Ergonomics - Atlas Copco

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Normal use of grinders does not involve fast movements. Frequency is less than 6 times per minute and duration more than 10 seconds per operation. Total duration can vary a great deal. Try to find the real total duration for the workplace in question. If that is not possible use the values in Table 3.10. Drills The important forces are force and torque from the feed force, the torque from the drill operation and the trigger force. For pistol grip drills feed force is hori- zontal or vertical push force. A torque is generated equal to the distance from the main axes of the tool to the center of the hand, multiplied by the feed force used. This torque is an ulnar-flexion torque. The torque from the drilling operation is a supination torque. The maximal torque can be calculated when the power of the tool is known. Assuming the maximum power is when the tool is loaded down to half the free-running speed, the maximum power torque can be calculated as: Max. power torque = Max. power 10 / free-running speed Pistol grip tools normally have a trigger operated with the index or long finger, depending on the grip chosen. For straight tools the maximal feed force is the standing or sitting push-down or push-forward force depending on the workstation design. Torque in the wrist to counteract the torque from the drilling acts as a dorsal-flexion torque. In some cases, where the handle has low friction the gripping force can be the limiting force. For angle drills, when operated with one hand, the feed force results in an ulnar-flexion torque. Torque is calculated as the feed force needed multiplied by the distance from the drill bit to the center of the hand. Normal use of drills does not involve fast movements. Frequency is less than 6 times per minute and duration more than 10 seconds per operation. Total duration can vary considerably. Try to find the real total duration for the workplace being analysed. Use the number of holes drilled multiplied by the duration, i.e., the time taken to drill one hole. If that is not possible use the values given in Table 3.10. Percussive tools The important forces are the feed force, and the trigger force. Feed force for chipping hammers acts as a standing push down force. For riveting hammers it is a standing push forward force. 83
84 The trigger is either operated by the thumb or by the index finger depending on the design of the tool. Straight chipping hammers normally have triggers operated by more than one finger. Normal use of chipping hammers does not involve fast movements. Frequency is less than 6 times per minute and duration more than 10 seconds per operation. Riveting hammers are often used with frequencies higher than 6 times per minute and the duration of the operation is less than one second. Total duration can vary a lot. Try to find the real total duration for the workplace being analysed. If that is not possible, use the values in Table 3.10. Screwdrivers The important forces are torque from the tightening, the feed force, and the trigger force. For straight tools the force from the tightening torque is experienced as a wrist dorsal-flexion torque. It is transferred to the hand as friction between the hand and the tool surface. For surfaces with low friction the grip-force can be the limiting factor. The maximal torque that a given grip-force can transfer can be calculated as the grip-force times the coefficient of friction times the diameter of the handle. Normally the wrist’s ability to handle the torque is the limiting factor. For certain types of screws, e.g., self-tap- ping screws, a considerable amount of feed force might be needed. For those cases the grip-force can be the limiting factor for the feed force. Trigger forces are normally low and distributed over several fingers. For pistol grip screwdrivers tightening torque, weight distribution, feed force and trigger forces should all be taken into ac- count. Tightening torque is experienced as a supination torque in the wrist. Bad weight distribution might give a radial-flexion torque equal to the weight of the tool times the distance from the center of gravity to the center of the handle. This torque might be a problem while the tool is moved to and from the bolt. Force and torque from the feed force is assessed as for drills. Trigger force is normally handled with the index or long finger. Normal use of screwdrivers involves fast movements. Frequency is more than 6 times per minute and duration is less than 3 seconds per screw. Total duration can vary considerably. Try to find the real total duration for the workplace being analysed. The number of screws multiplied by the duration, i.e., time
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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
Page 33 and 34: 32 Grinders Grinders and sanders ar
Page 35 and 36: 34 HanDle DeSiGn The hand grips on
Page 37 and 38: 36 DUSt anD oil Although the machin
Page 39 and 40: 38 Working environment In general,
Page 41 and 42: 40 SHoCK reaCtion Sudden changes in
Page 43 and 44: 42 practice. Sometimes the chisel h
Page 45 and 46: 44 SHoCK reaCtion These tools do no
Page 47 and 48: 46 heavy, assembly work is often hi
Page 49 and 50: 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: 82 Comments for different tool type
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 and 102: 100 High motor power and fast clutc
Page 103 and 104: 102 Score 40 30 20 10 0 shock react
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
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134 Grinder GTG 40 F085 The relevan
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136 were simulated by fitting a whe
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138 Drill LBB 26 EPX-060 The releva
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140 applied to the center of the dr
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142 Chipping hammer RRF 31 The rele
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144 SHOCK REACTION There are no sho
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146 Riveting hammer RRH 06 The rele
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148 WEIGHT The weight is 1.3 kg, sc
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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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