Gripping force
Gripping force
(OP)
Hello Guys,
I need help in calculating the gripping force. I have to use a pneumatic cylinder which has linear mition and I am planning to use scissor tongs to carry this motion into gripping force. Can anybody help me with the selection of cylinder w.r.t displacement or force?
Thanks in advance
Arcka
I need help in calculating the gripping force. I have to use a pneumatic cylinder which has linear mition and I am planning to use scissor tongs to carry this motion into gripping force. Can anybody help me with the selection of cylinder w.r.t displacement or force?
Thanks in advance
Arcka





RE: Gripping force
You have to be far more descriptive than you have been in your OP. We can’t see it from here, nor do we have any idea what you are really trying to do. Do a simple, well proportioned sketch, with some dimensions, forced needed, general idea of the mechanism you are talking about, so we can see what you are thinking. There are plenty of smart people here willing to help you once we understand what you need and can see how to manipulate the variables.
RE: Gripping force
A 'reasonable' sized cylinder will often deliver far more power than necessary. Ask a supplier, or buy a sylinder giving a total force considerably higher than the weight of the item. Experiment and limit the pressure to give needed force. pressure regulator, pressure indicator, pressure switch,throtteling valve,checkvalve when necessary, and correct sized items of all. Or in addition: downsize or enlarge the cylinder if necesarry.
You can also experiment and calculate to find the correct friction coefficient between the two surfaces and guesstimate necessary force from that.
Google physics for the formula.
RE: Gripping force
RE: Gripping force
RE: Gripping force
RE: Gripping force
RE: Gripping force
You said 'scissor', why instead drawn as an open claw?
RE: Gripping force
RE: Gripping force
Normal practice would be to start with your load, workout the mechanism and then select a suitable cylinder, what you appear to be doing is the reverse.
RE: Gripping force
RE: Gripping force
Well get rid of the two links dimensioned 90 and mount the cylinder horizontal between the top end of the links dimensioned 200.
Move the pivot points down as close to the grips marked 30, let's say the pivot points are 50 off the bottom end of the links where the grips are, now you have a ratio of 150/50 which is roughly 3.1 which means if you 25 iN force total at the gripper end you would need 8.3kN at the cylinder.
RE: Gripping force
another day in paradise, or is paradise one day closer ?
RE: Gripping force
Need help with Geometry?
Need help with Trigonometry?
Need help with Conservation of energy?
RE: Gripping force
Pretty simple trigonometry.
My motto: Learn something new every day
Also: There's usually a good reason why everyone does it that way
RE: Gripping force
RE: Gripping force
as desertfox posted, if you have the hydraulic cyclinder driving both arms of the claw, and you connect the two hinge points together, then your 25kN force is applied with an 8kN cylinder. but stroke on the cylinder will be 3x the movement at the jaws.
another day in paradise, or is paradise one day closer ?
RE: Gripping force
Well I am pleased that you at least read and understood my post.
Thanks
Desertfox
RE: Gripping force
I understand now that I do not get to choose the mechanical system, because this system already exists. My company needs to work on the alterations (changing only the cylinders - image attached). I would need to calculate Force 'F' at the end of the device. I will be thankful if someone helps me. http://imgur.com/6aV5Fxk
RE: Gripping force
you know the force from the hydraulic cylinder, applied to two links.
the links are 2 force members, reacting the applied hydraulic cylinder force axially
this axial force is causing torque on the gripper arm (about the white bolt)
which is applying force to the subject, P = Plink*190.6*sin(theta)/75
another day in paradise, or is paradise one day closer ?
RE: Gripping force
-tg
http://xternal.me
RE: Gripping force
http://www.engineeringtoolbox.com/levers-d_1304.ht...
http://iqa.evergreenps.org/science/phy_science/ma....
RE: Gripping force
As a few people here are telling you, there is no single force because it changes as the cylinder moves from nearly zero to the maximum when the tan coloured links are nearly at 90 degrees to the cylinder.
The key dimensions you need are the fixed or stated distance your jaws are apart / diameter of the rod, the distance between the pins at the end of the tan coloured links and the length of the tan coloured links and their distance from each other plus how the distance between the tan coloured links and the jaws vary (e.g.130mm links gap = 25mm jaw gap, 131 = 24.75 or whatever)
Then if you have a fixed rod diameter, just draw out the centreline between the pins, work out the angle of the tan links to the cylinder and you can get your force. If you have a variety of rod diameters then draw a variety of diagrams and get a variance in force. If the rod is thicker than you've shown on the drawing then the force will be less.
Of course this ignores any compression of the rod or embedment of any teeth, but this should be relatively small in comparison to the jaw movement. Of course if your rod is too small then force is zero....
I can only assume you have a fully dimensioned drawing or can interrogate your drawing to discover all these dimensions.
Good luck and let us know how you worked it out.
My motto: Learn something new every day
Also: There's usually a good reason why everyone does it that way
RE: Gripping force
"On the human scale, the laws of Newtonian Physics are non-negotiable"
RE: Gripping force