Job status was listed as "outstanding" and joined que of other Maint issues. Now Highlighted as Urgent, will be prioritised after current breakdown.

Transcription

1 Carrs HS Jobs Submission Date :56:21 Item HS Reference CNC Guarding Due Date Status Comments/Notes Completed Job status was listed as "outstanding" and joined que of other Maint issues. Now Highlighted as Urgent, will be prioritised after current breakdown. Guarding need to be improved around the cutting heads of the CNC machines.. 13/04/15 Guard is now in place Attachment _ jpg Job Type HS Job

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5 Carrs of Sheffield Manufacturing Ltd (And Associated Companies) Safe Working Procedure H&S Ref: SWP 10 Procedure Horizontal Milling Machine Mandatory Requirements Provision and Use of Work Equipment Regulations 1998 Introduction The incorrect use of plant and machinery can result in serious injury and sometimes permanent disablement. In order to prevent this, and also to comply with the Provision and Use of Work Equipment Regulations 1998, the following rules must be followed. Horizontal Milling Machines: (a) (b) (c) (d) (e) Only trained and authorised persons are permitted to use the machine. The cutters of every horizontal milling machine must be fenced by a strong guard enclosing the whole surface except the part exposed for the milling work. Except in the case of face milling, the guard must: - be provided with adequate side flanges; or - extended on each side of the cutters to the end of the arbour, or not less than half the diameter of the cutter. Guards must be kept in position while the cutters are in motion. Sufficient starting and stopping devices must be easily accessible to the operator. Declaration I was given a copy of this SWP and the opportunity to ask questions relating to the SWP. I fully understand the requirements, and will perform my duties in accordance with the SWP. Name of employee: Signature of employee:.. Date.. I confirm the above named employee has been trained in all aspects relating to the SWP and fully understands the need to comply with the requirements of the SWP. Name of instructor:. Signature of instructor: Date. SWP 10 - Horizontal Milling Machine Safety Page 1 of 1

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7 Health and Safety Executive Safe use of horizontal boring machines HSE information sheet Engineering Information Sheet No 28 (Revision 1) Interlocked guard Interlocked sliding panel Hold-to-run control Fixed guard Fixed guard Figure 1 Fixed and interlocked guards prevent access to the work zone. The height of perimeter fencing will be determined by using the values given in BS EN ISO Introduction This guidance is for employers and operators of existing horizontal boring machines. It gives practical guidance on the safe use of horizontal boring machines. It has been produced in order to assist with meeting legal duties under the Provision and Use of Work Equipment Regulations 1998 (PUWER 98). 2 This guidance applies to both manual and computer numerically controlled (CNC) types of horizontal boring machines. Hazards and risks The hazards associated with horizontal boring machines include entanglement at the rotating chuck and cutting tools. Crushing or trapping may also arise from other moving parts, eg from the moving table. The automated nature of CNC machines means that additional risks to safety may be present as machine movement is not always reliable or predictable. Injuries may occur during: machining observation; setting and adjustment; or swarf removal. Accident history shows that serious injuries, including severe lacerations, crushing or amputation, occur on these machines. Other injuries include skull fracture and broken limbs. Fatal accidents have also occurred. What the law says Management of Health and Safety at Work Regulations You must carry out a suitable and sufficient risk assessment to determine the appropriate safeguarding measures required to control the risks. 1 of 4 pages

