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Hey you all!
I had some personal deadlines and could not answer in june.
Here are the updated plans!
Right now we are working on Version 2! More safety and a better handling.
But still we need two persons to shred the plastic;)
first of all, we found some errors in the files for the casing parts.
we will fix it and then we will upload it again. sorry!
mostly we shred pp. a few weeks ago i tested hdpe bottle caps. the thickness is up to 1,5 or 2mm i guess. at the moment we have no date about how much kg per hour. i think it’s a little bit more then the normal pp shredder produce.
We have to check how long they last. but you have enough material to resharp them 2-3 times.
mhm, we build the frame to put it on any 28″ bike. it’s not easy to find a design which fits to every bike, so we focused on 28″ because these are very common in europe.
and that’s the video!
whooop, we’re finally ready to share with you all our drawings, files, etc…
here are the blueprints!
the problems you mentioned are the major problems we have with our precious plastic shredder. with our “new” design we are a lot better.
a little bit of dust yes, but not that much. for all i know the big industrial ones are producing dust too. we focused on getting the shredder as much leakproof as we could. the hopper is crucial, furthermore it’s good for the safety;-)
statically charged. it’s like the dust. a little bit but not in comparison to our other model. we are using a metal box for the collection box, so maybe this beneficial to “discharge” the plastic.how fast rotates your shredder?
thanks! we are still working on a proper documentation. I think we will publish the video and the files during february. furthermore you can contact me personal via direct messages and i will give you some unpolished files, so you can start to work on that shredder!
@btmetz shared some photos of a high rotating shredder. we build one pretty similar – just smaller. This shredder is working great… even with a power of an bicycle! We have 4 rotating blades and 2 fixed on the casing. The blades are out of hardened steel. We focused on that design because it’s working more like the industrial standard, which is high speed (about 1100rpm). It doesn’t need that much power. Successfully we tested a motor with 0,3kW/230V and a 28″ bicycle.
We doesn’t made an exact comparison test, but we think that this design is working more efficient than the current pp shredder. Another good benefit is, that the plastic isn’t that much electrified. This was on of the main problems we struggled with the current pp shredder.
At the moment we try to simplify our construciton, especially the axle.
I’ve started a topic in the forum, but it’s been a few weeks since I posted something. But there will be a video in the next few months about the building time and the cad files are also nearly finished…
For the shredding unit we also have considered two variants.
1. The fast one (about 1100RPM / 180-250W)
– low torque fluctuation
– we have a working prototype
– special cutting knives and axe
– very fast -> maybe more dangerous than a slow one
2. The slow one (about 100RPM / ~2000W)
– we have a working shredding unit in our workspace (but with a big electric motor)
– less dangerous speed
– a lot of power / torque is necessary
– fluctuating torque -> not good for any drive source
– heavy -> a lot of lasercut parts
We comoared both variants with the proporties of a bicycle. It is possible for a person to get 200W out of a bike and with the right transmission we are able to reach a RPM over 1000. A power of about 2000W respectively a very high torque is more complex to realise on a bike.
With this comparison we decided to work on option 1. Furthermore we ththoug that it would be safer because to get the high torque for option 2 it is necessary to have a flywheel and imagine something gets stuck in the shredder and the machines stops to turn, but the energy is still there. So maybe the chain jump or the belt break like the people in Shanghai experienced with.
@siemenc i do not think that this is necessary. With normal waste we do not have any problems to shred it. It would make the machine heavy and more difficult to stop
The pictures show the principle of the shredding unit and our first protoype with an electric motor (230V/250W) in a case out of acrylicglas and aluminium.
We made a completely different blade design and we are working with a high RPM and low torque. More or less it is exactly the opposite of the ‘normal’ precious pladtic shredder.
We precut the plastic in pieces that fit in our hopper. Until now we just have tested PP and i think the max. Thickness was about 2mm.
I will write a detailed post about the shredding unit this evening. With some pictures, drawings and facts…
It all started with an analysis about what does the machine have to do:
– mobility -> has to be carried on a bike
– human powered / independently from electricity -> we transport it with a bike so we also have to create the energy to shred plastic
– lightweight, compact and solid -> not that easy:)
– maximum safety priority and easy to use -> we work a lot with kids or youth groups. So everything has to be safe and simple to understand.
