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Just out of curiosity, why do you need a shredder? At the small scale that your example shredder would provide, the injection machine and the press both could use manually cut plastic. The extrusion machine is the only one that really needs small size plastic. Do you already have an extrusion machine? If so, you may want to look at the designs that could use the same motor and transmission that you are using for your extrusion machine. You may want to size the blades to the torque available in your motor/transmission.
These are the most promising results I’ve seen on PP. Great job!
The fact that you were able to fairly easily turn some nasty degraded beach plastic (that degraded poly rope looked horrible) into solid material is a great result. I wasn’t sure what the Maldives expedition would achieve but you’ve proven the benefit of on-site research and education. Hopefully you can find products in the local marketplace that are expensive to import but you could make.
Also hopefully Project Kamp does not use up all the PP resources and more of these on-site workshops can be done.
Again, Great Job! your results should also make grant applications more competitive. Thanks
Gee, if you are measuring the torque in person-weight units, you might have to slip on an extension. I think the luggage scales max out at 50 Kg or so….well below my person-weight.
Looks like a great list of upgrades.
With some care, you may be able to use wood for experimental molds. One example in this thread https://davehakkens.nl/community/forums/topic/portable-desktop-injection-machine/ . The temperature is not as much of a problem as the pressure that tends to split normal wood. Using plywood, an external metal frame, or just understanding where the grain is weak will help. The plastic will stick to the grain. You can use aluminum tape, or you can try to seal the surface, but that sealer will need to survive the temperature.
It will definitely be an experiment.
Those oven heating elements are big and high power for just a mold, though you could sit the mold on a hot plate I guess.
If you search cartridge heater or cartridge mold heater on ebay, there are many to choose from. I used the 9.5mm x 80mm 300w version. Either drill a hole or cut an external groove to clamp them on. They should very easily heat an aluminum mold. Ebay prices are between 2 and 5 USD depending on where and how many. If you buy them from engineering supply they will be quite a bit more.
I think heating the molds with a cartridge heater and the standard PID controller should be a low cost solution. The heaters and the thermocouples are very cheap so you could dedicate them to each mold.
If possible, measuring the torque or applied force that it takes to fill a typical mold may give some idea on how much the piston diameter could increase. A luggage scale might be sufficient to do this. It might be a path to significantly larger injection volumes than the V3 PP machine.
I have not seen the Taller Esferica machine, but yours is a pretty clean product.
@pporg , Thank you. It is very generous of you to publish the details of your great design, given all the hours you put into it.
Did you see the bicycle shredder discussion in this same topic page?
@replasticuk , That is a large plastic volume. Since they are going on a wall, maybe change the design to a sconce planter for less volume?
I think the precious plastic injector does not scale up easily. If you are willing to experiment, the rack and gear (arbor press) actuated machine may scale up to the size you need. There is an example in the bazar https://bazar.preciousplastic.com/en/listings/727598-arbor-injection-press-catalonia . The nice thing about this approach is the stroke length can be long without impacting the force it takes to actuate. It also has higher leverage so you can go with a larger diameter. Those two size increases may get you to what you need for your design. I would size for at least 50% margin, maybe 5 cm diameter and 45 cm stroke as an example. I think one advantage of your design is that you don’t have any narrow passages so the injection pressure required may not be that high and you can use a larger diameter piston. If the machine ends up being too tall, that design can work in a horizontal configuration. It may be worth contacting the seller (not me) and ask about possible scaling.
I think even with the injection machine, the cycle time will not be super fast. The plastic still needs to be loaded, heated, compacted before it is ready. The mold will take some time to cool as well.
The other option is a version of the press machine that uses heated molds instead of an oven. @andyn showed a wonderful example in the video in this thread https://davehakkens.nl/community/forums/topic/v4-beyondplastic-process-heatable-mould/ . You could possibly have several molds being heated and then pressed in sequence.
You are pushing the injection limits here, please post what you end up selecting as the approach.
