giáo trình automation và 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) T , where T1a = M 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]: 50 .4. 3600 180000 4[sec/ unit] (2) T2a 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. δ = 0.38–0.7 [mm], D – “centring” diameter between item 1 and item 2 Download free eBooks at bookboon.com 10 Automation and Robotics Automation & Robotics: An Optimized Loudspeaker Assembly for a Mechanized Serial Production Line 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 δ = 0.38 ÷ 0.7 mm (and δ1) 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 δ (and also δ1) 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 δ 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 δ 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. Download free eBooks at bookboon.com 11 Automation and Robotics 1.2.4 Automation & Robotics: An Optimized Loudspeaker Assembly for a Mechanized Serial Production Line 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 = 2δ2, where δ2 is sufficient to insert the coil of the voice oscillator (item 7 in Figure 2) and leave a radial gap of δ = 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 = δ and δ = 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). Download free eBooks at bookboon.com 12 Automation and Robotics Automation & Robotics: An Optimized Loudspeaker Assembly for a Mechanized Serial Production Line 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). Download free eBooks at bookboon.com 13 Automation and Robotics 1.2.5 Click on the ad to read more Automation & Robotics: An Optimized Loudspeaker Assembly for a Mechanized Serial Production Line 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 δ = 0.35 ÷ 0.7δ = 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]. Download free eBooks at bookboon.com 14 Automation & Robotics: An Optimized Loudspeaker Assembly for a Mechanized Serial Production Line Automation and Robotics 8 6 11 1 -X 7 5 r Conv eyo L S b 4 а 2 S а1 12 13 10 I 9 II 14 15 S IV 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