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Innovations in Injection Molding machinery

The plastic processing industry is one of the world's fastest growing industries. The two major plastic processing methods are injection moulding and extrusion. Approximately 40percent of all plastics processed goes through injection moulding machines. The advantages of injection moulding machines is that the moulded parts can be produced economically in unlimited quantities with little or no finishing operations.

As a result of the perpetual changes in the standard of living and new products required by the market, the demands placed on the processors are arising with each passing day. This drives machinery manufacturer to develop innovative machinery upgrading their machinery. This new generation injection-moulding machines are expected to meet the processor's requirements because of consistency, accuracy, repeatability, energy efficiency and productivity, which will yield maximum returns.

Since 1872 when the first injection moulding machine (Plunger type stuffing machines) was used, the machinery has come a long way. The changing needs reflect the dynamic growth of the industry. Apart from its own normal growth, the injection moulding machinery technology has been influenced by the advancement of other technologies like hydraulics, electronics, computers, robotics and the demands of modern, engineering-grade moulding materials.

When we consider the developments in injection mouldings, two distinct areas are very evident. While one is the machine, the other is the process, and though these are separate, both are closely inter-related. Developments in process might require changes/modifications in the machinery. Changes in machine design might require different process settings when compared with conventional methods.

Although the needs of the customers are satisfied, there are a few needs which are difficult to satisfy, and machine manufacturers striver hard to meet these needs.

Some of them are:

Large mould area to accommodate different sizes and shapes of mould.
Ease to setting and retrieving of process parameters.
Consistency and repeatability of the process.
Ease of mould loading.
Ease of maintenance.
Low cost of maintenance.
Less power consumption.
Lower cost of the machine.

It is very difficult to satisfy all these demands in a single machine. Hence, we find different types of machines being offered by machine manufacturers. Also, raw material suppliers try to blend different materials to achieve the desired properties if the end product. There are others who work on innovative ideas and various processes and come out with new concepts of moulding.

Innovations in the injection moulding process have products and special processes such as:

Fully closed loop high tech injection moulding machines.
Tiebarless injection moulding machines.
Tiebarless injection moulding machines.
All electric injection moulding machines.
Co-injection moulding machines.
Vertical insert injection moulding machines
Two Platen injection moulding machines
Structural foam / web injection moulding
The gas pressure process
The mono sandwich process

HIGH Technology Fully Closed Loop Machine

These machines are equipped with user-friendly, modern processors for faster data processing. The machine and process functions are software-driven. The proportionally acting hydraulic systems control the closed loop velocity and pressure parameters. This results in precise moulding and minimal part rejections.

The hydraulic systems incorporated in these machines make use of integrated hydraulic components comprising multiple variable volume pumps/servo pumps with extensive usage of cartridge and proportional valves.

Finite element analysis of casting, special feed screw designs and integrated hydraulics contribute to reducing energy consumption through reduced weight control and improved performances. The options available among injection units used to plasticize the materials optimise the machine for specific requirements. These machines are frequently used in electronics, automobile, furniture and container industries.

Tiebarless Injection Moulding Machine

The practice of loading bigger/bulkier moulds into smaller machines along with the necessity of frequent mould changes to meet just in time (JIT) production needs led to the origin of Tiebarless machines. Tiebarless designs have the advantage of providing maximum platen mounting surface access to minimise the hassles of contending with interference from strainrods during mould installation and machine operation. Moulds with projection cores and unusual dimensions can be easily loaded on to the platen mounting surfaces. Innovative designs of linear deflection platens, compensating cylinders and advanced sculptured cast frames control platen deflection during tonnage. These machines are basically closed-loop machines used in specific applications.

Tiebarless machines offer several advantages for processors; moulds of all configurations are easier to load and unload by crane from the top or by forklift from the side; easy integration of peripherals and auxiliaries (including robots, parts removal and secondary operation system); quick die change systems and other automated systems. The machine operator also has easier access for part removal.

The machine frame is often more rigid than conventional machines thereby making the installation easier and simpler.

All Electric Injection Moulding Machine

As energy consumption awareness gained momentum, innovative ideas for the reduction of energy usage resulted in the development of all electric machines. These machines have the potential of reducing energy consumption by 50 percent when compared with conventional machines. The functions performed by pumps, directional valves, cylinders and hydraulic motors, which are used to control and move the machine's axis, are replaced with electrical servomotors, ballscrews, and track-and-pinions. Since hydraulic oil is not used, these machines can be termed more eco-friendly than hydraulic equipment. Electric machines generate and release less heat into the environment thus reducing the cost of air conditioning and heat build-up in production buildings. Due to its combination with gear mechanisms, servomotors make less noise and yet deliver highly precise and quick operation. These machines are ideal wherever precise and strict control of the finished part is required.

Co-injection Moulding Machine

Co-injection basically means that two or more plastics are laminated together during the molding process. The plastics could be the same material with different coloration or totally different materials. When different plastics are used, they must be compatible in order to provide proper adhesion and to meld at approximately the same temperature. The term co-injection can either denote different products such as sandwich moulding or two-color moulding.

