I’m very surprised and disappointed, in the videos I’ve seen thus far , that there aren’t any safety devices incorporated. I certainly have lots of suggestions and at least one not only doesn’t cost anything but makes the machine a lot cheaper. I would not use a geared motor but loosely bound pulleys to do the speed reduction. A geared motor won’t even slow down if you get caught in it. A shear pin in the coupling between motor shaft and cutter arbor, would be a thing. A fuse on the power line. A hinged lid with a switch. Pedal operated on the power line. The fancy “anti tie down” with two switch operation. Jeez. any of these are cheap. If a person builds one of these, lets someone else operate it and they get seriously injured, be prepared to get wiped out financially in a law suit and/or serious fines by the government safety authorities.
I was pretty concerned after watching just the grinder assembly video at the lack of any consideration to safety. A geared motor would be my last choice for the grinder as it wouldn’t even slow down if someone got caught in it. Two handed operation with separate switches and anti tie down devices to detect if someone clamped one of the switches permanently on. A shear pin that breaks when a load threshold is passed. Loosely bound pulley driven cutters that can stall out. A switched lid on the hopper. These are all ways to improve the design. I would not even think of operating myself or allowing others to operate these machines as they are designed. They are a tragedy waiting to happen.
With that said, I suggest you to create a new topic with the list of improvements you suggest to make the machines safer to use, so Dave can include them in a future Precious Plastic 4.0 release.
I agree with your comments @abraxas, but the Precious Plastic machine designs are not written in stone, anyone can customize the machines as much as they want and make them as safe as they want, the PP designs are just the bare minimum required for the machines to work.
On regards of Law Suits, Who is going to get sued and under which charge? No one is forcing you to make the machines in first place. Dave created those models and released them for free so that anyone can use them at their will, and the creative commons license used for this project release the creator from any damage or injuries from using the designs.
I guess its just a matter of common sense, if you are playing with fire, you should now how to handle it so you dont get burned.
It’s far cheaper than the cost when someone loses a hand, particularly a child. These safety features certainly aren’t expensive. Foot pedal operation, is cheap. Switching from a geared motored to a pulley system is not only not expensive but considerably cheaper than a geared motor. How much would a hinged lid on the hopper, with a push button switch cost ? 20 bucks ? Hell, anti tie downs are less than $100 USD. I see some on Ebay for 20 dollars !! I’m a veteran machinist and I wouldn’t even think of operating one of these grinders without some sort of safety. And if i designed a grinder without any safety devices, I wouldn’t publish the design lest I lose everything in a law suit, or maybe get thrown in jail.
These are great sentiments @abraxas – and as someone who has seen a lot of idustrial accidents over the years, I’d agree that safety should be a major consideration. However, the more features we design into the machines – whether for safety or for perfomance – the less affordable they become. This isn’t to say that we should ignore safety – only that there is always a play-off between safety and monetary cost, whether we like it or not, and a line has to be drawn somewhere. Sometimes the line is drawn at a point that makes certain activities unfeasable – and that is fine, if we are prepared to stop the activity alltogether (e.g. indusrial processes that involve the use of certain carcinogenic substances, such as hexavalent chrome).
There is a machine development section of the Precious Plastics project, and I’m sure people there would welcome practical help in the redesign, or modification, of (particularly) the shredder – to be able to improve relative safety within sensible cost constraints.