RepRap: Blog

It’s been quite a while since I've done an update on the metal printing front, so I thought I'd do an update of where we are. In my last blog post I set out about choosing a low melting point metal which would have some unusual properties which would help with printability - mainly choosing a temperature which would minimise damage to our traditionally printed plastic components on to which our metal would be deposited, and also using a non-eutectic to attempt to minimise the effects of surface tension.

One of the main problems I previously had was solubility. Running molten metals were acting as solvents for my heated nozzle - resulting in the nozzle slowly dissolving during a print. At the end of my last post I'd just tried using anodising to create a strong oxide layer on the surface of an aluminium nozzle to protect it, and that the results were promising after little running - I've done hundreds of hours printing since and as far as I can tell no damage has been done and its still in its original condition. I'd anticipate that a stainless steel nozzle would also be useable as it also has a strong oxide layer.

Previously the plastic and metal were printed on separate machines. Anyway, I've heavily modified my X carriage to take one Bowden extruder (for the plastic) and one "standard" extruder for the metal such that I can (in theory) do one shot printing. The metal extruder is fairly standard, the only major modifications are the inclusion of an O ring to reduce leaking, and running the PEEK insulator right to the end of extruder to minimise the melt zone - the result is a slow extruder - I'm currently printing track at about 100mm/min - but hopefully one which we have the most control over.

I printed the above about a month or so ago. The plastic housing contains a female hole for supporting an ATMEL644P PDIP chip, as found in our Sanguino electronics. The metal tracks are housed within 0.7x0.25 rectangular channels. Surface tension would suggest that the metal would naturally want to take a circular cross section - however given the size of the track I'd be unable to get anywhere near this hence the rectangles. The component was inserted into the plastic and the metal track automatically deposited on top before being covered with more plastic. Importantly we can see that the plastic extruder isn't excessively melting the metal tracks when covered.

Since that print I've been battling a few bugs with the setup - namely reliably keeping the offset between my plastic and metal extruder - the sprung mounts flexed under the compression of the bowden cable - and getting somewhere near a reliable metal filament drive - It turns out my standard hobbed bolt I used to do the driving wasn't good enough - I think the problem was due increased wear of the bolt due to the higher stiffness/hardness of the filament and a lack of compliance in the filament reducing the contact area. Anyway creating a new stainless steel hobbed bolt seems to have improved things massively:

Here is a stab at the Arduino compatible Sanguino board (albeit simplified). It's pretty standard except we've removed the reset circuitry and alot of the pins. We still have 4 controllable pins, one for the LED and three spare for something fun in future. Once again the plastic was printed before dropping in pre-tinned components and finally printing the metal tracks. I have previously done some tests which show we need to have a radius on each corners of printed tracks, ideally at least 1.5mm, but for compactness I squared these off resulting in poorer quality but nevertheless its quite a big step forward from where we were a few years ago. Four extra tracks are required on a second layer to get the circuit fully working; I've done this manually for the time being. In addition I had to manually solder in 2/3 pins as the track had not connected properly, however I think I can correct this by extending sections of track beyond their required endpoints and utilising the bigger radii at corners that I've already mentioned. It's still a little blobby, but nevertheless here it is working running a simple blink program, although we can still reflash the chip to do something else with the spare pins:

Printrboard is now available ($130, $145 shipped to the US)

Printrbot has created their own all on board branch of the Teensylu.  I have not tested it, nor have I seen it in the wild yet, but the reason I bring it up is it's price/features.  $145 puts it at a very close second to the Gen6 by MakeMendel for $140, shipped to the US.  I think this set of electronics does have advantages over the slightly cheaper MakeMendel Gen6:

Fan driver
Heated Build plate control control
Built in SD card reader
Molex style connectors (.1" connectors can drive you crazy)


Pocket Printer has arrived

D Kennell posted this beauty on Thingiverse, I am a sucker for extruded aluminum and Brustruders (I did design the 1st one so what do you expect?).  This looks like the dark Cthulhu spawn of a ORD, Thingomatic, and Mendelmax  I can't find  video of this printing yet but man its awesome looking little bot?  I can't wait to see more out of the development.


Pronterface update for Windows & Mac!

If you like me and have a non Linux computer, or don't like to compile from the Github, today is the day you have been waiting 3 months for.  Kliment has compiled a new version of Pronterface for Windows and Mac.  In this update Pronterface gains

-Experimental projector stuff: The folks over in the Lemoncurry SLA RepRap channel are using Pronterface to control the projector between layers.  Kliment has made this functionality part of the main branch of Pronterface.

-Temp graph:  With the troubleshooting I do in the RepRap IRC, I find a lot of people have very poorly tuned PID settings (swings of 10C are way more common than they should be).  One easy way to get people to fix it is to put a temp graph on in the host software.  Unfortunately PID tuning can be a bit of a pain, fortunately EvdZ has added AutoPID tuning to Marlin..
-Slic3r as default (and bundled):  Slic3r is my preferred Gcode generation software for RepRap, and Kliment has integrated it into Pronterface from the start.  With Slic3r if you have all 4 of your axis calibrated, and give it the proper Filament/Nozzle diameter, you should get almost perfect prints out of the box.  Of course getting people to properly calibrate before using their magic machine is like pulling teeth!