8 Health and Safety Executive In your risk assessment, you will need to consider all operations where access to the work zone is required. This will include routine machining operations, observation and adjustment requirements and breakdowns and maintenance tasks. Risks associated with the machine being used for other machining operations, eg drilling or milling, will also need to be included in the risk assessment. Provision and Use of Work Equipment Regulations Effective measures must be taken to prevent access to any dangerous parts of machinery. The hierarchy of controls specified in the Regulations must be applied when safeguarding solutions are being determined. A safeguarding solution will need to be developed based on the specific functions of the individual horizontal boring machine. You will need to take into account the size and configuration of the machine and the specific applications for which the machine will be used. Control measures Primary safeguards During routine machining operations, access to the work zone should be prevented by fixed and/ or interlocking guards (see Figure 1). The height, position and construction of any new guards should meet appropriate standards (see References and Further reading). If physical guarding is not practicable, alternative types of safety devices may be used, eg light curtains or pressure sensitive mats. Access into the enclosure inside the perimeter fencing should be via an interlocked gate, that either: includes guard locking, to prevent entry when the machine is in use; or stops movement of all the dangerous parts if the gate is opened during use. Safe systems of work for all operations are required, including activities such as safe swarf removal. Trip probes (see Figures 2 and 3) Trip probes with braking devices may form part of the safeguarding solution where the risk assessment permits. However, when considering the use of trip probes as a primary safeguard, all of the following conditions should apply: Movement of the machine table is slow and inadvertent contact by the operator may be considered to be low risk. In these circumstances, the primary risk remains from the rotating chuck and cutting tool. Various individual non-standard components are being machined and a high degree of close observation is required for setting the machines. The limitations of these devices must be recognised, both in terms of their practicability of use and the level of protection they provide. A magnetic based trip probe is able to provide improved protection as it can be moved to the most appropriate position, depending on the particular workpiece being machined. Trip probes do not directly prevent entanglement but mitigate the extent of injury, when actuated, by applying the brake to stop the machine quickly. Trip devices alone do not protect against other hazards such as crushing and trapping between fixed and moving parts of the machine or workpiece. Your risk assessment should determine if trip devices will be effective for the range of hazards present. A detailed risk assessment will be required to justify that other safety measures are not practicable. Where an interlocking enclosure is not practicable and cannot be installed you should: Provide perimeter fencing around the machine in order to restrict general access by personnel not associated with the machine. Ensure any access gates are spring-closure and include a latch arrangement, such that a deliberate two stage opening of the gate is required (ie raising the latch and pushing against the spring pressure). Ensure any ancillary equipment, storage facility or other non-essential items are removed from the enclosure. Your risk assessment will need to clearly demonstrate why a full interlocked enclosure is not practicable. Figure 2 Application of telescopic trip device 2 of 4 pages

9 Health and Safety Executive should also enable the braking arrangements, eg DC injection braking. On release of the hold-to-run control (or enabling device), the braking system should be applied. This principle may be incorporated into an existing pendant control. These aspects of the control system are safety-critical and should be designed to meet the requirements of regulation 18 of PUWER (Note: New machines should be supplied with safety arrangements which provide for this kind of intervention.) Figure 3 Application of magnetic telescopic trip device CNC functionality must be disabled if use of trip probes is to be considered, due to the possibility of unexpected movement. Braking systems It is not possible to specify a minimum stopping performance for braking systems. This is because of the wide range of machine sizes and other design characteristics. The objective should be to stop the machine as quickly as possible taking into account the particular circumstances. Where brakes are fitted to older machines care should be taken to ensure that the machine is capable of withstanding the stresses induced by the effects of braking (see PD 5304).4 A braking system may be mechanical or electrical or a combination of both. Supplementary safeguards during setting A safe system of work must be prepared for setting operations and include management arrangements for the training of operators and monitoring that the system is implemented correctly. Where powered movement of machine elements is necessary for setting operations, and access by the operator into the work zone must be justified by the risk assessment and the risks reduced by using supplementary safeguards. In these cases the primary safeguard, i.e. guard interlocking, may be suspended by a nominated competent person using a key-operated selector switch. The key must be controlled by the competent person and not left in the machine. Any further hazardous movement of the machine should only be possible by using a hold-to-run control arrangement or enabling device. The selector switch Machine controls Other machine controls, eg the start button or feed and speed selectors, should be clearly visible and identifiable with appropriate marking where necessary. The main controls should be positioned so that people are not at risk when operating them. One or more emergency stop controls should be provided where appropriate. Emergency stop controls should be readily accessible. Where emergency stop controls are activated, the machine should only be able to be restarted when the emergency stop device has been reset manually and normal operating controls are used to restart the machine. Other hazards Other hazardous parts such as transmission machinery including shafts, gears, pulleys, etc should be guarded using fixed guards. Where routine access is required to any of these parts, interlocked guards should be fitted. Guards should prevent access to the dangerous parts of swarf conveyors or elevators. Information, instruction and training All relevant health and safety information and, where appropriate, written instructions on the use of horizontal boring machines must be made available to operators. Operators must be competent to use the machine safely and to follow all safe systems of work. Adequate training should be given to ensure they have the correct skill, knowledge and risk awareness, and to ensure that they are physically suited to the task. Particular attention should be given to: dangers at the machine; location and operation of controls; precautions to reduce the risk of entanglement; correct use of guards and other safety devices; any tests, eg daily test of trip devices and the system for reporting defects; and 3 of 4 pages

