CAPÍTULO 2. Método de la Doble Relación para el ajuste de los parámetros del
2.2 Métodos de sintonización de controladores
For testing the disc fixture, sheet metal parts were made which supported the fixture modules. The sheet metal part was made from laser cutting and slots were made to adjust the gap between the fixture modules. The objective of the test was to determine the optimum face to face distance between the fixture modules to ensure placement of the all the disc (of respective sub-group).
The fixture modules were carefully assembled on the support plates. Three different positions with gap of 10mm, 15mm and 20mm were fixed for DN40-DN200 fixtures. And similarly, for DN 150-DN350 two positions were considered with 25mm & 40mm gap.
The discs were placed in the fixtures to check if they fit in perfectly on the steps as per the corresponding sizes. Also, the possibility of interference was checked. From the test it was clear that for 10mm gap the DN200 disc was not resting on the fillets and got stuck in the gap (Figure 52), whereas with 20 mm gap the DN40 fixture had no supports and it fell down the gap (Figure 523)
Figure 52: DN200 in fixture with gap of 20mm & 10mm respectively. Figure 53: DN40 Disc in fixture with gap of 15mm & 20mm respectively. All the other sizes were also checked at all three positions and it was determined that an 15mm gap is
optimum to place all the discs in the fixture (Table 5: Placement of discs in the disc fixture with a gap 15 mm Gap
of 15mmThe smaller size discs (DN40-DN80) had a higher possibility of movement (tilting/rotation) about the axis passing through the shaft holes, but it is not a major issue and the system could deal with it.
Table 5: Placement of discs in the disc fixture with a gap of 15mm
DN
Size
Disc position in the fixture
DN
Size
Disc position in the fixture
DN40
DN50
DN65
DN80
DN100
DN125
DN150
DN200
Similarly, the test was performed for DN150-DN350 disc fixture (Appendix F) and it was determined that the 25mm gap is optimum to accommodate all the discs of different sizes.
Other than optimum position, following parameters were also checked.
Characteristic
Description
Analysis
Clearance from the base plate.
The smallest size of the sub-groups is placed on the last step in the fixture and hence it should be clear from the base plate.
Any contact would cause damage to the machined surface of the disc.
33 Gap between the
fixture modules.
The fixture holds the discs on the fillets near the holes for the drive and bottom shaft holes.
Here it was checked that the no other part of the disc is touching the flat faces of the fixture modules in the gap.
Positioning by the fillets
The fixture was given fillets so that the disc could be placed and guided in the fixture.
Here, the curvature on the disc are perfectly tangential to fillets.
Tilting of the disc
There is a possibility that the discs could tilt about their central axis.
In such cases the disc could not be touching the neighbouring disc.
It was found that tilting was not issue.
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Summary & Current State
The initial goal of the assignment was to design a modular pallet for placing the bodies and discs in order to be picked and placed by a robot on a product carrier on the assembly line. From careful analysis on the type and size of bodies & discs, feasible orientations were proposed and evaluated. In order to attain the finalized orientation, there was a need to design a fixture. Hence, conceptual design of fixtures was proposed and evaluated. The most feasible fixture for body and disc was manufactured for prototyping and performance was evaluated. The disc fixture effectively fulfilled the task for holding the discs in positions, but the design of mounting pin for bodies was revised after 1st
prototype test. The 2nd prototype testing was not rigorous but was only checked for accurate fit and it resulted in accurate fit.
Currently, it is decided that the pallet design and the robot for picking and placing the bodies and discs from the pallet wouldn’t be implemented in the initial phase of project implementation. It would probably be implemented in the next phase of the project based on the performance and productivity of the semi-automated line. Because of the uncertainty, the quantity of the pallets and corresponding fixtures could not be determined. Though the fixtures designs are fulfilling their design requirements to the fullest, but some design modifications have to be done based on the manufacturing process suitable for mass production.
The design of the pallet module along with the fixtures as per the sub-group is completed and requires a full-scale testing to check the compatibility and operating efficiency along with the robot.
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Conclusion
Based on the Testing performed, the following conclusion were derived:
1. The proposed designs for mounting pin and modular fixture fulfil the initial requirements.
The mounting pin for the bodies was designed to mount bodies of different sizes. The body rests on the pin on the counter bored hole at the bottom. The clearance between the pin and the split sleeve bearing eases the mounting and removal of the bodies on and from the pin. The pins are robust enough to carry the weight of the bodies, but dynamic testing (under real time usage conditions) of the pins has to be done.
The fixture for the disc firmly holds all the types and sizes of discs in their position. The profile of the disc fixture is tangentially in contact with the profile of the disc and it ensures minimum movement. The support plates are effective in bearing the weight of the disc and it is equally distributed on all four modules and hence provides stability.
2. The optimum gap between fixture modules for disc fixture.
The prototype testing of the disc fixtures also helped determine the optimum position to fasten the fixture modules. For DN40-DN200 size discs the optimum gap was 15mm and for DN150- DN350 size discs it was 25mm. With this gap the convex and flat disc types could be placed without any adjustment in the gap between the modules.
The discs always remained inside the fixture and hence there was no possibility of contact with neighbouring discs.
3. Full size pallet could not be tested because of the uncertainty of automating the entire process in the initial phase. Hence, a virtual testing was performed in Solidworks to ensure that the bodies and discs could be placed on determined positions without any interference.
From a full size assembled model, it was clear that there was sufficient space between two adjacent bodies and discs to let the gripper fingers to make a full stroke.
Combination of different sized bodies and discs was also tested which confirmed that it is possible to combine different orders.
There was no interference between adjacent bodies and discs. Rotation of the bodies about their central axis (through the bottom & top hole) would cause the bodies to touch each other but the possibility of rotation was less and even if they rotated, the bodies make contact on the vulcanized rubber line of the other body which protects it from damage.
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Technical Drawings
37
39
41
43
Figure 62: Disc Fixture Assembly DN150-DN350
Figure 64:Pallet module Lay-In DN40-DN125 Figure 65:Pallet module Lay-In DN40-DN200
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Figure 67: Modular Pallet assembly- DN40-DN200
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References
I. http://www.weepallet.com/plastic-pallet-manufacturing-process/ II. https://www.wouterwitzel.nl/about-us/ III. https://schunk.com/de_en/gripping-systems/seriesaccessory/pgn-plus/product/699-0371108-pgn- plus-240-1/ IV. https://schunk.com/ru_en/gripping-systems/product/6212-0308692-jgp-300-1-is/47