Forum Replies Created
With your building skills, an injection machine should be accessible. I used an alternate arbor press design https://davehakkens.nl/community/forums/topic/portable-desktop-injection-machine/ (unfortunately some of the posts in that thread are missing). If you are going to do the melt and press, be aware of the fume issue.
I guess my question is why do you need to shred the bottle caps? Are you extruding them? Are they bigger than the inlet to your injection machine? For a lot of what I do cutting them in half is sufficient. If you look in the Bazar the people pressing clock faces or table tops leave them in one piece for a more interesting look. I use a metal shear, utility knife, or scissors for laundry bottles, caps, etc.
I do like the grinder to blender concept in your video. A more extreme bend on the blades and a plunger to push the caps down may get it to work.
Interesting. I’m looking forward to the results of your research. You might try searching the Map database for work spaces and builders. Also perhaps you can request from the administrators the statistics on machine and product sales in the Bazar. I’m not sure why those are not published.
@kiranmantha , Thank you, that is a good paper. It does suggest that this would not be a casual build to make it safe and efficient. It seems to me that it would be an ideal project for a university to produce a well engineered small scale device and put it in the public domain. Did you see the Dung Beetle project link in this thread?
Interesting. I’m not sure the tires would make a good mold. If you have the rims, one option might be to make the plastic tires in sections and bolt them on. That way you don’t even need an extrusion machine and just make a press mold. One advantage would be that you can make them as wide as you need.
That’s a great application, thanks for posting. You don’t see a lot of products where the injector adds just a portion of the product. Same thing for encapsulating electronics, even if it is just decorative LEDs, a good addition to custom decorative items.
Yeah, a TED talk without any T content is yet another “raising awareness” fundraising exercise. To be open source they probably should post some design information for the pyrolysis machine they built. Not sure why they need to shred the plastic though.
For the price of the voyage they could probably build a thousand units and get them in peoples hands. But, hey if you can get sponsors, a voyage is better PR.
Looks like a great start. Do you have a way of monitoring how hard the motor is working?
What nozzle size do you plan on using? I noticed that when I create a bead of hdpe with my injection machine, it tends to expand quite a bit.
Actually, your back-up plan of bolting it to a CNC machine sounds like a great trial run for optimizing the print parameters.
Good luck, great work
A playlist would be great. I think this thread was meant more for the humorous and loosely related videos. Maybe start an new thread to collect more on topic videos.
Thanks for posting the link. It is an interesting price point. At $4K it is similar to a suite of PP machines. For some people a turn-key system is probably the safest way to go. It would be nice if the site had some basic technical data.
The Precious Plastic approach works well for marked PE and PP but for everything else more work is needed and pyrolysis may be the answer for some of it.
Yes, please post what you find
Thanks, that will be useful.
For those that may want to know what is important on youtube….
It appears that an 8 year old promoting plastic toys was ahead of the save the world from plastic channels….Looks like there is some work to do
Gamers and toy reviews…How do you convince a kid to go learn engineering
Thank you for posting this. I had not seen the hangprinter materials. Sounds like you have and exciting project for your thesis.
A few questions and comments:
How did you size the stepper motor/gearbox for your extruder? What does the leadscrew profile look like?
Doing a scooter frame design with HDPE or PP sounds challenging given the low structural properties. I wonder if you will end up with mostly solid cross sections.
The hangprinter design appears to be sensitive to printhead inertia. Putting your extruded on the print head will increase both the mass and the moment of inertia. The printhead that @3dseed https://davehakkens.nl/community/forums/topic/3d-printer-for-pet-particles-no-filament-ever/ is using in his design appears to be a lot smaller. Perhaps for larger prints, develop a larger or flexible hopper that can feed a smaller printhead.
Please post updates, this is an interesting approach.
@btmetz , Thank you for posting this. I admire your perseverance and ingenuity. I wish more builders and workspaces posted their real world successes and setbacks.
I think your adaptations of the machines to local conditions and availability has been a great contribution to the designs.
