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Spool holder with built-in scale

Posted: November 3rd, 2016, 5:33 pm
by reibuehl
I was wondering if it would be possible to print a spool holder with a built in load cell that is read by a little controller that shows the weight of the filament that is still left on the spool. Does that sound plausible?

Re: Spool holder with built-in scale

Posted: November 3rd, 2016, 6:57 pm
by danilius
Interesting.

Re: Spool holder with built-in scale

Posted: November 4th, 2016, 6:04 am
by reibuehl
I just ordered a 3KG load cell and a hx711 load cell amplifier board... I hope it arrives before Christmas so that I can experiment with it :)

Re: Spool holder with built-in scale

Posted: November 4th, 2016, 6:36 am
by MTVDNA
Take a look here: http://marcuswolschon.blogspot.nl/2016/ ... emote.html
This guy built a filament sensor with a load cell in the spool holder ;)

Re: Spool holder with built-in scale

Posted: November 4th, 2016, 8:10 am
by reibuehl
The load cell and amplifier he used look like they are similar to what I ordered. So I seem to be on the right track :)

Re: Spool holder with built-in scale

Posted: November 6th, 2016, 8:08 am
by Titus
Interesting thought! Calibration and stuff will be tough, but once you get that working it should be quite reliable.

Re: Spool holder with built-in scale

Posted: November 6th, 2016, 11:01 am
by reibuehl
I was hoping to get away cheap by using an empty and a full spool and then adjusting the values so that the result matches the one I get from my kitchen scale... :)

Re: Spool holder with built-in scale

Posted: November 6th, 2016, 11:03 am
by reibuehl
My intension is more to have a rough estimate available to see before a print if it will work or not.

Re: Spool holder with built-in scale

Posted: November 7th, 2016, 5:19 am
by Titus
Ah I thought you wanted to use it for either pricing or fault detection.

Simple estimate should work yesh

Re: Spool holder with built-in scale

Posted: November 8th, 2016, 4:48 am
by nallath
The problem with scales is that they don't measure right if they are not nice & flat. So if you bump against your printer, it will give wrong readings.

Re: Spool holder with built-in scale

Posted: November 8th, 2016, 7:57 am
by reibuehl
If that becomes a problem, I might have to take a bunch of samples and compare them to detect such glitches.

Re: Spool holder with built-in scale

Posted: November 9th, 2016, 6:53 am
by nallath
I think the (de)accelerations of the head will also influence the results. They can generate quite a bit of vibrations.

Re: Spool holder with built-in scale

Posted: November 9th, 2016, 7:08 am
by reibuehl
My plans are not so advanced as the ones of the guy that @MTVDNA linked to :-)

As a first step, I would only like see how much is left before I start a print without having to unload the filament and put it on the kitchen scale. Then I can compare it with the filament weight calculation I get from Cura and the printer firmware to have a rough idea if the rest on the spool will be sufficient for that print.

Re: Spool holder with built-in scale

Posted: November 9th, 2016, 9:08 am
by Neotko
nallath wrote:I think the (de)accelerations of the head will also influence the results. They can generate quite a bit of vibrations.
Indeed. Specially with half size smaller bearings...

Anyhow a system like this could work like current tags. You know how much you have before printing (no vibrations) and if weight = length = ok, then you print. At the end of the print thr length used is check vs the weight and updated to the user. You don't need to check constantly how much weights but if you can print the amount asked.

Re: Spool holder with built-in scale

Posted: January 7th, 2017, 6:33 am
by reibuehl
I finally got all the printed and sourced parts together to setup a test. Here is the first prototype:
2017-01-07 12.21.27.jpg
I calibrated it and now need to refine the code and add a small display :-)

I am a little unsure on what features are really needed - maybe a selectable "empty spool value" that gets automatically deducted from the measured weight...