MATERIAL HANDLING

Bases on Design features and operational characteristics, material handling equipment may be broadly classified as:

Hoisting Equipment’s:

It constitute a group of equipment which are employed mainly for lifting or lowering of unit load or piece goods in batches. This group of equipment’s can be further sub classified into:

1. Pure Hoisting Machineries

• Jack
• Winches
• Hand Hoists
• Pulley Blocks

2. Cranes

• EOT Crane
• Jib Crane
• Cantilever Crane

3. Elevators

• Lift
• Bucket Elevators

Conveying Equipment’s:

It comprises of a number of equipment which are employed for handling principally bulk load (occasionally piece goods or unit load may also be handled) in continuous flow. Such machines do not have separate lifting or lowering gear. This group of equipment also can have further sub classifications as:

1. Belt Conveyor

2. Hydraulic Conveyor

3. Pneumatic Conveyor

4. Apron Conveyor

5. Screw Conveyor

6. Flight Conveyor

Surface/ Overhead Equipment’s:

These are the group of equipment’s which are employed for handling unit load or bulk load in batches on a horizontal surface. This group of equipment may be further sub classified into:

1. Truck and Lorries

2. Railway Cars and Wagons

3. Fork Lifts

4. Overhead mono-rail / Equipment

5. Scrapers and Skidders

Types of Material Handling Equipment Loads:

It usually classified into:

1. Unit Load

2. Bulk Load

Unit Load:

Unit loads are those which are counted by numbers or units. A component of a machine, a complete machine, a structural element, a beam, a girder, building block are some examples of unit load.

Sometimes certain quantities of free flowing materials can be placed in a container and can be handled as unit load. Hoisting equipment are primarily used for handling unit load. Unit loads are usually specified by it’s weight.

Bulk Load:

When the load is in the form of particles or lumps of homogeneous materials or powder like materials, which can not be counted by numbers, it is called as “Bulk load”.

Examples are:

Sand, Cement, Coal, Mineral, Stone, Clay etc.,

A bulk material may be classified by it’s:

1. Bulk Density

2. Lump-Size

3. Flowability

4. Abrasiveness

5. Miscellaneous Characteristics

CONVEYOR

Conveyor Take-up Arrangement:

All belt conveyors require the use of some form of take-up device for the following reasons:

• To ensure adequate tension of the belt leaving the drive pulley so as to avoid any slippage of the belt
• To ensure proper belt tension at the loading and other points along the conveyor
• To compensate for changes in belt length due to elongation
• To provide extra length of belt when necessary for splicing purpose.

Usually there are two types of take up arrangements.

• Fixed take up device that may be adjusted periodically by manual operation
• Automatic take up devices for constant load type

In a screw take up system the take up pulley rotates in two bearing blocks which may slide on stationery guide ways with the help of two screws. The tension is created by the two screws which are tightened and periodically adjusted with a spanner. It is preferable to use screws with trapezoidal thread t decrease the effort required to tighten the belt.

The main problem with the use of manual take-up is that it requires a vigilant and careful operator to observe when take up adjustment is required. Perfect tension adjustment with this system is also not possible. For this reason these devices are used only in case of short conveyors of up 60 m length and light duty.

In automatic take up arrangement the take up pulley is mounted on slides or on a trolley which is pulled backwards by means of a steel rope and deflecting pulleys. The carriage travels on guide ways mounted parallel to the longitudinal axis of the conveyor, i.e., horizontally in horizontal conveyors and at an incline in inclined conveyors. Hydraulic, pneumatic and electrical take up devices are also used.

Automatic take-up has the following features:

• It is self adjusting and automatic
• Greater take-up movement is possible.

BLOW MOULDING PROCESS

Today, when walking in your supermarket, it is increasingly difficult to find items packed in glass and jars.  Packaging for soft drinks, healthcare and beauty products, household chemicals and medicines, among other products, have switched from glass or metal to plastics.  Today the Blow Molding industry has expanded from simple plastic containers to plastic drums, gas tanks, automobile parts and toys in all shapes and sizes.

Blow Molding (BM) process makes it possible to manufacture molded products economically, in unlimited quantities, with virtually no finishing required.  The basic process of blow molding involves a softened thermoplastic hollow form which is inflated against the cooled surface of a closed mold.  The expanded plastic form solidifies  into a hollow product.

Blow molded components are now seen all over the markets and industries for traditional materials, particularly in liquid packaging applications.  The last few decades saw the introduction of  Poly Ethylene (PE) squeeze bottles for washing liquids, Poly Vinyl Chloride (PVC) for cooking oil and fruits squash bottles, and Poly Ethylene Terephthalate (PET) for carbonated beverage bottles.  Nowadays, it is also used for the production of toys, automobile parts, accessories and many engineering components.

