Form2 Error Handling

I just received my replacement printer after a catastrophic failure. The print that caused the failure adhered to the bed and the wiper must have kept trying to wipe, which must have caused the resin to spill over the tank wall (happened twice, the second was catastrophic). The part was small, so the amount of resin required was also small. However, the resin cartridge was completely dispensed while it tried to fill. Considering that it was a brand new cartridge, you can imagine the amount of resin that was spilled.

I have a lot of questions/recommendations:


  1. Known value - how much resin is dispensed (open loop) AND how much
    resin the print will use - using half a tank head pressure (average), plot
    amount dispensed per unit time. If exceeded, then fault

  2. Known value - time between dispenses and number of dispenses - if
    unusual amount, then fault

  3. If the part is welded to the tank bed, then the wiper cannot fully
    actuate. There is a wiper homing sensor there. If the sensor is not broken during a
    wipe, there is a problem and fault. Or, during a wipe, if the wiper is
    stuck on the sensor, then fault.

Is there any socket communications to monitor the step of operation? I cannot have this same problem again. If the error handling cannot be implemented for whatever reason, I need to monitor it externally in order to stop the print under what I deem an error condition.

  1. I can wire in parallel the homing sensor on a PLC to see if the wiper is stuck or not actuating or put in an encoder to see if it is moving. I need to know when this wiping operation is happening in order to check this. I would like a socket communication that will send me the printer status so I can parse it and check

  2. I can add a paddle flowmeter to the cartridge to see how much resin is being dispensed. At a very minimum, I can check wire in the solenoid output on the valve to count the number of valve open commands and the duration and find an average flow for the average head pressure of the resin. I would like a socket communication that will send me the printer status so I can parse it and check.

  3. Oh, and I need a way to send a command to the printer to stop the print. I really dont want to have to put the main power on a relay and slam power when my PLC suspects an error

Thanks. I am hesitant to use the new printer until I deem that this problem is solved and I can have confidence in it again.

Sounds like your running a nuclear plant.

No, I am the engineer at a robotics R&D facility.

Glad to hear that you’ve received your replacement unit and here’s to hoping you’re up and running again.

We have a few of your suggestions implemented currently. The wiper does have checks to detect if it collides with an object. In some cases, small geometries stuck to the bottom of the tank won’t have a perceptible effect on the wiper’s path but can lead to a spill. It sounds like this was the case here and while this isn’t a common error mode, it’s something we’ll continue working to prevent.

Detecting the resin output via the bite valve open time is a great idea but we’ve found that it’s not a reliable metric. The bite valve has some variability in rate of resin flow so it’s tricky to reliably calculate how much has been dispensed based on just the open time. Using a flowmeter could work here.

We’re looking into sending commands to a printer remotely but there are a few challenges to iron out. A smart switch like the WeMo could work here and avoid the need to cut an entire relay. I use these switches coupled with a few checks for my FDM printers at home (they seem to be especially adept at catastrophic failure…).

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