3d printer

[donkey]

ok guys and girls I am going to make a 3d printer with a little help(ok he is doing most of the work) from a member on this forum.
the first run will be an easy reprap mendelmax, a few modifications have been made due to availability of metal. I am going to be very generous and hope we get this going in 4 weeks (damn postage of parts). when its up and going I will come back and share our little experience.
if all goes well I intend to upsize the sucker inside of 3 months. when I get to that part I will have to hit you guys up for ideas on how to improve a design. anyway wish me and the other member luck. (I am sure he will make himself known if he wants too)

 

[sirch]

Good luck with it! I've been debating whether to build one for the last year or so but keep finding it hard to justify the cost and there always seems to be a new model coming up - personally at the moment I think the Rostock looks like a cool way of doing it.

 

[Raven Luni]

Greetings,

I'd be very interested in seeing how this goes. I've been wanting to do the same thing myself. Personally I think the mechanical side of it is the biggest challenge - getting a decent mechanism that will run smoothly, carry the functional parts, be in perfect alignment etc. You also need a very sharp cooling point above the nozzle - probably something like a peltier cell and a heavy heatsink and fan.

I bought a 'spare' nozzle assembly for my UP (for the express purpose of building a new printer with it but sshhhh)

 

[donkey]

why do I need a cooler? abs plastic warps when its cooled too quickly. in fact a lot of designs have a heat bed that it gets printed on so there is less warping

 

[Raven Luni]

The cooler is at the nozzle end where you feed the plastic in - it has to go from solid to liquid relatively quickly or else you get all kinds of problems with the feed - either that or I guess you would need a much longer channel

Warping is the opposite - need to keep the model temperature even so an oven type design is best

 

[donkey]

The cooler is at the nozzle end where you feed the plastic in - it has to go from solid to liquid relatively quickly

so that's why you need heat... why would I need to cool it? I see it on a few designs but it doesn't make sense to me

 

[donkey]

oh wait. I just thought of something for that fan. the barrel itself is ABS plastic and the nozzle is brass with a heating element on it. the idea is to get the nozzle hot enough to melt the feeder ABS plastic so I am guessing the fan is there to stop the heat melting the rest of the body, in that case I will be making mine from metal and putting a fan on it.

 

[sirch]

From what I have seen the brass hot-end is thermally isolated from the extruder body. I have seen people add fans to cool the extruded plastic. A hot plate is used to keep flat areas from warping as they cool but if you are building up walls you need the plastic you just laid down to cool before you put the next layer on.

 

[Raven Luni]

I think its more to do with the feeding process itself. Youre basically forcing a relatively wide filament through a pinhole. the filament is gripped by a roller which is powered by a stepper motor so its imperative that it is in a cold (solid) state at this point and not soft from heating.

 

[donkey]

but if its cooled it won't bond. it needs to still be semi molten to bond. right?

 

[Raven Luni]

It does that at the hot end, not the cool end

 

[donkey]

ok since my last post we have been waiting on parts. the worst part is most people give links to digikey which works great if you live in America but in other countries they charge too much for delivery, 4 ptc fuses weighing less than an ounce and each about the size of a stamp cost $45 delivery. the parts were only $4.....
the last of the parts should be here soon and the frame has been pretty much done. when we get the wiring going I will start the project log. I hate waiting for parts, its holding me up on a really fun project.
total cost for 2 printers so far is about $700au, we are using scrap metal for first design though so we can troubleshoot errors down the track.

 

[Mongrel Shark]

We can use Bamboo to thermally isolate the hot nozzle, and Guide the plastic in. http://garyhodgson.com/reprap/2011/05/bamboo-as-alternative-to-peek-or-ptfe/


Whats getting me, is why use NEMA 17 stepper for the plastic feed? Seems like a bad idea. Its too heavy for fast direction changes on the y axis, and I cant see all the torque being needed. Especially with the gears that will likely be there.... The weight provides a number of issues, in that it has to move on 2 axis's. so 2 of the other motors are moving a third motor at all times... up-down and left-right. Up down is less of an issue. as its a slow movement provided by 8mm threaded rod, which is overkill. Its the side to side thats bothering me... All that weight changing directions a few hundred times a minute... Got to try and get the weight of the extruder feed down as much as possible. That way we get faster more accurate printing.

I'll be back in a bit with some pics of where we are up to with the frame. Which is mostly made from C-channel from a Plasma tv, and recycled screws from stuff I pulled apart.

Also pulled apart a few 2d printers, and hope to use an inkjet cartridge holder bit, on its rails, to be the extruder slider. Has own belt, just needs bigger motor to give the weight of the extruder motor. Hoping to use a smaller 2 phase stepper from a printer for extruder feed, and it will simplify a number of mechanical challenges. Those cartridges weigh a bit though, I think we can get a motor in the ball park, and brace up the rolling bit if needed...

Circuit board for the RAMPS 1.4 is in my vice and ready to solder. Will be using some new components, and some second hand. We had through hole resistors and caps sorted, then the board turns up and a lot of it is smd, Lucky I have a ton of SMD parts from salvage... finding the right resistors is going to be a pain though. I wish I had a good system for storing those...

Going to get that soldered up this morning, then off to Donkey's house, to see if we can get a stepper turning the way we want...

Off to get coffee, and I'll be back with some pics. If you just cant wait that long. I have a video up already, showing the frame and roughly what we are planning.

Can anyone tell me how fast our NEMA 17's go? and how fast can they stop and go the other way? Donkey has links to Data sheet.

 

[Mongrel Shark]

Ok so I found a bit of a hold up. I was planning on going over circuit boards with some SMD probes on my DMM to find the right capacitors and resistors. Should still work for resistors (which are marked anyway), but a lot of the caps on the boards I have, are in networks with other caps. So I cant measure them until I de-solder, which I'm not sure is worth the time for all of them especially once I measure and sort them No markings means its going to be a pain to store them in any organized way... They are little yellow ones. First one I need is 100nf. None of them seem to be marked. I have hundreds to chose from though. Any suggestions?

 

[Mongrel Shark]

Here are some pics of the frame. With some inkjet x axis stuff that I hope to be able to use with up-sized stepper. These will be wound up and down the z axis by threaded rod. Y axis movement will be provided by a moving bed.

The C-channel is wall mount/sub frame from a Plasma TV.

 

[donkey]

ok shark is out in the shed as I write this soldering up the board. the RAMPS 1.4 board has some issues, for starters its SMD for seconds they made the solder tabs too small not leaving us enough room for soldering and all components. not a good start.
for what is meant to be a hobbyists 3d printer they are making it tough. a redesign of the board may be due but it being multi layered is a bit above my expertise. I leave shark to the soldering and me to the whining lol.
am looking to see if breadboarding the design will be worth the effort or not. if not then making a new pcb definitely will.
anyone willing to help us out on this will get so much respect its not funny