Machining optical plastic components
Overview
This standard identifies the competences you need to carry out machining operations on optical plastic materials, using optical plastic process machines, in accordance with approved procedures. You will be required to set up and operate a range of machines, in order to produce components that combine a mixture of processes identified for plastic materials, using a selection of specified optical plastic lens and flat materials. You will be expected to produce a range of components that combine a number of different features, such as centre thickness, diameters, generated blanks, optical lens form, power, and stress and strain analysis.
You will be required to set up and operate the machine in line with safe working practices and approved procedures, and to continuously monitor the machining operations, making any necessary adjustments in order to ensure that the work output is to the required quality and accuracy. Meeting production targets will be an important issue, and your production records must show consistent and satisfactory performance.
Your responsibilities will require you to comply with organisational policy and procedures for the optical machining activities undertaken, and to report any problems with the setting-up procedures, optical machining activities, materials or equipment used, that you cannot personally resolve, or that are outside your permitted authority, to the relevant people. You will be expected to work with a minimum of supervision, taking personal responsibility for your own actions and for the quality and accuracy of the work that you carry out.
Your underpinning knowledge will provide a good understanding of your work, and will provide an informed approach to applying optical plastic machining procedures. You will understand the optical machining processes used, and their application, and be familiar with the equipment, materials and consumables, in adequate depth to provide a sound basis for setting up the equipment, carrying out the activities, correcting faults and ensuring that the work output is to the required specification.
You will understand the safety precautions required when working with the machines and with the associated tools and equipment. You will be required to demonstrate safe working practices throughout, and will understand the responsibility you owe to yourself and others in the workplace.
Performance criteria
You must be able to:
- work safely at all times, complying with health and safety and other relevant regulations, directives and guidelines
- confirm that the machine is set up and ready for the machining activities to be carried out
- operate the machine tool controls safely and correctly, in line with operational procedures
- produce components to the required quality and within the specified dimensional accuracy
- carry out quality sampling checks at suitable intervals
- complete the required production documentation
- deal promptly and effectively with problems within your control and report those that cannot be solved
- shut down the equipment to a safe condition on conclusion of the machining activities
Knowledge and Understanding
You need to know and understand:
- how to work safely at all times, complying with health and safety and other relevant regulations, directives and guidelines
- the safety mechanisms on the machine, and the procedure for checking that they function correctly
- the operation of the machine controls, and how to stop the machine in an emergency
- the personal protective equipment (PPE) to be worn, and where this can be obtained
- the hazards associated with carrying out plastic lens machining operations, and how to minimise them and reduce any risks
- the importance of keeping the work area clean and tidy
- how to extract and use information from engineering drawings and related specifications (to include symbols and conventions to appropriate standards) in relation to work undertaken
- how to interpret first and third angle drawings, imperial and metric systems of measurement, workpiece reference points and system of tolerancing
- the various plastic prism/lens operations that can be performed, and the shapes and types of tooling that can be used (such as fly cutters, diamond abrasive wheels, polyurethane polishers, pitch polishers)
- the methods that can be used to set up the workpiece, prior to the operation, to minimise optical wedge and parallelism in relation to the cutting tool
- the characteristics of the plastics used in optical components
- how to achieve the required level of finish using hand smoothing and polishing techniques
- the effect of backlash in machines slides, dials and screws, and how this can be overcome
- how to handle and store all cutting tools and kit required, safely and correctly
- factors which affect the selection of cutting feeds, pressures and speeds required and the depth of cut that can be taken (such as workpiece rigidity, machine condition, types of tooling used, material used, finish and tolerance required)
- how tool wear affects surface finish and dimensional accuracy
- how the various types of materials will affect the way the operation is performed
- the application of cutting fluids with regard to the range of material being machined
- the effect of clamping the workpiece, and how this can cause distortion in the finished component
- how to recognise machine faults, and how to identify when tooling needs refurbishment
- the problems that can occur with plastic lens/prism machining activities, and how they can be overcome
- the quality controls procedures used, inspection checks to be carried out, and the equipment used for this
- the extent of your own responsibility and to whom you should report if you have problems that you cannot resolve
Scope/range
Scope Performance
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- Carry out all of the following during the machining activities:
- obtain and interpret correctly the documentation for the type of lens being machined
- adhere to procedures or systems in place for risk assessment, personal protective equipment and other relevant safety regulations and procedures to realise a safe system of work
- ensure that machine guards/safety mechanisms are in place and correctly adjusted at all times
- ensure that components are correctly positioned and held securely, without damage or distortion
- ensure that tooling is appropriate for the operations and is maintained in a suitable condition
- set the tooling and machine operating parameters to achieve the component specification
- adjust machine settings, as required, during the machining activities to maintain component accuracy
- use safe working practices and machine operating procedures at all times
- leave the machine and work area in a safe and clean condition on completion of the machining activities
- Set up and operate five types of optical plastic processes from the following:
- automated process
- prism/flat smoothing process
- plastic diamond turning process
- lens generating process
- hand smooth process
- prism/flat polishing process
- lens edging process
- hand polish process
- optical special materials process
- lens smoothing process
- plastic stabilisation process
- special plastic cleaning process
- Produce machined optical components that combine different operations, and cover six of the following:
- centre thickness
- lens form analysis
- lens cosmetic defects
- lens diameter
- lens power analysis
- lens truncation and cap height
- lens concentricity
- lens surface generation
- angular collimating
- flat parallelism
- Machine one of the following types of plastic material:
- cyclic olefin
- acrylic
- polyethyrene
- polyetherimide
- sulfones
- polycarbonate
- other optical grade plastic
- During production, carry out the necessary checks for accuracy, to include five of the following:
- optical bevels
- optical truncations
- lens diameters
- optical lens wedge
- lens cap height
- lens surface finish
- optical parallelism
- lens chamfers
- lens surface power/radius error
- lens centre thickness
- lens surface form error
- prism angles
- truncations
- Produce components with dimensional accuracy, form and surface quality to one of the following:
- BS, ISO or EN standards and procedures
- customer (contractual) standards and requirements
- company standards and procedures
- other accepted international standards