Quote Originally Posted by ralphzoontjens View Post
That is a very good idea.

However measuring the spool angle doesn't work because it unrolls with jerks.
So what you want to do is measure the filament pullthrough rate so you have to invent something to mount onto the extruder drive.
It's a good idea for a Kickstarter project, in the spirit of AlignG. You also want to be able to make decisions based on the input - pausing or stopping the print, adjusting feed rate etc.

I have another idea but I have no schedule where I can develop it.
The idea is to add binder /adhesive between each print layer to drastically improve part strength by adding a ball roller next to the nozzle attached to a liquid container.
Special software will have to be written to determine the gcode path for the roller. Printing a layer would go like this: extrude filament - apply binder - move fan over the layer until desired level of dryness of binder is reached - print next layer etc.
Topic 1: jerkiness
You are correct that most filament spools "jerk" or unroll at an uneven rate. However, though not perfect, I believe my design unrolls much more smoothly than your typical hanger/roller. At the link is a short 20 second video to show an example of what I am talking about.
https://youtu.be/nfBTYKQTa1g
Notice the tensioner that is inserted through the hub of the spool. With just 2 rubber bands, it adds just enough light tension so that the spool unrolls only as much as the extruder pulls it. As well, the spool rolls smoothly on 4 ball bearings. Without the tensioner, the spool would unwind far too much. I also considered adding Bowden tubing (the pull becomes even smoother) but I like my designs to be as unconstricted as possible.

Thanks for your observation, that was certainly a problem I worked on solving. After watching the video please let me know if the unrolling is still too jerky. I am interested in your evaluation.

Topic 2: Pausing, stopping, adjusting feed rate, etc
Unfortunately, this involves modifying printer software which is an area where I have very little control. I am constantly revising the mechanical, electronic, and software characteristics to make this product easily compatible with as many existing printers in the market as possible. Currently I am pursuing the following actions:
a) I revised the interface so that the board can be remotely shutdown and hard-reset via GPIO
b) I revised the interface to add a simple GPIO error signal (0: okay, 1: error detected) so it can be used as a "smart switch" and integrated with other "out-of-filament" solutions already developed
c) I am beginning testing with OctoPrint to ensure that these two products are compatible --> pause print functionality
d) I am assembling and testing an inline version of this sensor that can be mounted anywhere on your printer

My main goal is easy integration and simple-to-use interfaces. I thought my initial design was correct, but feedback is telling me otherwise. I appreciate your feedback.

Topic 3: filament binder and application apparatus
I think your idea will take a lot of effort and money to develop and test. The simplest method would be a homemade applicator such as you find for canola oil and PLA. Another method would be to develop a formula for ABS + bonding agent and then manufacture this into its own filament. I am not knowledgabe in chemistry and am not aware of any commercially available binding or bonding agents for ABS (or any other filament material). An electromechanical solution sounds elaborate (i.e. expensive and prone to breakage). However, you will never know unless you try and find out.

Best of luck to you in developing your idea.