@zacvass , I’ve looked but I don’t think you will find significant or sufficient fume safety information on this site. Since you are at a university, collaboration with the chemistry and biomedical departments is a much better approach. The university safety department may be another required participant.
Online there are some starting points http://www.hse.gov.uk/pubns/ppis13.pdf and http://www.dupont.com/content/dam/dupont/products-and-services/plastics-polymers-and-resins/thermoplastics/documents/General%20Processing%20Principles/Proper%20Use%20of%20Exhaust%20Ventilation.pdf and of course the safety data sheets for the materials. These are all introductory, your process should be assessed individually.
Actually, the results of your university’s safety assessment would be great information to post here to help raise the information level. I have not seen any posts from the V4 team on the planned safety task. We are recreating industrial processes without the resources and rigor required in industry. Concerns about safety should always be present.
Great topic, I hope you get more input.
I use the same approach for removing the paper labels. Once started with the heat gun, often, with slow steady pull at 90 degrees to the surface I can get the label off with little residue. I use a little mineral spirits to get wipe of any residue.
I have not found a way to remove the labels from laundry detergent bottles. Right now I just cut them off and save them for once I figure that out.
Unfortunately none of these methods are convenient for high volume.
These really look great. From some of the other threads, it looks like there is an educational institution demand that these would be ideal for. I hope that works out.
Thank you. Do you apply force to the plug or is it just friction resistance?
Did you see @timslab post in this thread? https://davehakkens.nl/community/forums/topic/mobile-pyrolysis-plant-turning-waste-into-fuel/ The Dung Beetle Project looks similar to what you are considering.
Just curious. What do you do with shredded circuit boards? Also I thought wire was usually stripped for recycling rather than shredded. How do you use the shredded cable?
My desktop machine also uses a 4 mm nozzle and works with HDPE.
If your control thremocouple is close to the heaters, you may be controlling more on local heater temperature than on the plastic volume and the HDPE is actually cooler. It may be worth getting a separate thermocouple and readout that you can use for diagnostic measurements. They are very low cost.
Are you compacting the plastic while it is heating up? I do that (with the nozzle blocked) a number of times during the heatup to get the air out of the plastic and to make sure it is uniformly heated.
If your mold design has a narrow channel and lots of aluminum mass near the entrance, cartridge mold heaters are very low cost, a heat gun can also help.
For some molds, make sure the injection motion is quick and continuous so you can get a plug solidifying near the entrance.
Not sure, the shrinkage takes place on cooldown when the heater is off (I don’t ramp down the temperature control). The tube is fairly thick wall aluminum which is why I tried just one heater. The holes for the mount block go through, so there is a chance for the part to preferentially stick to one or two places. I also maintain compression during the solidification, not sure how that plays out. It is HDPE so the shrinkage is pretty high.
All good reasons to do more experimentation
So I turned the round stock to get rid of a flat spot and make it round. Ended up with a 36 mm diameter 150 mm long HDPE rod. Smooth, no pits or visible voids. Density is .85 g/cc.
Overall a useful piece of stock material.
I wanted to see if the arbor press actuated desktop injection machine could be used to compress a heated mold to make some stock material that is larger than the small injection volume. I took an aluminum tube about 41 mm ID and 184 mm long. I made a block that could be used to clamp a cartridge heater (300w) to the side. Both the tube and the block have a groove to accommodate the round heater (some aluminum tape is also used as filler). A second small block mounts the control thermocouple. The arbor press has a rod attached with piston sized to the tube. The bottom of the tube has a plug with a thread to allow attachment to the wooden base for stability. You can see all the parts in the attached pictures.
The mold heated up quickly. I filled it with large flakes from milk jugs (HDPE). To mostly fill the tube, it took a number of top-off and compaction steps. Once full I let it sit under compression and temperature for about 15 min and then let it slowly air cool. The result is a pretty solid, usable piece of round stock (though shrinkage away from the wall is not quite even and it is not quite round) . I have not cut it apart but I don’t see any voids near the surface.
