I am slowly working my way through replacing a uPrint trajectory control board with a Duet3D.

I am doing this partly to help my uni but mainly for my sanity (I needed an integration challenge)

Primary constraints were to make no permanent modifications to the printer and to be able to return the machine to factory functionality. Primary goal was to reduce operating costs and retain a reliable ABS capability. I intend to make the files available once I have an acceptable level of functionality. There has to be a stack of these machines tucked away in corners gather dust, just waiting for a new lease on life. Fully appreciate the build volume is tiny for the footprint but reliable, economical ABS printing has its uses.

As I am working on this part time, updates will be sporadic, but they will come. Financially the project is too far along to just walk away from it. Besides, professional pride won't let me walk away anyway

Currently I can read cabinet and hotend thermocouples. These aren't calibrated yet but they do move in the right direction.

I can control the cabinet and both hotends individually and each will maintain a set (uncalibrated) temperature.

I can move the X/Y gantry and Z platform in the correct sense and roughly correct distances. Many thanks to the work done by drphil3d on steps/mm here; https://forum.duet3d.com/topic/10982/stratasys-uprint-retrofit-finally-complete

X/Y endstops work, so X/Y homing works reliably.

Top few items on a very long TODO list;
Z probe, leading to full homing and mesh bed levelling
Thermocouple calibration
Rebuild the blocked hotend (that's how I received the printer)
Start figuring out the extruder drive.

TL:DR success using analog-linear.

I have one (of three) thermocouples working using analog-linear, so the software handles the ADC correctly. The other two thermocouples have a different signal path and I need to figure out what is different in how the chassis handles them.

I also need to work out the exact scaling factor for the thermocouple I can read but that should just be a case of looking at the configuration around the signal conditioning IC (ran out of time today).

On further digging, I'm having issues getting the calibration factors configured correctly.

My signal source is configured for 10mV / degree C.
I have spent a heap of time iterating the zero and max cal figures with the most useful setting being a zero of 70 and a max at 260 (from memory). These figures get me close to correct indications between 190 and 220C. The description for Analog Linear temperature sensor

Biggest issue currently is that my readings top out at 229C indicated by the Duet but actual hotend temperature continues to climb.

I know I need to go back through the OEM signal path and figure out exactly what is happening. This probably isn't helping my interpretation of the sensor description; the sensor test point does do 10mV/C as expected but it is going wonky somewhere downstream from there.

One idea I am thinking about is changing ADVREF from 3v3 to 5v. This way I can remove the 3v3 zener clamp from the signal path.

I'm also starting to consider building a replacement signal conditioning board to convert the TC's to SPI signalling.

I'm trying to post a useful reply but the stupid akismet spam filter keeps blocking me for some reason

Small world :). The provided explanation was really helpful. When I first saw the circuit diagram and design constraints I just knew it was for a uPrint.

Pins arrived today for my extruder splice loom. No connectors though

Had a quick look through the wiki page; nice and concise. Would have saved me a bunch of work

@AJ-Quick said in Another Stratasys uPrint retrofit:

Pete,

Have you continued to make progress?

Yes

Would you be able to share what you have done to make the integration a success so far? For example how connections have been made between the Duet and the Stratasys boards? Have you managed to integrate the material bay in anyway?

Biggest problem I hit when trying to be drop-in replacement was the driving the steppers. The TMC drivers appear to be adequate to drive the stepper motors but they are too smart for their own good. If you try to drive the uPrint power amplifiers with the TMC drivers, the TMC's get confused since there isn't a real stepper on the output providing back EMF and all the other goodies that let the TMC driver do it's job. If you use the Duex outputs of step/direction then you are limited to whole steps I believe and then we waste the potential of such a rigid motion gantry. I ended up just running an umbilical out through the grommet on the LHS of the electronics cabinet. With each motor having its' own connector into the cabinet, this was simple and still non invasive.

For now I'm not touching the material bays. I'd like to come back to that problem at a later date since the load/unload mechanism is really nice.

I have been working on something very similar. The goal was to make it completely plug and play. Ethernet Duet in, while still completely maintaining the Stratasys motor controllers, thermocouplers, servo drive and dual extruders. Something that can be dropped into any uPrint and be operational in only 30 minutes or so.

Some questions I have:

How did you change from the Duet's Step / Direction signals into the PWM signal the Stratasys board requires? Did you bypass the Stratasys board to run the steppers from the Duet directly?

My understanding of the stepper power amplifier block is that it functions basically like one side of an H-Bridge but it provides current limiting for each winding. It still takes step/direction inputs. I have a link someplace where the question was asked and explained. It is an unusual implementation of the driver chip, but it does work. As mentioned above, it doesn't work with the TMC drivers on the Duet so I bypassed the whole lot.

The extruder is a DC servo motor, hence the PicServo. I haven't gotten very far with that because (again), I got wrapped around the axles trying to use the existing power amplifier hardware. I will be bypassing that also. Just waiting on the required connectors to test the prototype idea.

I am keeping all of the mechanical hardware completely original; Stratasys did a fantastic job and I don't want the headaches of trying to make a reliable hotend assy when the hardware in there is excellent.

If you want to share / work together I'd love to help get something off the ground here. I have lots of information, pinouts.. etc written down somewhere. If I ever got it working, I'd be doing open source and conversion kits. Now that I know more people are trying to achieve the same, I'd be happy to start compiling data and code to post on Github.

My intention has always been to make the BOM, wiring data and gerbers available. I have no desire to supply hardware kits; been there, done that, not interested. I have started pushing bits and pieces up to github but I'm still getting my head around that ( I'm a system integrator, not a software guy).