Just curious, what happens to all the student shredders after the thesis is done?
Thank you again for posting.
That’s a good question. If you were injecting or extruding, just mixing may be good enough. If you are oven heating and then pressing, I would try cutting it into smaller pieces and then fold and press or fold and twist a few times during the melt process.
I saw someone online melting PE in high temperature cooking oil. Not really that good for most things but for a chew toy that may work OK, though more likely to eat the parts.
I’m not sure you want a harder material rather than tougher. The harder material is likely to crack off in sharp flakes. What about going the other way and trying LDPE to make a more chewy toy? Lots of LDPE food container parts around. Or mix with HDPE to experiment with a range of hardness and toughness…Looks like you have a capable testing facility.
Wow, I didn’t expect to see that. That’s acting like some insulation between the heater and the tube. I assume it was put there just to mechanically fill the gap that still existed with the heater closed as far as it will go. Do you have a way (caliper) to measure the diameter of the tube? Those layers of mesh look like they add up to close to a mm thick.
I would take the mesh out of there, I assume it is not connected to the heater. You will need something thicker than soda can to fill that gap. Ideally you would fill it with one layer but it will depend on what you have on hand and what you can shape around the pipe. Some options might be aluminum from pie tins, hardware stores have sheets of aluminum (roof flashing?), brass, or copper in various thickness. Another option may be if you find a piece of thin walled copper pipe that is close to the diameter of the tube, you can cut a slit so it is C-shaped and compress it under the heater.
If this mesh was where the thermocouple was located, I am not surprised by the bad readings.
Good luck, sorry that you have to do all this rework.
@bernard-kervynmekongplus-org Thank you for posting. I think one of the underutilized capabilities of this forum is to collect information on the status of plastic trash around the world
Do you know which of the plastics have enough value for the collector/sorter? Our part of the US ships/sells our collected recyclables to places like Vietnam. I was wondering how much of that is not worth the effort for the sorters and gets dumped. If lets say 10-20% of what we send is unused and gets dumped or burned as trash then our recycling program may be doing more harm than good.
I wonder if for collection, you could make a smaller version of one of these https://www.nationalgeographic.com/news/2017/02/mr-trash-wheels-professor-trash-wheels-baltimore-harbor-ocean-trash-pickup/ . It looks complicated but functionally it is just a waterwheel turning some forks to scoop the plastic. At a small scale, you may not need much of a conveyor belt if at all.
@btmetz has a great design for a chain driven shredder https://davehakkens.nl/community/forums/topic/philippines-shredders-and-mods/ .
Potentially you could mount them both to a strong base but the gearbox you linked seemed to have a low torque rating.
People have done chain and sprocket as an alternative as well
@upcycletaranakinz , Thank you for posting. What a great program and great results. Having the kids generate actual quantitative material property comparisons is a wonderful lesson in science fundamentals.
Did you see the work https://davehakkens.nl/community/forums/topic/ocean-plastic-research/ the PP team did in the Maldives where they turned some very nasty looking degraded beach plastic into stuff. Similar conclusion that the degraded plastic is usable.
From your first and second picture it looks like you are injecting through a small hole so your part is trapped in the top piece. Are you doing that to help remove the part from the bottom pieces? You could add some jack screws in the perimeter frame to help separate the stack.
Yeah, a little more grind and polish to smooth the surface would help as well.
Did you see the plastics melting temperature chart on the PP site https://preciousplastic.com/en/videos/plastics.html ? It shows that the common plastics tend to stay fairly viscous even when they melt. Not sure how pouring them will work. I think you will need to press them in some fashion. Also note that at those temperatures you should have safety gear for the fumes and burn risks.
As you tighten the bolt, the heaters should be compressed against the tube before the you lose the gap in the cylinder portion. It should be tight enough that you can’t twist the heater on the tube with your hand.
