Friday, August 20, 2010

The Makerbot Mk5 Extruder has exited the Botcave

I love my Makerbot, I hate my Mk4 extruder.  Ohh the pain it has caused:

-Idler wheel loosening up over time
-Idler wheel snapping in half
-PFTE bulging
-PFTE popping off (before the bolt became standard)
-Nicrome frying itself
-Broken retainer rings
-Gunked up drive pulleys

I looks like Makerbot has eliminated the possibility of all the common Mk4 failure modes..  Now don't get me wrong, I am absolutely sure we (at least me :) ) will figure out how to break this thing, but it looks like the weak link of the Cupcake, the extruder, has been solved (we hope).

I though it would be a fun excersize to play "find the fix" with this design.  Like all good ideas, it's a copy's a lot  of other designs that work well.

The Mk5 drive gear:


Hobbled gears have been around for a while in the hobby, but they where made famous by Wade's wonderful geared extruder.  The 1st time I ever saw one works was Nophead's Tiny Stepper Torques Big post.  Ever since the 1st time I saw it, I wanted that for Makerbot.  I have used my Mk5 drive gear in my Mk4 Makerbot since the 1st day they offered it, and honestly it really does improve the Mk4, but it didn't fix it.  The Mk5 looks like the final Fix.

Tensioner


The Tensioner was 1st introduced by Charles Pax for his Paxtruder 0.1.  I remember reading his blog and thinking, god I wish I could buy that thing...  well it only took a year :)  I still think the spring and 608 approach is better, but for a laser cut design, this is likely as close to perfect as you can get.

The Power Resistor Heater

The heater looks to be derived from the work of Nophead's.  Funny how SO many things in this hobby go back to Nophead, we need to throw him, Adrian, and Zack a party..  Oldest reference i can remember actually using power resistors was his Pear Shaped Post.  Cool thing is if you want something like this on the Mk4 you can buy a kit over at Makergear, but it does not require a relay, and only uses 1 smaller Power resistor.  I have not used it yet..  My hot end is still working, and I have a backup that Rick over at Makergear put together, but I hear it heats up slower than Nichrome.  The Mk5 looks like it will heat up nice and quick with it's relay:).

Thermal Barrier
The Thermal Barrier looks to have been heavily inspired by the Bit's From Bytes Thermal Barrier
PFTE tube constrained by a stainless tube.  It's brilliant really.  Slick, strong.  It's great stuff.  I 1st read about it at the Rapman Blog.  Unfortunately it's not "Fab-able".  But as the Rapman has shown for over a year now, it's a rock sold and relaible design.

The Nozzle
The nozzle looks basically the same (besides now being a male instead of a female), but honestly looks much closer to the Makergear Big Head Nozzle than the old mk4 nozzle.  I know the people who have tried the larger headed nozzles have found that the larger head acted as a thermal battery, holding the heat and allowing for a more consistent extrusion. 

Plastruder Mk5 looks like the a true changing point for Makerbot.  There was very little difference between the Mk1 and the Mk4 Plastruder.  Sure there where changes, but in the end it was always the Child of the Hercules.  Mk5 brings marks the end of the Hercules generations of Plastruders, and begins the Paxtruder generations of Plastruder..

As much as I like this design, it does mark 1 real change for Makerbot.  No longer can it be said that you can build the Makerbot extruder with a laser cutter and a drill press.  The hot end has now entered the only makeable with a lathe world.  Guess I can't get too bent out of shape over it, Adrain's new nozzle is a Lathe only design.   At least RepRap and Makerbot both did a LOT OF WORK making the fab-able nozzle design as relaible as it could possibly be.

Makerbot now has a Paxstruderesque  tensioner, Wades Extruderesque drive gear , a Rapmanesque thermal barrier, a Nopheadesque heater core, and a Makergear big head nozzlesque nozzle.

That's why open source is so great, we all build on the shoulders of Giants.  How long before we see this hot end on a Wades Geared extruder, for the ultimate extrusion Machine! :)

4 comments:

  1. this is a very good thing to see, i think this will be one of the bigger stepping stones for this project has a whole.

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  2. Anyone want to place a bet on how long be knock off nozzle and extruder parts are going to be available on Ebay? :)

    It took 2 weeks for knock off wormgear to show up ! http://cgi.ebay.com/Reprap-Bronze-Threaded-Pulley-/180539917273?pt=LH_DefaultDomain_0

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  3. I'm already thinking about ways to incorporate some of the features into a no-lathe-required design. Some of it just confirms what I was already thinking would be a good way to do something, but there are a few pieces of this that might help me.

    I was confused when I saw how low the resistance for the power resistors (wired in parallel!) was, until I saw that they were using the relay board. With a standard mosfet-powered hot end weighing in at 6 ohms, if you backed off from the 2.5 ohm resistors in this to 3 ohms, you could make the relay optional, just wire it in series for direct mosfet power with a slower heat-up.

    I also like the idea of connecting the heater block to the extruder body without using the barrel as a structural part. If you could keep the cold end of the barrel cool enough to not soften the plastic, you could even have a significant air gap between it and the extruder body. Nophead has suggested that a short hot zone is preferable, and this has led me to the idea of a heater block that couples with a bowden cable directly, no barrel required. To use this heater block with a carriage-mounted extruder, you would just need a 1-2" piece of the bowden cable tubing.

    One thing I really like is the male-threaded nozzle. I have been wishing for this for a while, and it's the real reason that I may buy one of these hot end kits to experiment with. I'm anxious to see what Makergear's response will be to this. If they start making parts to be used with the MK 5, it will be a nice new breeding ground for hot end designs. I always thought nichrome was kinda stupid, and have hated it since I first saw Nophead's post about the power resistor heater. What I really want is a nozzle machined directly into the aluminum heater block, though I've determined that the bevel around the hole is necessary, which would make that a lot more difficult (lathe definitely required, and one with a four-jaw chuck). The male-threaded nozzle is a nice compromise.

    Also, with all of the problems I've been hearing about (including some of my own) cause by poorly-hobbed bolts in Wade's extruders, I'm eyeing that MK 5 drive gear for a possible redesign. Anyone have the measurements for that? The dimensional drawings I can find all have the dimensions left blank!

    ReplyDelete
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