recycle, re-use, re-purpose – part ii

Continuing with the work to re-purpose a computer mouse as a filament movement detection device, I designed and printed some parts for this. The bottom part is perhaps 5mm in height from the spool itself and is reasonably a good distance to see changes.

I’ve edited the earlier Python script which originally detected the scroll wheel button; it’s now detecting movements of Y as if the mouse were being moved on a mousepad. It will only do this if I take the white assembly and move it around on a patterned surface, however.

To help the mouse detect movement better, I’ve tried using both grid paper and a polar version of same. I don’t love the feedback loop that’s going now. I’m sure there’s a better way to get this movement detected all the time, though.

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recycle, re-use, re-purpose

This week’s project involves dealing with filament-delivery problems on my 3D printer. Out of the box, the filament runout detection never worked. Frankly, it was a terrible design to begin with from the manufacturer and I’m convinced that someone at the factory just turned off that behavior anyway.

As a result of this, I’ve lost a few print jobs over the last year. In only two cases, I simply ran out of filament for large parts. In all the remaining cases, a number of problems contributed to the loss of filament delivery to the printed part:

  1. simple end-of-roll loss of filament
  2. spool sticking to manufacturer’s poorly-designed spool holder
  3. cross-threading of the filament on the roll
  4. hot-spooling the filament at the factory which resulted in filament which sticks together
  5. filament like carbon fiber—infused which likes to stick to itself
  6. old filament which is now brittle and breaks as a result
  7. overall poor design of the spool (boxy) shape itself, resulting in cross-threading
  8. overall poor design of the filament delivery path itself, resulting in too much force needed to extrude
  9. filament thickness quality issues as combined with PTFE feed tubing, resulting in stuck filament in the tube
  10. too-flexible filament as combined with any of the conditions above, resulting in filament notching at the bowden gear
  11. z-offset too close to the bed, resulting in hotend jamming
  12. poor first-layer adhesion, leading to a build-up of filament and ultimate hotend jamming

Now granted, the bowden drive for this printer is one of the beefiest NEMA 17 style of stepper motors I’ve seen. And yet the number of filament delivery—related problems is just too high to continue to ignore. So I’ve decided to finally deal with the issue rather than working around it.

Ideas & inventions

Remove the stock holder, add bearings to its replacement

I designed, printed and assembled a very good dual-spool filament delivery system which worked much better than the stock filament holder. I sometimes still use it.

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Dual runout switches

Perhaps six months ago, I designed, printed, sourced parts for and assembled a very good dual-spool filament runout detection block to replace the stock part. I have yet to install it since I’m not in love with the idea of the filament path beginning at the table level. Time has taught me that the spools need to be higher than the printer for this to be optimal. As designed, though, it works in principle to detect loss of filament from both spools.

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And yet, this entire concept does not directly address the problems associated with cross-linked filament. It only addresses the loss of filament as seen in a switch.

Parabolic spool guides and re-purposed monitor stand

Additionally, I designed, printed and assembled parabolic spool guides to better deliver filament (especially for hot-spooled or otherwise sticky filaments like carbon fiber). This I combined with a designed/re-purposed dual-monitor stand to move the spools above the printer rather than below.

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Remove the temperature gradient

First-layer adhesion was aided by adding a foam enclosure/door and a temperature-monitoring Raspberry Pi 3B to the inside (opposite the internal webcam). The latter helps to heat up the print volume area, keeping things from 90-100 degrees Fahrenheit.

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Remove the PTFE tubing

Filament diameter inconsistencies resulted in filament getting stuck in the PTFE tubing. I now rarely route the filament through the tubing, having removed the awkward bottom-to-top filament delivery path from earlier.

And finally, a filament movement detection mechanism

This weeks work then revolves around fixing the underlying problem. The solution isn’t filament runout detection. The more accurate problem and better solution is actually loss of filament movement and its detection.

When I began to think of solutions, in my head I was adding black/white encoder rings to the sides of the spools themselves. I would need to add those to all spools of course. I’d also need to design something which reads those as ones and zeroes.