The point of the exercise was to see how well locally heated compression molds would work without an oven. Thermally, the aluminum mold heated up quickly and took a long time to air cool so it is reasonably efficient (compared to heating up an entire oven). I could have used a band heater for this cylinder but I wanted to test the clamp on block approach which would be usable with flat molds. The part extraction process took a little trial and error, but given how cheap the cartridge heaters are, you could easily have a handful of molds ready to go. The arbor press was useful for all the intermediate fill/compaction steps, otherwise clamps would work as well.
Overall, while there is some process tweaking to be done, I’m happy with the results.
I don’t have directly what you are asking for but here are some thoughts that may help. Unfortunately, the PP V4 plan (link on this page https://next.preciousplastic.com/ ) does not mention any work towards an education module and there have not been any reports published on the planned safety task, so that makes your task somewhat harder. The Monash work is at the university level so it may have more resources. The PP machine designs don’t appear to have any formal safety review or certifications so you may have to do some additional effort to use them in a school environment. As a minimum you will need to address the fume management/exposure, as a chemistry teacher you have the background for this. The machines also need an electrician to review the design. All parts of the structure need to be well grounded, since you are using mains voltages on the heaters and a broken wire could short to the structure that the students are in contact with.
The Monash example of making small flat plate items (jewelry etc.) is probably a good starting point. Molds can be relatively easy to make and a small machine can provide results. Depending on your resources at the school, you can assess if producing a machine is feasible. The injection machine can be simplified to a desktop machine that a school shop could produce. Some discussion here https://davehakkens.nl/community/forums/topic/portable-desktop-injection-machine/and there are also machines available in the Bazar.
Even without machines, some valuable topics can be addressed, such as sorting plastics by density, investigating earth friendly processes/solvents for removing labels, etc.
If you end up pursuing this, your project will be of great use to others here.
Those rods look really good. Are you seeing any voids? Have you cut one up to see if there are any internal voids?
Great work, thanks for sharing.
Both the modern landfill and plastic optimized combustion are better alternatives to having the plastic go in the ocean or nature. A modern landfill seals the contents, so a relatively inert plastic is entombed in the landfill volume sort of like putting the oil back in the ground
A well designed plastic burner operates at high temperature and does not produce the toxic smoke that an open pit burn would. Since we will be using combustion for energy for the foreseeable future it is better than pulling new oil out of the ground and using additional energy for transport and processing.
Yes, reuse and recycle are first choice, but for certain materials (Styrofoam?) and in certain locations, using difficult to recycle plastics for energy makes sense.
Yes proposing combustion is controversial until you compare the alternatives.
This is VERY cool, yes please post more info.
The topic of fiber reinforcement is an interesting topic. @lagrenouille is using it for surfboard fins https://davehakkens.nl/community/forums/topic/surfboard-fins-by-injection/ While there is some discussion about future recyclability, it definitely expands the possible applications for recycled plastic.
Thanks for the links
Plastic is good stuff for a lot of applications. The issue is management of its life cycle so it does not end up loose in the environment.
@aghanem Good luck in pursuing grant money. You may be aware of the announcement from China last year that they are severely limiting import of recyclables. Here in the US, especially on the west coast this has shaken up the recycling programs. Instead of just sending it to China in empty shipping containers, we need to figure out what to do with it other than the expedient send it to the landfill.
On the plus side, this should create an environment where research study money is available. Topics such as affects of co-mingling of plastic types, how clean is clean enough, how do properties degrade with number of recycles, extended sun exposure, etc. All should be of interest and potential sources of funding. Perhaps even generate some graduate level projects.
One advantage of this supply change is that the products your students come up with don’t have to be overly material efficient. They can compensate for the relatively poor mechanical properties with just more cross section…The world is eager to get rid of this stuff.
It is great to see the potential for university activity in this area. There has been a lot of great work done here in exploring small scale processing of recyclables, but there are certain topics that can’t be addressed without more specialized knowledge and equipment. One is understanding the fumes generated at these processing temperatures and the other is the mechanical properties of the resulting materials. If there is any chance of your project class touching on those topics, it would be of great help to the community.
Thank you again for telling us about your project.