Operating CNC grinding machines
Overview
This standard identifies the competences you need to carry out grinding operations, in accordance with approved procedures, using Computer Numerical Control (CNC) machines, such as universal grinding machines, gear grinding machines, thread grinding machines, ring grinding machines and grinding machining centres. You will confirm with the machine setter that the machine is ready for the operations to be performed and that all the required components/materials and consumables are available. 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.
You will be expected to produce a range of components that combine a number of different features, such as ground plain diameters, external screw threads, stepped diameters, flat faces and shoulders, chamfers, special forms, internal and external profiles, tapered diameters and faces, grooves/undercuts, parallel and tapered bores.
You will be required to operate the CNC machine in line with safe working practices and approved procedures, to continuously monitor the machining operations and, where necessary, make minor adjustments or seek the help of the setter to make the required 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 machining activities undertaken, and to report any problems with the 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, with a minimum of supervision, taking personal responsibility for your actions and for the quality and accuracy of the work that you produce.
Your underpinning knowledge will be sufficient to provide a sound basis for your work, and will enable you to adopt an informed approach to applying machining procedures. You will have an understanding of the CNC grinding process used, and its application, and will know about the equipment, materials and consumables in adequate depth to provide a sound background for carrying out the activities to the required specification.
You will understand the safety precautions required when working with the machine, 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 programming, tooling and associated workholding devices, is the subject of another standard and is the responsibility of the machine-tool setter.
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 CNC grinding machine is set up and ready for operation
P3 operate the machine controls in accordance with safe working practices and operational procedures
P4 deal with problems within your control and report those that cannot be solved
P5 operate the CNC grinding machine to produce machined components
P6 monitor the computer process and ensure that the production output is to the required specification
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 CNC grinding machine, and the procedure for checking that they function correctly
K3 how to stop the CNC grinding machine in both normal and emergency situations, and the procedure for restarting after an emergency
K4 the importance of wearing the appropriate personal protective equipment (PPE), and of keeping the work area clean and tidy
K5 the operation of the various hand and automatic modes of machine control
K6 how to use the visual display and understand the various messages displayed
K7 the function of error messages, and what to do when an error message is displayed
K8 how to find the correct restart point in the program when the machine has been stopped before completion of the program
K9 where to obtain the component drawings, specifications and/or job instructions required for the components to be machined
K10 how to extract and use information from engineering drawings or data and related specifications in relation to work undertaken
K11 how to use imperial and metric systems of measurement
K12 the main features of the CNC grinding machine, and the accessories that can be used
K13 the various CNC grinding operations that can be performed, and the methods and equipment used
K14 how to handle and store grinding wheels safely and correctly
K15 the application of roughing and finishing cuts, and the effect on wheel life, surface finish and dimensional accuracy
K16 the application of cutting fluids with regard to a range of different materials
K17 the effects of clamping the work piece in a chuck/work holding device, and how this can cause distortion in the finished components
K18 how to recognise CNC grinding machining faults, and identify when adjustments need to be made
K19 the quality control procedures used, inspection checks to be carried out, and the equipment that will need to be used
K20 the issues that can occur with the CNC grinding activities, and how these can be overcome
K21 the extent of your own responsibility and to whom you should report if you have problems that you cannot resolve
Scope/range
Scope Performance
1. Confirm that the machine is ready for operation by checking all of the following:
1.1 obtain and use the appropriate documentation (such as job instructions, drawings, quality control documentation)
1.2 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
1.3 confirm with the machine setter that the machine is ready for production
1.4 where appropriate, seek any necessary instruction/training on the operation of the machine
1.5 ensure that machine guards are in place and are correctly adjusted
1.6 hold components securely, without distortion
1.7 check that the operating program is at the correct start point and the workpiece is clear of the machine spindle
1.8 follow the defined operating procedures and apply safe working practices and procedures at all times
1.9 ensure that machine settings are adjusted as and when required (either by yourself or the setter) to maintain the required accuracy
1.10 ensure that the components produced meet the required specification for quality and accuracy
1.11 leave the work area and machine in a safe and appropriate condition on completion of the activities
2. Operate one of the following CNC grinding machines:
2.1 CNC universal grinder
2.2 CNC gear grinder
2.3 CNC thread grinder
2.4 CNC grinding machining centre
2.5 other specific CNC grinding machine
3. Produce ground components which cover four of the following, as applicable to the machine type used:
3.1 plain diameters
3.2 internal and external profiles
3.3 parallel bores
3.4 stepped diameters
3.5 eccentric diameters
3.6 tapered bores
3.7 tapered diameters
3.8 external screw threads
3.9 involutes and helical forms
3.10 flat faces and shoulders
3.11 chamfers and radii
3.12 curvic couplings
3.13 special forms (such as concave, convex)
3.14 internal/external undercuts/bearing tracks
4. Machine one type of material from the following:
4.1 ferrous
4.2 non-ferrous
4.3 non-metallic
5. Use appropriate gauges or instruments to carry out the necessary checks for accuracy, during production, of three of the following:
5.1 dimensions
5.2 profile
5.3 surface texture
5.4 ovality/lobing
5.5 parallelism
5.6 concentricity
5.7 angle/taper
5.8 hole size
5.9 squareness
5.10 thread form
6. Produce component with dimensional accuracy, form and surface texture within all of the following quality and accuracy standards as is applicable to the operations performed:
6.1 dimensional tolerance equivalent to relevant standard
6.2 flatness and squareness within 0.0005” per inch or 0.0125mm per 25mm
6.3 angles within +/- 0.5 degree
6.4 surface finish 16 µin or 0.8 µm
6.5 ground bores/holes within H8
6.6 screw threads BS medium fit