Marlin Firmware adds Auto PID tuning

PID is what controls the way your firmware flutters the power to the Hot End of your 3d printer to keep the temperature even.  Unfortunately it's not as easy as just turning the power on when too low and off when too high (Which is for the most part how Hot Bed are controlled), because if you do that you end up with a HUGE 20-40C swing in your nozzle temp.  Most people with untuned PID settings are only getting 5-10C swings but for good quality prints the temp needs to stay dead on one temp or the qualities of the plastic will randomly change during a print.  There are some good guides out there for PID tuning, but no matter what it requires a bit of algebra and experimentation to get it right. 

EvdZ has added a Gcode command called M303 to Marlin.  What this does is when you enter M303 in the Pronterface terminal Marlin will automatically start raising the temp of your nozzle to 150C.  It will then
try to calculate the PID settings that best match what your hardware is achieving.  Be sure to let it run its cycle 4-5 times before you write down the values, because each time it calculates the PID it live updates to the new PID, bringing you closer to perfect PID tuning.

After each rotation of calibration if will give you a value for the Kp, Ki and Kd using a standard, some overshoot, or no overshoot profile.  You then load the copy of Marlin you have on your computer, open Configuration_h, search the word "PID", and change the values for Kp, Ki, and Kd to the new values of your choice (EvdZ suggests some overshoot for faster warming of the nozzle), compile and reupload.

When I did this I went from having a 3C variation (I know, here I am wearing an admin feather ha5 and have a 3C temp variation on my hot end... bad me), to having a .1C variation +&- of the value requested.




MiniMax by Lulzbot

Lulzbot (which posts things to Thingiverse as AlephObjects ) has developed a Mendel sized alteration of the Mendelmax format.  Honestly my Mendelmax uses All the RP parts from MiniMax with the extrusion lengths of a Mendelmax.  Lulzbot is not going to be selling a kit for this machine, but selling it fully assembled.  But like any company I love they are following the release early and often philosphy.  If your like me and love self sourcing printers all the parts to assemble this bot in it's current state have been posted to Thingiverse.  Jebba assures me that the design is no where near done, they have some more work they want to do on the Z axis, but they will continue to post the STL for the upgrade to Thingiverse.  They have been getting Ultimaker + X/Y speeds & zero Z wobble on this machine.  I can't wait till they post a video of that!

Resin print by Arthur Wolf

It's truly amazing to see how fast the DIY SLA group is progressing in the Lemon Curry IRC.  It seems that you can get faster development when Resin is $40 a quart.  After asking Joe Moe/practicing01 who had the best print quality I was shocked to see this print by Arthur.  That's a lot of progress for 1 week!

Brian Benchoff of HackaDay wrote a great article expressing his opinion of what is wrong with RepRap.  He made some very interesting points.


As one of the 20ish Admins that he seems to be interested in vesting with power over the future of Reprap, I figured I should respond to his coronation.  I try very hard to be 100% positive on this blog since Adrian was nice enough to get my keys, so my response is over at my personal Blog where i an be a bit more blunt.


But to sum it up quickly, RepRap is 100% controlled by those that do, not those that dictate.  Adrian, and the Admins try to exert as little control over this community as we can, and to date that has been effectively none. 


The front page of the Wiki is pretty self explanatory, if you don't know what to build, build a Prusa (Every RepRap listed on the front page has some basic instructions and has printed before so no reason to get rid of them).  We refuse to pick a commercial provider that is the "official" RepRap because there is no way for that to be fair.  IMHO the "official" RepRap is find a friend/org who owns a 3d Printer, hang out at their place for 14-20 hours and print your own, or bribe them with a few cold drinks to print it for you.  Find the components you like, and build your self one for $400-$700.
Enough of that, now back to those awsome people that really run RepRap, the devs.


Smoothie Electronics / Firmware


For some people an Arduino is just not going to cut it, they need to feel the power of an ARM Cortex M3 to feel truely happy.  Smoothie firmware and electronics have been in active beta testing for many weeks now and it looks like Arthur will actually make his Juneish timeline for his Smoothieboard.  If you want to join him in the beta testing, Arthur and his team have put together a breadboard version of their electronics you can test now on your RepRap, Lasercutter, or CNC.


DLP-Based Resin RepRap, ohh and $40 a Quart Resin!


ScibbleJ did a great write up on a DIY DLP Projector based resin 3d Printer he has been working on.  You might wonder why RepRap, an org based around accessible 3d printers would be intersted in a printing technology that requires $400 a liter printing solution, well part of the reason is Bucktown Polymers (started by A2Sheds, developer of the Lemon Curry DLP based Resin Printer) is selling Resin for DLP printing for $40 a quart.  That's almost as cheap as PLA!


To give you an idea of what this form of 3d Printing could look like once it matures... check this out:


Different project entirely but that's what the goal is.  Ohh isn't the future grand!