Tag: reject

So Many Holes

Published on by Brian FarnoLeave a comment

I remember the book and movie about a young teenager who gets sent to a prison/ work camp that all they do is dig holes. Yeah, there’s a much deeper story line there and that isn’t the point of this blog. The point is, that movie is all I thought of when I encountered this customer’s nozzle solution. Their ejector nozzle on a recycling conveyor was using too much air and was too noisy.

Upon receiving the nozzle to do a free EXAIR Efficiency Lab, we were absolutely amazed at the level of care taken to make something like this. The nozzle was purpose built and definitely got the job done, it also drained their compressed air system at times and made a lot of noise while it did the work. So what did this nozzle look like, now keep in mind, this was not the customer’s design, it was a solution from the machine manufacturer.

For an idea, the customer nozzle was a 3″ overall length, and had a total of 162 holes in it. There were two inlets for 3/8″ push to connect tubing. The holes were very cleanly drilled and we used a discharge through orifice chart to estimate the consumption before testing. Operating pressure were tested at 80 psig inlet pressure.

Discharge through an orifice table.

Our estimations were taken from the table above. We used a pin gauge to determine the hole size and it came close to a 1/32″ diameter. With the table below we selected the 1.34 CFM per hole and used a 0.61 multiplier as the holes appeared to have crisp edges.

Estimation Calculation

Then, we went to our lab and tested. The volumetric flow came out to be measured at 130.71 SCFM. This reassured us that our level of estimation is correct. We then measured the noise level at 95.3 dBA from 3′ away. Lastly, we tested what could replace the nozzle and came up with a 3″ Super Air Knife with a .004″ thick shim installed. To reach this solution we actually tested in a similar setup to the customer’s for functionality as they sent us some of their material.

Now for the savings, since this customer was focused on air savings, that’s what we focused on. The 3″ Super Air Knife w/ .004″ thick shim installed utilizes 5.8 SCFM per inch of knife length when operated at 80 psig inlet pressure. So the consumption looks like below

That’s an astounding amount of air saved for each nozzle that is replaced on this line. The line has 4 nozzles that they want to immediately change out. For a single nozzle, the savings and simple ROI looks like the table below.

Air Savings / Simple ROI

That’s right, they will save 115.02 SCFM per minute of operation. These units operate for seconds at a time so the amount of actual savings is still to be determined after a time study. In videos shared, there was not many seconds out of a minute where one of the four nozzles was not activated. Once the final operation per minute is received we can rework our calculations and see how many hours of line operation it will take to pay back each knife purchase.

If you have any point of use blowoff or part ejection and even have a “nice looking” blowoff in place, don’t hesitate to reach out. These are still very different from our Engineered Solutions. We will help you as much as we can and provide test data, pictures, and even video of testing when possible.

Brian Farno
Application Engineer
BrianFarno@EXAIR.com
@EXAIR_BF

Light Duty Line Vac For Part Rejection

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Today I worked with a long standing customer that was interested in using the Line Vac technology to provide a method for part rejection.  The parts come out of a bin and travel to the next station for final assembly.  There is an accept/reject analysis system along the way, and it was decided that the Line Vac would offer an easy way to remove the part from the conveyor and transport it to a reject bin.

The parts are very small, with 0.093″ to 0.187″ OD and 0.178″ to 0.335″ lengths.  Part weights were 0.27 grams or less, so a very small and light weight item.  Maximum part processing was estimated at less than 6 parts per minute, so low speed and low transfer rates apply.  The final piece of information was the distance for conveyance, and here it was only a few inches up and then 4′ over to the reject bin.

Based on all the information about the parts, the process and the transfer distance, it was determined that the 3/4″ Light Duty Line Vac would be an ideal choice for the application. The unit is available as part of the  model 132075 Light Duty Line Vac Kit, which includes a Automatic Drain Filter Separator and a Pressure Regulator.  The Pressure Regulator is especially important in this application, as it will allow for pressure adjustment to provide the best performance while keeping the compressed air usage to a minimum.

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The EXAIR Family of Line Vacs

 

EXAIR manufactures 3 styles of Line Vac- Light Duty, Standard, and Heavy Duty with either smooth bore hose or NPT threaded ends.  They are offered in 4 types of materials- Aluminum, Type 303 and Type 316 Stainless Steel, and a hardened alloy construction. An important factor in material selection is the abrasiveness of the material to be conveyed.

To discuss your application and how an EXAIR Intelligent Compressed Air Product can help your process, feel free to contact EXAIR and myself or one of our Application Engineers can help you determine the best solution.

Brian Bergmann
Application Engineer

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How Much Force Does It Take?

Published on by Brian FarnoLeave a comment

In case you weren’t aware, the answer to “How much force does it take?” is always going to be, ALL OF IT.   At least that is what we generally think when trying to blow product off a conveyor belt or diverting parts into bin, etc. Speed and efficiency play a direct role in to what nozzle or blow off device you should use in order to get the job done and be able to repeat the process.

