EEVblog #843 - David's rPrint 3D Printer

[george graves]

I'll have to watch the whole thing.  But I hope that bubble comes off easy!  Or that's a deal breaker for a 3d printer.

[electr_peter]

Will we see this 3D printer in action or pictures of sample prints?
How does it compare in terms of speed and resolution to other 3D printers?

[lukier]

The video mentioned $12,000 in sunk costs and a projected parts cost in volume of $1400 per unit which is indeed substantial amounts of money, it was considered excessive when I spent $1000 on parts for my Thesis project so this steps it up another order of magnitude.

My thesis project (2D pong playing robot - linear bearing rail, paddle on a motorized timing belt, 87 fps uEye USB 2.0 camera above the table and computer vision algorithm running on the PC, sending commands to the NXP LPC23xx based PID motor controller) was also around $1000 and it was considered expensive, that's why I'm so shocked a student can afford to spend $12k. But I did my project in 2008 and it was in Poland, so quite different circumstances.

I worked 3 jobs to pay for the project (not all simultaneously, only 2 at a time), was also studying full time.

Chapeau bas!  This is serious commitment.

Motion control is great fun, did you ever make real world measurements of your system? I worked for most of a year on precision positioning for some scientific applications and when we actually measured the results the trapezoidal profile was as far as we needed to go, anything more complicated added no further accuracy or speed.

Not really, just messing around. Couple of years ago I bought CNC-3020T, wired STM32F4 to the original controller (LPT based) and wrote various bits of code, motion control, fancy C++ g-code parser. I've implemented this first: http://staff.bath.ac.uk/ensmns/Publications/pc074.pdf (it has a downside - profile has to be symmetrical), then something inspired by TinyG code, but in the end I wanted the machine working, not just occupying desk space, so I dropped STM32 and my C++ experiments and wired Beagle Bone Black with LinuxCNC (MachineKit) and got the machine running in no time.

From my brief experience trapezoidal profiles seem to be perfectly fine for heavier, damped machines, based on leadscrews etc - such as my Chinese CNC. Maybe for 3D printers with very lightweight extruders and timing belts S-curves make much more sense as they limit the jerk. You have to admit that this TinyG demo video is quite impressive:
 
Another thing that bothers me in 3D printers and cheap CNCs is the lack of feedback loops. A while ago I bought AS5311 linear magnetic encoder and 300 mm magnetic adhesive strip from Austria Microsystems when I find some spare time I want to experiment with that.

[eneuro]

... so I dropped STM32 and my C++ experiments and wired Beagle Bone Black with LinuxCNC (MachineKit) and got the machine running in no time. ...

I've decided to do not mess with custom g-code parsers, but use LinuxCNC too, in my CNC project-one can make diskless Linux machine and boot from network, so no worry about data storage, and control laptop with IP cameras can be far away from CNC machine, which will need better air conditioning, etc.
Writing own kinematics module for LinuxCNC is quite easy.

Anyway, what is working area/volume for this 3D printer-I mean -it can print anything else than a small toy for fun?

By adding aka 3D printer head to my CNC machine I'm talking about manufacturing eg. concrete monuments w few meters long 

[SnakeBite]

well done David!! very nice job!

did you payed on the project from your own money or you had a sponser/university grant ?

[android]

About parsing the string data: Why not run the ASCII text through a preprocessor which would convert the numerical data into binary format - no real parsing necessary any more?

If I recall correctly that was the major reason for the creation of the RepetierHost and RepetierFirmware github forks a few years back. The binary protocol was called Repetier protocol.

https://github.com/repetier/Repetier-Firmware

Hmmm...seems to be listed as a minor feature now as simply "Standard ASCII and improved binary (Repetier protocol) communication."

[snoopy]

Hi David

Put this project on kickstarter or Indiegogo and don't feel guilty about taking peoples money upfront. A lot lesser project has taken a lot of money and some have bombed out too. People can see that you have put a lot of thought into this and matched it with real tangible results. This is not some hare brained grab for cash and then see if it works project like those sleep therapy devices  You already have the runs on the board.

If you go commercial do you have to pay royalties to the Uni ?

cheers

[kony]

David - why not double extruder? You can have water soluble supporting material in secondary extruder, and no need for designing mixing nozzle. Also if you swap ABS ot different fillament material, moisture absorbtion won't be that bad to affect dimensional accuracy much, I think. It's certainly something I'd appreciate to have on prototyping machine.