I decided that a roller/follower which is turned by the spool is also a solution. I then envisioned writing drivers and creating a small circuit board for all this so that it could talk to Raspbian, the operating system which OctoPrint runs on.

Mouse to the rescue

Finally, it hit me that a standard computer mouse does this naturally. The older style of ball mouse has a follower which detects when the ball is moving. Even the newer style of mice still have a scroll wheel which is covered in rubber and would do nicely. In my imagination, the first iteration of this had the filament trapped against that rubber wheel. In today’s version, the wheel merely comes in contact with the side of the spool itself for the win.

As a bonus, the computer mouse already has the serial communication and Linux driver built-in. It was trivial to write a small Python script to detect scrolling events.

no mice will be harmed … in the making of this gadget.

The mouse should fit nicely and without any modifications to a 3D-printed holder. The serial connection goes to the Raspberry Pi and is then detected in an OctoPrint plugin. During a print job the scrolling events will be monitored; any loss of scrolling over the sampling period will then pause the job and alert the operator with a sound event.

rat on computer mouse

old-fashioned milk bottles

Once upon a time, you’d get milk delivered in the morning in glass bottles. Okay, honestly, it was other people who got that but I do know this from watching old movies.

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Now that I’m old enough to go shopping myself, I have a fondness for buying my milk in bottles like this. For most people, I’d guess, the thought of adding an extra $2 for the glass rubs them the wrong way. For me, I see it as an excellent way of picking up a great deal. It would cost about $10.84 for that same glass two-quart container from Amazon.

Re-use, recycle, re-invent

So what would I do with the extra bottle? Almost anything that can fit through the top is a good candidate but food is what I primarily store in mine. I have at least 30 bottles storing dry goods, two storing refrigerated drinks and perhaps eight storing filtered water.

When I make waffles, I usually mix up several batches of the batter and that will go into the pint-sized glass bottle. Turbinado sugar also goes into the pint-sized version, making it easy to spoon straight out from there.

I purchase the Mueller’s pot-sized spaghetti which fits nicely into the quart-sized bottles. Most flours as packaged by Bob’s Red Mill will exactly fill the quart-sized version. Potato flakes? Check. Granola? Check.

I have rows of beans and lentils, pastas of all shapes, flours, starches, coconut flakes and almond slices. There’s trailmix in one. I have semolina, masa, corn meal, oatmeal, Scottish oats and Creme of Wheat.

In the refrigerator today I just added two quarts of iced tea and a quart of iced coffee. Three visits to a local coffee shop would probably set me back $12 for three drinks and I’ve just stored away the same amount for a fraction of that cost.

Perhaps the best benefit of storing most of your pantry in glass is that you no longer have to deal with pests. This is the first time in my life that I have literally zero bugs trying to eat my food.

Enter the 3D printer

The tie-in, then, to the 3D printer involves me designing a replacement funnel using Autodesk Fusion 360 for the purchased funnel I’ve used up until now. Hopefully it turns out, it’s about as big as my printer could do.

The previous funnel was okay but it wasn’t a great fit for the bottle. Big items like granola would constantly get stuck in the too-small funnel neck. This one should fit perfectly.

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Food safety and plastic

Some of you may then caution about the use of printed plastic in conjunction with food. I’m sure the PLA filament (which is made of a polymer of corn starch) is actually closer to be food-safe than the funnel which I’d purchased from a car parts store earlier.

Some of the typical concerns with food versus printed plastic is that the small grooves in the plastic allow for bacteria to grow. Okay, but this is the same for most of the plastic utensils which we routinely include in our kitchen, right?

Another concern is regarding the existence of lead in some of the nozzles used. Yes, but that must be so minuscule as to be outside of the realm of concern. In response, I could site the many harsh chemicals used in the processing of naturally-green soybeans to create an unnaturally-white soy milk product, for example.

For dry goods, the PLA funnel should be a non-issue. With reasonable cleaning I think that it will do fine with liquids as well as long as I don’t use it to funnel boiling water, for example.