Forum Replies Created
I would start taking some measurements with a multimeter.
– Confirm that both PID’s are producing the right output that matches what the SSR needs (the PIDs look identical but have different dash numbers for the different type)
– Confirm you got mains power coming to the SSR and check whether it switches on.
– Check continuity in your heater loop
– Check that your thermocouple is mounted with the tip pressed against the tube.
You’ve probably done many of these, just a check list
What Olivier said.
Also, you said thermistor, did you mean thermocouple? I think the sensor hookup for resistance thermometers is a little different from the thermocouple models.
When you say not working, what does that mean? Does the PID show a reasonable PV temperature? When you set the temperature higher, does the output light come on? Does your PID output match the SSR (low voltage signal) etc.
Yeah, some pictures or symptoms will help
As I mentioned, with a big open cavity mold may not need as much pressure to fill but pressure also helps reduce voids.
…………..You can always work your way up by making the pallina ball first
To estimate the material, just get an estimate of the volume of the part (for a rectangular beam just a product of the width, thickness and length) and multiply it by the density of the plastic you are using. For example for HDPE the density is a little less than the density of water (1g/cc) so a 2x2x100 cm beam would use a little less than 400g or just under a lb. For beams with other cross sections, just calculate the cross section area times the length.
The density you produce will vary, and there may be voids but these estimates should be a good starting point.
If you are following the guides in the download kit https://preciousplastic.com/en/videos/download.html , the recommended starting temperatures for PP are in the 190-210 C range. Your temperatures (if they are in C) are way off to the point of potentially generating some nasty fumes. Be careful. I don’t understand some of your temperature terminology. If you have a typical setup with two temperature controllers (barrel and nozzle) you should have a set value and an actual value displayed for each location. If your numbers are in C, I would not do any more until you get the temperature control sorted out.
Post some pictures of how your thermocouples are mounted and the PID display.
The shredder is fun (and therapeutic). I think there would be a lot more recycling if people could watch that shampoo bottle being shredded.
The extruder machine is the only one that needs small plastic flakes. The other machines can use larger, hand cut pieces. Sometimes (especially in the press machine) you get more interesting color patterns with larger pieces.
In the PP injector design, when you increase the diameter of the barrel, the pressure you can generate decreases and given the linkage geometry it can be challenging to get it back up. Pressure may not be that important for a large volume mold like a bocce ball, but making smaller parts may be harder. For large volume, I would consider the rack and gear type machine. This design separates the stroke length from the injection force, so you can increase the stroke length.
My machine has a 40 mm ID barrel but I use an arbor press to provide the rack and gear function.
I think you will need margin on the 600CC volume. I find it hard to get a part that is more than 75% of the stroke volume.
When you succeed, I think you will have the largest injected part reported on the forum.
But why start with the shredder?
Glad to hear you stuck with it and are in production. 12 per hour is a very good throughput. That’s a nice wax comb.
The injection machine is relatively easy to build without a lot of resources but you will need the heaters and temperature controller(s). To use the injection machine you will need to make some molds. These can be simple bolted together or welded for simple geometries, or can become complex machine parts. There are also size limitations for the items produced.
The hot press machine can also be relatively easy to produce and can generate basic shapes that can be assembled into larger more complex items.
It would help if you told us what experience and shop resources you have in metal fabrication.
If you have not already done so, browse through the Bazar and see what items people are making and which you think you would have the capability to make.
The machines are just tools, they don’t make anything by themselves.
There are many geometry and optical variants possible on your configuration. The question is how sensitive your plastic typing algorithm is to uncertainty in the individual reflectance measurements. Does your algorithm report those parameters or do you need to determine it externally with a sensitivity analysis (Monte Carlo type?)
The plastic will have a reflectance that is both angle and wavelength dependent. The question is how well the calibration or learning process capture the possible variations for any one material type.
The sensitivity analysis will be useful for other parameters as well. Things like LED intensity stability, dealing with translucent materials, etc.
No need to get bogged down in what could be a thesis level study, just establish the boundaries whre the learning algorithm runs into problems. This can help guide any geometry or optical modifications if needed.
Again, great work
Do you have a picture of your mold or design?
The problem with plastic and fossil fuels is that they are really good solutions for what they were designed to do so eliminating them is not an easy engineering problem.
The shallow approach of some of the “plastic is bad” slogan type articles does not really help much. More useful would be to have a conversation about near term priorities. Perhaps the biggest concern is about plastic going in the ocean or the environment where it is exposed to sunlight and degrades. Next might be burning in an open pit. Pyrolysis or burning for energy in a properly designed furnace may be on the same level of concern as fossil fuels in general, at least additional resources were not used to get it out of the ground. Burial in a well designed landfill takes advantage of the general inertness of the plastics and in a sense puts the carbon back in the ground. The most preferred might be recycling, reuse, and avoidance but those are not realistic for 100% of the material.
