Machining components using 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 take charge of the prepared machine and check that it is ready for the grinding 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 ground plain diameters, eccentric diameters, external threads, stepped diameters, flat faces and shoulders, chamfers and radii, special forms and profiles, tapered diameters and faces, internal and external profiles, grooves/undercuts, gear teeth, bearing tracks, parallel and tapered bores and curvic couplings. 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 equipment, tooling, program, materials or activities that you cannot personally resolve, or 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 be sufficient to provide a good understanding of your work, and will enable you to adopt an informed approach to applying CNC grinding procedures. You will have an understanding of the CNC grinding process, and its application, and will know about the machine, grinding wheels, materials, consumables and grinding activities, in adequate depth to provide a sound background to 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 the machine, its tooling and associated workholding devices, are the subjects of other standards.
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 procedures for checking that they are operating correctly
- how to start and stop the machine in both normal and emergency situations
- the hazards associated with working on CNC grinding machines and how to minimise them and reduce any risks
- the Grinding Wheel Regulations covering the use and operation of grinding wheels and equipment
- the importance of wearing the appropriate protective clothing (PPE) and equipment, and of keeping the work area clean and tidy
- the application of a range of CNC grinding machines
- 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 use 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 program operating and control buttons
- how to operate the machine using single block run, full program run and feed/speed override controls
- why you would conduct a full dry run and single block run
- how to make adjustments to the program operating parameters to take account of wheel wear
- 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
- the various types of grinding wheels used, and how they are located and secured to the machine spindle, tool holders and tool magazine or carousel
- the safe and correct handling and storage of grinding wheels
- how to check that the grinding wheel is in a serviceable condition, and the effects that worn/burnished tooling will have on the workpiece surface finish and tolerances
- the problems that can occur with grinding activities, and how these can be overcome
- the application of cutting fluids with regard to different materials being machined
- the quality control procedures used, inspection checks that need to be carried out, and the equipment that is used
- where to obtain component drawings, specifications and/or job instructions required for the components being machined
- 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 grinding wheels correctly dressed, and 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 grinding machines:
- CNC universal grinder
- CNC grinding machining centre
- CNC gear grinder
- CNC thread grinder
- CNC ring grinder
- Produce ground components, which combine different operations and cover eight of the following:
- plain diameters
- internal profiles
- external profiles
- parallel bores
- stepped diameters
- eccentric diameters
- tapered bores
- tapered diameters
- external screw threads
- involute forms
- helical forms
- flat faces and shoulders
- chamfers (including gear tip chamfers)
- radii (including gear root)
- curvic couplings
- special forms (such as concave, convex)
- internal/external undercuts/bearing tracks
- Machine one different type of material from:
- ferrous
- non-ferrous
- non-metallic
- Carry out the necessary checks for accuracy during production of six of the following:
- dimensions
- profile
- surface texture
- ovality/lobing
- parallelism
- concentricity
- angle/taper
- hole size
- squareness
- thread form
- Produce component within all of the following quality and accuracy standards, as applicable to the operations performed:
- dimensional tolerance equivalent to relevant standards
- flatness and squareness 0.0005" per inch or 0.012mm per 25mm
- angles within +/- 0.25 degree
- surface finish 16µin or 0.4µm
- ground bores/holes within H8
- screw threads BS medium fit
- company standard
- spur and helical gears to current relevant standards