Archive for the ‘MANUFACTURING PROCESS’ category

Water Jet Cutting

September 21, 2012
Water Jet Cutter Diagram

 

What is it?

A water jet cutter is a tool capable of slicing into metal or other materials using a jet of water at a very high velocity and pressure, the water can be mixed with other abrasive particles to aid the erosion of the metal. These abrasive particles can be in the form of suspended grit or aluminium oxide. To get the pressure used into context the pressure fired out the end of the nozzle in a water jet cutter is around 30 times more than a car pressure washer.

 

What can it do?

Water jet cutting can be very versatile in its potential, e.g. it can be used to cut things such as fish sticks all the way to titanium, however some tempered glass cannot be water jet cut, some ceramics also have this problem, while diamond is just too tough.
The cut kerf (width) can be adjusted by changing the nozzle parts along with the abrasive grain size.
The typical cutting jet size when using abrasive particles is around 1mm-1.3mm, although this can be reduced to almost 0.5mm. When cutting without the use of abrasive particles then the jet size can be further reduced to around 0.08mm.

 

How fast does a water jet cut?

An abrasive jet can cut half-inch thick titanium at the rate of 7 inches per minute when a 30 HP pump is used. The abrasive jet moves in a manner very similar to a slowed-down pen plotter.

 

Advantages of water jet cutting

Water jet cutting does not apply heat to the material it is cutting, therefore there is no possibility of work hardening happening.
Water jet cutters are also capable of producing rather intricate cuts in material. With specialized software and 3-D machining heads, complex 3-D shapes can be produced.
Water jets are capable of achieving an accuracy of 0.13 mm

Water jet cutting is safer for operators and the environment – avoids vapour, dust and smoke and does not require expensive coolants
Clean finished product eliminates secondary cleaning operations

 

Disadvantages of water jet cutting

Cutting hard metals such as tool steel seriously affects the cutting speed, therefore water jet cutting is not an efficient method of machining these hardened materials.
Cutting thick materials results in a taper down the cut resulting from the water jet widening as it get further away from the nozzle. This means dimensional accuracy in thick cuts becomes a problem.

Plastic injection moulding

September 21, 2012

Plastic injection moulding is a hugely common method of plastic forming, it is used in a wide variety of objects you see and use in day to day life, things like shampoo bottles, hair brush handles, children’s toys, car dashboards, games consoles. Plastic injection moulding is more efficient when producing parts with thicknesses no larger than around 3mm, this is because thicker parts take longer to cool off before they are released from the mould. Thicker walls in moulded parts also risk having problems with material shrinkage, to combat this when wall strength is required the use of ribs or fillets are implemented.

Plastic Ribs

Plastic Injection Mould

Above shows the use of ribs to help strengthen the plastic structure.  The inside face of a plastic injection mould

Moulds

Moulds have two plates, the injection mould and the ejector mould, plastic resin is injected under pressure into the mould cavity via runners or channels, these runners are grooves machined out of the mould which allow the plastic resin to be directed to points throughout the mould where it can enter and fill the cavity. Small air vents are machined into the moulds to help air escape, however if air became trapped within the mould it would prevent plastic resin flow from filling its space causing a defect. Once the mould cavity is filled the plastic is usually helped to cool off with a coolant which runs through machined channels within the mould plate.

Advantages of injection moulding

Injection moulding is an efficient means of mass producing parts to the same high tolerances over and over. Injection moulding is not labour intensive and little waste is produced from the process as there is little in the way of off-cuts. The moulding process leaves a good finish therefore further finishing is not always required.

Disadvantages of injection moulding

The initial set up cost is high, this is because all of the required moulds must be produced first, also all parts must be designed with the ability to be moulded in mind.

Injection moulding machine

Laser cutting

September 21, 2012

Laser cutter head

Laser Cutter Head Diagram

What is it laser cutting?

Laser cutting is a fairly new technology that allows metals and some non metallic materials to be cut with extreme precision if required. The laser beam is typically 0.2 mm in diameter with a power of 1-2 kW .