There are basically four types of blow moulding used in the production of plastic bottles, jugs and jars. These four types are:

1. Extrusion blow molding,
2. Injection blow molding,
3. Stretch blow molding and
4. Reheat and blow molding.

Extrusion blow molding is perhaps the simplest type of blow molding, whereby a hot tube of plastic material is dropped from an extruder and captured in a water cooled mold. Once the molds are closed, air is injected through the top or the neck of the container; just as if one were blowing up a balloon. When the hot plastic material is blown up and touches the walls of the mold the material “freezes” and the container now maintains its rigid shape. There are various types of shuttle, reciprocating and wheel style machines for the production of extrusion blown bottles. Shuttle or reciprocating type machines can be used for small, medium and high volume production with wheel machines being the most efficient for huge volume production of certain resins.

A typical apparatus consists of following major components i.e. blow pin, plunger, accumulator and lastly a mold.

Actually the process utilizes air pressure to inflate softened thermoplastic tube which is sealed at one end (also called as parision). This parision is constantly inflated and extruded. Then later on it is cut according to required dimensions. The temperature in Accumulator is maintained around 400 degree Celsius or so.

The mold consists of two split parts which have a semi-circular cross-section. Usually the air pressure which is applied in low pressure molding is about 50 to 250 psi. Various forms of blow molding used in industry today on a wide scale are Injection Blow Molding.

Injection Blow Molding though not used in industry, has very limited and specific applications like making small medicine plastic bottles etc. Extrusion blow molding is the simplest form of blow molding. A tube of plastic material which is generally maintained hot, is dropped from an extruder only to be captured in a water cooled mold. Once the molds are closed, air is injected through the top or the neck of the container and the tube is inflated just like a balloon. When the hot plastic material is blown up and touches the walls of the mold the material is cooled and the container now maintains a solid, rigid shape.

Now Stretch blow molding, this process requires the raw material to be formed in a pre-form using injection molding and later on stretch blow molding process can be applied.

The product range varies from various cylindrical components like bottles, cans, floats heater ducts in automobile parts and various small pipe fittings and hollow cylindrical parts can be produced in mass production.

The advantages are many like the tooling costs are very less as compared to injection molding, the part performance is excellent under pressure. Then the products have excellent environmental stress crack resistance. The products also perform excellently in high speed impact strength than even the metal components the process can be automated and used in mass production.

The disadvantages mainly raise environmental concerns. It depends on petroleum industry as any plastic industry depends. Also the cylindrical shapes are delicate so if the dimensions are not accurate then they result in scrap.

QTC

QTC is a composite made from micron-sized metallic filler particles (Silicone Rubber) mixed into an elastomeric matrix. Quantum tunnelling composite is a flexible polymer that exhibits extraordinary electrical properties. In its normal state it is a perfect insulator, but when compressed it becomes a more or less perfect conductor and able to pass very high currents.

History:

First produced in 1996, QTC is a composite material made from conductive filler particles combined with an elastomeric binder, typically silicone rubber. The unique method of combining these raw materials results in a composite which exhibits significantly different electrical properties when compared with any other electrically conductive material.

Types of QTC:

1. Elastomeric (Material: Silicone Rubber) (The particle move close together)

2. Ink / Coating Solvent or Aqueous Polymer

3. Granular Sensors

Working of Quantum tunnelling composite:

QTC usually comes in the form of pills or sheet. QTC pills are just tiny little pieces of the material. The sheets are composed of one layer of QTC, one layer of a conductive material, and a third layer of a plastic insulator. While QTC sheets switch quickly between high and low resistances, QTC pills are pressure sensitive variable resistors.

Application:

– Touch switches (sheet)
– Force/pressure sensors (pills)
– Motor speed control using force (pills)

Benefits:

• QTC is a pressure/force sensing material. It can be easily integrated into existing products to enable force sensing opportunities and solutions.
• Product surfaces can be incorporated, coated or impregnated with QTC to impart the properties of force sensing into or onto the host surface.
• QTC material can be formed or moulded into virtually any size, thickness or shape, permitting redesign of product interfaces and providing improved ergonomics, aesthetics and user comfort.
• QTC is an enabling technology which is simple and reliable to use.
• QTC material is durable – it has no moving parts to wear out.
• QTC material is mechanically strong.
• QTC material can be made to withstand extreme temperatures limits.
• QTC material is versatile, both electrically and physically e.g. Its range and sensitivity can be altered. QTC material is also intrinsically safe – the material is a contactless switch, ideal for sparkless operation.
• QTC material can be directly interfaced to standard electronic and electrical devices.
• QTC material and/or technology can be customized for customer requirements, applications and products.