10 Health and Safety Executive safe systems of work for cleaning, maintenance, setting and adjustment, loading of workpieces etc. Do not let unauthorised, unqualified or untrained people use machinery. Never allow young people under the minimum school leaving age, eg on work experience, to operate or help at machines. Some workers, eg new starters, young people or those with disabilities, may be particularly at risk and need additional instruction, training or supervision. References 1 BS EN ISO 13857:2008 Safety of machinery. Safety distances to prevent hazard zones being reached by upper and lower limbs British Standards Institution 2 Safe use of work equipment Provision and Use of Work Equipment Regulations Approved Code of Practice and guidance L22 (Fourth edition) HSE Books Management of health and safety at work. Management of Health and Safety at Work Regulations Approved Code of Practice and guidance L21 (Second edition) HSE Books PD 5304:2014 Guidance on safe use of machinery British Standards Institution Further reading Further information for suppliers, installers and users of new and second-hand machinery can be found on HSE s Work equipment and machinery webpages Further information For information about health and safety, or to report inconsistencies or inaccuracies in this guidance, visit You can view HSE guidance online and order priced publications from the website. HSE priced publications are also available from bookshops. This guidance is issued by the Health and Safety Executive. Following the guidance is not compulsory, unless specifically stated, and you are free to take other action. But if you do follow the guidance you will normally be doing enough to comply with the law. Health and safety inspectors seek to secure compliance with the law and may refer to this guidance. British Standards can be obtained in PDF or hard copy formats from BSI: or by contacting BSI Customer Services for hard copies only Tel: cservices@bsigroup.com. This document is available at: Crown copyright If you wish to reuse this information visit for details. First published 09/98. BS EN ISO 13850:2008 Safety of machinery. Emergency stop. Principles for design British Standards Institution BS EN 953:1997+A1:2009 Safety of machinery. Guards. General requirements for the design and construction of fixed and movable guards British Standards Institution BS EN ISO 12100:2010 Safety of machinery. General principles for design. Risk assessment and risk reduction British Standards Institution BS EN :2006+A1:2009 Safety of machinery. Electrical equipment of machines: General requirements British Standards Institution BS EN ISO 14119:2013 Safety of machinery. Interlocking devices associated with guards. Principles for design and selection British Standards Institution Published by the Health and Safety Executive EIS28(rev1) 10/15 4 of 4 pages