Types of laser cutting

Depending on the application of the laser cutter a selection of different gases are used in conjunction with the cutting. For general boring, cutting and engraving then Co2 is typically used.
If high powered laser pulses are used then neodymium (Nd) gas is required, this set up is mainly associated with boring. For a constant high powered beam neodymium yttrium-aluminium-garnet (Nd-YAG) is used.

Gaseous laser cutting uses an electrical current pumped through the gas which gives the laser its cutting properties, however this has recently been revised and RF energy is now preferred as this method does not require the use of electrodes like the DC current does. These electrodes were susceptible to erosion

What can it do?

Laser cutting can cut through a wide range of different materials, these can range from acrylic, wood, paper and foam core to high carbon and stainless steels, Laser cutting is not best suited to metals such as aluminium and copper alloys as they have good heat conductive and light reflective properties, these materials require the use of a more powerful laser. Laser cutters are generally best suited to thin materials of <12mm.

Advantages

Contamination of materials while laser cutting is reduced as there is no real physical contact between metal and cutter.

Great accuracy as laser can be focused into very small points, and there is also no wear in a laser while it is cutting as there is with more conventional methods, such as milling.

There is also a reduced chance of warping the material when laser cutting as the laser only generates a small area of heat.

No mechanical force is applied therefore no physical damage can occur.

Disadvantages

Laser cutting has high energy consumption, and can draw a lot of power to perform its cutting. Although it uses a large amount of power it goes some way to making up for this cost with its fast and precise cutting speed. The cost and setup of a laser cutter can also be expensive when compared to other methods.

Work hardening along the edges of cuts can mean harder work if any further machining is required.

Manufacturing Engineering Basics

January 6, 2012

02-manufacturing engineering-manufacturing engineering and Technology-manufacturing basics-industrial engineering

Engineering activities involved in the creation and operation of the technical and economic processes that convert raw materials, energy, and purchased items into components for sale to other manufacturers or into end products for sale to the customer.

Defined in this way, manufacturing engineering includes product design and manufacturing system design as well as operation of the factory.

01-manufcaturing Engineering process- manufacturing Engineering layout

More specifically manufacturing engineering involves the analysis and modification of product designs so as to assure manufacturability; the design, selection, specification and optimization of the required equipment, tooling, processes and operations and the determination of other technical matters required to make a given product according to the desired volume, timetable, cost, quality level and other specifications.

Manufacturing process:

Manufacturing process is science and technology by which a material is converted into a useful shape, with a structure and properties. In a simple technical definition of a material processing might be “all that is done to convert stuff into things”.

Manufacturing is an economic term for making good and services available to satisfy human needs. Manufacturing implies creating value by applying useful mental or physical labour.

01-manufacturing process-manufacturing layout

Modern manufacturing Environment:

In a modern manufacturing environment, an organizations strategy for highly automated systems and the role for workers in these systems are generally based on one of two distinct philosophical approaches.

One approach views workers within the planet as the greatest source of error. This approach uses computer integrated manufacturing technology to reduce the workers influence on the manufacturing process.

The second approach uses computer integrated manufacturing technology to help the workers make the best product possible. It implies that workers use the technology to control variance, detect and correct error, and adapt to a changing marketplace.

A high technology development in computing and electronics, designed to enhance manufacturing capabilities. Advanced manufacturing technology is used in all areas of manufacturing includes design control, fabrication and assembly.

This family of technologies included Robotics, Computer Aided Design (CAD), Computer Aided Engineering (CAE), MRP II, Automated material handling systems, Electronic Data Interchange (EDI), Computer Integrated Manufacturing (CIM), Flexible Manufacturing Systems (FMS), and Group Technology (GT).

The best approach utilizes the attributes of employees in the factory to produce products in response to customer demand.

This viewpoint enables the employees to exert some control over the system, rather than simply serving it. The employees can then use the system as a tool to achieve production goals.

01-manufacturing process-manufacturing technology

As technology and automation have advanced, it has become necessary for manufacturing engineers to gain a much broader perspective.

They must be able to function in an integrated activity involving product design, product manufacture, and product use. They also have to consider how the product will be destroyed as well as the efficient recovery of the materials used in its manufacture.