Ergonomics - Atlas Copco

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Evaluation of shock reaction There are no standards for the evaluation of shock reaction. The standard ISO 6544 describes a procedure for measuring the impulse from a machine with the handle supported. Current knowledge cannot tell us how many shocks an operator can be exposed to before they pose a risk. As mentioned earlier, the shock reaction depends on the impulse entering the machine during the tightening sequence. Since every tool has a torque range, the shock reaction Torque (Nm) M T t u t d Time (s) Fig. 3.12 A typical tightening sequence. The area under the curve represents the impulse. lm will vary with the torque setting, for the same joint characteristics. The subjective perception of the torque reaction will also vary according to the work posture. The evaluation proce- dures must be very simple to be practical. We suggest that the scaling factor is directly proportional to the impulse measured in accordance with ISO 6544 for the hard joint. In most cases, the soft joint used in the standard gives a tightening time in excess of 300 ms and, according to our definition, this is not a shock. The other reason for selecting the hard joint is that requests for information about impulses from tools working on this joint are received from time to time, particularly from the automotive industry. Many manu- facturers and users have access to this joint and can perform measurements. In other words, there are data available. At the beginning of this chapter it was mentioned that the operator’s perception of the shock will be worse when the joint gets softer, and for medium-soft joints his or her perception will be more positive again. Using the hard joint we will be unable to find the worst joint for each torque setting. However, when comparing different tools at different joints, the one with the lowest impulse will always be preferred. Three functions are used to evaluate the 101
102 Score 40 30 20 10 0 shock reaction, one for straight tools, one for pistol grips, and one for angle nutrunners. The reading from the inline transducer is the installed torque during tightening. To calculate the force at the operator’s hand, the torque data is divided by the diameter of the straight tool. Or, for a pistol grip tool and an angle nutrunner, the torque data are divided by the effective length of the tool measured from the center of the grip handle to the spindle center. Force as a function of time is integrated and the value in Ns is compared with the evaluation curve to get the score. straíght tool pistol grip angle nutrunner 0 10 20 30 40 Impulse (Ns) Bibliography ISO 5393 Rotary tools for threaded fasteners – Performance test method. ISO 6544 Hand-held pneumatic assembly tools for installing threaded fasteners – Reaction torque and torque impulse measurements. Bo Lindqvist: 1993, Torque reaction in angled nutrunners, Applied <strong>Ergonomics</strong>, 24 (3) 174-180. Fig. 3.13 Score for shock reaction for straight, pistol grip and angle nutrunners.
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Power Tool Ergonomics E V A L U A T
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Acknowledgements While doing resear
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How to get the best out of this boo
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Work with international standards I
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Good ergonomics is good economics W
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10 SOCIOLOGY INDUSTRIAL SOCIOLOGY S
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12 Work organization No organizatio
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1 outside the production system, an
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1 A seated operator usually has goo
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1 without stretching the trunk. The
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20 The arm sling as a preventive me
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22 Extreme working postures in real
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2 Working with high feed forces req
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2 Working areas of a standing works
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2 body is lifted or tilted, or the
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30 The team is an important factor
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32 Grinders Grinders and sanders ar
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34 HanDle DeSiGn The hand grips on
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36 DUSt anD oil Although the machin
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38 Working environment In general,
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40 SHoCK reaCtion Sudden changes in
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42 practice. Sometimes the chisel h
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44 SHoCK reaCtion These tools do no
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46 heavy, assembly work is often hi
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48 depends on its inertia. The same
Page 51 and 52: 50 bolts. Unfortunately there are a
Page 53 and 54: 52 The low reaction torque in impul
Page 55 and 56: 54 the working environment A typica
Page 57 and 58: 56 Today, the angle nutrunner can b
Page 59 and 60: 58 High torque nutrunners for use w
Page 61 and 62: 60 Wheel nuts on trucks and buses a
Page 63 and 64: 62 Introduction A basic ergonomic p
Page 65 and 66: 64 Handle design The handle of a ha
Page 67 and 68: 66 Arteries Veins (superficial) Vei
Page 69 and 70: 68 Handle size Since a tool handle
Page 71 and 72: 70 However, if the texture is too c
Page 73 and 74: 72 Bibliography Chaffin, D.B. and A
Page 75 and 76: 74 Fig. 3.3 The same feed force app
Page 77 and 78: 76 Pushing and pulling Pushing a to
Page 79 and 80: 78 the object, the shape of the obj
Page 81 and 82: 80 Safety factor a 2 Frequency of t
Page 83 and 84: 82 Comments for different tool type
Page 85 and 86: 84 The trigger is either operated b
Page 87 and 88: 86 used in one handed operations. T
Page 89 and 90: 88 Weight The weight of a hand-held
Page 91 and 92: 90 stability of grip, the center of
Page 93 and 94: 92 Temperature Hand-held power tool
Page 95 and 96: 94 To ensure physical comfort durin
Page 97 and 98: 96 Score 40 30 20 10 0 Bibliography
Page 99 and 100: 98 the dynamic properties of the ma
Page 101: 100 High motor power and fast clutc
Page 105 and 106: 104 piezo-electric crystal. When th
Page 107 and 108: 106 EN 50144 and EN 60745. Both ISO
Page 109 and 110: 108 hole of the wheel are wider tha
Page 111 and 112: 110 In the GTG 40 grinding machine,
Page 113 and 114: 112 RRH machines serves two functio
Page 115 and 116: 114 be noted that declared values b
Page 117 and 118: 116 Noise Noise was the first envir
Page 119 and 120: 118 value for 8 hours’ exposure t
Page 121 and 122: 120 We can start by looking at the
Page 123 and 124: 122 This is done with a minimum inc
Page 125 and 126: 124 microphones at a distance of 1
Page 127 and 128: 126 coated with dust or damaged by
Page 129 and 130: 128 This method has not been used b
Page 131 and 132: 130 tool cabinet. Many workplaces h
Page 133 and 134: 132 lubrication. Made from a compos
Page 135 and 136: 134 Grinder GTG 40 F085 The relevan
Page 137 and 138: 136 were simulated by fitting a whe
Page 139 and 140: 138 Drill LBB 26 EPX-060 The releva
Page 141 and 142: 140 applied to the center of the dr
Page 143 and 144: 142 Chipping hammer RRF 31 The rele
Page 145 and 146: 144 SHOCK REACTION There are no sho
Page 147 and 148: 146 Riveting hammer RRH 06 The rele
Page 149 and 150: 148 WEIGHT The weight is 1.3 kg, sc
Page 151 and 152: 150 Screwdriver LUM 22 PR4 The rele
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152 This gives a score of 9. In pra
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154 Impulse nutrunner EP9 PTX80-HR1
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156 Due to friction in the hydrauli
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158 Electric nutrunner ETP ST32-05-
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160 WEIGHT The electric nutrunner i
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162 Angle nutrunner LTV 29 R30-10 T
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164 operator equal to installed tor
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166 Electric angle nutrunner Tensor
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168 WEIGHT The electric nutrunner i
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170 High torque nutrunner LTP 51 Th
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172 Score 40 30 20 10 0 NOISE The d
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