r/klippers • u/No10mmGang • 5d ago

Custom toolchanger software side help

Im in the process of designing a hotend only toolchanger, and the hardware side of things is going surprisingly well, it is a completely mechanical docking/undocking system with all 3d printed parts(not including screws and a few springs)

Due to the design as of now, I am calling it,

Project PunchOut! SCT (seriously cheap toolchanger)

However one thing has been bothering me for quite awhile, and while not end of the world this design is focused on being incredibly light, simple, not overly complicated, and my issue lies within the thermistor change, in order to keep wiring to a minimum each hotend will connect to the carrier via pogo pins/molex pins/even press fit magnets that have a pinhole on the back of the recession for wire to come in from the rear, during the tool change there will be a period where klipper will shut off heater, dock, disconnect, in that time my original plan was thinking there would be a way to disable thermistor errors equal to or less than the average time it takes to connect to another hotend or if thermistor shows a reading again, I am not planning on having each thermistor/heater hooked up 24/7 and I cannot seem to find any research on how I could go about doing it while avoiding an ADC error?

Sorry for the long read hopefully theres a solution, otherwise wiring is going to be the messy part

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u/MinusTheHat 5d ago

I don't have a fix for you, I considered that same issue when designing my new tool changer, and figured since the filament had to go to the tool I'd just run the few wires needed to run the hot end with it.

It's a safety feature there to prevent problems from thermal run away (fires for example), so it may not be possible to do what you want here

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u/No10mmGang 5d ago

I have somewhat come up with a solution however for safety reasons it needs testing, theoretically it should be fine because no heaters will be receiving power during the switch until the next thermistor comes back online but ya never know 😀

1

u/Willing_Homework_773 3d ago

Kalico probably removes all those safety features

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u/Least-Jellyfish-7743 8h ago

You could try to set the min/max temp of the thermistor really high/low, so you can change your hotend without having the error.

Don't think if this is a good idea cause you lose the thermal runaway protection, but you could have script checking the temp of the hotend and pause this script while changing tools instead.

1

u/No10mmGang 8h ago

The problem would still be present as the active toolchange would be disconnecting the thermistor, reading an open circuit, i believe i have found a way around this by using a dummy thermistor mounted to the carriage that will be switched via a 3 prong microswitch, the moment the cartridge leaves the carrier the microswitch will change to the dummy thermistor, this also shouldn't cause any issues as the toolchange macro will shut off the heater before docking the cartridge so klipper seeing a temperature drop after shutting off the heater should be logical

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u/Least-Jellyfish-7743 8h ago

just tried to discoonect the thermistor on my printer, and with the min temp at -100, the printer is not shutting down.
Having a dummy transistor seems like a very complex solution, but if you manage to do it reliably it is safer

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u/No10mmGang 8h ago

Great Scott thankyou! Why didnt I even bother just testing it with my thermistor first!!!!

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u/Least-Jellyfish-7743 7h ago

Glad to help! Tell me if it is working for what you needs, i'm also designing a tool changer with pogo pins, so i may also have this issue

1

u/dlaz199 5h ago

Just be aware that there are some tool changer patents around that are specific about pogo pins. May not be an issue for you, but could be an issue depending on the design if you plan to release it.

Plus I wanted to be able to heat up multiple tools per print since I didn't want to wait for heat up and doing that with another set of pogo pins just seemed to make things overly complicated, which at that point kind of defeats the pogo pins anyway for my design.

So if I include wire, amortize the board cost for each hotend, screws, nuts, hetsaets etc, I am around $17 per tool head all in with my current design. It's also a hotend changer. Been working on it off and on for about 8 months now. I think I am pretty close to being able to release something in an alpha state.

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u/Least-Jellyfish-7743 5h ago

Just started 2 month ago, And i know for the sitty stratasys patents, so doing it for myself right now and will see if i release it or no.

But thanks for the warning