End quote ---

If all you care about is knowing if your stepper missed a step,  ignore all of the following and put a encoder on your stepper;

Assuming you are going to do a true servo control loop on the axis and you care about bidirectional accuracy and  repeatbility:

1. Rotary encoder with gearing is the worst. the backlash in the geartrain will add a large amount of position error on top of #2 below. Also will make servo tuning to a fine level next to impossible.

2. Rotary encoder directly on the leadscrew or pulley of a belt system.  Still has the play or reversal error of the leadscrew/nut or pulley/belt combination.

3. linear encoder is the best. It measures the position directly and bypasses most all mechanical innacuracies of the axis. (there are still a huge number of things to consider to get the most out of the linear encoder feedback).  It does not mean you can have a sloppy mechanical system. You will never get the servo loop tuned if the mechanics are sloppy. You may also need to have a separate motor encoder for closing the velocity loop of your control system independent of the positional control loop that is closed by the linear encoder.

--- End quote ---

What about an optical encoder? They are more robust than mechanical ones and I believe they are more reliable as well. If they are going to include a servo loop, they should control it with a separate processor that can compensate for inertia instead of moving the whole axis back because of overshoot.

--- End quote ---

I was only talking about optical encoders.  There is no overshoot in a well tuned servoloop.


--- Quote from: ivan747 on August 15, 2012, 09:04:57 pm ---Makerbot should make something that looks like this:

-soliddoodle image-


--- End quote ---
Looking closely at the results of the soliddoodle device I must say I'm not impressed.


--- Quote from: EEVblog on August 15, 2012, 02:21:53 am ---...
Acrylic is probably a very bad idea. It it's clear then you can see all the guts and ugly wiring etc (just look at the Thing-O-Matic). And if it's opaque colour then it's going to look pretty gimmicky and "plasticy".

--- End quote ---

You could do what Apple did... and one of my personal favorite prototype tricks.  Make it out of clear plastic and apply the color to the inside.

...or sandblast the inside.

I agree with comments regarding how 3D printers could be improved.  Currently, I can't justify the price given the poor resolution, restrictions and DIY'esk support.  If the price dropped and/or the product improved... I'm sure they would become ubiquitous. 

Even at work I find it's worth the relatively small cost to have a place like Shapeways make it.  Completely hassle free, better resolution/quality, alternate/useful matterials (metal/ceramic), no design restrictions (overhangs) and relatively cheap. 

A desktop unit like the Replicator or this knockoff is convenient, but the speed isn't worth the trade-offs IMHO... at that price.  I would rather spend three times as much and get a better quality professional unit.

The RepRap project goals are ridiculous.  Instead of trying (and to date failing) to 'self-replicate', design a 3D printer that can be manufactured cheaply.  There are plenty of individuals brave enough to form a company around an open source design. Maybe that would be a good project for this forum?

There's a machine I worked on which detected its position in 3D space with some kind of oscillating magnetic field.  The concept still has me puzzled.

Oh BTW, the guy behind TangiBot (Matt Strong) recently commented regarding support:
"Adjunct Engineering LLC,

I in no way plan on pushing off support to Makerbot. I am building a company and in doing so I plan on supporting my own community.

Matt Strong"


--- Quote from: bxs on August 10, 2012, 06:25:12 pm ---I think is a little sad...

--- End quote ---

me too.  he should have really teamed up with Makerbot to innovate and reduce the price, because they'll be up against the big boys soon!  I couldn't justify the cost of either of these myself; I'd have to print lots of stuff to get my money back, with the basic choice of colours my house would quickly look like an early learning centre for kids.


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