I need help figuring out the most efficient way (NOT electronically) to manually compress plastic in a small confined space. I was thinking there were small compression shocks that would help to triple my human body force but have been unsuccessful in finding something that works.


closed as too broad by Air Oct 14 '16 at 16:47

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  • $\begingroup$ Hi jaehowell, welcome to Engineering SE. There is rarely any "most efficient" approach to an engineering problem so early in your design process. Instead you will find there are a million and one different solutions, some of them more or less cost-efficient, some of them more or less energy-efficient, and so on. If you don't want to add more detail because of your concern about patents, that's up to you, but I think you are overestimating the risk involved. If you want to hire an engineer to partner with you, our Q&A is not the place to do that. $\endgroup$ – Air Oct 14 '16 at 16:55

Levers are your friends: a lever allows you to multiply up the force of your own strength. Here's a manual can crusher, demonstrating this:

enter image description here source

Your hand moves three or four times the distance that the crushing part does; as a result, the crushing part moves with three or four times the force that your hand does.

  • $\begingroup$ The image you have is not just a lever its a fourbar with a lever. The fourbar can actually vary the load over the movement for even better power distribution. alternates could be screw mechanisms coupled with bar mechanisms. $\endgroup$ – joojaa Oct 12 '16 at 14:42

A bench press or arbor press, combined with a suitable die for horizontal containment, will allow you to produce rather high forces and pressures.

typical arbor press

Do you have any numbers — volume, pressure, etc. — regarding exactly what it is you're trying to achieve?

EDIT: I have to confess that I missed the tag on my first reading, so my first suggestion isn't very practical in that application. Probably the most compact mechanism that can provide both the required force (about a ton) and the travel distance (18" to 24") is the "scissors jack" — but it requires a lot of cranking to operate that might not sit well with users.

enter image description here

  • $\begingroup$ Hey Dave, I'll elaborate a bit. Please keep to yourself and Im going out on a limb saying this in all trust, but I have designed a manual trash compactor and about to make a prototype and have a patent research done on it, but the kicker is the manual mechanism to use that is compact enough to put pressure on trash, LIKE a plug in trash compactor, but be all powered by hand and with little moving parts. If you can help me get past this phase there will be some royalties in it for you. : ) Im an honest mom who is tired of taking some much trash out and KNOWS there is a better way! $\endgroup$ – jaehowell Oct 13 '16 at 0:42
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    $\begingroup$ Interesting. In this part of the world (northeast USA), trash compacting is falling out of favor, with "single stream recycling" handling most of the waste, including most plastics. They prefer that the recycled materials NOT be compacted so that they are easier to separate and process after collection. I'm just saying that in addition to the practical difficulties of producing about a ton of force over a travel distance of 18 - 24" with a hand-operated device, there might be less of a market for it than you think. $\endgroup$ – Dave Tweed Oct 13 '16 at 10:08
  • $\begingroup$ @jaehowell you wrote: "Please keep to yourself" - you did just post that on a public website indexed by google. $\endgroup$ – EnergyNumbers Oct 13 '16 at 13:56
  • $\begingroup$ Yes! I figured that out AFTER I posted and searched and searched for how to delete and there is no delete on this for a post. $\endgroup$ – jaehowell Oct 14 '16 at 12:11
  • $\begingroup$ So any help with that would be appreciated please. $\endgroup$ – jaehowell Oct 14 '16 at 12:12

I'm not clear from your question if you are trying to crush a plastic object, or manipulate hot plastic (eg for injection molding.) Lever systems are certainly a good option as has been mentioned in other posts, but depending on your application, a compact lever may not provide enough force for you..

If you need more force, hand-pumped hydraulic jacks will let you get a serious amount of force in a small space. For example, Enerpac makes a 2.25"x1.5" cylinder that generates 5 tons of force or a 5"x5" cylinder that generates 60 tons of force. Hydraulic hand pumps are readily available although the cylinder will move very slowly.

enter image description here

  • $\begingroup$ The question is tagged waste-disposal, so I guess the application is more likely to be crushing plastic objects $\endgroup$ – EnergyNumbers Oct 12 '16 at 15:09

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