My thanks to Carl, AKEric and Sheffdog for your plans and posts. I'm about a third of the way through my "beast". I have the XY and Z mechanical built. As I move on to wiring and electronics, I'm noticing stiffness in the lead screws as I turn them by hand.

Is this normal? I have no experience short of owning a Up! Plus2 and building quadcopters, so I'm not sure what to expect (on a number of levels). I've oiled the screws. I'm using the "Nut Block for 8mm Acme Lead Screw" from OpenBuilds. Just want to get an idea from your experiences.

 

Actually, now that I look at my image, the left lead screw looks like its block is curving it. That could be a problem...

 

You can get the motors and blocks aligned by loosening the screws so they are free to move. Then lower the bed. That will cause them to align as it lowers. When all the way down, tighten the screws back up.

 

Thanks, Elmo. I may have to revisit those mounts as well. I have a hunch there might be a problem with my prints (raft lifted up from bed).

 

Looks great! I like the ears, because they do provide some support. I would think that you'd want to move the bearing hole back toward where it attaches to the extrusion, because right now it is centered 20.55mm from the edge. If it were 6mm closer to the extrusion, that would reduce the force on the flex point (where the mount begins to extend out from the extrusion) by almost 25% as reduction of the torque arm. If you did that then there'd be no room for the support you mentioned, but I think with those cool swooopy sides you'd have more than enough support even without the ears.

My extruder troubles are ongoing! I bought a new MK8 gear and here's what I got this time!


I emailed the seller about it and they said

I did try it and guess what? It doesn't work very well. Trying run PLA through an E3DV6 at 230C at 3mm/s, extruding 100mm I get about 20mm of extrusion. If I squeeze the idler wheel against the gear as tightly as I can, I can get about 70mm of extrusion. I mark the filament every 5mm or so so I can see it moving and it moves and stops and moves and stops. Argh!

 

Try http://deezmaker.com/store/#!/Tatsu-v2-Drive-Gear-Hobbed-Filament-Drive-Gear/p/24043350 for a drive wheel. http://www.tridprinting.com/Mechanical-Parts/#3D-Printer-Hobbed-Drive-Gear That hardened gear is a gorgeous gear, Its too bad that it didnt fit my application. I have not used it but it is quality

If I were using a bowden drive, thats what I would use. I have been using http://www.unclechucks3dprinterstuff.com/catalog parts 3.htm lately.

Heres an interesting conversation about drive gears if your bored, there is microscope printer pron.
https://groups.google.com/d/msg/makerbot-users/Z4ZXFFumhQk/glEa3qhXX-sJ

 

No kidding, right? I thought for sure maybe some would be better than others but the first two are absolute garbage. I ordered one from Amazon that looks just like yours does Carl and it has actual grooves in it. I couldn't wait another week and this has been holding me up for like a month now, so I shipped it overnight.

I printed the parts for Airtripper's filament pressure test rig and got some actual numbers.

The first one, purchased from eBay seller sidewinderinc starts slipping at about 2kg (the graph scale is 0-5kg).


Next the "special" one from eBay seller rp_one_labs which was able to achieve about 2.6kg of force before it started letting loose.


Finally the new brass one from Amazon. The stepper started slipping at 0.5A ~3kg so I upped that to 0.75A. This one was hard to get a screenshot because the feedrate had to be super high to get it to slip. I think it was feeding 10mm/s at this point and pushing over 4.2kg.


Printing some infill at 60mm/s I took this screenshot to show how the extruder temperature can affect the pressure to the point it slips. At 220C the large swath of straight infill runs about 1.8kg-1.9kg. Drop the temperature to 200C and the force slides up as the extruder cools, up to 2.3kg. I had been trying to print at 200C, and this is the point that the other MK8s were losing their grip. Surprising that PLA would need 220C.


Yes I know that kilograms is not a unit of force, but you can convert it to newtons if you want. The relationship is the same. The device looks like this, which is hard to make out the parts on account of them all being the same color, but it is a mount that goes on the printer frame, with a load cell bar in it that the stepper motor is strapped to.



The load cell is read using a cheap HX711 I got from eBay for a couple of bucks. I find the whole thing pretty fascinating watching the force/pressure on the filament as various features are printed. The infill with the temperature too low is really interesting because it doesn't just jump up to the full force, the extrudite coming out just doesn't keep up with how much the extruder is pushing so it steadily climbs until it levels out or starts to skip. Either way you're not getting the requested amount of plastic laid down.

 

Awesome CptnBry - I'm loving this discussion.
I just returned from a 3D Hub meetup. I was the only one there with a home built machine and it attracted a lot of attention. Carl, you are a celebrity now. You should see it in the Raleigh News & Observer tomorrow. I still have some machine tweaks and Slic3r learning to do b4 I can print the torture test but I am working on it. Primary thing now is the cooling, and my current arrangement is not sufficient. Someone at the meeting suggested an air compressor and a water hose!! There was also mention of a teeter-totter mechanism that allowed raising one or the other extruder so as to prevent ANY interference on the surface of a print from the none flowing extruder when u r using both. Anybody seen something like that? The carriage runs into a ramp on one side or the other to tip it. I can't imagine it being stable enough, but then I imagine I would print a "print-in-place" model either.