The question we are often asked by customers is, “How much force to I need to move this?”  That is a question that we cannot often answer without asking more questions.  The good part of this is, there is a formula to calculate just how much force you need to move an object.   A good video explaining friction is shown below.

In order to answer the question of how much force do I need, we really need to know all of the following:

Weight of the object
Distance from target
Is it on an incline or level
Distance needed to move
Then, the usually unknown variable, the coefficient of friction between the target and what it is sitting on.

Often times it is the thought process of, my target weighs 5 pounds, I need 5 pounds of force in order to move it from the center of this conveyor belt to the edge, this is not the case.   If you wanted to lift the object over a break between two conveyors then you would need slightly more than 5 pounds in order to ensure you are lifting the front edge of the unit high enough to meet the other conveyor.

Whether you know all of the variables or only a few, if you need to get an object moved and you want to try using compressed air to do so, give us a call and we will help you find the best engineered solution for your application.  Then, we’ll back all stock products with a 30 day guarantee if you don’t like how the system performs – but rest assured, we get it right almost every time.

30 Day Guarantee
The EXAIR 30 Day Guarantee

Brian Farno
Application Engineer Manager
BrianFarno@EXAIR.com
@EXAIR_BF

Friction Measurement

Published on by johnball2014Leave a comment

I had a customer wanting to reject a container off a conveyor belt.  The container held fruit, and when an optic detected a reject, they wanted to operate a solenoid to have a nozzle blow the container into the reject bin.  They had a range of containers that went from 6 oz. (170 grams) to 5 lbs (2,270 grams).  He wanted me to suggest one nozzle for all sizes, as they would automatically regulate the pressure for the full range of container sizes.  In looking at the largest size, this container will need the most force to remove.  The two factors that affects the force in this application is weight and friction.  When it comes to friction, it is generally an unknown for customers.  Here are a couple of things to help in determining the friction in your application.

Strawberry Delight
Strawberry Delight

Friction is a dimensionless number that represents the resistance created between two surfaces.  We have two types; static friction, ms, and kinetic friction, mk.  Static friction is the maximum amount of resistance before the object begins to slide.  Kinetic friction is the amount of resistance that is created when the object is sliding.  So, Static friction is always greater than kinetic friction, ms > mk.  For this application, we will have the air nozzle shoot horizontally to hit the target.  This is the most common and efficient way.

Let’s take a look our customer’s application.  We have a system to reject a non-conforming part with air.  The conveyor is a urethane belt.  The container is plastic.  We need to determine the correct nozzle to reject the 5 lb (2,270 gram) container.

Being that the conveyor belt is only 12” (30.5 cm) wide, we can determine that if we get the part moving, it will continue off the belt and into the reject bin.  The equation for the maximum amount of force required to move the container is Fs = ms * W(Equation 1).

Fs – Static Force – lbs (grams)

ms  – Static Friction

W – Weight lbs (grams)

One way to determine the amount of force is to use a spring scale.  The spring scale should have a maximum indicator to help tell you the maximum amount of force.  You will have to attach the scale to the container on the conveyor belt. Static friction is the resistance between two surfaces; so, you will have to use the same conditions as required for the operation.  Keep the scale parallel to the conveyor.  While slowly pulling on the scale, watch the dial.  Once the part begins to move, record the weight.  For the exercise above, it showed 1.82 lbs (826 grams) of force to move the 5 lb (2,270 gram) object.

Another way would be to determine the static friction, ms.  Static friction can be found by the angle at which an object starts to move.  By placing the container on a section of supported urethane conveyor belt and lifting one end of the conveyor belt until the object starts to slide, you can measure the angle or the height of the lift.  As an example, we take 3 foot (0.9 meter) of supported urethane conveyor belt and we lifted one end to a height of 1 foot (0.3 meters) before the 5 lb (2,270 gram) container moved.  To determine static friction, it is the tangent of the angle that you lifted, ms = tan(B) (Equation 2 below).  In this example, B = 20o.  Therefore Equation 2 gives us, ms = tan(20o) = 0.364.  If we plug this into Equation 1, we get the following:

Imperial Units                                                    SI Units

Fs = ms * W                                                         Fs = ms * W

= 0.364 * 5 lbs                                                    = 0.364 * 2,270 grams

= 1.82 lbs of force                                               = 826 grams of force
Now that we have the static force, we want to be slightly higher than that.  In looking at the force requirements that are in the EXAIR catalog, it shows that a model 1104 nozzle has a 1.9 lb (850 grams) of force.  This is at a 12” (30.5 cm) distance with a pressure of 80 psig (5.5 bar).  This nozzle will be able to slide the largest containers into a reject bin. With pressure manipulation, the customer can also use this same nozzle for the smaller containers.  If you have any applications that need products to be moved, you can always contact the application engineers at EXAIR to help you with a solution.

Variety of Nozzles
Variety of Nozzles

John Ball
Application Engineer
Email: johnball@exair.com
Twitter: @EXAIR_jb

 

Image courtesy of Chobist, Creative Commons License