The magic behind bowl feed manufacturing

Thursday July 14, 2016 at 4:44pm
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Part 1 – Range of products and assessment of suitability.

One of the joys of the sector of engineering we work in is the variety. A major part of the appeal and interest in our business is its one-off nature. The huge variety of products that we are asked to consider for bowl feeding solutions is endless. The range of sizes is huge and the complexity of the product can be vastly different.

Not all components can be sorted using a vibratory feeder; some may not separate, or worse, lock together during vibration. Others do not have features that would allow for orientation or differentiation.

It perhaps seems obvious to say, but the first stage in any feeding solution is an assessment of suitability for vibratory sorting. When considering this a number of factors are important…

• Do the parts easily separate.
• Are there sufficient features to allow for orientating.
• Is the part stable enough to transport along tooling.
• Does the product have sufficient weight to allow for orientation.
• Is there dimensional differences to allow for sorting.
• Are the physical sizes of the component suitable for vibratory feeding.
• Etc…..

The best approach, if you have sufficient quantity of components is to run them in a bowlfeeder. You will see from this how the components behave and interact with each other and you should see if there is a particular bias to the orientation of the component.

After the initial considerations regarding suitability are done it is then time to begin understanding the specific requirements for the project…

• Required orientation of the product.
• Feed rate or output for the feeder.
• Quantity of product required in the feeder.
• Any special noise reduction requirements.
• What physical space is available for the unit.
• How are the components used after exiting from the feeder.
• Etc….

Now comes the skill, or for some, the art. The task ahead is to visualise the method to be used for sorting, orientating and manipulating the product. Last time I checked there was no college course or degree qualification in bowl feeder tooling. Experience is the answer and years of it. Over time our bowl feed engineers have seen many different parts to feed and this variety always forms the foundation for the feeding system. By considering how similar parts feed and react they can visualise how to manufacture tooling to suit this product.

Production and manufacture of a feeder solution is a little different to most engineering applications that tend to be designed and manufactured. A bowl feeder is more a development of a concept, which usually has no formal design completed. This often evolves and ‘develops’ as it is manufactured with tooling being changed, tweaked or modified to address specific issues that may arise.

There is a further question to ask when formulating a concept for a system, and that is related to the style of feeder to be used. This is often driven by either the environmental requirements for the equipment or by the sorting and orientating method chosen for the parts.

Some common bowl types to consider….

• Conical
• Stepped
• Cylindrical or parallel
• Cast aluminium
• Stainless steel fabrication

Each has their merits and distinct advantages for certain solutions and deciding on this early on will ensure the correct solution is costed.

Part 2 – Manufacturing the feeder.

During this episode I will consider the manufacture of the tooling, the common practices used and highlight some pitfalls that are always prone to trip us up when we least need it.

So the stage is set. We understand the style of feeder we are creating and we have a clear instruction of the specific product requirements.

It is far too easy to try to concentrate on all aspects of the unit in one go, but in the experience of our engineers it is much more effective to mentally break the bowl down into stages and concentrate on a stage at a time before bringing all the elements together.

So for example….

• Consider wipers to thin the quantity of parts, to make orientation more effective.
• Manufacture some tooling to orientate the components.
• Include a stage where the wrongly orientated parts are discarded.
• Provide some control to ensure that the orientation of product is maintained.
• Review the quantity of correctly orientated parts you are getting and install tooling to increase this when required.
• Consider the effects of discarded product falling back down the bowl on correctly orientated parts.
• Etc…..

Let us assume for this example that we are using a cast aluminium, stepped bowl feeder as the basis for the system. As standard we have a range of sizes cast to our patterns, the various sizes cover a wide range of application and the size of bowl that is chosen is really dependent upon the component dimensions to be sorted.

Onto this base casting our engineers will begin to construct, manufacture and attach numerous tooling features considering the stages that were highlighted earlier.

This is another area where the skill and the art of the engineer is demonstrated. They use many different techniques, from metal forming and rolling to welding and conventional machining. It is easy to believe that we are creating a sculpture or a piece of modern art when you see some of the finished systems.

Over a number of hours the tooling begins to take shape, the parts are continuously tested in the bowl to verify that the tooling design is perfect. Although it is not our preferred solution, we often need to incorporate ‘air jets’ to control, sort or discard components along the way, these will get carefully mounted through the side wall of the casting and the final position of these is usually critical.

Consideration is given along the way to a number of factors that would potentially affect the efficiency of the feeder…

• Debris from the parts, if not removed or contained this will 
degrade the feeding efficiency as it builds up. It is better to ensure that debris is not present but in cases where this is not possible we can install traps or gates to allow for removal.
• Component tolerances; In an ideal world every component will be identical, we unfortunately don’t live in an ideal world so by considering a range of parts we can make an assessment on the tolerance band and apply this to clearance on tooling features.
• Inconsistency; This is a major factor in the performance of every feeder and automation system, these systems rely on having a good level of consistency within the product, areas of flash or other manufacturing defects often result in ‘jams’ or incorrectly orientated product reaching the next stage.
• Sometimes we are faced with product that will tangle or lock together either during the feeding process or prior to loading to the feeder. If these cannot be separated then a judgment will need to be made regarding clear-out and separation, as it is unlikely that the tooling can be made to accommodate this.