So I think all of the solutions need to be compared to the reality that for a lot of countries Recycling really means send it to places like southeast asia where it is picked through and what is not useful is dumped or burned. In the western US we export over 400,000 tons of plastic. If even 20% is not useful or contaminated, and goes into the environment, then we are remote-dumping. Realizing that, I wonder if it wouldn’t be better to put the plastic in the trash and let it get buried in a regulated landfill.
So I think articles that warn against imperfect solutions need to compare them against the current reality
From the curves in the paper I linked, it looks like there are a lot of features above the 1550 nm in your chart. Digikey has 1650 and 1720 nm led’s. Have you tried any of those?
Looking at the geometry of your illuminators, are you sensitive to surface gloss or tilt/non-flatness?
These are just observations, not criticism.
Great idea, great work
If you are just getting started, the shredder does not recycle plastic by itself, it just makes flakes. The only machine that really needs small flakes is the extruder. If you have not already built an extruder, then you may not need the shredder. If you already built an extruder, then you already needed and have a strong motor.
I would start with a hot press machine or and injection machine. Both of them can readily use hand cut plastic and are much easier/cheaper to build.
@realrecycling , Thanks for posting. I think the PP-V4 was/is working on a low cost Raman type sorting approach it would be great to be able compare both.
A couple of questions:
I like your approach of putting the color selection on the illumination side. What color LED’s were you able to get? Looking at the spectral response in some of the published papers (example: https://www.researchgate.net/publication/285330830_Identification_and_classification_of_plastic_resins_using_near_infrared_reflectance_spectroscopy ) How do your colors compare?
It will be interesting how the machine learning developed algorithm accommodates colors and additives.
Great work, thanks for sharing it with us.
Thanks for the link. Unfortunately the article goes off on a perpetual motion tangent. For waste, how do you compare inefficiency of pyrolysis to the plastic just being dumped into the ocean or burned in an open pit?
I don’t have one of these but it looks like they use sticks (fairly expensive) rather than thin continuous filament, almost like hot glue guns. You may even be able to injection mold these which could be done fairly cheaply. I would guess that a child care or afterschool program that uses these could recycle a lot of those artistic creations.
Thanks, I think I see a winter project forming.
You may be able to put a larger pipe on the outside and blow a heatgun through the gap.
@snyder-devin the HF concrete drill bit approach is exactly what I’ve been considering. Did you use the 21 inch kit https://www.harborfreight.com/21-in-sds-max-type-masonry-drill-bit-set-3-pc-62793.html ? Once you take off the bits at the end the fluted portion fits the 3/4 inch pipe or did you have to drill or ream the pipe?
Nice, I like the simplicity of the wood frame build. What are you using for the extrusion screw?
Interesting, I tried something similar with an injection machine and got something similar. A description and some section views here https://davehakkens.nl/community/forums/topic/portable-desktop-injection-machine/page/4/ . I think the V4 beam production efforts made similar observations https://davehakkens.nl/community/forums/topic/beam-production-v4/ . I’m not sure if you can get the plastic to slide along the wall as opposed to coating it and then shearing internally. If it is shearing internally, then it is a battle between the push force (a function of the pressure and area) and the shear force ( a function of the viscosity, perimeter, and length). For small diameters like you and I tried, the shear force wins pretty quickly, for the V4 sized beams it takes longer. One option might be to really heat the mold and raise the plastic temperature to keep the viscosity low.
Thanks for posting, it is interesting that we got to the same results using completely different machines.
I think someone posted links to higher quality heaters but I just use the Banggood type stuff for what I do. I would just make sure the tube and structure is grounded in case one of the cheap heaters fails in a bad way.
They are readily available online (amazon, Ebay, your favorite Chinese vendor).
The best deal is to get the PID/SSR/Thermocouple bundle which can be found at very low cost.
Well it depends on what you need. If you are not using an extruder and don’t need fine flakes, there are some lower cost options. For thicker plastic (laundry bottles etc.) I use a manual metal shear and can get to ~2cm flakes pretty quickly. I also bought one of the geared, low speed garden chipper for really thick material https://davehakkens.nl/community/forums/topic/recycling-larger-items/ .
For thin material (milk jugs, etc) a medium size CD capable cross-cut or micro-cut office shredder works as well. Each of these options is in the under $150 range….
…..or you can get a big bottle of ibuprofen.
If you search the forum for PET and transparency, you may find some threads on the topic. If I remember correctly, they stated that fine temperature control and dry material were key. It was not an easy process, though small scale may help . Also depends on how transparent as opposed to translucent is good enough.
Since you are using a modular frame, maybe switch to the more typical cantilevered configuration by moving the outboard support just to the left of the hopper. You can then wrap the hot end as shown in the @kaboom photo. If that does not reduce the burns enough, you can start adding thermal isolation to the support path. You can also cover the hot portions of the frame with wood so it does not burn you.
The number of heater bands is an interesting topic. I wonder if you can add a probe into the PID to monitor the duty cycle once the system is at temperature.
Yes, very nice build
The link to the Bazar is probably your best place to look.