I can’t see what holds the bottom heater on. Is it just the spring of the band? I’m guessing that what is turning is the bottom pipe fitting, it looks like you have some plastic oozing from that joint. If the heater just slips off, take it off and you can take a couple of pipe wrenches and tighten the fitting to the pipe. Hopefully the outside of that pipe fitting is a nice round cylinder for the heater to sit on without lumps or ledges to form gaps. There should not be any plastic between the pipe fitting and the heater. If that bottom heater is a loose fit without a clamping bolt you may need to add something to compress it. I would mount the bottom thermocouple on the tube just above that pipe fitting/bottom heater.
Yes, I figured that round thing had a better looking side. Note, depending on the plastic, it can take longer than 12 min for the plastic to fully melt in the tube. I would give it more time instead of raising the temperature. It also helps to cap or block off the nozzle while the plastic is melting and compress/compact the plastic a few times. It also helps to maintain pressure for a while while the plastic is starting to solidify in the mold.
I don’t know why PP chose to clamp the thermocouple under the heaters. You really don’t want to measure the heater temperature, you want to measure the pipe. Adding a separate hose clamp to mount the TCs would have been an easy alternative. This is especially true of the typical low PID/SSR/TC kit that comes with a threaded mount for the TC tip. Instead of removing the threaded tip and chancing breaking the TC bead, just use a hose clamp to secure a threaded block or even just a nut to the tube and then screw the TC in until the tip is pressed against the tube. Easy and robust.
Getting back to @karenrpcv , If the builder is not around to fix this, and you are on your own, here are some simple things you can try.
First a question: From your photos (especially the second one) it looks like on some of your heaters the two ends of the cylindrical portion meet where the clamping bolt is. There should be a gap, otherwise the heaters are oversized and don’t clamp the pipe fully/tightly. Is that true? If it is, that would help explain why the thermocouple is not clamped properly. One way to fix this could be to cut up some aluminum cans into strips the same width as the heater and a little shorter than the perimeter of the tube. Add one or two of these to the tube as shims until you can tighten the heater without the two ends of the split cylinder touching when you tighten the bolt.
To solve the thermocouple issue, I would use a metal hose clamp to clamp the thermocouple bead to the tube between the heaters. I would use a couple of small strips of aluminum can between the hose clamp and the TC bead so the bead does not get pushed into the typical gaps in the hose clamp. Tighten the hose clamp but you don’t need to crush it. Also I would use a bare wire (otherwise the insulation may smoke) to secure the stainless wire near the TC so accidental tugs on the wire don’t pull on the TC bead. I would do this for both of the thermocouples.
With the thermal control working properly, you should not need to have the set temperatures above the 190-210C range suggested in the manual.
Also, if you can, during use, move the injection machine outside. You can not see the plastic fumes but they are there, even at 200C.
Hopefully with these minor issues out of the way, you can enjoy your new machine and make may of those round …whatever they are.. parts
Good luck and let us know how it worked out.
The thermocouples are the two thin wires with the stainless braid on the outside. Looks like they are mounted by being clamped under the heater bands. I think that’s the way the Precious Plastic design recommends but there can be issues. Without breaking the thermocouple wires, do they feel like they are clamped snugly (gentle wiggle does not move them)?
When you first turn on the PID controllers, do they show the right temperature (room temperature)? Does the upper one then shoot up quickly past the set point?
Looks like in your system the top three heaters are wired to the PID/SSR and the bottom two (near the nozzle) to the bottom PID/SSR, is that right?
Sounds like you may not have built the system, Is the builder local to you?
I can’t see how the thermocouples are mounted in those pictures but I would not run more plastic until the temperature control is working well. Can you take a picture of the two thermocouples as they are mounted on the tube?
For heat welding, look at some of the work @imuh did https://davehakkens.nl/community/forums/topic/v4-adhesives/#post-139270 .
Looks like most of you structure is made from angle stock. You could either press directly to that shape or make flat stock and bend it by reheating and press into a mold. You may want to look through some of the threads in the V4 section of the forum, especially the furniture making and joinery.