Stratasys Dimension SST Extruder sensor repair

Refurbishing a behemoth of an industrial 3D-printer to working condition after it has been left for dead in the shed of a big company

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Repair of a professional, industrial-grade ±$40k 3D-printer with a €1 part. In this case, an infrared reflection sensor that determined which extruder (model or support) was activated.
Most RepRap-clones that have more than 1 extruder use open-loop control while switching the active extruder; these industrial machines have a sensor which checks if the correct extruder was actually activated. Except, because of the heated build chamber (also lacking on consumer printers because of IP challenges), components are under more thermal stress.
When the white LEDs that light the build chamber fail, there is no problem. But when the LED in the IR reflection sensor (which is an LED/phototransistor pair) fails, the machine stops intermittently because it thinks the extruder was not switched when it had to (or switched when it shouldn't have).

Many large, industrial scale 3D-printers that cost several tens of thousands of Dollars (or Euro's) not very long ago (about the same time RepRap, Makerbot, Ultimaker et al. became popular) are being decommissioned for trivial problems. Some have software errors, some have clogged extruders. Some ran out of filament. Many get dumped because their owners make a cost/benefit calculation, and with the annual retainer for a service contract being about the cost of a RepRap descendant, that calculation quickly tips into the "time to write-off" side.

These are also complex machines with many sensors, actuators and several layers of software all working together. This makes them error-prone, and, being closed-source (and maintenance literature hard to find), hard to repair.

Thus, they can be picked up for a snap (in monetary terms, being bulky they carry a lot of mass). My particular unit booted, initialized, calibrated and even printed the first layers, but would intermittently stop with the error code "14, 129", which the service manual for another printer of the same line (probably running the same software) indicates as an extruder problem: "Toggle Head failure".

While taking apart the extruder head, I noticed a small PCB (outlined orange in one of the photos) with two IR reflection sensors (QRE1113 or equivalent) on the back. They shine their light on a black and silver metallic sticker which is on the rod that moves the extruders into and out of the way.

Because the white LED's of the interior lighting had failed (probably due to prolonged activation in an environment of 70 degrees Celcius), I thought the same must have happened to the IR LED. Swap out the sensors for fresh ones (an easy SMT repair job), reassemble the machine (not so easy) and do a test run: no more problems!

Other common errors on Dimension machines:

- the wiring on the extruder servo motor encoder fails due to shaking and thermal exposure

- bubbling support / build materials (and because of that clogged/blocked extruders, etc.) indicate

- empty backup battery coin cell on motherboard corrupts memory of installed cartridges (which manifests as weird "Shutting down - Continue"-errors while initializing)

- When these work they're wonderful (true tolerance, real ABS prints with soluble support and zero warping!) but my god are they error-prone

Hopefully, this saves other machines from landfill!

  • 2 × QRE1113 Sensors / Angle, Position

  • 1
    Step 1

    You can either take apart the whole extruder head, or try to loosen the two screws that hold the sensor PCB from the side (which clearly wasn't supposed to work but can save you a ton of time). Taking apart the whole head has the added benefit of being able to clean it thoroughly, which might be a good idea while you're at it. The sensor PCB is connected via a dupont-style connector, so is easy to disconnect. You can then take the bare PCB and perform the SMT-rework;

    - removing the old sensors (note their orientation first, as that is missing on the PCB)

    - cleaning the pads, maybe adding some fresh solder

    - use hot-air or normal soldering iron to attach new sensors. These cannot withstand high temperatures for long, so take care while doing this.

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alarmedresponder wrote 07/19/2022 at 15:51 point


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