Machining oprical cylinders and domes
Overview
This standard identifies the competences you need to carry out machining and hand finishing operations on optical cylinders and domes, using optical process machines, in accordance with approved procedures.
For domes, you will be required to machine components that combine a mixture of processes identified for optical domes, using a selection of specified optical dome 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 form, and optical power (radius of curvature).
For cylinders, you will need to carry out optical cylinder processing in accordance with optical approved procedures, including hand preparation, and smoothing and polishing, using a selection of specified optical cylinder materials. You will be expected to produce a range of cylinder components that combine different features, such as centre thickness, angles, axis, blocking, parallelism, and optical power and form error.
You will be required to set up and operate the machines 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 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 machining procedures. You will understand the optical cylinder and dome materials, the processes used, and their application and will know about the setting-up procedures, equipment, materials and consumables, in adequate depth to provide a sound basis for 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 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 optical cylinder/dome process 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 optical cylinder/dome operations that can be performed, and the shapes and types of tooling that can be used (dome diamond abrasive wheels, dome polyurethane polishers, cylinder/dome pitch-polishers, silk polishers and smoothing tools)
- 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 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 depth of cuts that can be taken
- how tool wear affects surface finish and dimensional accuracy
- how the various types of material will affect the way the operation is performed
- the application of cutting fluids and polishing mediums 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 optical cylinder/dome machining activities, and how they can be overcome
- the quality control procedures used, inspection checks to be carried out, and the equipment to be 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 setting-up and machining activities:
- obtain and interpret correctly the documentation for the type of optical cylinder or dome 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 that it 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
- Either: Set up and operate all of the following types of optical cylinder processes:
- cylinder preparation process
- cylinder pitch polishing process
- cylinder hand lapping to axis/angle process
- cylinder silk polishing process
- cylindrical test plate manufacture process
Or: Set up and operate four of the following types of optical dome processes:
6. dome preparation process
7. dome silk polishing process
8. dome surface generation process
9. dome pitch polishing process
10. dome polyurethane process
- Produce machined optical components that combine different operations, and cover six of the following:
- cylinder/dome centre thickness
- cylinder/dome power analysis (radius)
- cylinder/dome concentricity
- cylinder/dome form error analysis
- cylinder/dome cosmetic defects
- cylinder parallelism
- cylinder/dome diameter
- cylinder hand lapping process
- cylinder/dome truncation
- dome transmitted wave-front analysis
- dome preparation/smoothing process
- dome transmission analysis
- cylinder/dome surface generation
- Either: Machine four different types of cylinder materials from the following:
- germanium
- anomalous dispersion flour crowns
- barium crowns
- optical orange filter glass
- dense flints
- optical blue filter glass
- flints/light flints
- borosilicate crowns
- lanthanum crowns
- magnesium fluoride
- barium dense flints
- optical neutral density cut glass
- other specific material
Or: Machine two different types of dome materials from the following:
14. germanium
15. magnesium fluoride
16. zinc selenide
17. zinc sulphide
18. other specific material
- During production, carry out the necessary checks for accuracy, to include five of the following:
- dome diameter
- cylinder/dome bevels
- cylinder parallelism
- cylinder/dome chamfers
- cylinder/dome truncation
- cylinder/dome cap height
- cylinder/dome centre thickness
- cylinder/dome surface power error
- cylinder/dome cosmetic surface finishes
- cylinder/dome surface form error
- 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