2010
10.22

More Stratasys disassembly

My use of generic ABS and HIPS in the Stratasys finally has caused some annoying issues (more than just drooping filaments on infill).  The photo of what awaited me after after the first build weekend with generic materials should speak for itself.  It looks like the machine literally barfed all over.

I wondered if perhaps the support filament was to blame, as it had jumped off of the spool and wrapped around the spool shaft in testing a few times (due to me winding the HIPS onto the spool all the way to the rim).  I looked in the dry box, but all was well.  I then opened up the head for a look inside, and it looked like an accident at a spaghetti factory.  HIPS was stuffed all around, and required removal of the motor blocks, so I figured this was a good time to photograph details of the head (the only peek inside a Stratasys head that I’ve found online is at Bouke’s blog) for others to see.  Plus, a good cleaning was in order – the generic ABS and HIPS appear to have a great deal of volatile compounds, and there was a good amount of soot and burnt plastic sticking to the nozzles (plus, there was enough melted plastic gunk between the two nozzle rings that the support nozzle wasn’t able to travel up and down freely).  This is a big concern when looking for what materials to run through the Stratasys – I had no issues with the OEM material (even with the material left cooking for half a day), but the generics from NIP like to stick to the nozzles and char (note all the brown lumps in the photo).

After cleanup and re-assembly the ABS nozzle is still extruding very nicely, but the HIPS nozzle may very well have some buildup inside.  I could only extrude perhaps 10 inches or so of HIPS before the filament would buckle between the feed rollers and liquifier entrance, which is what caused the impressive birdsnest in the head in the first place.  I haven’t tried extruding more OEM support material through however, so maybe I’m just hitting a limitation of the material itself.  Still, I think the support nozzle has some sort of buildup, as the material is not coming out straight – as soon as it exits the nozzle, it curls back around and sticks to the nozzle, after which some sort of mess is inevitable on a long build.  Nophead notes in his latest blog entry that he needed to clear out one of his nozzles with a drill bit to restore proper extrusion. I ordered a 0.011″ drill bit from McMaster-Carr, and then found that the pin vise I have can’t properly grip such a tiny bit, so I await a better pin vise before I can see if this re-boring fixes the issue.

On to the photos!

After the head is removed, this is what you see.  There’s three vacuum cleaner hoses that run to the rear of the block – the large center one carries cooling air (which gets expelled from the central nozzle) as well as the two filaments (which poke out on either size of the nozzle through adjustable grommets).  The two smaller hoses at the top are for the air return.  The brass brush at the lower right helps keep the nozzles clean – after every 2 build layers, the head zig-zags the nozzles over the brush to wipe off excess filament that has oozed out.  Of course, this only really works with the OEM filament, as it doesn’t adhere and melt onto the hot nozzle surface like the generic ABS and HIPS likes to do.

This is a top view of the head – there’s a locating pin at the center front and rear to make sure that it is perfectly aligned when the latches are secured.  The front cover protects the solenoid.

This is what the rear of the head looks like, with one of the motor blocks removed.  Each filament passes first through the black plastic guide bushing, then through the pinch wheels, then finally into the entrance of the liquifier.  I’m not sure what type of plastic the reddish-brown liquifier end caps are, but it’s obviously a high temperature material.  Right between the two liquifier entrances is the point at which the cool air is directed – it’s important to keep the filament solid before getting to the liquifier.

Here’s a close look at the motor block itself.  I’m guessing the amber colored insulator plate is the same plastic used on the top of the head.  The toothed roller (appears to be black anodized aluminum) is the driven one.  The MicroMo gearmotor label reads as follows:

1624T012S123 X0520

16/7 415:1K703

HEM1624T16 KW 45/96

It turns out that these 3 lines specify the motor, gearhead and encoder.

This is what the underside looks like after the nozzles and protective rings are removed.  Note that the black ring on the nozzle is actually a seal (though I’m not sure what material – Kalrez or other perfluoroelastomer, perhaps).  Yuck, look at all that black crud.  I tried cleaning the rings and nozzles by soaking them in acetone, but it really didn’t help much.  I’m assuming that the relatively volatile styrene (which acetone dissolves) had been cooked out already (again, why the OEM material doesn’t degrade in this manner is still a mystery).  The rings look to protect the bottom of the foil and insulation wrap.  The picture really doesn’t show it, but the heating elements come all the way down to where the foil ends.

Here we have the real guts of the head.  Each liquifier (build material on the left, support material on the right) has a thinwall stainless tube at its core (according to Stratasys patents, anyhow – I’m not about to start unwrapping insulation to find out).  It looks like there must be some sort of other material around this core, over which the heaters are spiral wrapped and then covered with a layer of what appears to be fiberglass and foil.  The cylindrical spring-ended parts that flank the liquifiers are the RTDs that actually measure the temperature. The cylindrical caps at the top of each liquifier are Klixon thermal circuit breakers. If the temperature controllers are improperly set (easy to do, and the manual warns that seeing ‘100′ with the ‘M’ LED on does not mean 100 degrees, but rather 100% output), the circuit breakers should keep the liquifiers from overheating. I don’t know what this cutoff temperature is, however – the circuit breakers don’t appear to have any markings other than ‘Klixon’.  Note the rear of the right liquifier, specifically the two aluminum blocks on either side.  These are actually pivot blocks – there’s a pin on either side of the support liquifier to allow the whole unit to tilt downwards by perhaps 1/16″ or so.  You can just make out the extension spring (and pin that the spring attaches to) at the front of the liquifier that keeps it in the ‘up’ position when not in use.  And what moves it downward, you ask?