– shred plastic efficient
Solving approaches of the main parts
Mobility. Here we considered 2 options:
1. One bike firmly connected with the shredding unit
– one single functional system
– super mobil, everthing is on the bike
– in case the bike is defective the shredder is not working
– heavy bike
2. Modular shredding unit you can connect to every bike
– the shredding unit without the bike is compact to store
– people can use their own bike to shred plastic
– some people are smaller some are bigger -> we are able to change the bike for differnt body sizes
– no process gurantee -> every bike is a litler bit different. We can’t be sure that ther shredder is working with ever bike.
We decided to make option 2 with restriction: Only 28″ bikes
This is one of the first sketches:
and another two
here it is. the most importand rules to design our nozzle are:
1. make sure you can heat it up nice and quickly
2. make sure you can fix the mould on a fast and save way,
we don’t use threads because it takes a long time to get the mould ready on the injection machine. that’s why we are using a car jack to press our moulds against our redesigned nozzle.
here are some pics:
thanks to all of you!
When everythin is nice and smooth we are about 30 clamps during one hour. But we are using a car jack to press the mould against the nozzle. That’s a lot faster then threat. and we have less waste because our sprue shorter.
Wow! Good Work!
Do you have any daft angel? When the mould gets warm, the clamp is easy to get out.
Yes we will share the drawings. Licensed under a CC BY-SA 4.0
These are the files we used. pick what you need.
Hey, sorry to all of you! The past month I was travalling through Kenya without internet…
I have just arrived… for these two points i need some time 😉
1. I’ll have to check what I can share with you. I’m sure we will upload the files. But Kunststoffschmiede is a group of a few people and I have to check if the majority agrees with it.
2. Translate the technical drawings into english
Take some good stuff with you from your workspace;) we can trade with #piranhaclamps :)))
well yes, we didn’t test other types:) but for all we know, pp is one of the most flexible types of plastic.
maybe we will use an external tool to brand. currently we are testing the dremel versa tip. in this case we would be free to try other types. but for every clamp it’s another step.
we don’t cool or preheat the mould. all natural:)
in the beginning the clamp shrinks a lot and it’s a little bit difficult to demould it. after some injections the mould is a little bit cozy, then it’s very easy to demould the clamp.
as a generel rule you can work with 2-3% of shrinking. it also depends on how much pressure you give.
The last steps we have to make is the engraving of the plastic type (we purposely left it out to test if PP is the right plastic) and to find the fastest way to open and close the mould
I hope I could explain it to you well! Feel free to write every question or remark in this topic;-)
Besides we are testing all use cases we can imagine;-)
What comes next?
First they milled a positiv of the clamp out of copper. This copper electrode was used to burn (EDM technique) the form of the clamp into the metal mould. Here are some pictures of the production.
In the meantime, we have been able to establish contact with an injection molding company. The Schicktanz GmbH: 70km away from our workspace and very supportive.
They have their own workshop to build high-end moulds.
It ended up that they made the mould for the #piranhaclamp for free. Thank you!
Even if the mould was for free, it was a huge charge on our team to supply the right files. It is quite different if you make a testmould with plexiglas or give something in order, which is worth several thousand euros.
We made the last prototypes with the 3D printer.
And after a few hours of discussion we decided us for one design and made all files ready for Schicktanz GmbH.
Here some specs:
parting line: central
draft angle: 3%
engraving depth: about 0,5mm
curves: 0,5mm radius
As well as the first clothes peg, we made our first prototypes in plexiglas/acrylic glas (You want to know how it works? Watch the turorial on youtube: https://www.youtube.com/watch?v=24ECE3VL13k)
We tested it and it worked. Yes it worked:) Such a good feeling!
But we also had to notice that plexiglas isn’t the right material for the mould. Not in the long run. Because in the current design of the #piranhaclamp we have this tiny bridge from the inner circle to the outside. This bridge is too weak, so it easy breaks when you demould your clamp.
At first we had a working mould and a bad design. Now we had a bad mould and a good design. It did not feel like failure, but we still had not achieved our goal…
So our main advise in product development: Failure is essential.
We made the spring thicker, thinner, shapeless and even, but it did not help. She was still breaking. So we came to the realization that we need a completely different design.
Anna made a research about clamps. There’re so many way’s of clamping your laundry. We never would have thought that:)
We wanted to have a clothes peg with just one part and Anna found a design on thingiverse:) https://www.thingiverse.com/thing:339768
In summer of 2017 we finished building the injection machine, and made the first tests. One of these first test was the clothes peg.
We tried an old design from DDR. We replaced the metal spring with a plastic spring, but it didn’t worked out very well. The spring fractured quite often:( So sad…
Nevertheless it was a success, because we learned a lot about plastic, made an undercut injection mould and presented the first try with many other fancy community creations at the DDW’17.