RepStrap Blog

Thoughts on an Extruder Barrel assembly

2009-08-26T16:29:00.000-07:00

Well I made what I thought would be the hard part of my extruder, though I haven't tested it yet, but now I need to make the barrel assembly. I have a few ideas at the moment...the first is to use a design similar to Forrest's (thats a hyperlink by the way), but that requires a bit of brazing, and 3mm ID copper pipe, something that is not available at any of my 3 local hardware stores (yes its crazy 2 of them are about 3 minutes from each other). So I can either order copper sheet metal and copper tube from mcmaster, braze them and hope it works...or I could just buy all the parts for the extruder barrel assembly from maker bot. From mcmaster I would need copper tube, copper sheet, a ptfe tube, and a .5mm drill bit, totaling $11.70. Or I could order the mk3 heater barrel, thermal barrier, and nozzle for about $20. I haven't decided which way to go yet.

I need a name for this thing in my room!

2009-08-24T21:13:00.000-07:00

I need a name! I'm tired of calling it my RepStrap! Please post your suggestions in the comments page! If someone would like to tell me how to have a poll, I will do that, otherwise, just reply with suggestions, in a future post I will ask you to vote on the best one!

Time to update my pics

2009-08-24T21:07:00.000-07:00

Well here are some new pics, the monitor isnt installed at the moment, and niether is the keyboard (its a long story), but everything else is there (including my safety glasses lol)
its sideways but I cant figure out how to rotate it so, Sorry.

USB->TTL cable, AVR ISP, and some Kapton tape are on the way

2009-08-24T20:59:00.000-07:00

Yea well the title pretty much says it, I ordered a USB->TTL cable, the recommended ISP (USBtinyISP AVR Programmer if anyone doesn't know and cares), and some Kapton tape for my yet to be built extruder barrel. I hope it will be here by this weekend so I can continue work on my positioning system. I resisted the urge to buy some skate bearings and another 10 feet of nichrome "just in case I need them", but I still caved and bought 2 feet of nichrome...

Design for a pinch wheel extruder

2009-08-23T18:47:00.000-07:00

I had some free time today so I designed and build a pinch wheel extruder out of stuff I had laying around. I thought I could either work for 5 hours to buy the pinch wheel extruder kit from makerbot or just build one from scratch from stuff I had (which was a good choice considering I dont have a job :)). Here are some pics, tell me what you think! The motor is a 6 wire stepper I will be running as bipolar, the metal pieces holding the motor are "U" extrusions hotglued to each other the plywood and the motor (like I said I was using things i had), the main piece of wood is of course plywood (dont remember the thickness just a piece I had next to my table), the piece coming off the stepper is a piece of a 1/4 -20 bolt, attached to the stepper with 3/8in silicone tubing and hotglue (i really like hotglue :)), the wooden wheel is also plywood, cut with a holesaw, and attached with a 1/4-20 machine screw, a nut below the wheel and above the plywood to allow the wheel to spin and the bolt to be tightly attached to the plywood. I had to grind the bold down slightly so that the wheel wasnt too far from the main piece of plywood. I dremeled it at an angle so that the nut could be sufficently big but the wheel could angle back to the plywood before it meets the 1/4-20 bold coming off the stepper. I drilled a slot in the back plywood so that the wheel can be moved twards and away from the bolt on the stepper (known as the bolt from now on, it is a piece of a 1/4-20 bolt that I knurled with a cutoff wheel on my dremel, I think i already said that but whatever). According to my calculations, the stepper should have to run at at speed of (kits drive from the motor is 10.3mm, mine is 1/4in (about 6.4 mm) which is close enough to %60 of the diameter of the kits gear size, so the kits drive has to run at %60 the speed of mine, so since the kits motor runs at 2RPM, mine has to run at 3.33RPM, so at 200 steps per revolution it has to run at 666 steps per minuite or 11.1 steps per second, which is (obviosly, and yes i know i spelled that wrong i just have no clue how to spell it right) 22.2 half steps per second) 22.2 half steps per second. I hope that my stepper will have enough torque at that speed without any gearing. Unfortunatly I dont have any ABS right now, and Makerbot is out of stock, so I will not be able to test it yet. Please comment with your thoughts on this design (if anyone is even reading this, I have 1 follower, lol, thanks Dave!)

