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Miltiadis A. Boboulos
Automation and Robotics
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Automation and Robotics 1st edition © 2010 Miltiadis A. Boboulos & bookboon.com ISBN 978-87-7681-696-4
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Automation and Robotics
Contents
Contents Abstract
7
1 Automation & Robotics: An Optimized Loudspeaker Assembly for a Mechanized Serial Production Line
8
1.1 Introduction 1.2
8
Developing a dolly removal strategy
10
1.2.5 Involvement of the dolly in the coil assembly operation, motor unit assembly and dust cap cone
14
1.3
General assembly strategy
17
1.4
Feeder design
25
1.5
Assembly cell design
32
References
40
2 Design of speakers production: assembly line of capacity 180,000/month, 15 product variants
42
2.1 Introduction
42
2.2
42
Strategy for the “dolly” removal
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Automation and Robotics
Contents
2.3
General strategy
51
2.4
Feeder design
59
2.5
Evaluation of the assembly unit
73
References
81
3 Strategic approaches to resource husbandry and recovery: the superwash combo case study
83
3.1 Introduction
83
3.2
The team’s work
84
3.3
The performers
87
3.4 Quality
88
3.5
Market & production line
89
3.6
Environmental impact
92
3.7 Machines
93
3.8
Process technology & management
95
3.9
Raw materials & component parts
97
3.10 Conclusions
98
References
98
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Automation and Robotics
Contents
4 Software engineering and data communications: an automatic laminating plant
100
4.1
Enviromental model
100
4.2
Behavioural model
103
References
117
5 Robot grip mechanism: control loop design considerations
118
5.1 Introduction
118
5.2
Open loop system
119
5.3
Closed loop control system
120
5.4
Other control loop design considerations
125
5.5 Conlcusion
126
References
126
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Automation and Robotics
Abstract
Abstract In this book for the optimisation of assembly conveyor lines we are dealing with series part production featured by a medium complexity degree and a medium number of individual components and assembly technique alternatives. Modern production techniques for medium to large series products or mass production usually involve assembly conveyor lines. They still use hand labour more or less automated. The aim is to have monotonous and similar in type operations or such causing fatigue, stress and production traumas, gradually replaced by automated assembly cycles, means and techniques. This usually widely involves industrial robots and handlers. Higher productivity, lower cost and higher quality of assembled products are usually required. Recently, latest assembly techniques for simpler or more complicated products in engineering, device manufacturing and electronics involve computer-aided automated assembly means in Flexible Automated Production Lines or other types of automated conveyor lines, which provide full automation and human labour replacement. Assembly alternatives involving automation, and mechanisation, programmable and adaptive control have been analyzed in Chapters 3–5. Practically, this means no large investment in the modernisation and expansion of the production capacity and the product’s nomenclature.
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Automation and Robotics
Automation & Robotics: An Optimized Loudspeaker Assembly for a Mechanized Serial Production Line
1 Automation & Robotics: An Optimized Loudspeaker Assembly for a Mechanized Serial Production Line 1.1 Introduction Modern manufacturing of products in small and large scale series production utilise conveyors and automated assembly lines. The purpose is usually to reduce and replace as much as possible labour intensive and dangerous assembly operations with automated ones. Thus, productivity and quality can also be increased. Many current production processes involve computerised assembly using robots or flexible automated production systems where manual assembly operations are completely replaced by machines [1]. The aim is to have monotonous and similar in type operations or such causing fatigue, stress and production traumas, gradually replaced by automated assembly cycles, means and techniques. This usually widely involves industrial robots and handlers. Higher productivity, lower cost and higher quality of assembled products are usually required here. Recently, latest assembly techniques for simpler or more complicated products in engineering, device manufacturing and electronics involve computer-aided automated assembly means in Flexible Automated Production Lines or other types of automated conveyor lines, which provide full automation and human labour replacement [1]. In this loudspeaker production case study, we have a typical example of a series production, which provides opportunities for improved and automated assembly. Regardless of the wide variety of loudspeaker types and dimensions, this product is of average and even low complexity: it comprises 15 to 30 component parts. These can be assembled using mechanised assembly means with only a limited number of manually performed operations [2]. This data is used to calculate current assembly and conveyor parameters and eventually, assembly and conveyor parameters after the modifications and improvements in organisation.
