RepRap: Builders

A quick heads up for another webcam based 3D Capture Technique that claims rapid capture.

http://mi.eng.cam.ac.uk/~qp202/

I started building my Ponoko Darwin about a year ago. Got everything put together in about two months. Needed to upgrade the PC connected to the reprap, took on a job working for a start-up, and had no free time whatsoever. I still need to have a reprap, so I got started working on it again. Found several problems:
1) I have a Reprap Mother Board v 1.0, which isn't documented. Had to buzz out the pins.
2) I'd failed to solder the motherboard's stepper connectors; just diagonal pins.
3) In spite of what the website says, the Reprap's opto end sensors are inverting. When empty, they emit +5v. When interrupted, they emit 0.45v. Had to invert the sense. Perhaps the Sanguino test firmware should say "ran into endstop" when that happens?
The tests are running now. The X and Y operate fairly smoothly. Z is a bodge. WAY too much friction, even though I used a dry teflon libricant. Fails to move even when I have the stepper driver cranked all the way up. Will only move if I help it along. I suspect the problem is in the ball chain's mating with the gears. Advice cheerfully accepted for alternatives.

Labels: Darwin, ponoko, rmb, testing

Mo stopped by today to pick up the set of Darwin parts I printed out for his team of engineering physics students at UBC. They've got some interesting plans for their Darwin, but I'll let them explain what they're up to.

Instead of a case of beer, Mo, Jacob and Bing paid for this set with a box of MXL pulleys suitable for Mendels and Darwins that Bing imported from China, plus a hardcover copy of Cory Doctorow's novel Little Brother. I've been a fan of Cory's novels ever since I read Printcrime, which I was introduced to by the RepRap forums, and his latest novel features an interesting take on 3d printers. Sooner or later I'm going to have to send Cory a set of parts!

So, next up, Mendels!

Wade

Labels: Darwin, replication

We printed the traditional minimug after a morning tuning the system. This was my first try at printing the minimug. I was running the extruder 5 degrees too hot for the batch of ABS that I was using and the y-axis drive shaft was loose. You can see how the top melted from the extruder running too hot.



Here you see the taping of the first successful minimug print with a tripod-mounted Flip.



The completed minimug on its print raft.



The completed minimug peeled off of the printing platform



A closeup of the completed minimug. There are a few print hairs on the inside which were easily removed.



Thanks are due to the many fellow Rapman builders at the BitsFromBytes Forums and especially to Bogdan Kecman who has been an constant source of useful advice on getting past the little problems one encounters in getting the excellent Rapman Reprap printer going successfully.

Okay, I think I'm getting the hang of Skeinforge.



There was a little displacement for the first 10 layers because of a loose y-axis belt. I paused the print and tightened the belt. After that the print went smooth as silk.

Forty percent fill, 50 mm 15 toothed involute profile gear. Printed at 16 mm/sec in about 45 minutes.

In the hopes of increasing my printing speed, and to confirm that it is actually possible to make a RepRap with RepRapped parts, I've printed out and assembled a child Darwin. It's mechanically complete, and the axis all run quite nicely - at least 3000 mm/min so far on the X and Y. I have yet to get a firmware that will run the stepper based pinchwheel extruder, so no minimug yet, but I thought I'd post my results so far. I'd love to hear from anyone who has a stepper driven extruder running with any of the Arduino/Sanguino/Extruder controller firmwares. Also, a big thank you to Barry, who soldered up and donated the stepper drivers and opto endstops!

Three millimeter filament generally comes packed in two formats, first as ...



coils as seen with the four 5 lb lots of PLA at the seen on top of a standard shipping spool of ABS seen carrying 20 lbs and capable of carrying 40 lbs which is the second format.

While several solutions have been confected to deal with coiled filament, I wanted to use ABS directly off the spool. Having lived and worked in Guangdong in China for several years I became happily acquainted with the lazy susan tables which enabled hungry Cantonese dinner parties to load their rice bowls at dim sum restaurants with a minimum of fuss.

The ball bearing race mechanisms for such tables are readily available in larger US hardware stores for about $10.



I also bought a pair of precut plywood rounds at the same store. Once I locked the race down, I lubricated with a light oil spray.

What you wind up with is a mounting table for quite a heavy spool of ABS which uncoils with about an ounce of force.



I suspect that one could knock together a much smaller spool for coiled filament and use the lazy susan arrangement for those as well. Given that most extruders exert kilograms of force to push filament into the extruder barrel this arrangement shouldn't cause feed problems. I'll keep you posted on how it works out.

To follow on from the basic twin extruder test in the last blog, here we have the results of my first test using support material

The machine is loaded with two colours of ABS, mainly for convenience at this stage, Black for the object and Yellow for the support material.

The file chosen is a bearing cap, printed from the bearing axis up, this has a semi-circular void that runs front to rear of the part. Actually this file prints very well without support material but it is a small part suitable for testing the head change.

Small it may be, but it still contains a fair number of layers and therefore lots of head swapping!

The first test was done with a hand edited file, I added several new lines of G_Code to manage an orderly change over from one head to the other. On more complex parts, it would not be practical, the new codes need to be added by Skienforge.

Skienforge already deals with support material by issuing a temperature change to flag the start and end, I need several other codes inserting at this point. To do this I have made a simple modification to Skienforge to pick out the support material, then insert my new codes as required.



The image shows the first complete part made by running the file from Skienforge.
Finish on the part is crude as the G_Code has been generated with 0.4mm layer thickness, this ensures a relatively quick build and gives a manageable file size.



The print is far from perfect, but I have to say I am encouraged by the results.

An item of interest I found when worrying the web about gears.

Meccano Gear Cutting Machine

It is a machine made from meccano that can cut more meccano compatible gears using a Threading Tap. It uses an existing Meccano spur gear as a template for the one to be cut.

A novel way to make gears without a lathe.

Interestingly enough it should be only a small set of modifications to make the machine able to cut worm gears by hand also without the need for a lathe.

I don't have any Meccano but thought this would be useful enough to cover here for those who might.