Talk:Extruder/Mendel

Thermoplast Extruder 2.0/BOM

Jkeegan 07:43, 7 November 2009 (UTC) - Referring to the Thermoplast Extruder Version 2.0 page for most of the instructions seems fine at first, but it does become a bit confusing once you've gone to the page and start looking at a bill of materials.. there's mention of pre-generation-3.0 electronics, for instance.. it took me at least a minute to realize that the PWM Driver 1.1, Stepper Motor Driver v2.3, and Thermocouple Sensor v1.0 were all unnecessary now that a generation 3 Extruder Controller board exists. Eventually the necessary (and only the necessary) pieces from the Thermoplast Extruder page should be duplicated/adapted into the Mendel extruder page (or alternatively, the Thermoplast Extruder page should be modified to make mention of which pieces to ignore/replace while building an extruder for Mendel).

Permanently attached thermal barrier

So, as I'm getting closer to actually being ready to permanently glue my favorite mendel RP piece to a PTFE barrel, I have to ask - can anyone that has a working Mendel (Adrian?) comment on whether there's some reason to believe that we'll need to replace the PTFE barrel less with Mendel? I've been using a MakerBot for a month and a half to make Mendel parts, and I've gone through at least four PTFE barrels (this last time, even with a hose clamp on it, extruding PLA). Even if that was just because of an initial learning curve, that would still seem to indicate that tying the fate of the RP'ed Mendel piece to the PTFE barrel is costly, no? Is there a reason why we shouldn't have some non-permanent attachment, where the PTFE is bolted via some washer or retainer ring as they have on the MakerBot plastruder? For instance, are there reasons against that related to tool switching in the upcoming Mendel updates, or does a damaged PTFE barrel break the pinch wheel piece anyway, or something along those lines? I'm a big fan of making the "official" RepRap versions as good as possible, and don't want to stray too much myself into custom modification land, lest we have an official mainline version that no one uses directly and has problems. (I'm also weakening on the idea of using that bucket of fire cement that I bought, what with kapton tape being cheap, but I haven't switched over on that idea yet). But I digress. Thoughts? --Jkeegan 15:38, 2 January 2010 (UTC)

Jkeegan, try asking in the forum: http://dev.forums.reprap.org/list.php?70

I think we need a [email protected] mailing list so that queries like this don't fall off the radar.

Having a non-permanent attachment sounds superior. Do you want to write it up in http://objects.reprap.org/wiki/Mendel_extruder/Patch

Custom modification is the whole point of RepRap; the tricky bit is "checking in" user/builder innovations and inventions and then presenting them as the "official" version. For example, we don't have a lasercut extruder on the wiki yet. --Sebastien Bailard 17:51, 2 January 2010 (UTC)

The permanent PTFE bugs me as well, I have seen the exact same thing on the makerbot (at one time i was foolish enough to believe that purchasing 5 spare PTFE barriers would last a long time..) however I was not using a nut on the thermal barrier back then and hope this will solve my makerbot PTFE destruction problems.

My concern is this nut does not exist in the current Mendel design leaving the PTFE to slowly deform from high heat and gravity as well as the occasional ramming of the extruder head into the build platform (which really can't be good).

What I plan to do is to implement the exact same thing the Makerbot has; a nut sandwiched between the PTFE barrier and a tightened down peice of sheet metal or very large washer with two screws drilled through it and the extruder RR'd piece that holds the stepper. Heres a diagram:

|               |
|               |
|    RR'd Part  |
+---------------+
 |   +-----+   |
 |   |     |   |
 |   |     |   |
 |   |PTFE |   |
 |   |     |   |
 |   |     |   |
 |   +-----+   | <- long screw
 |   +-----+   |
 |   | nut |   | (nut is trapped between the large washer and the PTFE)
 |   +-----+   |
+---------------+ <- sheet metal or large washer
 -    |   |    -
      |   |
      |   |
      |   |  <- extruder barrel
      |   |
      |   |
       \ /

This way the vertical forces act on the nut not the threads of the PTFE so the PTFE should not die as quickly or easily or, hopefully, at all --TheOtherRob 18:16, 2 February 2010 (UTC)

The tricky part about doing this on a Mendel seems (at least to me) to be how to do this without causing heat to travel through the washer and screws into the extruder piece (which might be printed in PLA, and could then melt). That's the whole reason we have the PTFE insulator, and it seems that any metal pieces we add that are attached to the heater barrel run this risk.

What I've been planning (that I'll try soon) is to have a piece of MDF underneath the entire X carriage (held on by at least the middle M4 bolts on each side of the carriage) which itself has two holes on the Y axis that those long screws in your picture can go through. The MDF acts as thermal insulation between the bolts and the RP extruder piece, and holds the long screws that will take the pressure.

A redesign of the carriage will probably make modifications like this easier. I'm stuck in the situation where the parts I have are all I'm going to get until I have a working Mendel, so I'll probably try what's described above before anything else (if I don't just give in, glue a perfect PTFE insulator into my extruder piece, and hope that my Mendel prints well enough that I can immediately print out several extruder replacement parts). - Jkeegan 17:02, 17 March 2010 (UTC)