Happy holidays everyone!  Tis' the season for giving.  And what better present to bestow upon someone than a RepRap printer!  Every day during the holiday season, new parts are revealed for the Kliment's Holiday Prusa Mendel found on Thingiverse.com, and by December 24th, a complete set.  Throw in a friendly contest, some eggnog  and someone on Santa's nice list and you've got a chance for some great prizes!

We are proud to help co-sponsor, along with RepRapSource.com, the Holiday Mendel Build Contest.  It is being hosted by our friends at IkMaak.nl.  Just build Kliment's Holiday Prusa Mendel, give to someone as a present and document yourself, the receiver and the process.  Some great prizes are being awarded for the best project.  You can view all the details and rules at IkMaak.nl. 

Twas the night before Christmas,
And all through the shop,
The RepRaps were printing like crazy,
non-stop!

Kliment's Holiday Prusa Mendel,
It was finally here,
to build and give away
to someone that's dear.

Now print away, print away,
print away with good cheer!
Happy building to everyone,
and may it last through the year!

 

We have successfully etched a circuit board using our RepRap Mendel to draw the etch resist. We mounted a Sharpie ultra fine marker on our Mendel and printed up a RepRap motherboard. It worked way better than we anticipated.

The marker tip is ~0.7mm. We are reliably printing 0.7mm traces with 0.6mm clearance. Printing the resist took about 1 hour per coat. Feedrates could easily have been higher. Two coats is giving effective etch resist. We etched with MG ferric chloride acid* outside in 80 something F and it took about 20 minutes. After etching we washed the board with water to stop the process and removed the marker residue with acetone. Then off to the drill press for the tons of holes (I think drilling should have been done by Mendel too). This is in no way a substitute for spoolhead or other needed RepRap circuit technologies that are in the works by other RepRappers, but it works, and...  Yeah!

We now have a working stacking shield for Arduino MEGA that fits all the electronics for our Mendel into one tight little package. We have been posting our work and source on the RepRap Wiki here. There has already been significant development and testing for the Arduino MEGA and Pololu A4983 stepper driver for RepRap control, and we have our Mendel running on this set up now. It is far optimal, but an improvement all the same I think. 

Adrian has his Pololu Electronics that we loved, and several other people have been using the Arduino Mega and Pololu stepper drivers. Dissidence is working on almost the same thing on his blog. Joaz at RepRap Source is using the Arduino MEGA to control the ShaperCube. His firmware is quite stable and available on GitHub. We had the Arduino MEGA prototype shields in stock so we went down the road of knocking off Adrian's design with our own optimizations including - smaller total footprint, access to potentiometers, more mosfet outputs, standard power jack, cleaner installation with less wires, and less connections to add to the cost and failure opportunities.

One of our favorite tricks was placing the capacitor and resistor needed for each driver under it. We are also using connectors that I remember from hobby servos. They are 2.54mm pitch connectors that claim a rating of 3A.  The shield I have has room for an additional stepper driver or pair of mosfets. The eagle design includes both :) We are about to start printing tests of a housing for the electronics.

One of our main goals is to make this board on Mendel. This board is drawn up on Eagle with as fat of traces and wide of gaps. This is our first PCB design, so comments and criticisms are welcome. One issue we are trying to resolve is protection for the mosfet circuits. The heater wires became shorted during testing due to careless connection at the tight quarters of the heater terminal block and the mosfet branded my finger tip pretty good. The honking big mosfets are dangerous unwatched I think, especially mixed with cheap brick style power supplies.

Again, our source files and progress on instructions / notes is at http://reprap.org/wiki/Arduino_Mega_Pololu_Shield.

BTW, sorry for the lapse in blog entries (and the non stellar quality of this one, we do have a nice camera - just more concerned with production than promotion at this point). We've been a little preoccupied making sure everybody's orders go out the same day, and adding new COOL PLA COLORS, and electronics, individual components, etc. Hope you forgive us :)

Here are some more of our experiences with a little different PTFE extruder. This is what we are using for the heater/nozzle on our makerbot. It takes 4 bolts through the washer to attempt hold it together.It uses two extra bolts and an extra washer to restrain the PTFE melt chamber.

Here you can see my current melt zone on the left, heater and nozzle on right. The aluminum plate actually sits at the top (E above), it combined with retaining plate it is fitted against act as a heatsink. The filament melts in the PTFE and enters the heater mostly liquid allowing extrusion with low input pressures when it works. It has experienced the following failures: the PTFE hole being smashed in by excessive clamping force,  leakage if the PTFE doesn't get clamped hard enough, after time it creeps in on the filament clamping it to a stall..

It is easier to rebuild, after the PTFE is deformed I have been able to reuse it after filing a little length off the PTFE and redrill the filament hole. Still far from optimum as I have had to rebuild it several times. We have used this extruder to print Toby's Mendel and another half so far.

This is our first attempt at Mendel barrel. We turned the PTFE barrier to slide inside the heater a little on hope the pressure help with the seal.  The machining is overly complicated. We have done a slight amount of extrusion, but don't expect the PTFE to resist deformation or leaking for long, but will update you with the failure.

We have only been printing with PLA. We are still playing with finding the bombproof extruder, but it is looking like we will have to fully imitate Nophead or BfB to get there. I really like the extremely low friction of PTFE and imagine it has to be easier to push plastic through than stainless steel, but it is so soft. Current plans are to try glass filled PTFE.

UltiMachine now has green and black PLA available manufactured specifically for RepRap. Now you can have easy bio-friendly printing that looks sexy too. The pigments are PolyOne OnColor BIO Colorants, so they are just as friendly to the environment as they are to the eyes. There are numerous other pigments that would be suitable, PolyOne just happened to be the first brand we tested. They turned out really good, so we probably will not be looking further. It is PLA4042D and measures 2.9mm +/-0.1mm and comes in 5lb coils. Get yours here.

Tonok completed his Mendel a couple weeks ago. As far as I can find it is the first Mendel in the Western Hemishere. All the parts are printed entirely from UltiMachine PLA on his McWire. Video of his Mendel printing below after his photos :Update: Tonok now has a blog http://tonokip.blogspot.com/ Congratulations to Tonok on this accomplishment. We hope to have our Mendel completed any day now and Tonok has helped us with more than one problem over at the RepRap IRC. It should be mentioned that this is not the first Mendel in the wild I know of. As far as I know Kulitorum (creator of RepSnapper had the first functioning Mendel other than the good Mr. Bowyer. If anyone else has one I would love to know and correct my story.

When changing materials make sure to stay at the higher of the two materials for a sufficient length of time  to clear the higher temperature material is cleared from your extruder. Trying to extrude remains of a material at a lower temperature than it melts at can break your extruder. When switching from ABS to PLA we extruded for 10 + minutes before lowering the temperature.

For new or experiamental materials like switching to PLA we recommend setting your temperature by hand, meaning: after we sufficiently cleared all the old material releasing  the drive and tested how much force we needed to push the filament through by hand. We started low at about 150C for PLA 4042D and worked our way up until we could easily push it by hand.

We found Vik's Christmas Angel on Thingiverse last night and had to print it this morning. Vik donated it to the world two days ago in New Zealand and we are decorating fo in US today. It took our Makerbot two hours and forty five minutes to print one out of PLA. You can see it immediately after print still on the MakerBot build platform. Short video of it flashing on top of our tree below.

from thingiverse

We cut her a dress from one of Britt's fabric scraps and transplanted a LED flasher out of our old star tree topper. I think she is quite beautiful. The camera washed out most of the LED, but they carry most of the way through her wings.