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Bulding the extruder HELP!!

Posted by bobt 
Bulding the extruder HELP!!
January 09, 2008 11:16PM
I have just received the parts for my 2 extruders. Upon examination of the instructions on how to build the extruder there appear to be a lot of assumptions about knowing how all the parts fit together. Is it possible that the instructions be redone showing the addition on no more than one part at a time so that anyone can assemble the extruder. My reason for requesting this is that I have just spent 30 minutes playing "tinker toys" with the parts to see if I could position them so that they looked like the pictures are. "VERRY INTERESTING" results at times ( old laugh-in tv program reference from the 1980's ).
If we want anyone to put this together from a given set of parts then the instructions need to be "bullet proof". As it is now there are a lot of questions being asked by me about this.

Bob Teeter
"What Box?"
Re: Bulding the extruder HELP!!
January 10, 2008 08:44AM
Yeah, the way the extruder fits together isn't very intuitive, with the Ts going in opposite directions and all. There are probably enough photos from various blogs that could be incorporated into the main build instructions. That might help a bit. I just did a Google image search on the words "reprap" and "extruder" and got 150 hits. Quite a few good shots. Also a picture of Mickey Mouse, for some reason.

By the way, I'm feeling a bit old right now for knowing that Laugh-In aired in the late 60s. Also having flashbacks of a 20-something Goldie Hawn in a bikini. :-)
Anonymous User
Re: Bulding the extruder HELP!!
January 11, 2008 12:39PM
Ok, here is another question for anyone who can answer it. (Although I think I already know the answer.)
Last night I JB Welded and this morning I re-read the instructions. I think you see where I

Edited 1 time(s). Last edit at 01/11/2008 12:45PM by Cheap!.
open | download - JB Weld Drying 001.jpg (30.7 KB)
Re: Bulding the extruder HELP!!
January 11, 2008 01:03PM
The wire is probably pretty close to 8 ohms anyway. If you measure it and it looks a bit high, you could lower it slightly by removing a bit of insulation and moving your contact points closer to the barrel. I think the nichrome is about 1 ohm per inch.

Edited 1 time(s). Last edit at 01/11/2008 01:04PM by Steve DeGroof.
Re: Bulding the extruder HELP!!
January 11, 2008 01:45PM
If it is a little bit too high you can compensate by increasing the voltage a bit. Because power is V^2/R you don't have to increase it much. An easy way to do it is to replace the Darlington transistor with a MOSFET. That will give you about 1.5V more.

If you look at this thread: [forums.reprap.org] I think d0ubled found a drop in replacement.

Anonymous User
Re: Bulding the extruder HELP!!
January 11, 2008 02:46PM
Steve and nophead,
Thanks. I will try this advice in the following order.
1. Take an omhs reading.
Depending on this I will
a. Let it go if I am very close or right on 8 omhs.
b. Check for how hard the JB weld got today to see if I could rescue some of the wire from under the glue.
c. Check to see if I could increase the voltage. I may have some extra MOSFETs laying around that might be just what I need. On the plug-in hybrid project we ran into trouble using Darlington transistors because of their fall off value, so we went to MOSFET with much better results.
D. Suck it up and go to Home Depot and to our local "EPO" (Electric Parts Outlet) to get what I need. Return home to use the drill press and start over.
Re: Bulding the extruder HELP!!
January 12, 2008 12:21PM

Thanks for posting that mistake. I'm about to do my nichrome wire with JB Weld and I'm pretty sure I would have done the same thing. Good to be reminded.

Anonymous User
Re: Bulding the extruder HELP!!
January 13, 2008 12:48AM
Strange thing is when I got home I'm only getting a reading of 6.7 omhs...so, I'm going to go for it. One other thing I noticed was that the capa spreads everywhere so once I got my bearings to sit right, I let it all cool and I checked how easily the drive screw turned. It didn't, so I went in and I cleaned out all the capa that was not directly under the half bearings. It runs really smooth now. I finished putting everything together and rechecked all the possible adjustments of the parts.

I am hopeful tomorrow I will be extruding plastic with the help of the Houston RepRap Users Group, including RoundSparrow.

Also, will Dylan

Edited 1 time(s). Last edit at 01/13/2008 12:49AM by Cheap!.
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