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12 HSE Health & Safety Executive HSE information sheet CNC turning machines: Controlling risks from ejected parts Engineering Information Sheet No 33 Introduction This guidance aims to help machine users carry out an assessment of the risks from accidental ejection at CNC turning machines and confirm that the risk control measures are effective. Because of the variables involved it is difficult to make a precise assessment. The following guidance is intended to provide a best estimate upon which judgements about risk can be made. The guidance is mainly concerned with guard strength but other means to minimise risks from ejection are also considered. Recent research has shown that polycarbonate materials used in CNC turning-machine vision panels can degrade after exposure to the metalworking fluids and lubricants used in the machining process. This can result in a significant reduction in the impact resistance of the material and may be as much as 10% per year in a typical manufacturing machine-shop environment, as shown in Figure 1 1 below. (NB: Table 2, not the data contained in the figure, should be used as a basis for determining the residual impact resistance of vision panels.) There are significant safety implications because of the potential for high-energy ejections at turning machines. Operators may be at risk of injury because, in time, vision panels may not be able to contain ejected parts. Legal requirements The Provision and Use of Work Equipment Regulations require that risks from ejection are controlled by engineering means where it is reasonably practicable to do so (regulation 12) and that these safeguards are properly maintained (regulation 5). The requirements for equipment suitability (regulation 4) and appropriate information, training, instruction and supervision are also relevant. Ejection Most ejections at CNC turning machines are caused as a result of operator/setter error and failure to properly maintain work-holding devices. The likelihood of ejection can vary considerably depending upon the type of work being done. Work involving faceplates and other turning fixtures need special care in operation while bar-fed machines, using collets for small components, are less hazardous. To determine if the machine guard will be strong enough to contain ejected parts the first step is to identify which part(s) could foreseeably be ejected due to its rotation and off-centre location. Particular attention should be given to chuck jaw assemblies, workpiece clamps, faceplate balance weights and component parts of turning fixtures. The potential for over-speed conditions, collisions and other kinds of reasonably foreseeable errors should be considered. The circumstances of previous ejection incidents should also be considered, whether or not any injuries were caused. The existing and intended applications of the machine should be assessed. Other factors making ejection likely include: (a) (b) (c) (d) rotational speed for the particular application; weight and type of gripping jaws if non-standard; radius at which gripping jaws/clamping devices are operating; gripping force applied to the workpiece (static/dynamic conditions); Figure 1 Ageing of polycarbonate vision panels No exposure to metalworking fluids (MWFs) Protected on both sides (construction not damaged) Protected on workzone side (no damage, operator s side not exposed to MWFs) Stock material Exposed to MWFs Panel not protected Protected on workzone side Glass damaged on operator s side Damage to glass on operator s side and edge seal

13 (e) (f) (g) (h) whether the workpiece is gripped externally or internally; condition of chuck/fixture, eg inadequate lubrication/maintenance; state of balance; magnitude of the cutting forces involved (depth, feed rate and workpiece overhang). The worst case situations should be identified based on an estimate of the weight of the part, its radius from the spindle centreline and its speed. (Remember when estimating that doubling the weight doubles the energy but doubling either the speed (rpm) or the ejection radius increases energy by a factor of four, ie smaller parts may represent a greater hazard). Any situation where the ejected part would be directly in line with the vision panel should be investigated. On some machines the chuck area may be protected by a steel portion of the guard, but a new chuck or modified work-holding arrangement may change this situation. More accurate measurements should be taken for these worst case situations. The approximate ejection energy of the parts can then be determined using Table 1 3 against the following values: (a) (b) (c) weight of the part in kilos; ejection radius (point of release radius): Generally the centre of gravity position of the item relative to the spindle centreline will constitute the release radius but for chuck jaw assemblies, as the release radius is outside the chuck body periphery, a factor of 1.25 of the chuck diameter should be applied; maximum rotational speed: Consider the possible failure to limit maximum rpm on machines with constant surface speed (CSS). Using the above values read off the corresponding ejection energy (kj). Where a particular weight, radius or rpm is not given in Table 1 use the nearest higher values to obtain an estimate. Record the results obtained. A worked example is given below. Table 1: Ejection energy (kj) Engineering controls The next step will be to determine the suitability of the existing guard design and the materials used in its construction to contain the anticipated maximum ejection energy. (It should be noted that machine guards are not designed to contain ejections in all circumstances. New machines constructed to European Standards 4 normally apply values based on the strength needed to contain an ejected chuck jaw rotating at the maximum spindle speed.) Materials The materials used for the guard and vision panel should be identified. The vision panel is likely to be polycarbonate (a clear ductile plastic when new), glass, or a combined lamination of glass and polycarbonate. The thickness of the guard and vision panel material will need to be measured. Glass: Single sheets of glass will generally be 4-6 mm thick and, even if toughened, will be of inadequate strength to resist a high-energy ejection impact. Polycarbonate will be recognisable as a plastic material ranging from 4 to 20 mm in thickness. Deep scratches or discoloration will indicate a deteriorated condition and any cracked or damaged material is unsuitable for continued use. Laminated constructions may be of two-layer glass/polycarbonate or three-layer glass/polycarbonate/glass or polycarbonate. Overall laminate thickness will range from 8 to 30 mm. Only the polycarbonate layer provides impact resistance. The two-layer units will suffer from degradation in the same way as single unprotected sheets of polycarbonate. However, the three-layer units can be considered to have retained their original strength so long as metalcutting fluid has not entered the assembly and the Ejected weight Ejection radius At maximum spindle revolutions per minute of kj kj kj kj kj kj kj kj kj kj kj 1.0 kg 400 mm 350 mm 300 mm 250 mm 200 mm 175 mm 150 mm 125 mm 100 mm 75 mm 63 mm 50 mm 38 mm Beyond viable range

