Author Topic: Useful info from Bimba for using pneumatics  (Read 65 times)

Louis L

  • Administrator
  • Hero Member
  • *****
  • Posts: 561
Useful info from Bimba for using pneumatics
« on: January 11, 2019, 01:43:06 PM »
I pulled two Technical Tips from the Bimba web site ( Bimba is a sponsor of FIRST. These are useful for anyone starting out with using pneumatics.

(1) How to Determine the Right-sized Cylinder for Your Job

"Specifying the right cylinder for the right job results in better and longer cylinder performance. And that means lower overall operating costs. Proper cylinder size selection begins by calculating 1) the weight of the load, 2) the required velocity, and 3) the air pressure used. Letís take a closer look at each of these three factors.
Weight of the load:
This is set by the machine design. In order to move the load, youíll obviously need a cylinder that pro-vides force
greater than the load. We recommend allowing an additional factor of 25% force over the load to compensate for friction.
Velocity:Velocity is also usually set by machine design, but thereís usually some latitude within a range. Low speeds (up to 4 in/sec) require 25% more force than the load, moderate speeds (4 to 16 in/sec) about 50% more and high speeds (greater than 16 in/sec) about twice as much.
Air pressure:You need consistent air flow at the minimum effective pressure to maintain the desired velocity. Operating the cylinder at too high a pressure accelerates seal wear and creates stress on the cylinder. Inconsistent pressure can cause system malfunction or failure.

Next youíll need to determine bore size. Letís look at an example assuming a maximum load of 100 lbs, a minimum velocity of 8 in/sec and a minimum pressure of 60 psi. The velocity is moderate, but the force should be about 50% greater than the load, or 150 lbs. Dividing the force (150) by the pressure (60) gives you a power factor of 2.5. A 2Ē bore cylinder, with a power factor of 3.1, provides the needed force.
Youíll also have to consider stroke length, spring force and overall dimensions of the space. But this is only the start."

(2) Power Factors
Rather than copying and pasting the contents of the table in their Technical Tips, I'm attaching the entire PDF file. Please refer to its contents.
  • For our uses, look at the first set of columns under "ORIGINAL LINE".
  • The Bore Size is the left-most column. This is the diameter of the cylinder bore in inches.
  • The Power Factor is a multiplier you use to determine what you need. Do the math and you'll see that it's really just the surface area of the bore in square inches. Extend and Retract are asymmetric because the piston rod takes up space and reduces the surface area of the bore.
  • We'll most likely be operating at 60 PSI so use the FORCE(#) values in that column. Do more math and you'll see that this is just 60 times the POWER FACTOR. If we end up using less than 60 PSI, it's easy to calculate the new numbers.
The numbers in this table apply not just to Bimba. We have and will order from other manufacturers as well and all of this still applies. As the PDF notes, this is just for reference but it'll get you close. The rest is up to you :)