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Automation & Robotics: An Optimized Loudspeaker Assembly for a Mechanized Serial Production Line
Automation and Robotics
Figure 1 Initial organisation diagram
The work stations are positioned along the conveyor and various types and loudspeakers variants can be manufactured either in parallel time or consecutively in time (consecutive manufacturing of individual variants, individual production lots are run consecutively) [2]. In the alternative “a” each individual assembly unit is used to assemble one or maximum two types of loudspeakers. Therefore, it is equipped with fewer and simpler attachments and assembly equipment. (In this alternative, the skills required for assembly workers are not high) – Figure 1-a. In the alternative “b” individual workstations included in the assembly unit (section) are supposed to be highly specialised and equipped with the necessary assembly means required to manufacture all variants of loudspeaker types. – Figure 1-b. From Figure 1 it is understood that the alternative “a” is not applicable in our case since if only a single product type is to be manufactured at a time, assembly units designed for other products will be idle this being unacceptable.
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Automation & Robotics: An Optimized Loudspeaker Assembly for a Mechanized Serial Production Line
Automation and Robotics
Assembly line output & conveyor operation For the initial arrangement, 120 000/month – 6 variants (product types), the time required to manufacture a single loudspeaker assembly (T1a ) will be: (1)
T1a =
TM , where NM
TM – operational time for 1 month [hours], and
NM – the number of products manufactured per month.
T1a
50.4 120000
200 120000
0.00166[h / unit ] , where 4 is the number of weeks in a month.
T1a = 0.00166.3600 = 6[sec/ 1unit ] Thus, with the initial line rate, six (6) seconds will be required to assemble a single loudspeaker unit. After subsequent modifications, we can calculate from expression (1) above for NM = 180 000 [units/month]: (2)
T2 a
50.4.3600 180000
4[sec/ unit ]
1.2
Developing a dolly removal strategy
1.2.1
Loudspeaker arrangement
In general, every loudspeaker features the type of design illustrated in Figure 2. Item
Designation
Number
Material
1
Body (support chassis)
1
Fe, Al metal
2
Magnetic motor unit (system)
1
Fe, etc.
3
Membrane – conical shape
1
Composites
4
Packing – dust cap
1
Composites
5
Oscillator – corrugated, centring
1
Composites
6
Collar – corrugated, together with the conical membrane
1
Composites
7
Voice coil oscillator
1
Constituent assembly with coil
8
Electrical wiring – terminals and cable wiring for the coil
1
Electrical assembly made up of several components
9
Bonding and connecting elements (materials)
1
Glues, etc.
d = 0.38–0.7 [mm], D – “centring” diameter between item 1 and item 2
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Automation & Robotics: An Optimized Loudspeaker Assembly for a Mechanized Serial Production Line
Automation and Robotics
δ
δ1
Figure 2
1.2.2 Operation The electrical pulse transmitted via 8 to the coil 7 causes vertical oscillations as a result of the interaction between the electrical magnetic field of the coil and permanent magnets of 2. Oscillations are transferred to the conical membrane 3 and the centring oscillator 5 which maintains the gap d = 0.38 ÷ 0.7 mm (and d1) constant. 1.2.3
Description of assembly and characteristic features
The body 1, which is usually made of stamped steel or aluminium sheet is connected to the rest of the component parts by means of glue applied on its contact surfaces (only rarely by means of welding or riveting). The sequence of assembly operations is such that it allows for consecutive addition of individual component parts or sub-assemblies constituting the product and most important, good quality of bonding and connections, ensuring the gap d (and also d1) is maintained. For the purpose of all said above, sub-assembly 2 (motor unit) could be pre-assembled separately and then in turn assembled with the body 1. Separate pre-assembly can also be made for component parts included in the voice coil and the suspension 5, 7 and this whole assembly can later be glued to 9 to join it with 1 + 2, ensuring the gap d is maintained for the dolly. The last parts to be assembled should be the cone 3 and the cover 4 and the wiring from the coil 7 to the terminals 8 and point a located on the cone 3. This results from the fact that it is impossible to glue 5 to 1 (with 9) when the cone 3 is assembled. If the cone 3 and the corrugated oscillator 5 are assembled at the same time, there is a risk of changing the gap d after the dolly is removed because of the relatively heavier weight and higher “toughness” of the cone 3 when it has not been manufactured sufficiently precisely. Some lack of concentricity might arise when 6 is not properly glued to the body 1.