Out with Gen2 in with Gen3

2009-08-23T18:37:00.001-07:00

Well this is my first real post in a long time...anyway I replaced all me electronics with the reprap Gen 3 electronics. My repstrap now looks a lot better without all those messy red wires, now its just a few black cat5 cables running around. Unfortunatly when I ordered the electronics I didn't order the ISP or the USB->ttl cable. I will order those tonight and hopefully they will be there by next weekend. I now have all my electronics mounted and wired up, and I have gone through the firmware and made all the nescarry configuration changes, all thats left to do on the positioning electronics is burn the bootloaders for the reprap motherboard and the extruder controller. I saved all of the gen2 electronics, so hopefully I will be able to use them in other projects (well the boards that work anyway, the main reason I swapped in the Gen 3 electronics was that I had built the gen2 electronics on stripboard (its a long story) with parts from mouser, and well they didnt work, and it was just too hard to sift through all of the wire to find the problem.) I have a robotics competition for school sometime so I will probably use my old arduino and maybe the PWM drivers for that. Ok i'm done rambling for this post anyway!

Fan remved from power supply

2009-04-18T20:15:00.001-07:00

Well I got tired of hearing my PSUs fan squeak all the time (it has a bad bearing) so I removed it...So far I haven't had any temperature issues but I have not run it for more that 5min we'll see. My idea was that in a PC the fan is used more to remove hot air from the case than to cool the power supply but please tell me if I'm wrong before I burn down the house:)

Stepper Motor Driver Issues Resolved!!!

2009-04-18T20:14:00.001-07:00

I have finnaly finished debugging my Stepper Motor drive circuit! This is one giant leap for me and my repstrap and I can now move onto less tedious things (I hope) like building an extruder and buying a bigger PSU for my repstrap mine outputs 5A at 12V, My steppers are 6V but I am running them at 12V for extra power, running 3 stepper in high torque mode (2 phases at once for extra torque) since my steppers are 1.3amps phase this gives me 2.6A per stepper=7.2 amps for all 3, my power supply only produces 5A at 12V, whoops :), I guess I will need a new PSU or I will have to drive my steppers in Wave Drive mode.

Stepper Motor Driver Issues

2009-04-14T18:52:00.001-07:00

Well I started the switch from NPN transistors to HEXFETs. So far it hasn't gone so well. I tested my circuit before I conencted the HEXFETs and it worked as i should, but once I connected them the whole circuit stoppd working :(. I am now trouble shooting the problem and will get back once I find/correct it.

EDIT: Well I have had to post the problem on the RepRap forums so I guess I wont be the one fixing my circuit... It will probably be some electronics whiz working on the reprap project :)

2009-04-12T09:56:00.000-07:00

I have established communications between the PC controlling my repstrap which I will call my RC (RepStrap computer) from now on. Now when I tell my RC to "print" an object, I get the appropriate voltages on the appropriate pins (YAHOO!) sorry that took me a long time to figure out. Any way next step is to power up my electronics and hope it works :).
BTW Happy Easter All!!

First Real Post

2009-04-11T20:05:00.000-07:00

So I dont think anyone is reading this as it comes out so I'll just let it get anyone up to speed as to what I have done so far that decides to look this far back. I set out to design a low cost RepStrap after I learned that Tommelise 2 was above my price range. Anyway so far I have finished (I think) the hardware part and my external electronics have been tested as much as possible without the software part working. My repstrap is controlled by 3 unipolar steppers turning 1/4 20 threaded rods running through captive nuts on all of the axis. The stepper motors are controlled by stepgenie stepper controllers currently activating NPN transistors but I plan to switch to HEXFETs before I start printing. Everything else is the standard RepRap electronics. I have decided to mount a dedicated repstrap pc on my repstrap, it is a compaq laptop with a cracked screen plugged into an lcd monitor and external keyboard/mouse. I am using the RepRap host to control my RepStrap through an Arduino. If you are reading this blog I expect you to have a knowledge of RepRap/RepStrap systems and if you dont please head over to www.reprap.org to learn before reading. I have decided to use a dedicated repstrap pc because I dont want printing things getting in the way of me using my main pc. I dont want to not use my repstrap because I need to use my pc. Anyway if you have any questions feel free to ask in a comment.

First Post

2009-04-11T16:37:00.000-07:00

Well I have decided to start a blog about my Rep(St)Rap Adventures. Here it is... my main Rep(St)Rap site is www.repstrap.weebly.com. Thanks for reading stay tuned. Sorry about the ads, I have to keep the project funded though :).