Multi-tool circuit printer

I'm on a tear this week. 

Things I did  yesterday and today: 

• Added a downward facing camera for alignment of the printhead to the camera. This allows registered prints. 
• Added a flex cable holder for the camera cable 
• Added lights to the side and hooked up to the tool-changer
• Hooked up a Jetson Nano to the case back for image processing

A photo with the lights, but without the camera ribbon cable guide installed. 

I'm slowly but surely working my way up to silver ink printing. I was able to print another set of lines using time-pressure dispensing. This method involves using pressure from an air pump to dispense the conductive material. The main drawback of time-pressure dispensing is the associated tools - it requires an air pump. The current design I would prefer to use is the stepper extrusion method which uses a stepper-driven plunger to extrude the ink. This method requires a way to retract the plunger to a specific point after printing is finished however, which I have yet to work out. Stall detection perhaps? 

I was finally able to hit a big milestone, the first successful prints. I printed a series of lines across the sheet. 

For my first prints I used a 150um tip. I'm currently testing extrusion and retraction distances. 

Going to need a way to filter out the fumes from curing, as well as a way to get mesh bed leveling working and auto Z height compensation. Right now it's manual, and the bed is so even that I'm not seeing any issues, which speaks a lot about the E3D's mechanical design. On the other hand I did have to almost immediately fix the Z endstop, just like on the Jubilee. Those endstop switches break if you look at them the wrong way. 

I still have more work to dial in the retraction settings. I'm also considering a time-pressure method of extrusion, but that would require a compressor, so I'm going to hold off for now. 

So it's been a while since I've put an update on here, but I have been busy. 

I made about three revisions of the paste extruder, that all use a luer lock syringe to hold the ink, and a stepper motor and M3 screw for the linear motion. 

I'm in the process of working on getting the z zeroing to work. The luer-lock tip has to be re-zeroed after each changeout, and the Z deviation the traces can stand is in the range of below 50 microns, ideally 20microns. 

After testing the Z zero and seeing the compensation was not precise enough with a limit switch, I redesigned the limit switch to hold a BLTouch. Made a mistake on the first one, so had to redesign, didn't allow for the screw height in the first version. Tried to take a shortcut by not adding all the hardware and finishing the modeling and it costed me a few hours, and a second print. 

Fixed the Z zeroing issue, but looks like my temporary Z sensor - a limit switch - is nowhere near precise enough, it varies by ~1mm after probing. I've been a bit busy the last two days building a jubilee for a co-worker, but waiting on a part to come in so I'll focus more on extrusion and getting the BL-Touch working this weekend. 

Success! I have mounted a syringe onto a tool mount and demonstrated a successful toolchange with the syringe mounted. Turns out the steps/mm was incorrect, and I had to disable checking the extruder heater status to get the toolchange to work, but after some help from the Jubilee discord channel I got it working. Now time to test the syringe dispensing. 

I also need to verify the Z zeroing is consistent enough to maintain a consistent height above, hoping to do that soon this week. I bought some acrylic inks with a similar viscosity as the silver ink I'm planning on using when everything is working.

Still have a few issues: 

1. The bed leveling route is compensating the opposite way it is supposed to and is increasing the bed angle instead of decreasing it, might be just due to the motors being switched. 
2. Also need to add another Z zero sensor onto the toolchange carriage instead of the tool. The original sensor broke the second time I used it so I had to improvise. 
3. The syringe does not work backwards, and it not very precise. I need to modify the syringe design.

A few updates, I've gotten a few things done: 

1. Fixed the Z zeroing - modified the bed.g file

2. Changed the tool mount to be smaller & shorter. Printed successfully and assembled (left) shown next to the original (right)

3. Designed and printed a 5cc syringe adapter - press fit, and the top portion is just slightly too big but it's really close. Also made an adapter for makerbeam that screws onto the detachable plate.

Printed parts

Mount with syringe

Syringe on the tool plate 

Mounted and ready for a toolchange

I tested the Z zeroing with the sensor in a different location - I mounted it on the tool instead of the tool mount. Looks like I need to change the Z zero points. Also not sure how I'm going to zero the syringe in the end, was thinking maybe a piezo touch plate? I'm open to ideas if anyone has any, but for now it will probably be a piezo or maybe a contact switch that only requires a light pressure.

Still haven't been able to get the BLTouch working yet mostly due to a lack of time, I'm focusing on the extruder now. 

Also - still working on getting the toolchanging working. The jubilee has a torque based toolchanger, and I found an issue where the locking is failing because the torque is too low, so I have had to reprint the v-groove locking plate a few times.

I've looked at a few choices for the extruder, the one I built first isn't going to work. Looks like I'm going to need the syringe to be held in place better, this design seems to be better for less precise designs, maybe for larger volumes that don't have to be as precise. 

Ystruder - looks promising, but a little more than I need, includes a force sensor and control electronics. Might do this later on if I need feedback on the pressure

https://www.sciencedirect.com/science/article/pii/S2468067219300471

Open source syringe pump - I've printed a few parts to this one already but they aren't quite exact enough so I"ll need to adjust the designs and reprint. I like that it supports different syringe volumes. 

https://www.appropedia.org/Open-source_syringe_pump

Also bought a pneumatic solenoid valve that I'm going to test, it's the most similar to systems I've used before. Should be able to handle the highest viscosity fluids in my experience. Might be a little harder to integrate into an existing print workflow, and also requires a pump so it's not as cheap. 

https://www.amazon.com/gp/product/B07SJFV7S3/ref=ppx_yo_dt_b_asin_title_o00_s00?ie=UTF8&psc=1

Any suggestions from the community? Previous similar projects that used precision syringe extrusion?