Parts size changes according to availability

I am trying to build the shredder and the extrusion machines with the cheapest available parts. I would like some advice of whether these changes (deviates from the original Precious Plastics design) possible to make, what are the implications and If anyone willing to support with reconfiguring of the laser file.

1. Is it imperative to use Stainless steel for the hexagonal bar and mesh plate? My project would be to recycle CD/DVD for its precious Polycarbonate (PC). The reason of using PC, is the end product needs to be transparent and UV resistant, as PC material offers. If I use ordinary Steel, the rust that will eventually formed on the hexagonal bar and the mesh plate, might potentially contaminates the shredded PC. If it would, the clarity (transparency) of the end product will be compromised. Or if somehow it is possible, that the hexagonal bar could be completely covered by the knife plates, that the rust powder of the bar would not contaminates the plastic.
2. If using steel on the hexagonal bar, will the shredder has lower strength than using Stainless steel?
3. I found a 32mm steel hexagonal bar rather than the 27mm (original design). Will using this size of hexagonal Steel allows for more knifes mounted on the bar? How many is possible? Or since steel is of lower strength than Stainless steel, the knifes count would be the same as the original design? Anyone would like to lend a hand to make laser files for making the parts suit to 32mm hexagonal bar?
4. **Does changing the hexagonal bar to 32mm will make the cost of making the shredder much higher?

**5. If have an idea of putting a freewheel right on output of the motor, before coupled to the input of the gearbox. The wheel would spin at 1400 rpm as a kinetic energy reserve when the shredder subjected to hard/thick plastic to overcome. Anyone has tried to do it?

Extrusion machine:
1. I am having difficulties in finding 600mm auger bit. Would if be possible to weld 2 pieces of auger with 300mm length? Anyone has ever done this?
2. If the extrusion barrel used is Stainless steel SUS304 welded pipe with 33.4mm OD (Outer Diameter), 3.9mm thickness and 26.7mm ID (internal Diameter), will it have sufficient strength to contained the pressure of liquid plastic being pressed by the auger? Or should a seamless pipe be used?

Thank you

PS: at last I am successfully send message to a forum, now using computer. Last time, was unsuccessful on mobile phone.

1. it will be harder for you to work on the lathe, and if i’m not mistaken the result would be more brittle.
2.  I hope somebody more knowledgeable will answer that, but again – I wouldn’t advise that.

3. Hard question, I would suggest using the same amount if it’s your first shaft. mine is currently broken, a bigger axis is a better axis.

4. didn’t get the question

5. I have yet seen a feasible bicycle-chain shredder. bicycle parts and especially the chain can hardly stand the torque.


Couldn’t answer the questions regarding extrusion.