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6 axis head for mendel?

Posted by vizion 
6 axis head for mendel?
April 07, 2011 10:18AM
I want to be able to add an additional head for the mendel for ancilliary processes to be applied when a model has been built. It needs to be a 6 way head which would enable the items it controls to reach inside a built model post build.

The initial processes are
1. firing a laser
2. Controlling a miniature spray gun.

I can think of a lot of other tools which could be used in similar ways. Can anyone point me to design/build ideas/instructions.

Thanks in advance
Re: 6 axis head for mendel?
April 07, 2011 11:35AM
are you talking about rotating around the x and y axis directions? I can see this being doable with an extruder that can pivot in one direction and the y table has something that will spin the platform, between the 2 you could mechanically reach every angle as long as it isn't much larger than parallel to the platform...

of course the extra 2 dimensions would require new electronics... 2 drivers appropriate to the 2 new motors, and the extra electronics to support it.

the toughest part I imagine would be software. 2 big challenges would be to programatically determine when and how to use these new dimensions, and the issue of tracking the built object in 3d space to accurate move the 2 new dimensions around it.

I think I can help design the mechanical parts... the software part is a bit beyond my math confidence.
Re: 6 axis head for mendel?
April 07, 2011 12:35PM
Thank you for your offer of help it is much appreciated.

My plan is to build the Mendel, test it to be working accurately before adding any additional components. I have been reluctant to start the build in case I could not achieve the additional functions. Without them there is no project.

The laser diodes weigh a couple of grams and the spray material can be gravity fed using plastic tubes with an internal diameter around 4mm.

The way I see it the carriage should move to a position that enables the tool held in the jaws to reach the correct position within the model. For example the spray would need to point in the right direction and start spraying the correct amount of liquid. The laser would need to positioned at a a certain distance and angle from the built model. Distance and angle would be crucial to maintaining correct exposure.
Re: 6 axis head for mendel?
April 07, 2011 12:50PM
My first though is that the tool head for this machine will be significantly larger than the usual Wade's or Adrian's extruder. The standard Mendel work envelope may not be large enough for what you are doing. I'd advise you to start with something like a Prusa Mendel first. Learn to use it and get it working well before modifying. Design and build your articulated tool head, then build a larger, 2nd printer around that. You'll probably want a working printer while developing.

By the way, what are you going to do with a 6th axis? Extruders and lasers don't need to be oriented along their working axis. Will your spray gun by using a fan nozzle that needs to be oriented?
Re: 6 axis head for mendel?
April 09, 2011 01:02PM
Sounds sensible advice. For my purposes both the laser and spray head need to be orientated to point upwards/downwards and angled thru 360 degrees as well as in degrees as well correctly located in xyz axis. Finally they need to be able to find their way into nooks and crannies within the built model. So this implies extension arms/
Re: 6 axis head for mendel?
April 09, 2011 06:29PM
Sounds interesting.

Can something like EMC handle 6-axes?
Re: 6 axis head for mendel?
April 09, 2011 11:47PM
Sounds like a cool project, but I would caution you to focus on getting 3 axis working before you worry about #4,5, & 6.

That said, look in to stewart platforms. If you mount your hot end to a stewart platform, you'll suffer very little weight increase. If you want to see the consequence of a heavy hot end, contrast every other design's print speed to the ultimaker.

Projects that try to cram everything including the kitchen sink in to version 0.1 either never finish, or end up being behind schedule by a factor of 2.
That's why the first prototype is rarely version 1.0 anymore. It takes several iterations to get right.

I'm not sure what you're up to but you may find that it is infinitely easier to move mirrors than a laser.

For example, this image could be improved upon by replacing the laser with a hollow shaft, the laser relocated so it's horizontal & parallel with the gantry, and with a fixed mirror above the swivel, but not attached to it.

It would be tight, but a good hobby micro servo shouldn't be too hard to position out of the way of the laser.
Re: 6 axis head for mendel?
April 10, 2011 12:27PM
Thank you for the stewart platform idea - that make good sense and mirror for a laser is simple and smart solution. That leaves me looking for a spray head solution!

Can you point me to a suitable design for the Stewart?

I accept your kitchen sink advice!


Edited 2 time(s). Last edit at 04/10/2011 12:34PM by vizion.
Re: 6 axis head for mendel?
April 13, 2011 05:49PM
For spray transfer look in to "spray transfer welding". I've seen 2 stroke engines with too much oil in the fuel which spray castor oil out of the exhaust.

The goal is to atomize a plastic/adhesive in a flow of pressurized gas. That suggests to me spray transfer fuse deposition, or spray transfer adhesive with powder deposition for a composite solution. The second sounds easier to accomplish requiring no more than spray adhesive and a powder blower, but I think fuse deposition is more ideal.

Compressed air nozzle would work if the material to be melted was already hot and had a low viscosity like solder. I would guess a low specific heat would help in the solidification without runs.

2 part glue mixed at the nozzle? Paint spray gun?

It's an interesting problem for sure. Good Luck.
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