Tuesday, May 23, 2006


The frankenscrewdriver

My brother-in-law did not realise when he gave me an electric screwdriver this Xmas that he was in fact providing a handy geared motor for driving the RepRap's extruder with. The Black & Decker electric screwdriver takes 4XAA batteries normally, but I'm running it off an extruder board using a TIP120 transistor instead of the 754410 H-Bridge. The whole thing is held very firmly by a couple of bolts and a wad of Polymorph/CAPA. The aerial (top, left of centre) has a little wire loop on it, which can be telescoped up and down to hold the 3mm Polymorph/CAPA rod out of the way during operation:

The clamp holds down the switch so I can turn the thing on and off by just regulating the current - and recover the screwdriver if brother-in-law feels miffed :)

Vik :v)

Thanks for the photo, gets high marks for that feverish lab look! I like actually seeing what you guys are building. I've also found electric screwdrivers make pretty good inexpensive robo-parts with an rpm around 150/300. Durability is not too bad either but they do run rough. Could that be one of the sources of the irregularities (combined with the temp issue) in the extrusion?
I've another suspicion about the uneven feed. There's no speed control on the extruder motor yet, so any inconsistencies in our 3mm feedstock - say, a join - will cause variable feed rates as the motor has a harder or easier time of feeding the plastic rod through.

Also, while we wait for the nozzle to heat up after it has cooled down below minimum operating temperature, it gets a "runny nose". We'll fix that too - the extrusion algorithms are still at a fairly early stage.

Vik :v)
LOL! Well, hell! I thought I was the king of overkill. :-p
Looks lovely. I feel kind of silly asking, but what is that clamp for?

(I can't wait until you guys get to the point of actually making output -- then I can stop bemoaning my complete lack of woodworking skills, and instead beg you guys to make me a set of parts.)
...then I can stop bemoaning my complete lack of woodworking skills

Wood is easy. Get yourself a cheap mitre box and fine-toothed saw, they can usually be bought for a few dollars in any hardware store. Also get yourself something like a Dremel hobby set. That will give you enough of a drill to start screws to put the pieces of wood together.

I used poplar wood because it is fairly cheap, fine grained and light. It also comes in sizes that are near enough to what I want to do that I don't have to do a lot of sawing.

That's how I did Godzilla.

If I had it to do over again I'd probably buy a cheap little table saw and a planer and use scrap wood.

Recently Sebastien gave us a link to a guy who just bought what looks like sheet HDPE (think of a kitchen cutting board) and built a CNC out of that.


I expect that he used a table saw to cut that.

That approach makes a good-looking product.
Ah, the clamp. That serves the simple purpose of holding down the switch to make the thing turn round.

Vik :v)
Woodworking skills? Make with wads of hot CAPA/Polymorph :)

Vik :v)
You use CAPA like guys I knew in high school used automotive body putty. :-p
You say that like it's a bad thing :)

Sticks well to car body rust though...

Vik :v)
well, we took the mobile solar-powered unit out today and ended up in-advertantly running tests of doping materials beyond expectation... though we had demonstrated powder (such as makeup or paint dust) coloring successfully long ago and a number of composite structures (thread and mixed glues, for example) we had not used any proportionately large particles having worked on consistant flow;

the addition of various fine beach sand in .1, .5 and 1mm extrusion created an effective cement-style rigidity rather than generating fracture vulnerabilities as one might expect. in most cases the particulate was up to 1/2 the extrude diameter with slightly more liquid host medium.

more later... typically i do fea code models before running bulk permutations and physical tests...

Post a Comment

<< Home

This page is powered by Blogger. Isn't yours?

Subscribe to
Posts [Atom]