Tuesday, December 16, 2008


Frank back up and running...again...almost

I haven't posted on here but once. Back then it was to give notice that I had my RepStrap up and sort of running. I'm posting again...because I have my RepStrap back up and running...sort of. This is a long rambling post so bare with me. hehe

I've detailed Frank's vital statistics in the Builder's Wiki for everyone to see here. Frank is a McWire 'strap running Gen 1 electronics (full stepping firmware 0.8 host). My biggest problem with Frank has been the extruder--like most of us. For a long time I let Frank rest in the wings as I was working on the OIT RepStrap and didn't have time for him. Recently I got around to working on him again and wanted to clear up the rats nest of wires around the boards and tiding things up before tackling the Extruder issues again.

This turned out to be a great idea that was long overdue. Here is a picture of Frank pre-facelift:

And here is FrankNuvo!

There are several key changes in FrankNuvo. First of all there is the re-arranging of the boards. They are all lined up now and all th e wires run underneath them. Everything has plugs attached whereas before some things were hardwired in. The boards do not go directely out to the steppers or the opto-endstop but instead go to a row of screw terminals. This allows for easy test points--very handy--and also allows me to dismount the entire electronics section easily if I want to test just it or if I want to upgrade it later.

Another key addition are the fans above the electronics. These were salvaged off of a very nice Antec power supply that went belly up. They keep everything VERY cool on the boards and I don't really have much problem with their air currents cooling off the print in progress.

Another change--even though you can't see it--is the way the wires on and around the frame were routed. I simply cleaned things up, used lots of zip-ties and ran things in straight lines. Makes for a cleaner finish. The small loops of wire sticking up just before the screw terminals were to facilitate easy mounting since having too much tension in those wires makes it difficult to plug them in.

The next thing I did to Frank for his face lift wasn't so much astetically driven--not at all actually--but functional. There was simply way to much slip, wobble, and play in the extruder. So I clamped it down...seriously.

This turned out to be a key issue. After this, it wasn't a matter of how well Frank would extrude, it was getting him to extrude slow enough! However, after this was done and I had fired frank up to print a couple of things:

That first image was an attempt at a mini mug with .35 mm tip but I didn't have the height above the table set right at first so it detached. The second was another go at a heart for my girlfriend. The problem started on the heart.

You'll notice the singed ends and the discontinuous lines...my pump started loosing pressure during the build. This has happened before but not for this reason...I'd blown a hole in my PTFE wall. Take a look at where and what was oozing out:

That discolored spot on the PTFE about 1/3 up from the bottom is the hole. The discoloration is the hardened ABS in the hole. The little ram's horns to the right are what was oozing out of that and around the pipe clips holding the thermal barrel in. I bought the PTFE piece from the RRRF so I'm pretty sure it wasn't me messing it up. Apparently the wall was thin enough right there that it managed to tunnel through and leak out. Anyway, this caused all sorts of havoc with the heater barrel and eventually managed to dislodge it from the PTFE--I left it running because I saw no fix for it.

So, that's where FrankNuvo sits right now. I'm ordering a PTFE and heater Barrel from the fellow making the machined extruder parts--though not this week as I had thought, sorry guy--and will get FrankNuvo up and running again, again!

Demented Chihuahua

Hi. Nice write-up. The machine is a lot neater with those wires rearranged. Really something I should've done as well. I already had a fried chip because of a short.

B.t.w. we're going to try PEEK thermal barriers. That seems to be a better material in terms of strength and thermal rigidity. Teflon (PTFE) is pretty soft compared to it and it creeps under pressure. They have it at Farnell. It is pretty expensive to get 30 cm if you only need 2-3 cm, so maybe BfB can switch over to this...
Been reading about other people using it...wanted to try it but funds are tight right now...sucks. Instead I've been doing experiments with alternate setups. Nothing has worked well enough so far but I'm still looking. The whole use of PTFE bugs me, it just doesn't fit the idea of common and easily accessible.

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