One of the final focus areas of the feeder both prior and after the coating is applied is the feed rate. Probably the second most important factor for any feeder after the part orientation is the rate at which the product is delivered from the bowl.

The feed rate of any feeder can often be a battle and a balancing act. The engineer will work towards ensuring that as many ‘good’ parts are retained on the tooling to allow the highest possible feed rate at an optimum frequency of vibration. It is often the case that additional tooling is required to perform some pre-selection or manipulation of the part to achieve a higher percentage of ‘good’ parts.

The internal surfaces of each and every bowl are coated in order to enhance performance of the feeding and extend the service life. These coatings come in a multitude of different options, from bonded rubberised sheet to a spray polyurethane coating. The coating is usually considered to be that final stage of the manufacturing process and any work performed following is kept to a minimum in order to preserve the coating.

Consideration will also be given during the manufacture of the tooling to the equipment that the bowl will deliver parts onto. In many case we also provide the onward equipment. Vibratory linear feeders, belt conveyors, gravity tooling or blow tubes all require subtly different tooling techniques at the out-feed point of the bowl.

As this section draws to a close it would be fair to say that the skill and experience of the engineer has been used throughout. The knowledge of how products react and behave, the experience of how similar parts may have been handled previously and the manufacturing skill of a craftsman all go in to producing the highest possible quality of feeder system for the client.

Part 3 – Integration and effective use for the feeder.

Often the feeder solution is the first stage of any automated process. It is usually pivotal to the success or failure of the onward process. A poor feeder or a poorly integrated feeder can render the whole automated process a failure as a system without a consistent delivery of components is totally in efficient.

The correct mounting, integration and use of the feeder is almost as important as the tooling within the feeder, a wrongly mounted feeder for instance will perform poorly and will more often than not fail to feed correctly.

Once again, by following some simple considerations the whole system can be a success….

• Ensure the feeder is mounted on a strong robust frame, remember this unit is vibrating constantly and any loss of this vibration or transfer into the frame work will reduce the vibration within the bowl where it’s needed.
• Do not over-feed the bowl, if the onward linear feeder or conveyor is stopped the bowl should also stop in many cases.
• If a single part is required for each cycle, consider the effects of picking this single parts on the queue and then consider escapements.
• It is not recommended that parts are picked from vibrating tooling, so ensure where possible to feed the product onto static tooling for picking.
• Physical gaps must be introduced between items of vibrating tooling to ensure that these can freely vibrate without clashing with its mating part.

In many environments these days there are reduced noise level requirements, and unfortunately by nature of a vibratory feeder the vibrating parts generally make them noisy. Thank fully that doesn’t mean they have to stay noisy and with some careful design of acoustic enclosure a more acceptable noise level is easily achievable.

In order to achieve the best results from your new feeder system it is a good idea to spend some time at the outset considering the most suitable method for re-filling the bowl. This is important for various reasons. The function and the efficiency of the feeder can be significantly affected by too many or too few parts; it is easy to believe that the more parts in the feeder the longer they will last.

Accessibility to the bowl is an essential consideration during the design of both the system and the feeder. The feeder can be manufactured in either a clockwise or counter clockwise orientation and either may or may not be suitable for the overall system.

If the feeder is intended to be within the guarded area then ease of re-loading could well be compromised and attention needs to be given to providing a solution for this.

When a high feed rate or the quantity of product within the bowl dramatically affects the efficiency, a hopper feed should be reviewed for a solution. With a hopper feed, for which there are numerous types, the level of product in the bowl is controlled and maintained by integration of sensing techniques that allow for replenishment automatically from the hopper.

Cleanliness and maintenance.

Once the investment in your equipment is complete you then need to concentrate on ensuring the unit delivers efficiency for the longest period. Some simple steps can be followed to achieve reliability:

• Regular cleaning of the internal coating to remove residue left over from the product.
• Where compressed air jets are used, ensure clean dry is supplied as moisture build up in the feeder will impact performance.
• If the product is delivered with a film of oil, this will affect the efficiency of the feeder, sometimes it will be negligible but often this oil will build up in the feeder over time.
• The condition of the internal coating of the feeder will deteriorate over time, the length of time can vary considerably depending upon the components features and weight. It should be remembered though that for a relatively low investment this coating can be refurbished, returning the feeder to its original state.
• There is little to no maintenance requirement on a good feeder, there are no moving parts and although under constant vibration the feeder, its drive and tooling should all function without intervention.

As we draw to a close on this mini-series I am hopeful that some of the insights that I have shared will be useful and in some cases informative.

I would certainly like to believe that the skill of a bowl feed engineer is magical but the truth is that experience and skill are the foundations of this profession, experience that we are sure will help to give solutions to many manufacturers in the future.

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Unit 7 Wycliffe Industrial Park,
LE17 4HG. United Kingdom