B Vacuum surface area balance and force

[squeak83]

Evening all,

im not exactly sure where this lies in the prefix, so apologies if it is higher than that.

I am trying to figure out a device that uses fan vacuum and suction seal, and a little bit of ground effect with a fan to adhere to objects, I'm by no means a learned man, and i was wondering at a base principal, if you had a flat plate with a sealed vacuum against a surface, ( i know there are things available, on market but i want to get my head around the core principle )

Would increasing the inner surface area with a dimpled, pins or other geometry increase the surface area that is seen to the pressure. thereby lowering it?

likewise would increasing the outer surface area shown to atmosphere increase the force instead?

I saw the magdebug hemispheres and was thinking if the outer wall was larger in surface area than the inside would that mean more force applied,

i know this may be a simple topic , but thinking about it is driving me insane.

thank you for your time

Squeak​

​

 

[berkeman]

Welcome to PF.

I am trying to figure out a device that uses fan vacuum and suction seal, and a little bit of ground effect with a fan to adhere to objects

Is there a reason you want to use a fan to create the lower pressure? Can you say more about the application? What makes it so that regular mechanical suction cups won't work for your application?

https://www.doba.com/product/lPqpVv...ow-replacement-110lbs-load-capacityblack.html

 

[squeak83]

Welcome to PF.


Is there a reason you want to use a fan to create the lower pressure? Can you say more about the application? What makes it so that regular mechanical suction cups won't work for your application?

View attachment 349911

https://www.doba.com/product/lPqpVv...ow-replacement-110lbs-load-capacityblack.html

The surface can be contaminated and irregular and have things like weld beads and bolts, and the seal basically needs to be able to move and conform,

 

[squeak83]

The surface can be contaminated and irregular and have things like weld beads and bolts, and the seal basically needs to be able to move and conform, i was just trying to get my head around the actual surface area physics a bit like this

 

[jrmichler]

I once needed a machine to pick up and transport pieces of singleface. Singleface is corrugated cardboard with only one face, as shown in the lower sketch below.

The machine needed to pick it up by the top (rough) face, carry it to a second location, then drop it. We used a vacuum conveyor. The conveyor had a smooth conveyor belt with holes, and a vacuum plenum under (actually above) the conveyor belt. The vacuum was provided by a 1/2 hp blower. The system air flow rate was determined by the singleface leakage area, the vacuum hole size and spacing, the ducting, and the blower fan curve.

The key to designing a system for vacuum holding with a leaky sealing surface is to make the vacuum area as large as possible, design the vacuum system air flow resistance to be smaller than the leakage air flow resistance, and properly size the vacuum source.

The calculations start by determining how much vacuum force you need. The vacuum force needed is the force between your object and the surface. If the object needs to roll across the ceiling, the necessary force is the weight of the object plus a safety factor. If the object needs to stick to a wall, you need the coefficient of friction between the object and the wall.

Then you need the vacuum area - the area subject to vacuum that pulls it to the surface. The amount of vacuum is then the necessary force divided by the vacuum area. Low vacuums are normally specified in inches of water, higher vacuums are specified in inches of mercury.

Then you need to estimate or measure the leakage area. Knowing the vacuum level, and the leakage area, the vacuum flow rate can be estimated. At that point, you are ready to start looking for a vacuum source.

i know this may be a simple topic , but thinking about it is driving me insane.

Simple to an experienced engineer with experience in air flow and vacuum systems, not so simple to everybody else. Take it one step at a time, and finish each step before even thinking about the next step. We can help you get through it.