The outcomes and objectives from our team’s Week 2 workshops revolved around performing some trial tests with our current plastic grinder setup as well as benchmarking different laser diameter controllers for the extruding process and spooling process.

The first grinder tests were done as the baseline tests to see how well the grinder would perform as is. For the first time, we added on the metal mesh below the grinder to act as a “filter” for the plastic shavings. The initial mesh design consisted of a piece of iron sheet metal with various ¼ inch holes drilled across the piece that would sit below the grinder to act as the screen/filter. The parameters and results of the various tests are listed below.

Grinder Test with Mesh (Trial 1)
Removed 2 spacers on each side (to allow pieces to be brought back up)
Started to grind
Fineness was great & consistent
Eventually got more difficult to turn handles (w/ extension bars)
At location of removed spacers, blades were tangled with plastic shreds
Conclusion: Put spacers back where they were

Grinder Test with Mesh (Trial 2)
Place all spacers back in each slot
No tangling initially
Plastic objects may be too large and the teeth of the blades cannot catch
Only short duration of successful grind then clogs
New removable mesh idea to easily clear clogs
Removing jammed plastic from blades
Blades practically compressed/compacted the plastic around the center of the blades
Conclusion: Attempt removal of all spacers (spacers may be cause of clogging)
Potential solution to tangling between blades
Mesh basin sweeper to help sift filament and prevent build-up

Grinder Test with Mesh (Trial 3)
No spacers
Tangling of filament continues
Possible solution:
Add more blades
Half cylinder for mesh instead of flat mesh
Conclusion: Continue trials for consistent grinding

The overall outcomes from the three grinder tests showed that the holes for the mesh were possibly too small, not allowing for enough material to past through, which as a result, partially jammed the grinder. After these tests we concluded that we need to develop a new mesh design (that is possibly curved) as well as having a mesh design that allows for quick removal to recycle up the material that was collecting at the bottom, possibly adding to the jam. Overall, the effectiveness of the mesh was excellent and we were very happy with how fine and consistent we were able to get the grinds down to.

Jammed grinder blades (from trial 1 with 2 spacers removed on each side)

Box on left: plastic grinds after adding mesh ———— Box on Right: plastic grinds before mesh

Jammed grinder wheels and buildup of plastic on top of mesh

The following bulleted notes from Week 2’s workshops had to do with performing research and brainstorming to find a solution for our other big issue, assuring that the diameter of the extruded filament is consistent and the spooler and extruder are working in sync with one another (through the incorporation of a laser diameter controller and an arduino)

Gap Optimization
Plan for diameter control:
Micrometer will detect diameter of extruded material
During detection, micrometer will pass voltage to arduino and arduino will calculate voltage difference
There is a resistor connected to the micrometer and arduino will use that to calculate the current that passes through micrometer and resistor
The current will be used by the arduino to adjust the potentiometer of the spooler to match the current of the extruder.
There will be a loop statement that will continue to adjust the potentiometer by using a motor until the currents of the spooler and the extruder are matched

Multimeter Records

Spooler speed
Current
(mA)
Potentiometer
Resistance
(kΩ)
Lowest
4.8
Really low
R = 5.1V/4.8mA = 1.06
Highest
0.2
Really high
R = 5.1V/0.2mA =
25.5

Important error:
When multimeter is connected to spooler, it could either:
Speed up spooler wheel
Stop spooling wheel (spooler speed = 0)
What does this mean?
If we want to decrease spooling speed, we have to increase current and lower potentiometer resistance