A Lisk push-type solenoid pushes down on a paddle connected to the bottom of the support liquifier.  Note the hex nut at the bottom – this locks in place the set screw that adjusts the downward travel of the paddle.  Upward travel is adjusted via a screw attached to the cover that normally protects the solenoid (the solenoid core actually contacts the screw at the top of the solenoid’s travel).

In short, the head is pretty straightforward in terms of design and construction.  Would I want to scratchbuild one myself should this one become irreparably damaged?  Heck no, but it would certainly be possible.

15 comments so far

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  1. Wow! So, there is a ton of detail in this post, and a fair few concpets i’m not 100% on, but thanks, mike! I’ll be digging into this post over the next few days!

  2. Fascinating. Do you know why the liquifier module can tilt? Do both do it, or just the support material’s one?

    • Just the support material liquifier/nozzle assembly tilts. This is so that the support nozzle doesn’t drag across already-printed ABS when laying down support material (and consequently, the model nozzle doesn’t drag across support tracks).

  3. Hi,
    Do you know how machine deals with the ABS fumes. Does it have a waste air pipe or does it pass them through a filter?

    • My machine doesn’t appear to have any fume handling system at all – there is no mention of a filter anywhere in the manual, and as the interior is a heated chamber (which takes a good while to get up to temperature), nothing gets exhausted (though there are a number of fans internally to keep the hot air circulated around the build area).

      This brings up an important point – the Stratasys ABS and HIPS is remarkably ‘clean’. I never had any nozzle buildup issues until I started experimenting with the generic materials, after which I noted a lot of crud and condensed volatiles on the nozzles (which I note is a very common appearance on RepRap nozzles as well).

      Additionally, in my latest testing, I had the head detached from its mounting block and rested it on the platform. Looking at it close up in this way, I noticed tiny, barely visible puffs of vapor coming out of the nozzle when running the generic ABS and HIPS (no doubt the very source of the coalesced crud). I switched back to the OEM materials, and as hard as I stared at the nozzles, I could no longer see any vapor. Switched back to the generics and the vapor returned.

      I’m noticing more and more people concerned about potentially nasty compounds being released from their RepRapping endeavors. While I think this could be be best addressed by trying to find ‘cleaner’ materials such as what Stratasys uses, building an air scrubber (see page 3 of http://www.caswellplating.com/manual/pdf/section2.pdf) may be the best way to run ‘dirty’ filaments for anyone who can’t exhaust air to the outside.

  4. Ah, that might explain how the pp3dp UP printer gets away without any cover. They sell their own plastic, which IIRC they described as like Stratasys’. You might be able to run that in your machine as it is smaller diameter.

    The link you gave gives file not found.

    Thanks.

    • Fixed the link for you. I’ve been holding out for a domestic distributor of PP3DP filament so I don’t have to deal with exorbitant international shipping (plus I’m already waiting on a shipment of third party ‘Stratasys compatible’ material from a Canadian supplier to try out). Interestingly, I remember seeing somewhere on the PP3DP site that even better results can be obtained by using real Stratasys material. As well, I’ve been chatting a bit with Rick @ MakerGear, and it sounds like he’s eager to do some experimenting with 1.75mm filament formulations.

  5. Just in case you were curious about how the head is constructed … I had to rebuild mine and have the writeup here …
    http://www.incredilution.com/2011/01/engineering-to-save-5000/

    It was quite interesting a a little fun however the machine running properly is far more fun.

    • Fantastic work! Disassembling the liquifiers doesn’t seem as daunting now should I ever need it.

  6. Recently I became the owner of an FDM8000 with no head. I was wondering if you can provide a pinout of the head (I hope that the 8000 and the 2000 have the same head design). I have already managed to bypass the head and sensors to get the machine turned on and moving, and I am planning on rebuilding the head with a makerbot type head. Any help would be appreciated.
    Thanks, Lior.

  7. dear all,
    I get a 2002 prodigy plus recently, and I have the door lock who didn’t want to unlock the door, even when pausing or when the part is donethe only solution is to switch off the machine with the red button on the side.
    Does anyone have technical or maintenance documents because stratasys does not want to communicate these (and stratasys did not want to do any maintenance on these machine, ” buy a new they say…”).
    Thank you for your help
    Cedric

  8. dear all,
    does someone know how to lone the internal HD, to keep the original ina safe place.
    I tried to use clonezilla but it did not not work (original HD is a WD200 and the new one a WD400 so not the same size). I did not hear the starting beep with the clone and the machine won’t start.
    I will try with a DD command with linux, just in case
    If you have an idea, let me know
    Best regards
    cedric

    • I usually use Paragon Drive Backup, but it doesn’t always work (it didn’t properly copy my new Win8 drive, for example). DD is almost assured to get a good clone, though (obviously, you need to copy from a smaller drive to a larger one or use identical drives). Make sure to use the bs option with dd, else you’ll be waiting a very long time!

      • Finally, I have succesed to clone the original stratasys HD, You can clone it with clonezilla or DD under linux, no problem.
        My problem was the 2 hard drive were not the same size, and when booting, the mother board did not recognize the new hd (not the same number of cylindrer, head, … and the bios has no auto detect function apparently).
        I bought a used HD but the same model as the original and no more problem…
        another possibility is to plug a screen and keyboard on the mother board and change bios parameter, but it es another story
        I hope this will help someone!

  9. ps: my mother board is 186 processor with a nova 600 board