A vibratory bowl feeder is tooled for a particular component or a family of components. It gets the parts or components being fed in the right or correct orientation. To achieve this, the path on which the components or parts travel is made in such a way that only the right component goes forward while the rest which are wrongly oriented fall down and are recirculated. If possible, the orientation of the wrongly oriented components is changed into the correct way. This achieves a two fold effect, first of all, the wrong component does not come forward and secondly, if it comes forward, it is in the right direction. To achieve all this, bowl toolers use a variety of techniques like creating obstructions in the path of the components as they move up or down, create barriers etc. These are called wipers, bowl tooling, change over tooling etc. Another way of achieving this is the use of a small jet of air. The air flow helps in either eliminating the wrong component or else turning them around. Air jets are also used for improving the feed rate or speed of the vibratory feeder. For a high speed bowl feeder, an air jet can increase the speed of the vibratory feeder tremendously, upto even 25% with a single air jet. Air jets are also used for ensuring that the components flow in a single line and do not override one another. However, the use of a lot of air jets leads to the question, whether it is necessary to use air jets for bowl tooling and increasing the speed? Air, that too continous air jets are costly to say the least and increase the running cost of the bowl feeder tremendously. Hence, this is a very pertinent question and should be answered in detail.

First let us take the question of using air jet for component or part orientation. Is it really required? The answer is not in black and white i.e. yes or no. Its maybe, some components do require the use of air for orientation, mainly plastic ones which do not have any particular profile to hold on or there is no difference in the weight of any particular side. In such a case, there is no choice but to use air for achieving the required orientation. However, in case of most parts, air jets can be avoided for doing the orientation due to their huge running cost. Then why do bowl toolers use air for orienting even the easy parts like caps? The simple answer is to save them the tooling time and reduce their work! From a customer's point of view, he should ask at the order placement stage whether the bowl will be having air jets for orientation. He should inquire whether it is really required and if so, why. Is orientation possible without the of air? Why not? Asking such questions will make the bowl tooler re-evaluate the planned bowl tooling and if possible, achieve the orientation without the use of air.

Second use of air is for increasing the speed of a vibratory feeder. Air jet is used first to eliminate the dead spots of a vibratory feeder and for further improving the flow. Dead spot is the part of the bowl whether the components do not move forward. The reason might be due to the bowl being unwieldy or not properly tuned. This is something which can be easily avoided by making the bowl properly and tuning it. Using a cast aluminium bowl eliminates a lot of problems of the bowl becoming unwieldy or not properly tuned. Hence, insisting on a cast alumiunium bowl with polyurethane coating can help reduce the dead spots and result in the saving on the air jets being used to increase the speed of the bowl feeder. In case the speed required is quite high which cannot be possibly be achieved through a vibratory feeder, then the use of air jets would be unavoidable. Hence, it is always advisable to speak to the bowl feeder company and ask the reasons for the use of air. If they are unsatisfactory, then better to look for another company! Of course, I need not mention at this juncture that Elscint avoids the use of air for orientation and improving the feed rate unless it is utmost necessary.

There are various types of controllers for vibratory feeders. Each has its own utility as well as its own advantages and disadvantages. Knowing the features as well as advantages and disadvantages of each of them can help one take the right decision about choosing the correct controller -

1. Varriac / Dimmerstat / variable Transformer – This varies the voltage. It produces flux and therefore, reduces the voltage. It is the most simple controller available for a vibratory feeder. If a diode is used, it can even be used for half wave vibrators. The disadvantage of this is that there is no soft start provision available and hence it starts with a jerk, which can damage the vibrator coils. Another problem is that any change in the input voltage supply results in a corresponding change in the output supply. Even a change in the frequency or load on the vibrator has an effect on the working of the vibratory feeder. This is a very low cost option.  
2. Electronic Voltage Controllers – These work on the principle of chopping of the sine wave to ensure control over the voltage. This is superior to the varriac / dimmerstat as soft start and soft stop can be provided in the circuit and some amount of voltage fluctuation too can be taken care of. However, the disadvantage is that any change in frequency has an effect on the working of the vibratory feeder. Another disadvantage is that any change in the load on the vibrator has an effect of the working of the vibratory feeder. Additionally, overload cut-off provision can be provided. This is quite important as in case the current drawn exceeds set limit, the power supply to the vibrator is switched off automatically, thus saving the vibrator coils from getting burnt. The cost is quite reasonable and hence this type of controller is usually provided with majority of vibratory feeders.
3. Analog Frequency Controllers – These can vary the voltage and to some extent the frequency. Therefore, one can get constant voltage and constant frequency, thereby improving the functioning of the vibratory feeder. However, the problem of load remains whereby any change in the load on the vibratory feeder has an effect on its performance. The cost is more than that of a electronic controller.
4. Digital Frequency Controller – In addition to the above i.e. providing constant voltage and constant frequency, it can vary the frequency in order to find out the optimum frequency at which the vibratory feeder works best. Thus the time spent in manual tuning of the vibratory feeder can be eliminated as this can be done with the help of the Digital Frequency Controller. The cost of this type of controller is quite high.
5. Auto-Tuning with Digital Frequency Controller – This helps in finding the optimum frequency at which the vibratory feeder works best automatically, further reducing the manual error and time. However, this further increases the cost.
6. Feedback Control – In case of a Digital Frequency Controller, feedback control can be added whereby an accelerometer is provided. This not only improves the speed of the vibrator but acts as a load cell wherein it provides feedback to the controller about the load on the vibrator and the controller can adjust itself automatically. This can further improve the performance of the vibratory feeder. The price of an accelerometer is added to that of the digital frequency controller, making it more costly.
7. Double Speedy - In all the above Models, double speedy can be incorporated i.e. two potentiometers are given whereby one is used for course adjustment and one for fine adjustment. These are of tremendous use in case of weighing and batching systems.