Multi-colour/multi-component machines have opened up new fields of applications, particularly in injection moulding of rigid/soft composites. This process is already a well-established technology. Numerous innovative and revolutionary solutions have been developed in the last decade. Two melts are layered in a cylinder and then successively injected into the cavity. The basic machine can be combined with additional injection units of different sizes to give even more versatility. The mould determines the parameters required for injection units. These are also specific application machines.

Vertical Insert Moulding Machine

This is a substitute for horizontal insert moulding machines where time is lost during the cycle at the operator's station. In vertical insert moulding machine with rotary/shuttle tables, productivity increases through the use of a loading station while another mould is being processed in the machine.

Vertical machines are used when processes utilise insertion methods for medium lot sizes to very complex insertion processes for which a special handling system is required. The use of a rotary shuttle table with multiple moulds enables higher productivity as the inserts are placed in the mould while the moulding of another shot is taking place thus saving time. The Tiebarless frames facilitate faster placing of inserts. These machines are used for specific applications like encapsulating, metal insets etc.

Two Platen Injection Moulding Machine

These machines have some important benefits over the conventional benefits over the conventional design. The inherent design characteristics permit:

Larger clamp strokes compared with conventional machine
70-80 percent reductions in tonnage build time
faster clamp movements

The typical applications of this machine is in the household sector. The household moulds are generally deep cavity moulds that require longer clamp strokes. The payback period of these machines is less since productivity is generally higher.

Foam / Web moulding

This moulding concept has originated mainly for the moulding of large parts with ribs.

Structural Foam (SF) injection moulded plastic parts have a cellular foamed core surrounded by integral skins forming an indivisible structure. In this process, a foaming agent (N2 or CBA-Chemical Blowing Agent) is mixed with the polymer melt and injected through multiple nozzles into the mould in smaller volumes than required to mould a solid part. Both injection pressure and the expanding gas/polymer mixture act to fill the mould.

The melt, after coming in contact with the cool surface of the mould, forms and almost-solid skin. In the inner core, the foaming gas expands to form a cellular structure.

Structural Foam, with is rigid skin and foam core, is lighter, stronger, more durable and less expensive than other conventionally processed plastics, metal wood or fiberglass.

This process has greatly extended the range of product types and sizes that can be produced and offers significant advantages that include:

15-30 percent less part weight than solid plastics.
Larger parts with high degree of rigidity.
Low part stress and warpage.
Complex parts without sink marks.
Multiple parts can be moulded in a single cycle.
Most thermoplastic resins can be moulded.
Excellent part-to-part repeatability and dimensional stability.
Low cavity pressure permits use of lower cost aluminum molds.

Structural Web (SW)

moulding is closely related to SF moulding but uses injection of solid (non-foamed) polymers to create parts with other desirable characteristics. Parts moulded by the SW process are producers with a solid (non-cellular) plastic skin and a hollow cross section. The polymer melt is injected into the mould.

The inert gas is injected into the mould, packaging the melt against the mould walls forming solid web sections with hollow areas such as ribs. The exact configuration of these solid and hollow sections depends on the product's design and the moulding process.

The process can produce parts with three main different characteristics: products with a uniform wall thickness with a webbed interior; products with thin, solid walls and thick, hollow ribs; and thick-walled tubular products. Other beneficial characteristics are:

The SW process eliminates the structural foam surface swirl and permits smooth, solid-colour finishes in a cold mould.
Reduced cycle time due to shorter cooling time and ability to be painted immediately after removal. (SF requires up to 24 hours to de-gas before paint can be applied.)
Uniform surface replication - surface swirl and cavity pressure gradients found with SF are eliminated.
15-30 percent less part weight than solid plastics.
High stiffness-to-weight ratio.
Thicker parts and tubular shapes without sink marks - internal gas pressure packs out the polymer against the mould wall during cooling.
Transparent parts can be produced using clear polymers.

Airpress III - the perfect internal gas pressure process

When the Airpress III process is used, gas is directly taken into the molten plastic mass via injection needles in the mould. The gas then displaces, the excessive molten mass either into a separate side capacity or back into the plasticizing cylinder

Gas moulding saves material, reduces the required clamping force and avoids unwanted markers. Completely new fields of application are conceivable wherever a plastic part includes both thick and thin-walled areas.

The Mono Sandwich Process

The mono sandwich process allows for a simple production of sandwich structures form reclaimed (re-grind) material with minimum equipment.

The two melts are simply layered in a standard cylinder that are spatially separate and are then injected one after another into the cavity.

This process can save 40-60 percent of new material usage; has identical process control as used in conventional injection moulding and provides for simple colour changes.

Milacron Inc. has been successful in anticipating and developing new ideas for customers. Whether it is designing new products, developing new sequencing options or incorporating new feed screw profiles, Milacron's Plastics Technologies Group is continually seeking customer satisfaction and delight.

Complementary to innovative developments is the global manufacturing strategy. Global manufacturing helps Milacron to customise its technologies to local needs. Milacron's involvement in all the key areas of plastics processing and its worldwide coverage gives it a unique ability to transfer technology rapidly from different parts of the world and from different parts of the industry.

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