23. April 2011 10:33
Linear vibratory feeders are used for feeding of components to various Machines. The actuation / Vibrations take place by electromagnets. The Linear vibratory feeder is a device that converts Electro-magnetically produced vibrations into mechanical vibrations. These mechanical vibrations are utilised for movement of the workpiece along the track or tray.
Magnetic coil, which is fixed to the counter mass is energised with supply of electric current, producing a force, which in turn attracts and releases the magnet armature. As the magnet is rigidly fixed to the top spring holder, the vibrations are transferred to the spiral-conveying track of the bowl. Depending on the angle of gradient of the leaf springs and lead angle of the helix of conveying track, the workpieces move with every vibration above the track in small jumps.
During one period of 50 cycle AC mains the magnet attains its maximum attraction twice since the magnetic force is not dependent on the direction of current flow. Thus the magnet produces a vibrating frequency of 100 cycles, which is necessary for smooth & reliable movement of small & light weight workpieces. Some vibratory Feeder manufacturers use 50 Cycles / HALF WAVE Bowl Feeders too.
Thus a linear vibratory feeder consists of a tray or track mounted on a base by inclined leaf springs or packs of springs. The springs constrain the track / tray so that, as it travels vertically. As the components move up the track. One to two electromagnets, mounted on the lower counter weight / heavy base, generates the force to drive the track / tray feeder. The counter weight rests on rubber feet, which serve to isolate the vibration of the vibratory feeder.
The components are conveyed in the track / tray by one of two modes: sliding or hopping. In the sliding mode, motion is produced from friction between the part and the track / tray. As the track / tray rises and turns, the friction between the track and the part pushes the part forward with the track. When the track descends and turns backward, the force of friction is smaller and the part slides forward relative to the track / tray. In the hopping mode, the part moves forward with the track / tray as it rises and turns, but it experiences freefall when the track / tray's downward acceleration exceeds the acceleration of gravity. During free-fall, forward motion is created as the track / tray moves backward relative to the part.
14. April 2011 07:33
If you have an old vibratory feeder, which is not working properly, there is a list of nine basic points which one should check before calling for a service person. In fact, checking this on a regular basis would help you improve and maintain the performance of your old vibratory feeder. Each of these points is explained in detail in different places on this blog. However, you can find the complete comprehensive list with the links for each of these points below.
- Improving performance of an old vibratory feeder – Isolating Vibrations
- Improving performance of an old vibratory feeder – Gap Setting
- Improving performance of an old vibratory feeder – Tightening of Screws
- Improving performance of an old vibratory feeder – Changing Springs
- Improving performance of an old vibratory feeder – Tuning of the bowl feeder
- Improving performance of an old vibratory feeder – Cleaning the bowl
- Improving performance of an old vibratory feeder – Checking weldments
- Improving performance of an old vibratory feeder – Cleaning the bowl bottom
- Improving performance of an old vibratory feeder – Checking cracks in the bowl
7. April 2011 09:12
In most of the cases, it is better to have feeder bowls coated. Coatings can be either polyurethane spray coating, pasting of sheets on the bowl surface, teflon coating etc. The advantages and disadvantages of each of these are given below –
- Polyurethane Spray Coating - The advantages are firstly, in case of metallic components, the noise level can be drastically reduced by eliminating the metal to metal contact between the metallic bowl surface and the components. Another major problem faced by customers is of feeding oily components. Oily components reduce / eliminate the friction between the components and the bowl track. As vibratory feeders work on the principle of friction, this results in the components slipping and hence they are not able to feed properly. Proper type of coating can eliminate this. It is better to have a rough coating in case of oily components while in case of dry components, it is beneficial to have smooth coating. This improves the friction between the components and bowl, resulting in better movement of parts forward. In case of polyurethane spray coating, smooth as per as rough finish is possible, depending upon type of parts (oily or clean) which are to be fed in that bowl. Further FDA approved polyurethane coatings are also available.
- Pasted Coating – In this type, synthetic or polyurethane sheets are pasted to the bowl surface to act as lining. However, these have many disadvantages. First and foremost, in case the adhesion is not proper at any place, air bubbles get created and the whole sheet gets removed. Even if any adhesive is used, it gets removed in cases where there is oily residue on the components. This coating is applied as a bonded sheet. As a bowl lining, it is used primarily to reduce marking of plastic parts. It also provides impact protection from heavy parts.
- Teflon Coating – This can be pretty long lasting for certain parts however, they keep getting removed and the bowl will have to be recoated after some ime. This coating is sprayed on primed metal and baked at 800 degrees Fahrenheit. As a bowl lining, Teflon is used primarily to reduce friction of sticky parts and assist the feed characteristics. Teflon also very non-reactive and can be used where reactive or corrosive chemicals are present. In chemistry, polytetrafluoroethylene (PTFE) is a synthetic fluoropolymer of tetrafluoroethylene which finds numerous applications.
- Rubber coating – In this type, the bowl is coated with galvanized rubber. This is a very crude type of coating. It does not last long and is very rough, resulting in the parts not being fed properly.
In conclusion, the best solution is to go with polyurethane spray coatings which can give you either a rough or smooth finish and also are very long lasting.