Ergonomics - Atlas Copco

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Vibration All machines vibrate to some extent. Depending on the design, the vibration can cause malfunction, fatigue and breakage of the tool. When operators are exposed, vibration can also cause health problems. In power tools the magnitude of vibration is determined by oscillating forces acting on the machine mass, the excitation of the natural frequencies of machine parts, and vibration from the process itself. What is vibration? Vibration is the oscillating motion of an object caused by forces acting on that object, which may be a power tool. Although this back and forth motion, or displacement, can be oriented along one axis, in most cases it has a more complex pattern. To describe the motion you often need three axes and sometimes rotational axes as well, allowing description of movement in a number of different directions. If the frequency of the oscillating force coincides with the natural frequency of a component in the tool design, the displacement will be amplified. Machine parts such as handles, for example, can be considered as a mass spring system with their own natural frequencies. How do we measure vibration? Vibration can be described in many different ways. The most common method is to use acceleration as the parameter. By integrating the acceleration signal once, the motion is described as velocity. Integrating the velocity gives a description of the displacement. Acceleration is a rather abstract parameter to be used to describe a motion. There are, however, a number of reasons why it has become the most widely used method. The most common transducer is a piezo-electric accelerometer, which has a mass pre-loaded by a spring against a 103
104 piezo-electric crystal. When the accelerometer is subjected to acceleration, the mass acts on the crystal with a force proportional to the acceleration. The force exerted on the crystal will cause the crystal to send out a charge proportional to the acceleration. The signal can be fed into a computer for evalua- tion via a charge amplifier. When measuring vibration in a hand- held power tool with a complex motion, the location of the transducer obviously has a Charge amplifier Three operators Front end B&K Puls Fig. 3.14 Conducting laboratory measurements using EN/ISO 8662. significant influence on the result. Some literature, in particular that dealing with exposure measurements, suggests that the transducer should be located where the operator places his hands. If we take a grinding machine as an example, there are many points along the handle where the transducer can be placed. Each will give different readings. For some machines the lowest and highest reading may differ by a factor of five – sometimes Frequency spectra Computer with B&K Puls Software
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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
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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 and 102: 100 High motor power and fast clutc
Page 103: 102 Score 40 30 20 10 0 shock react
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
Page 153 and 154: 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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Ergonomics - Atlas Copco

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