Machining components using CNC milling machines
Overview
This standard identifies the competences you need to operate Computer Numerical Control (CNC) three axis, four axis or five axis milling machines or CNC machining centres, in accordance with approved procedures. You will take charge of the prepared machine and check that it is ready for the machining operations to be performed. This will involve checking that all the required components and consumables are present, and that the machine has been approved for production. In operating the machine, you will be expected to follow the correct procedures for calling up the operating program, dealing with any error messages, and executing the program activities safely and correctly.
The components produced will have a number of different features, including such things as flat faces, angled faces, internal and external profiles, slots, steps, holes which are linearly or circularly pitched, and special profiles such as convex or concave. You will be required to continuously monitor the machining operations, making any necessary adjustments to machine parameters, in line with your permitted authority. 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 activities undertaken, and to report any problems with the machine, tooling, materials or machining activities that you cannot personally resolve, or are outside your permitted authority, to the relevant people. You will be expected to work to instructions, taking personal responsibility for your own actions and for the quality and accuracy of the work that you produce.
Your underpinning knowledge will be sufficient to provide a good understanding of your work, and will enable you to adopt an informed approach to applying CNC milling procedures. You will have an understanding of the CNC milling process, and its application, and will know about the equipment, tooling, materials and consumables, in adequate depth to provide a sound background to the machine operation and for carrying out the activities to the required specification.
You will understand the safety precautions required when working with the machine and 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.
Setting up of the machine, its tooling and associated workholding devices, are the subjects of other standards.
Performance criteria
You must be able to:
P1 work safely at all times, complying with health and safety and other relevant regulations, directives and guidelines
P2 confirm that the equipment is set up and ready for operation
P3 follow the defined procedures for starting and running the operating system
P4 deal with problems within your control and report those that cannot be solved
P5 monitor the computer process and ensure that the production output is to the required specification
P6 produce machined components
P7 complete and store all relevant documentation in accordance with organisational requirements
P8 shut down the equipment to a safe condition on conclusion of the activities
Knowledge and Understanding
You need to know and understand:
K1 how to work safely at all times, complying with health and safety and other relevant regulations, directives and guidelines
K2 the safety mechanisms on the machine, and the procedures for checking that they are operating correctly
K3 how to start and stop the machine in both normal and emergency situations
K4 the hazards associated with working on CNC milling machines and how to minimise them and reduce any risks
K5 the importance of wearing the appropriate personal protective equipment (PPE), and of keeping the work area clean and tidy
K6 the application of a range of CNC milling machines, such as three axis, four axis, five axis and machining centres
K7 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
K8 how to interpret first and third angle drawings, imperial and metric systems of measurement, workpiece reference points and system of tolerancing
K9 how to interpret the visual display and understand the various messages displayed
K10 the function of error messages, and what to do when an error message is displayed
K11 how to find the correct restart point in the program when the machine has been stopped before completion of the program
K12 the operation of the various hand and automatic modes of machine control
K13 how to operate the machine using single block run, full program run, and feed/speed override controls
K14 why you would conduct a full dry run and single block run
K15 how to make adjustments to the program operating parameters to take account of tool wear
K16 how to set and secure the workpiece to the machine table/workholding device; the effects of clamping the workpiece; and how material removal can cause warping/distortion of the finished workpiece
K17 the various types of milling cutters used, and how they are located and secured to the machine spindle, tool magazine or carousel
K18 the safe and correct handling and storage of tooling
K19 how to check that the milling cutters are in a serviceable condition, and the effects that worn cutters will have on the finished work
K20 the issues that can occur with the milling activities, and how these can be overcome
K21 the application of cutting fluids with regard to different materials being machined
K22 the quality control procedures used, inspection checks that need to be carried out, and the equipment that is used
K23 where to obtain component drawings, specifications and/or job instructions required for the components being machined
K24 the extent of your own responsibility and to whom you should report if you have problems that you cannot resolve
Scope/range
Scope Performance
- Carry out all of the following during the machining activities:
- obtain and use the appropriate documentation
- 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
- check that the operating program is at the correct start point
- ensure that machine guards are in place and correctly adjusted
- ensure that components are correctly positioned and held securely without distortion
- check and maintain cutting tools in a safe and usable condition
- ensure that the workpiece is clear of the machine spindle before starting the machine
- use safe working practices and start up procedures at all times
- adjust machine settings, as required, to maintain the required accuracy
- leave the work area and machine in a safe and appropriate condition on completion of the activities
- Operate one of the following CNC milling machines:
- three axis milling machine
- four axis milling machine
- five axis milling machine
- machining centre
- Produce machined components, which combine different operations and cover nine of the following:
- flat faces
- holes on pitch circles
- external profiles
- steps/shoulders
- parallel faces
- holes linearly pitched
- enclosed slots/recesses
- angular faces
- circular/curved profiles
- internal profiles
- open ended slots
- tapped holes
- special forms (such as concave, convex)
- faces that are square to each other
- Machine components made from one of the following types of material:
- ferrous
- non-ferrous
- stainless
- non-metallic
- Carry out the necessary checks during production, for accuracy of six of the following
- dimensions
- hole size/fit
- angles
- slots
- squareness
- surface finish
- flatness
- recesses
- Produce components within all the relevant quality and accuracy standards, as applicable to the operations performed:
- Components to be free from false tool cuts, burrs and sharp edges
- surface finish 32µin or 0.86µm
- reamed and bored holes within H8
- flatness and squareness 0.001” per inch or 0.025mm per 25mm
- angles/tapers within +/- 0.25 degree