Supplementary Parts
Brief Discussion for Recent Design Changes
When realizing that the secondary grinder design was implausible to machine in house, the team was required to rethink the overall design in several aspects. In response to this, the following decisions and changes were made to the design to still ensure that all specifications were met. These changes eliminated the final uncertainty left in the project, and allowed the supplementary parts to be selected.
When looking at alternatives to our own design the following alternatives came up:
Roller mill
This was decided to not work as it would be more apt to grind brittle materials. While the necessary torque and power would have been met with this option, many of the plastics we will be highly deformable and would likely bend/stretch rather than actually reduce in size.
Modified burr grinder
This option was determined infeasible due to the amount of uncertainty around the potential result. The rate of movement through the burr grinder would create a bottle-neck within the system, even if it were to work. Similarly to the roller mill, there were concerns that the plastic would deform rather than reduce. With the system being compact and closed, this potential would add the serious risk of clog. Where this system would have been placed would not be convenient for maintenance, and the risk was therefore avoided.
Roller mill
Overall, this option is the best fit for our desired output. It would provide a sure way to reduce the plastic to a very specific range of value. However, the options that are available are both oversized and expensive. With the application being to introduce the machine into a lab setting, it would be difficult to find a roller mill that could fit in the desired criteria. It would add an extreme amount of cost, be very loud, and be much larger than the initial design, lowering the designs convenience factor.
So, a total redesign was necessary. This came in the form of the removal of the secondary shredder from the design, and a higher emphasis on the primary shredder as the sole size reduction tactic. To ensure that the shredder will have ample capability to reduce the higher volume of plastic, the team decided to move funds from the proposed budget for the secondary grinder to further improve the shredder. The following parts will now be used to complete the current design of the machine:
Maximization of the current shredder:
Blade Cleaning Kit
This will be added onto the sides of the shredder. This will help contain plastic from entering any small crevices through the shredder as well as ensuring that all plastic is optimally reduced, as there will be less available space for the plastic to escape.
Catch pan
To feed the plastic through until the desired reduction is completed, the user will now collect each pass of the plastic in a catch pan and feed it back through. This will be designed and created with sheet metal. This part of the redesign is both more cost effective and gives the researcher more power to experiment with the reduction size, if desired. Otherwise, the manual will list a standard after experimentation.
Finalization of the washing step:
The washing machine has changed as it will now be higher off the ground, due to the minimization of sizing concerns. This will allow for a simpler motor system.
Wheel track
This is a purchase that has still not been completed and will allow the basket to glide out easily.
Fine sieve material
The basket purchased has a mesh distance of about 3mm. Because this is on the high range of the desired output, a mesh will be tethered onto the basket to ensure minimal plastic escapes the basket.
Agitator
Experimentation will be done early week to decide between a modified immersion blender and a drill with a paint mixer attached to create the desired current within the washing machine.
Small motor
For future iterations of the design a motor of around 1/8 horsepower should be used. The torque is not a major concern for this aspect, rather a higher rpm. However, since there are no hard defined values or safety concerns around this, a less expensive option will work for the application.