 

My dream dual extruder would park one print head on either side of the print area, with a magnetic carriage to select. All three cars could share a common rail, an A or B electro magnet "should" be easy to implement using gcode and would be repeatable in position ( nozzle to carraige). As a bonus the print head would never need to drag around a drooling tip.


@CapnBry I am really interested in your load sensor setup, would you put up some more photos and info?

 

Question regarding Rumba setup:

My build is based on AK Eric's c-bot. The only mod is 900mm legs. I have the frame, XY & Z gantries and motors. Endstops wired but not yet mounted. Using Marlin 1.0.2, When running the printer using the LCD, I've been able to move the X & Y parameters and have sucessfully gotten them to move in the proper direction. However, there is no option to move the Z. "Move Z" is missing from the menu. This is my first go at a manual printer and I've searched for Vids and Sites to clarify what I need to do. Any ideas of what I'm doing wrong? Perhaps there's a site/vid that walks through a coreXY/Rumba setup.

 

I found it, I fat fingered some "extra code" into one of the parameters. They all show up now. XYZ and Extruder.

I also found the Reprap forum.

 

Just found the link for http://airtripper.com/1473/airtripper-extruder-filament-force-sensor-design-3d-print/. This might almost make me contemplate a bowden.

 

I was very interesting. Held at the local tech college by 3D-Hubs, which has established a presents world-wide now. The tech college has a 3D curriculum and was promoting that and looking for ideas so it was a good matchup.
u can find the article here - it is picture #2
http://www.newsobserver.com/news/local/education/article31210004.html
- and when I can print that red object on pic #1, I will have "arrived".

My nozzles r currently approx. 0.06mm apart.The diff between a cash reg receipt and 24# paper. How close is "good enough"????

 

Just got back from some vacation time:
@Raldan : That is a beast! My leadscrews were initially tight to turn by hand, mainly based on the friction in the black plastic blocks. The more I use it the easier it gets. You just want to make sure there is no binding at any point. I did a lot of eyeballing having the gantry at its lowest, and making sure the leadscrews perfectly fit into the flexible couplings. Ended up having a bit of back and forth with @sheffdog and he ended up changing the lead-screw stepper mounts to stick out a bit more to resolve the binding we had. I believe he's posted those designs.
@CapnBry : My hobbed gear looks like a bunch of little knife-blades that cut into the filament. I'm currently printing something and can't take a pic, but it looks way more dangerous than what you got. Those pics you posted look like mine, but with all the sharp edges rubbed off :S

 

You found the link! I posted it a couple pages back but it was easy to miss. I just printed up the design from the OpenSCAD file, modifying a lot of the screw hole sizes to fit what I had on hand. The original had like 18 different size screws and metric stuff is pretty hard to get locally so I just made the parameters fit what I had in my toolbox.

The software is just the HX711 example app modified to just spit out the weight constantly with no delay (which generates about 10 samples per second).

@AK Eric: Yeah my new gear Amazon extruder gear like you'd expect and can push more than enough force up past the 4kg mark. Past that point something has probably gone horribly wrong anyway. Silly how such a teeny thing was such a problem for me to get my hands on. Just get me a gear that resembles anything close to the picture!

I did manage to bork my printer again last night though. I use needle nose pliers to pull off oozy plastic from the nozzle tip before I print but last night my depth perception must have been off because I jammed them into the extruder fan and broke the blades off. Oh well! It gave me a chance to sit down and design a little LED panel mount to go under the carriage, and mount my Pi's camera and so some wire routing.

There's just really not a good clean way to run wires to the carriage other than just having them dangle off the back of the printer is there? I put them in a wire loom but still it looks sloppy.

 

I really hate to say it, but I'm glad I'm not the only clumsy one. I've done that to three fans so far. Once with a screwdriver, and twice with dangling filament too close to the fans. It's been a few months now, so maybe I've learned my lesson

 

Yeah! My i3 printer has Octoprint and a Pi with a camera on it, but I needed to adapt the camera mount to the extrusion (and also get a much longer cable (50cm) because my printer's so amazingly large! The camera is so great for being able to quickly check and see if things have run afoul. I like the time lapse videos capability as well, but on my i3 because the bed jerks back and forth it makes a really awful time lapse because the part moves all around in the frame.

I used Spiral Wrap currently which works ok, but it just sort of dangles off the back. I ran all the wires into the exrtrusion channels for everything else but I just don't think there's a great solution when the carriage moves in both directions like this. I will definitely print that fan guard. I replaced the fan with this Sunon MC30101V2-000U-A99 which moves the same amount of air but should be much quieter. I got 2 just in case!

 

I think i am finally at the point where I am pretty happy with the results. @Carl Feniak Thanks again, I learned a lot from putting together one of your printers. Just a quick video, PETG at 75mm/sec

I hear a few pieces of 3mm filament inside the umbilical does wonders.