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Automation & Robotics: An Optimized Loudspeaker Assembly for a Mechanized Serial Production Line
Automation and Robotics
1.2.4
Assemblies (sub-assemblies)
Considering Figure 1 and the original assignment, the sub-assemblies involved are: 1.2.4.1 The motor unit assembly This comprises 4 separate parts usually round in shape (Fig. 3). D, d, d1 are positioned concentric with each other and d1 – d = 2d2, where d2 is sufficient to insert the coil of the voice oscillator (item 7 in Figure 2) and leave a radial gap of d = 0.35 ÷ 0.7.
Figure 3 Key: 2.1 – central stud; 2.2 permanent magnet; 2.3 – top plate; 2.4 – bottom plate.
Component 2.1 riveted or pressed into 2.4 and 2.3, 2.2 and 2.4 are glued. The diameter D also serves to centre the sub-assembly in the body 1 (Figure 2) during the assembly operation. 1.2.4.2 Voice coil and suspension It comprises 2 parts (Figure 4): Oscillator, corrugated, centring (5 – Figure 4); 6. Coil (7 – Figure 4). d3 < d1 (Figure 3) and d2 < d (Figure 3) d2 – d = d and d = 0.35 ÷ 0.7[mm]. Components 5 and 7 are glued in between in the section M and the flange D1 is used to glue the subassembly to the body 1 (Figure 2).
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Automation & Robotics: An Optimized Loudspeaker Assembly for a Mechanized Serial Production Line
Automation and Robotics
δ
Figure 4
1.2.4.3 Cone and dust cap (Figure 2) This comprises 2 parts and is glued to 1 and to the voice coil and suspension with the glue applied to d4 (Figure 4).
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Automation and Robotics
Automation & Robotics: An Optimized Loudspeaker Assembly for a Mechanized Serial Production Line
1.2.5 Involvement of the dolly in the coil assembly operation, motor unit assembly and dust cap cone The dolly must be positioned between diameters d2 and d thus ensuring concentricity and maintaining the gap d = 0.35 ÷ 0.7d = 0.35 ÷ 0.7 (Figure 5) when the voice coil and suspension are glued along D to the body 2.
Figure 5 1. Device; 2. Loudspeaker body (chassis); 3. Dolly; 4. Oscillator, corrugated, centering; 5. Hole for installing the pulling handle (of the dolly); 1.1. Central stud; 4.1 Voice coil – constituent part of Item 4.
The arrangement shown in Figure 5 with an installed dolly in a “ready to remove” position is rather universal. The bottom section of the loudspeaker comprising the magnetic motor assembly is not shown in this arrangement but this is replaced by a simulation attachment, item 1.1.1, centred along D to item 2. Other alternatives of this arrangement are also possible where the “motor” (magnet and plates) can be pre-assembled in 2. Figure 5 shows the operation of gluing the oscillator 4 to 2, applying the glue on the flange M and pressing on it using the force F, with the dolly, item 3, carefully pre-inserted in d2 of the coil and then or at the same time installed over d. Before this operation is carried out, the oscillator 4 and the voice coil 4.1 are also assembled (glued) on N. Due to the difference in various designs of loudspeaker variants, the arrangement given in figure 5 also allows for observing the opposite order of operations for the assembly of the body 2 to match the order of adopted assembly operations [3]. 1.2.6
Recommendation for mechanisation of the manual operation for the Dolly removal
A considerable number of methods and schematic diagrams for Dolly removal are possible using the movement of the conveyor in the area of this specific assembly work station. Figure 6 shows a diagram of a suggested semi-automated mechanical device (attachment) [4].
