Glossary of terms used on this site

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Term Definition
2K Mixing Unit

The mixing ratio of paint to hardener to thinner must be kept accurate and consistent to ensure a good painting process and good quality parts. Some companies do this manually, trusting to the skill of the operator to keep it consistent. However, no person can match the consistency of a good 2K mixing unit which uses electronic pumps to ensure consistency.

Electric moulding machines

Moulding machines in the past were primarily hydraulic based. This means that one or two big electric motors are continuously turning hydraulic pumps which produce hydraulic pressure. This pressure is then directed to the region of the machine that requires it. So during the mould closing phase for example, the oil is pushed into the rear of the mould closing cylinder. During injection, the oil is pushed into the rear of the screw piston. However, there are disadvantages with this

•   There is a large wastage in energy as the electric motors are continuously running, even if the energy is required or not.
•   There is a time delay as the oil is directed through the various valves to the right place in the right proportion.
•   There is an inbuilt inconsistency as the hydraulic oil will perform differently when it is cold compared to when it is hot.
•   There is a lag in performance of hydraulic fluids that means accuracy to within 0.01 mm is practically impossible to achieve.
•   Usually the machine can only perform one function at a time
•   The hydraulic oil requires a constant supply of cooling water.

With All Electric machines, the one large or two large motors that power the hydraulic pumps are replaced by a series of electric motors that power each individual machine operation. This means the following • When no part of the machine is actually moving, i.e. during the cooling phase, no energy is being used. • Reaction time on electric motors is much faster • Good quality servo motors will have superb repeatability regardless of running time or climatic conditions. • They will be accurate to within 0.01mm. • Multiple functions can happen at one time, resulting in faster cycle times. • The only external cooling required is for the hopper throat.

Gas Injection Moulding

This involves the injection of nitrogen gas along with the polymer (usually just after the first injection phase is completed). The nitrogen can be injected either through a special machine nozzle and follows the path of the sprue / runner or it can be injected directly into the part through special nozzles built into the mould. The gas is then evacuated from the part during the later stages of the cooling phase. The advantage of this type of process is that parts that contain thick wall sections can be produced without the normal sink marks that normally occur in these types of areas. The resultant part will also be lighter, with a resultant cost saving and produced in a faster time.

RHCM

Rapid Heat Cycling Moulding - also known as hot and cold moulding, or steam moulding. This process is similar to conventional moulding with the following exception. Prior to the injection phase, the tool is heated to approx 150c by pumping steam through specially detailed channels within the mould. Upon reaching the set temperature the injection phase takes place. After injection, the steam is evacuated from the mould and cooling water is pumped through. The advantage of this type of process is that it is possible to achieve high gloss parts without visible weld lines, in a relatively short cycle time.

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