Machining components using CNC aspheric glass and diamond turning machines
Overview
This standard identifies the competences you need to carry out the machining of aspheric glass and diamond turned components, using computer numerical controlled (CNC) machines or CNC machining centres, in accordance with approved procedures. You will be required to produce a range of aspheric components of various infra-red and visible materials, which combine a range of different features, such as aspheric form, power, surface roughness, cap height. You will also be required to check and verify finished components, using a variety of metrology equipment, to ensure that they meet the required specifications.
You will be required to 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 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 produce.
Your underpinning knowledge will provide a good understanding of your work, and will provide an informed approach to applying optical machining procedures. You will understand the aspheric glass and diamond turning processes used, and their application, and will know about the equipment, materials and consumables, in adequate depth to provide a sound basis for carrying out the activities to the required specification.
You will understand the safety precautions required when working with the machine and with its 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 equipment is set up and ready for operation
- follow the defined procedures for starting and running the operating system
- deal promptly and effectively with error messages or equipment faults that are within your control, and report those that cannot be solved
- monitor the computer process and ensure that the production output is to the required specification
- produce machined components
- complete the required production documentation
- shut down the equipment to a safe condition on conclusion of the 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 in both set-up and run modes, 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 working on CNC machines (such as use of power operated chucks, moving machinery, automatic machine operation, handling cutting tools, lifting and handling workholding devices, hot and airborne particles), and how to minimise them and reduce any risks
- the hazards associated with carrying out aspheric lens process operations, and how they can be minimised
- the importance of wearing the appropriate protective clothing and equipment, and of keeping the work area clean and tidy
- how to extract and use information from engineering drawings or data 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
- how to read the visual display and understand the various messages displayed
- the function of error messages, and what to do when an error message is displayed
- how to find the correct restart point in the program when the machine has been stopped before completion of the program
- the operation of the various hand and automatic modes of machine control
- how to operate the machine using single block run, full program run and feed/speed override controls
- how to make adjustments to the program operating parameters to take account of tool wear
- the various types of cutting tool used, and how they are located and secured to the machine tool posts, turrets, slides and tool magazine or carousel (including diamond tip tools, diamond abrasive wheels and polishing tools)
- how to check that the indexible tooling is in a serviceable condition; and the effects that worn tooling will have on the workpiece surface finish and dimensional accuracy
- the lens mounting methods used to set up the workpiece prior to operation, to minimise wedge error, concentricity and astigmatism
- 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
- the application of cutting fluids with regard to the range of material being machined
- how to recognise machine faults, and how to identify when tooling needs refurbishment
- the quality control procedures used, inspection checks to be carried out, and the equipment used for this
- the problems that can occur with the aspheric lens generating, polishing and diamond turning activities, and how they can be overcome
- 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
- maintain cutting tools in a safe and suitable condition
- check that the operating program is at the correct start point
- check that the workpiece is clear of the machine spindle
- use safe working practices and machine start-up and operating procedures at all times
- adjust machine settings, as required, during the machining activities to maintain component accuracy
- leave the machine and work area in a safe and clean condition on completion of the machining activities
- Operate three of the following aspheric lens processes:
- glass aspheric generating process
- diamond turning aspheric process
- glass aspheric polishing process
- diamond turning diffractive/hybrid process
- Produce machined optical components that combine different operations, and cover six of the following:
- centre thickness
- lens cap height
- lens surface roughness
- lens cosmetic defects
- lens diameter/step feature, angle
- lens power analysis/radius
- lens concentricity
- lens aspheric form analysis
- lens diffractive step height
- Machine five different types of materials from the following:
- zinc selenide
- zinc sulphide
- optical silicon
- optical glass
- optical infra-red glass 4
- optical infra-red glass 5
- optical infra-red glass 6
- gallium arsenide
- acrylic
- optical grade germanium
- optical thallium ideobromide
- other specific optical material
- During production, carry out the necessary checks for accuracy, to include five of the following:
- lens diameter
- component surface finish
- component cosmetic defects
- centre thickness
- lens bevels/chamfers
- cap height
- component profiles
- surface form error
- angles
- surface/lens power error
- Produce components with dimensional accuracy, form and surface quality to one of the following standards:
- BS, ISO or EN standards and procedures
- customer (contractual) standards and requirements
- company standards and procedures
- other accepted international standards