14 protective layers are not cracked. Damage of this kind makes the vision panel unsuitable for continued use. The impact resistance of three-layer panels with an overall thickness of less than 12 mm should be based on no more than 4 mm of polycarbonate unless confirmed otherwise by the manufacturer. Steel: The guard and its supporting parts will generally be made of steel. Where a punched steel sheet or steel bars have been provided to supplement the vision panel, assess the spacing to determine if they will be able to contain all the sizes of ejection items identified. Guard and vision panel fixings The method of fixing the vision panel into the guard needs to be examined and assessed for its strength. A robust mechanical connection is needed to prevent a high-energy impact from separating the vision panel from the guard. Moulded rubber location arrangements have proved to be inadequate for this. There should be at least a 20 mm overlap of the vision panel all around the inside of the guard aperture. Clamping is the preferred method of retaining the vision panel in position rather than bolting through the vision panel material. Material impact resistance Provided the condition of the vision panel and its fixing to the guard are considered adequate, the next step is to determine the age of the polycarbonate. In assessing this it must be assumed that it is the original material/vision panel fitted to the machine, unless there is definite evidence of the date when the vision panel was replaced. (If the vision panel is changed it is recommended that a record is kept in the maintenance log or on a tag/sticker on the machine.) For vision panels which are not fully protected determine the residual impact resistance for the polycarbonate from Table 2 3 (see the worked example below). The value for the vision panel needs to be greater than the highest foreseeable ejection energy established from Table 1. The thickness of the steel guard in the ejection zone needs to be approximately one third of the required thickness of polycarbonate. If the steel guard is too thin or the vision panel strength values are below the foreseeable ejection energy it will be necessary to take remedial action. Worked example Assume that a machine is three years old and has a maximum spindle speed of 3300 rpm. It has a vision panel made of 8 mm thick polycarbonate with toughened glass on the inside but no other protection on its outer surface. The machine has a 180 mm diameter chuck and the maximum chuck jaw weight has been determined as 1.8 kg. If a chuck jaw was released its centre of gravity would be some 30 mm outside the chuck body. The release radius would therefore be half the chuck diameter plus the 30 mm, making a total of 110 mm. This gives sufficient information to proceed. Using the tables Table 1 is used to initially find the ejection energy for a 1 kg weight. The nearest higher release radius is 125 mm and the nearest higher maximum rotational speed is 3500 rpm. For these conditions the energy value is kj. Multiply this value by the actual weight of the chuck jaw. This gives an energy value of kj or rounded 1.9 kj. Now go to Table 2. In Table 2 the mass of the jaw assembly lies between the 1.25 kg and the 2.5 kg sections. In this case the data in the 1.25 kg section should be used. This is because the values in this section are calculated taking into account a smaller impact area for the ejected part. Smaller impact areas have a greater penetrating effect and this is compensated for by a slightly increased thickness of polycarbonate. Reading across from the 1.9 kj energy level for new polycarbonate a 6 mm thickness is required. The machine is, however, fitted with 8 mm polycarbonate that is three years old and has been subject to deterioration. Read across from the 8 mm polycarbonate thickness row, in the 1.25 kg section, to the 3 yrs column. This indicates that the material now has an impact resistance of only 1.8 kj. This is below the 1.9 kj required to contain the chuck jaw. For continued use some remedial action is required. Remedial measures In cases where the control measures are found to be deficient, further information should be sought from the manufacturer or supplier, wherever possible. The manufacturer should be able to provide information about design details of guards, the availability of guard upgrades, other recommended modifications and sources of suitable materials. The future maintenance requirements should also be considered as part of the assessment. In cases where long-term control measures are not going to be adopted and the circumstances of use will not change significantly this may include specifying periodic exchange intervals for vision panels. In the example above there are a number of measures that could be taken: (a) The CNC part-programmes could be amended to use a maximum spindle speed of 3000 rpm. This would extend the safe use of the machine for about a year but the polycarbonate would continue to deteriorate. (The maximum speed would need to be verified before start-up on a new partprogramme.);

