Is there any way to do this in SW 2004?

[HeavenlySolid]

I must select the correct bore for a Pneumatic Rodless Cylinder for moving 840 pound of weight at crawling speed, low speed application.

Question:
How can I have SW2004 calculate the thrust force needed to move this 840 pound of weight approximately 50 inches?

If SW2004 cannot do this then, would any of you guys know of a website where I can download a Calculator that will easily allow me to do this type of calculations?


Thanks

 

[handleman]

You have not provided sufficient information to make such a calculation. Since you don't seem to care about acceleration the only thing you need to look at is friction, which you have not mentioned at all. Is this load sliding on concrete or riding on LM guides? As far as speed, it should be regulated by using a speed control (a throttle valve) on the exhaust side of the cylinder. Don't try to regulate the speed by getting a cylinder that is "just big enough". It will wear out too quickly.

 

[HeavenlySolid]

handleman:

You are right, sorry about that!!

Load will be riding on 1” Shaft self supported Linear Guides with open linear bearings. Acceleration will be same as deceleration.\

 

[CorBlimeyLimey]

SW is not a design calculator. You will have to do the math yourself or contact a "Pneumatic Rodless Cylinder" manufacture/supplier for their recommendations.

​

Helpful SW websites faq559-520​

How to find answers ... faq559-1091​

 

[HeavenlySolid]

CorBlimeyLimey:

Before I run out and contact a "Pneumatic Rodless Cylinder" manufacture/supplier for their recommendations, can't I just learn how to do the calculation myself with the help of a knowledgeable member of this forum? Don’t you think this will be much wiser than depending all the time in this manufacture/supplier?

 

[handleman]

Again, there is insufficient information to "calculate" an "exact size" for this application. You have also not specified pneumatic pressure. Operating conditions will make a difference as well. If you are operating this mechanism in a cleanroom you can probably assume that the bearings/bushings will stay clean and free-running. However, if this is for a coal mine you can be sure bushing performance will decrease significantly such that a smaller cylinder no longer has sufficient force to move your load. That being said, a simple Google search for "cylinder force calculator" yields more than a few calculators. Knowing nothing about your application, I would venture a guess that you should probably go with a cylinder that can provide 850 lb force at your system pressure. Here is a link to the first Google result mentioned above:

http://www.pneumaticsonline.com/Calc2.asp

and here is a link to a PDF with information about metering valves/speed controls.

http://www.automation4less.com/pdfs/as_3054.pdf

 

[rfus]

Have you ever created an FBD.

Do you have a statics book? Do you have a dynamics book?

F=uN
W=FD

 

[handleman]

Also, I'm not intending to be rude, but these are some very elementary questions you're asking, and very elementary details are not included in the question. Is there not someone experienced at your company overseeing this design? If so, I would recommend that your first line of questioning should be directed at him/her, especially if anyone's safety is dependent in any way on this design.

 

[HeavenlySolid]

Thanks guys for all your great responses.

If you excuse me now I will go ahead and enroll myself in the University of “Mechanical engineers, who know all the questions, and all the answers and all the formulas for calculating just about anything and everything, who cannot experiment, invent on their own play around with their own machines and do heavy duty mechanical trial an error or think out side the box and do not allow electrical engineers to ask silly questions about stuff they learned in second grade”.

 

[dogarila]

Hey, you need a cylinder strong enough to overcome the friction in the linear guides. That is the friction coefficient multiplied be normal load (which I guess is 840 lbsf). The friction coefficent should be in the linear guides catalog. It should be something like 0.04. The cylinder force is the air pressure multiplied by piston area. For example: a 1" dia cylinder at 90 psi whould give you about 70 lbsf (pi x 1 square / 4 x 90). I suspect your "calculated" cylinder would be quite small so you may use other criteria to select it. You regulate the speed using a flow control (as handleman said). I would use flow controls on both supply end exhaust ports.

Hope this helps.

 

[dogarila]

And one more thing. Whatever you calculate, increase the size of the cylinder diameter by 25% or so, as a safety factor. For instance if you calculate a dia of 0.46" do not select a 1/2" cylinder. Go to a 5/8" one.

 

[HeavenlySolid]

dogarila:

Thanks a lot. This is the humble aswer I was looking for, just enough to get me started.

 

[handleman]

As I said, my intention was not to be rude, condescending, or belittling in any way. I'm only four years out of university myself, and there's sure a lot of stuff I don't know. However, my first line of questioning is always directed toward those at my job who have many more years experience than I do. These people know best what I'm trying to accomplish because they do the same job as I do, design the same type of machines I do for the same operating conditions I do. They can look at the whole picture of what I'm trying to do because they're here with me. If you don't have any such people at your firm then I feel truly sorry for you because any online forum, even one this good, is a poor substitute for one-on-one mentoring. A forum can give you correct answers to the questions you ask. A mentor can give you the right solution for your overall situation.

 

[CorBlimeyLimey]

Question:
How can I have SW2004 calculate the thrust force needed to move this 840 pound of weight approximately 50 inches?

My answer: "SW is not a design calculator."
In other words, no, SW2004 cannot do that calc.

If SW2004 cannot do this then, would any of you guys know of a website where I can download a Calculator that will easily allow me to do this type of calculations?

My answer (in part) "...or contact a "Pneumatic Rodless Cylinder" manufacture/supplier for their recommendations"
A google for "Pneumatic Rodless Cylinder" returns many hits. The first of which is

http://www.tolomatic.com/index.cfm

It has a tab named "Product Resources" which in turn has a tab named "Software". A sizing calculator can be downloaded from there.

can't I just learn how to do the calculation myself with the help of a knowledgeable member of this forum?

Of course you can, but that was not requested in your OP ... to which I was replying.

​

Helpful SW websites faq559-520​

How to find answers ... faq559-1091​

 

[HeavenlySolid]

No hard feeling guys, thanks again for such great members on an awesome forum.

Have a good one!!!

 

[SolidAir]

HeavenlySolid,

Not to be rude myself but, maybe this is the wrong forum to ask how to do the calculation. There is another forum in eng-tips: "Mechanical Engineering and other topics" that may be able to help. Other than that, the Linear Guide manufacture may have calculations in their catalog and the Machinery's Handbook has friction calculations in it.

SA

 

[SnowCrash]

Remember if you want the system to perform a retraction as well, you will have to account for the smaller effective area of the back side of the piston due to the cylinder rod.
"That should help, he said, expansivley"

--
Hardie "Crashj" Johnson
SW 2005 SP 4.0 (reluctant to change)
Nvidia Quadro FX 1000
AMD Athalon 1.8 GHz 2 Gig RAM

 

[handleman]

Not with a "Pneumatic Rodless Cylinder".