For expectation management, I'm doing this in slow time for my own enjoyment. I will eventually have something usable to release but I'm not setting any sort of deadline. Happy to collaborate if you are interested, flick me a PM and we'll take it offline.

@AJ-Quick sorry I have been away for a bit and received no notifications.

A bit pressed for time but I will come back and follow up in the next day or two. Short version; and I may be repeating myself but I haven't gone back to re-read.

Integration progresses slowly. I ended up driving the motion steppers directly from the Duet. On the uPrint, each stepper has a discrete connector into the electronics enclosure. So I just ran an umbillical direct to those connectors and bypassed the uPrint electronics entirely.

I used logic level shifters to fire the chamber heater and system power SSR's. Same for the extruder heaters. Same for endstop signals going back to the duet.

I tried a simple resistor voltage divider network for the thermocouple signals but that wasn't successful due to protective resistors on the uprint electronics. Then I realised at the 10 mV/ C signal level, any designed temperature was going to be within the duet ADC allowable levels so I scrapped the voltage divider and now have reliable cabinet temperature sensing. Extruder is being strange and I haven't quite figured out the slope / offset going on there or how I'm supposed to get that calibration in the linear analog mode of reprapfirmware.

I am now protecting the ADC inputs with a 3V3 zener across each input.

Started on the PicServo integration and ran into headaches trying to interface to the H-Bridge in the uprint. I am now waiting for parts to build a patch lead that will go between the applicable chassis loom / electronics enclosure that will let me pull out the servo power and encoder wiring direct to the picservo board. This way the modification is still entirely non invasive.

I actually had a call from the printer owner asking about lead time to return the printer to factory as they were being asked about printing face shields. Pity the build volume isn't big enough to actually run that print.

While I wait for parts I have gone back to a separate job of integrating a duet to an old Prusa clone. Had some issues where the duet smoked a borrowed PanelDUE and also failed it's WiFi module

Update.
M401 / M402 / T1 / T2 / G30 work but could do with tweeking.

Still ToDo
z steps calibration
Thermocouple calibration (adapter on order)
Extruder drive

@T3P3Tony Correct.

Driving the servo motor was one of my high risk items to solve. I'm planning to use step/direction from the Duex connector and glue logic from JRKerr https://www.jrkerr.com/icproducts.html#PICSERVO

The head uses a single motor to drive both tools. Changing tools requires a specific set of X/Y motion that tils the head and brings the required hotend into vertical orientation. This action also causes the required filament to be pinched against the extruder drive. As a bonus, the inactive hotend gains a few mm clearance from the print bed.

The toolchange actions are 'just' a gcode macro but I'm confident I can work that out. My concerns are ; How will the firmware handle E2 / E3 commands as using the same step/direction outputs but reversing the direction for the alternate extruder gcode commands.
And interfacing the the chassis H-Bridge hardware.

The gantry hardware and hotend/extruder looks to be identical between machines apart from build volume. I can see a lot of similarities between the power distribution board and the trajectory control board. I suspect the same core design team worked on both, so it wouldn't surprise me if the interconnects are the same pinouts.

Part of the machines capability comes directly from the tilting hotend design; If you are planning to use separate support material then I'd have serious think about making the factory hotend work.

I appreciate the input. It isn't as simple as a direct TC connection.

The printer chassis has signal conditioning for the TC's that should be outputting 10mV/ degree C. Given the rest of the logic is 5V based, I've run the conditioned signal through a voltage divider to drop the full scale signal down to 3V3.

When I power the hotends, it takes 25 seconds before there is any change in indicated temperature. When I heat the cabinet (only), the hotend temperature stays fixed. This leads me to believe there is a minimum temperature before the factory signal conditioning starts to react, but I'm not sure what that point is.

Luckily the wiring uses standard TC connectors, so once I track down a thermometer that takes the connection, I should be able to work out the cal factors.

I am slowly working my way through replacing a uPrint trajectory control board with a Duet3D.

I am doing this partly to help my uni but mainly for my sanity (I needed an integration challenge)

Primary constraints were to make no permanent modifications to the printer and to be able to return the machine to factory functionality. Primary goal was to reduce operating costs and retain a reliable ABS capability. I intend to make the files available once I have an acceptable level of functionality. There has to be a stack of these machines tucked away in corners gather dust, just waiting for a new lease on life. Fully appreciate the build volume is tiny for the footprint but reliable, economical ABS printing has its uses.

As I am working on this part time, updates will be sporadic, but they will come. Financially the project is too far along to just walk away from it. Besides, professional pride won't let me walk away anyway

Currently I can read cabinet and hotend thermocouples. These aren't calibrated yet but they do move in the right direction.

I can control the cabinet and both hotends individually and each will maintain a set (uncalibrated) temperature.

I can move the X/Y gantry and Z platform in the correct sense and roughly correct distances. Many thanks to the work done by drphil3d on steps/mm here; https://forum.duet3d.com/topic/10982/stratasys-uprint-retrofit-finally-complete

X/Y endstops work, so X/Y homing works reliably.

Top few items on a very long TODO list;
Z probe, leading to full homing and mesh bed levelling
Thermocouple calibration
Rebuild the blocked hotend (that's how I received the printer)
Start figuring out the extruder drive.

TL:DR success using analog-linear.

I have one (of three) thermocouples working using analog-linear, so the software handles the ADC correctly. The other two thermocouples have a different signal path and I need to figure out what is different in how the chassis handles them.

I also need to work out the exact scaling factor for the thermocouple I can read but that should just be a case of looking at the configuration around the signal conditioning IC (ran out of time today).