The story behind the #PIRANHACLAMP
I (@carlf from the Kunststoffschmiede) will share with you the process of how we got to our final mould. It took us nearly 9 months and a team of mainly 4 people.
Don’t even think that we were full time on this clamp, but be sure: Product development takes some time…
So here it is:
The way from an idea to a functioning mould.
First results, the first thing I noticed is that the mould is quite hard to open and extract the part, due to the relatively long circumference of the part. I added some ‘prising slots’ to the mould. I should have done this first of all but I wanted to see what it was like without.
I’m not overly impressed with the toggle clamps. I usually use socket head set screws in each corner which provide much better clamping, only need an allen key to undo them and really only take a few more seconds to remove. I ended up with quite a lot of flashing on the part on my first attempt, as the mould was not clamped together tightly enough.
By using a spanner to tighten the wing nuts (kind of defeats the point) I was able to minimise the flashing.
The red clamps are polypropylene. I then tried HDPE. It didn’t work too well. I wasn’t able to fully fill the mould and I noticed I had to apply a lot more pressure on the handle of the injection machine. I think I made the gate too small for HDPE, even so I think this shape is better suited to polypropylene.
All in all I’m pretty happy with the results, the clamps look good and they work!
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.
upload cad files
@sharma-sagar: please, scroll up a little, she made an attachment, and i made a post to a maintained github repo & external forum post
@anne-barbier oh didnt see it. thanks 🙂
No draft angle, just straight sides and a small radius on the corners, but I think you’re right, the part will be much easier to extract with a draft angle, I’m going to try this on the next one, I’ll have to grind a special cutter.
If you have the injection point on the side and are using a car jack to hold it against the nozzle then you are probably getting most of the clamping force out of the jack rather than the toggle clamps. The car jack is a good method, I think more people should use it, but I think most still just thread the moulds on, it’s simple and secure but not as fast, and you really need to split the mould along the sprue line to get the solidified plastic out.
When I have perfected the mould I will put it on the Bazar. I’m not 100% happy with it yet, it still needs a few small tweaks to get it just right.
Ok, here’s version 2. I made a few small changes. I went back to cap screws to close the mould, more secure and really doesn’t take much longer to open (I actually think they are less fiddly and faster to tighten as well).
I made this mould with a draft angle on all the edges except the actual teeth which are parallel. I made it slightly more than 3° and the part is much easier to extract from the mould. I used PP again for these tests (shredded flowerpots).
And here is the listing on the Bazar.
I’m not planning on selling the clamps themselves, just the moulds so people can make their own. I don’t think it really makes sense to sell plastic products in the Bazar, it adds a lot of unnecessary shipping when we should be focusing on tackling plastic waste at a local level. I don’t know if @kunststoffschmiede sell the clamps somewhere, perhaps they do, they would be closer to you than I am.
I probably won’t make enough of them myself to sell, but I may give them away locally and use them as an example of a useful product that can be made from plastic waste with low-tech equipment.
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:
and another two
So you develop your own nozzle, for sure the shorter the nozzle the faster you reach it’s temperature, I agree with you that the threaded nozzle is not good, I will try some different setup of the nozzle.
Thank you very much.
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