15 Table 2: Thickness of polycarbonate (mm) and residual impact resistance over time (years) Ejected Polycarbonate Age of polycarbonate (years) weight thickness New 1 yr 2 yrs 3 yrs 4 yrs 5 yrs 6 yrs 7 yrs 8 yrs mm kj kj kj kj kj kj kj kj kj kg Having impact area of mm kg Having impact area of mm kg Having impact area of mm kg Having impact area of mm kg Having impact area of mm

16 (b) (c) (d) The polycarbonate could be replaced with new 8 mm unprotected material and then changed periodically; The vision panel could be replaced with a completely sealed laminated assembly using a centre sheet of 6 mm new polycarbonate. (Important note: machine users should never attempt to manufacture their own laminated vision panels as these are specially made units which require specific bonding methods, adhesives and sealing materials. Only units supplied or recommended by the machine manufacturer should be used); A steel protection plate, properly supported and securely bolted to the guard, could be added over the vulnerable area of the vision panel. The thickness of steel would need to be approximately one third of the thickness of new polycarbonate required for the 1.9 kj energy value. (Note: Only a new fully laminated and sealed vision panel or the protective steel plate solutions can be considered as long-term solutions.) The following additional measures should also be considered, especially in cases where the manufacturer/agent no longer exists or technical data cannot be obtained: (a) (b) (c) (d) If possible reduce the mass (weight) of items which may be ejected; Improve the design/security of work-holding devices; Replace any defective/worn chucks and improve maintenance; Move high-risk work to a safer machine. Safe working practices In addition to improvements in guard strength the likelihood of ejection can be reduced by adopting good working practices and ensuring that equipment, particularly work-holding devices (eg chucks and fixtures), are properly maintained. Detailed information concerning the safe use of chucks should be available from the machine manufacturer or chuck supplier. Proper training of operators and machine setters is important to ensure that the correct machining parameters are selected and that programming errors are minimised. This guidance is not intended to apply to other types of machine tool as the data have been derived from work done specifically on turning machines. Further information This information sheet was prepared in conjunction with: Machine Tool Technologies Association (MTTA) Engineering Employers Federation (EEF) British Turned Parts Manufacturers Association (BTMA) References 1 Source of data in figure: D Mewes et al Strength of materials when subjected to impact stresses BIA Institut, St Augustin, Germany. 2 Safe use of work equipment. Provision and Use of Work Equipment Regulations Approved Code of Practice and guidance L22 HSE Books 1998 ISBN The data contained in Tables 1 and 2 are derived from formulae in BS EN : BS EN 12415:2000 Machine tools. Safety. Small numerically controlled turning machines and turning centres Further reading Health and safety in engineering workshops HSG HSE Books ISBN While every effort has been made to ensure the accuracy of the references listed in this publication, their future availability cannot be guaranteed. Further information HSE priced and free publications are available by mail order from HSE Books, PO Box 1999, Sudbury, Suffolk CO10 2WA. Tel: Fax: Website: (HSE priced publications are also available from bookshops.) For information about health and safety ring HSE's InfoLine Tel: , Fax: , hseinformationservices@natbrit.com or write to HSE Information Services, Caerphilly Business Park, Caerphilly CF83 3GG. You can also visit HSE s website: British Standards are available from BSI Customer Services, 389 Chiswick High Road, London W4 4AL. Tel: Fax: Website: This leaflet contains notes on good practice which are not compulsory but which you may find helpful in considering what you need to do. This publication may be freely reproduced, except for advertising, endorsement or commercial purposes. The information is current at 05/01. Please acknowledge the source as HSE.

17 Printed and published by the Health and Safety Executive 05/01 EIS33 C150