[sakujo7]

If I recall correctly that was the major reason for the creation of the RepetierHost and RepetierFirmware github forks a few years back. The binary protocol was called Repetier protocol.

https://github.com/repetier/Repetier-Firmware

Hmmm...seems to be listed as a minor feature now as simply "Standard ASCII and improved binary (Repetier protocol) communication."

Looks like a direct conversion of the ascii format to binary. Should be trivial to convert back and forth on a PC, and much faster to read on a micro. Any gcode-exporting software could offer this as well, no extra steps. No obvious disadvantages.

...Yet the older ascii format is still dominant, and the few people that care about performance focus on reading ascii faster.

The world doesn't make sense. 

[mxmarek]

Hello,
 have you tried using windows' PerformanceTimer for measuring time it takes to do the business ?
Regards, Marek

[coppice]

The video mentioned $12,000 in sunk costs and a projected parts cost in volume of $1400 per unit which is indeed substantial amounts of money, it was considered excessive when I spent $1000 on parts for my Thesis project so this steps it up another order of magnitude.

When I was at college projects like this were simply not allowed. There was a cap on expenditure, and it was pretty low. This caused considerable skew between projects of different types. A research oriented project might require no expenditure, but involve the heavy use of a lot of very expensive kit that was already around. A more development oriented project might be stifled by the lack of funds to put relatively simple hardware together. Overall, though, I think a severe limit on spending is a good thing.

[Rickbar]

Looking forward to your website opening and watching the progress from prototype to production.  You have a great idea/product.  Please consider a dual extruder for those who might be interested.  I would even challenge you to 3 extruders if there were enough room, maybe a larger frame and bed?  Something crazy to think about since 3 extruders would definitely be beyond the scope of many if not all 3D printers and it would make your printer the most unique on the market. (just a thought!) 

You can definitely count me in as one of the 1000 people who wants one of your beautiful printers.  By the way, it was amazing to see your ethics about crowdfunding.  I wish you many more successes in all your present and future endeavors.

Please keep us informed.

[Dubbie]

When I was at college projects like this were simply not allowed. There was a cap on expenditure, and it was pretty low. This caused considerable skew between projects of different types. A research oriented project might require no expenditure, but involve the heavy use of a lot of very expensive kit that was already around. A more development oriented project might be stifled by the lack of funds to put relatively simple hardware together. Overall, though, I think a severe limit on spending is a good thing.

The problem with this, is often the best solution to a mechanical problem often does cost a little bit more money.
For example, linear bearings and ballscrews have a lower bound to their cost. If the student is forced to use an inferior alternative, they will end up having to solve a ton of problems that are completely irrelevant to real life / industry. Everybody uses linear bearings and ballscrews because they have proven their worth over the years. This allows the student to focus on other more interesting problems rather than trying to solve/work around something that was already solved decades ago.

[electronico]

    this has been a lot of work. Congratulations!

[eneuro]

I'll have to watch the whole thing.  But I hope that bubble comes off easy! 

I was not able watch longer than  afew minutes,due to those nasty light reflections in this bubble-it is terrific challenge record any video with this thing on workdesk-in everyday waork job I wouldn't like have such bubble on my desk, too
No mater how much cost such custom buuble, seams not practical at all and cheap IP camera inside this printer could be much more uefull-one could controll it operation many meters away.
I hate light reflections, this disturbs environment, so take it easy-it doesn't fit into my room ligting standards, o dismiss such things no mater how many hours someone spends on it-other people spend a lot of time practicing sport... it is good for health.. and require  a lot of work too... watching light reflections in this printer bubble is not acceptable for me...

[jonw0224]

Great work, David! 

[AlienRelics]

I'm anxious to check out your filament feeder when it goes open source. I've started on a large Delta printer with 330mm diameter bed and 1.5m long legs. Printable height will be shorter than that, of course.

The plan is to put a 1mm nozzle on a Tornado on it so it doesn't take a month to print something large like a wing or fuselage. I was going to do Bowden feed because the usual stepper motor direct drive is too heavy, but I fear a meter of tubing is going to cause a LOT of problems with Bowden feed.

[grimmjaw]

David,

Where do you get the bubble manufactured?I'm looking to get a similar bubble manufacture for a project of mine, not a 3D printer tho.

[ajm8127]

Incredible work, David. The fact that you decided to tackle the mechanical aspects of the project will pay dividends in the future. So many EE/CS people are clueless when it comes to hand tools and mechanical assemblies. Having a good understanding of the mechanical aspects of the project just makes you a more well-rounded engineer.

Please do a follow up once you get the prototype complete. I would love to see some quantitative analysis of your printer against comparable products currently on the market. You seem more interested in making it work well than hitting a certain price point and the open source nature of the project is very appealing to me.