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Automation & Robotics: An Optimized Loudspeaker Assembly for a Mechanized Serial Production Line
Automation and Robotics
11
8 6
-X
1
7 5
yor nve o C
L
S
b
4
а 2
S
а1 12
13
9
10 14 15
IV S
I
II
3
Figure 6: 1. Conveyor; 2. Dolly; 3. Product (loudspeaker); 4. Hanger hook; 5. Horizontal arm; 6. Nut; 7. Guide; 8. Screw; 9. Gear drive; 10. Spring – horizontal; 11. Spring – vertical; 12. Rest; 13. Actuating lever; 14. Vertical lever; 15. Pedal; S – Spherical hinges; D – Gap between rests item 12 – pitch.
1.2.6.1 Structure of the device and mode of operation The device comprises the component parts as listed in Figure 6. The dolly 2 is located on the assembly work station where the centering oscillator is assembled to the loudspeaker body. The dolly is hung to the arm 5 by means of the hanger hook and the arm moves vertically along the guide 7 installed on the assembly device. The arm 5 ends on the nut 6 installed on the screw 8, which moves in both directions (clockwise and counterclockwise). The screw is seated on the pin II (z) and is driven by the gear drive 9 – pin I to pin II. The gear 9 (the larger one) is connected to the lever 13, which is equipped with an auxiliary hinge – pin III, such that the end section of the lever can move around the pin III at a certain distance along the ± Z axis. The entire lever 13 rotates at a specific angle around the pin I, for example at ± 90° (in the X0Y plane). The lever 13 is connected via a spherical hinge “S” to the vertical lever 14, which is in turn connected to the pedal 15 via “S” and the pedal moves in the clockwise and counterclockwise directions around the axis IV (Y). The lever 13 is kept horizontal and parallel to the X0Y plane by the spring 11 and it is kept in its starting position “a” by the spring 10.
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Automation & Robotics: An Optimized Loudspeaker Assembly for a Mechanized Serial Production Line
Automation and Robotics
The mode of operation of the device involves pressing by hand of the lever 13 in the Z direction or pressing the pedal 15 by operator’s foot until the end section of 13 moves from position “a” to position “a1“with the rest 12 installed on the side of the conveyor, resting against 13 and rotating it in position “b”, where it becomes disengaged from 13. Thus, the gear drive 9 is moved and the screw 8 is rotated and it in turn moves the nut 6 by means of the arm5r, the hinge S and 4 and dolly 2, respectively in the +Z direction, pulling on it directly along the direction of the axis from the product (the loudspeaker). Springs 10 and 11 restore the starting position of the hanger hook 4 ready for the next product, retracting the lever 13 in its “a” position. 1.2.6.2 Involvement of the conveyor According to the arrangement described above, the conveyor moves the device and pulls out the dolly in the +Z direction by means of the rests 12 installed at a specific pitch L along the conveyor. Thus the involvement of the worker is reduced to moving the lever 13 down using a low effort, not requiring a very high effort or alert attention (for accuracy of movement) [3]. This movement can be performed manually or by the foot using the pedal 15. One opportunity for improving this strategy for dolly removal is to move 13 until it engages with 12 of the moving conveyor by means of an electrical magnet and a simple electrical diagram (contactor and a time relay) with the operator only pressing on an electrical button. Another alternative exist for the pedal 15 to move the screw 8 or 5 directly, but the use of the conveyor is then eliminated [5].
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