Electricity costs are increasing day by day. In this scenario, it is the duty of every person to look for ways to reduce electricity / power costs in industry. Vibratory feeders are one area where one can look for power savings and subsequent cost reductions. In many cases, costs can be reduced by as much as 40% to 60% if full wave AC operated vibratory feeders are used instead of conventional DC / half wave feeders.

While full wave vibratory feeders i.e. with electromagnetic AC drives have been available for a long time, only a few manufacturers manufacture these type of vibratory feeders.  However, as energy costs have started to increase exponentially and energy sources are scarce in most countries, companies have began to realize that the electromagnetic AC drive (full wave) vibratory feeders vibratory feeders can offer a significant cost savings in power consumption while also improving the performance of the vibratory feeders.

The conventional DC operated / half wave electromagnetic vibratory feeders operate with an inefficient attract release system. A spring mounted moving mass is alternately attracted by a rectified pulsating direct current electromagnet (requiring a highly power consuming rectifier) and returns to its original position solely by the springs.

The full wave AC operated, variable speed electromagnetic drive system, on the other hand, incorporates a magnet (part of a spring mounted moving mass). The poles of the magnet are intermeshed with those of an electromagnet, which is powered directly by an alternating current line. This results in the spring-mounted moving mass being both attracted and repelled by the full wave / AC electromagnet equally on each half of the AC cycle.

The poles of the magnet are intermeshed in the air gaps of the AC electromagnet. The polarity of the magnet is fixed, while the polarity of the electromagnet alternates at line frequency. The electromagnet polarity is shown as it exists on one side of the AC sine wave. Both poles of the magnet are attracted toward the unlike electromagnet poles while being repelled in the same direction by the like poles. Thus, four forces are acting together to drive the armature and moving mass in the same direction.

This action has the effect of progressively closing the magnetizing circuit through the electromagnet core, providing a progressively increasing magnetizing force upon the magnet. The demagnetizing force is very minor, since the action described also has the effect of progressively opening the demagnetizing circuit.

On the opposite side of the sine wave, the polarities of the electromagnet are reversed. The armature is driven in the opposite direction, and a net magnetizing force once again acts on the magnet. A predominant magnetizing force always works upon the magnet, which prevents it from losing its strength.

Advantages of Full Wave / AC Drive Feeders

1. Highly Accurate - Since the amplitude of the vibrator feeder’s vibration depends directly upon the forces applied at the poles, and since these forces depend directly upon the applied AC voltage, a simple variation of the AC voltage from zero to 100% results in a corresponding amplitude variation from zero to 100%. With a half wave or DC vibratory feeder, a 10% increase in voltage might result in a 40% increase in feed; with a full wave or AC drive feeder, a 10% increase in voltage results in a 10% increase in feed. This level of accuracy makes the feeding much easier to control.

2. No Rectifier required – Full wave / AC vibrators do not require a rectifier, which means the vibrators consume less power resulting in huge energy savings.  (upto 60%)

3. Lower Maintenance – Full wave / AC Vibrators require less maintenance as the vibrations are smooth and not jerky, thus resulting in lesser breakages.

4. Smoother Vibrations – The vibrations are smooth and not jerky, hence are most suitable for fragile and light weight components.

Though there are tremendous advantages like increased feed accuracy, energy savings and lower maintenance requirements, there are no disadvantages or trade-offs in speed or capacity. The full wave drive feeders can handle light as well as bulky and heavy components at high speeds.

However, while the full wave / AC drive units provide increased feed accuracy, energy savings and lower maintenance requirements, there are no disadvantages or trade-offs in speed or capacity. The full wave / AC drive feeders can handle light as well as bulky and heavy components at high speeds.

Energy / power costs will continue to rise in the future as demand threatens to exceed the available supply. Fortunately, making even minor changes to a materials handling operation can significantly reduce power consumption. In many cases, using full wave or AC operated, variable-speed electromagnetic feeders instead of DC drive attract release feeders can help manufacturers save energy while also increase feed accuracy.

Cost Savings

Putting down the savings in monetary terms, a full wave / AC powered vibratory bowl feeder with a rating of 780 VA (having diameter 600 mm to 650 mm), results in power consumption of 3.6 units per eight hours while the equivalent half wave / DC operated vibratory feeder would result in power consumption of  about 9 units per eight hours. The savings can thus be monetized at 5.4 units per eight hours i.e. 146 units per month. At the prevailing rate of Rs. 8 (16 cents per unit), it results in savings of Rs. 1168 (US $ 23) per month by just running just one shift per month. 

Changeover to Full Wave vibratory feeders

Looking at the above cost savings, does it make sense to dump your present half wave vibratory feeder in favour of a full wave / AC operated one? It sure does. You can recover the price of a new full wave / AC operated vibratory feeder very soon!