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Design for low cost delta with 3 servos

Posted by Wiperman 
Design for low cost delta with 3 servos
November 30, 2010 10:54AM
Design for my low cost Delta
[www.enemygadgets.com]
Thinking of fitting a small syringe needle as the nozzle instead of manufacturing metal parts.
What da ya tink?
That way I'm hoping the fuse will be <0.1mm and Delta bots are fast when it comes to weaving.
And replacement nozzles will become easy to come by.
The nozzle will be immersed in molten lead - the molten lead coming from a small light weight SMT temperature controlled soldering iron hacked to fit a holder.
So the temperature control becomes fairly trivial to achieve.
Re: Design for low cost delta with 3 servos
November 30, 2010 02:28PM
The delta robot looks a really nice design and would be very useful for pick and place work.

I think a delta design like you have may not have the accuracy of movement you require for fuse deposition and if it does will not be able to achieve the speed of head movement you are looking for.

I did consider a servo driven delta for my Helium Frog design, but after reading up on them decided to go for vertical lead screws as this should in theory give the robot more precise but slower movement.

The design you have would if you could make it work be much better as all the main parts could be reprapped (lead screws cannot be easily fabricated) so I would encourage you to give it a go and see how it goes. Even if it doesn't work it is still usefu knowledge that can be shared.
Re: Design for low cost delta with 3 servos
December 01, 2010 10:55AM
Delta robots can be as accurate as needed, and speeds are horrendous - about the fastest thing robotic on earth for pick and place when made with carbon fiber rods. I was at MACH2010 and saw a very fast one there and thats what inspired me to build a cheap duplicate from acrylic sheet. Precision is not bad in relative terms for this application because the fuse tends to be less accurate than the robot positioning system.

I was amazed by the simplicity of a delta robot. The parts list: three servos as used in remote control toys, 12 bearings, some laser cut acrylic and some M3 screws. And it took me one day to design and next day to get it cut. Total cost under £20. And easy to replicate. Can I can feel that Gada prize calling?! cool smiley

I already have PIC based electronics and software to move the servos and it can control 6 of these delta bots at the same time.
I don't have a G-code interpreter written for it yet, but very tempting as a project in its own right.
Also very tempting is to turn the entire drawing into a parametric one so anyone can build their own version of this just by tapping in a few parameters into a Gambas program running in Linux and out pops the DXF file for laser cutting or a 3D format to get it into STL file for a 3D printer.

The biggest issue I can think of that hinders getting to a finished 3D printer is how to make a micro extruder. I think of attaching syringe needle to a soldering iron and keeping the needle hot by dipping the needle body into a molten jacket of lead solder, but even a light weight SMT version of an iron could be a lot bulkier than desired. The servos are 3kg.cm, and pushing that to 15kg.cm may make it work very well. I have another delta robot built with the center of the delta robot having a big hole and shorter arms. That is much more effective accurate and stable for lugging a big weight such as the extruder around.

How to build a micro extruder that doesn't weigh down a delta robot is what keeps me awake at night thinking.
Re: Design for low cost delta with 3 servos
December 02, 2010 12:53AM
Can I can feel that Gada prize calling?!
I hope so. (You'd want to put the files in the wiki, then.)

http://reprap.org/wiki/Enemy_Delta_Robotsmileys with beer
(It's a good name.)

So, you're doing a bowden extruder?


-Sebastien, RepRap.org library gnome.

Remember, you're all RepRap developers (once you've joined the super-secret developer mailing list), and the wiki, RepRap.org, [reprap.org] is for everyone and everything! grinning smiley
Re: Design for low cost delta with 3 servos
December 02, 2010 11:36AM
Soldering iron sounds quite heavy, but have you considered a diesel engine glow plug. They come in all shapes and sizes, but are generally around 5mm diameter and about 100mm long. They are very light and have a lying lead and connector attached.

There are also glow plugs used for Radio control car engines which are very small and screw in. If I remember rightly they run on 1.5 volts. There may be some for lawn mowers as well.

I did a few experiments with a diesel engine glow plug and the resistance is around 1 ohm and they run from 12volts. You would need a good power supply to give high current at such a low resistance, but the temperatures they achieve in a few seconds are incredible. They are not called Glow Plugs for no reason! I connected mine to a 13.8V 3A CB Radio power supply I had and this was enough to get it red hot.
Re: Design for low cost delta with 3 servos
December 02, 2010 12:38PM
The heater / nozzle design I used here: [hydraraptor.blogspot.com] is small and lightweight. Combined with Brian's hybrid insulator it makes a lightweight hot end.

Also makergear's grovemount and heatcore designs look about as small and light as you can get.


[www.hydraraptor.blogspot.com]
Re: Design for low cost delta with 3 servos
December 05, 2010 02:03PM
Quote

Can I can feel that Gada prize calling?!
I hope so. (You'd want to put the files in the wiki, then.)

[reprap.org]
(It's a good name.)

Set up the wiki page as suggested to the letter! spinning smiley sticking its tongue out
Probably will enter the Gada prize if I can manage my time.
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