Lesson 68 of Industrial Engineering ONLINE Course.
Lesson 69. Determining Depth of Cuts for Multiple Cuts - Process Planning and Process Industrial Engineering
After selecting the basic process, the first decision to be examined is the clamping points and the shape of the fixture.
If the body has an irregular shape, the support points have to be indicated by the designer on the drawing.
Jigs and Fixtures are built as an accessory to part processing and their function is to hold the part firmly in the machine. Chucks are covered under fixtures in the book by Halevi.
7. Positioning Workpiece and Clamping (Chapter Gideon Halevi)
Sections in the chapter
Technical Functions of A Fixture
Three Datum Positioning Concept
Clamping Positions an Clamping Forces
Development of an Algorithm Simulating Design of a Fixture
Conclusions - Economic Considerations in Fixture Design
After selecting the basic process, the first decision to be examined is the clamping points and the shape of the fixture.
If the body has an irregular shape, the support points have to be indicated by the designer on the drawing.
Jigs and Fixtures are built as an accessory to part processing and their function is to hold the part firmly in the machine. Chucks are covered under fixtures in the book by Halevi.
Technical Functions of A Fixture
Three Datum Positioning Concept
Chuck related issues
Three jaw chuck: Only cylindrical segments can be placed in the three jaw chuck. Length of contact between the jaws and the length of the chucked segment has to be at least 1.2 times the segment diameter. The minimum length in the chuck has to be at least 5 mm. If for any reason the length is less, the free end has to be checked for concentricity and adjusted. The three jaw chuck holding without any other support can be used up to ratio of length to diameter of 3.5.
Three jaw chuck with support is to be used when length to diameter is greater than 3.5 to 6.
Collet gives more accuracy but the part to be chucked in collet must have smooth surface.
Four jaw chuck: it is used for nonsymmetrical parts that must be adjusted for a centerline on the part.
Face plate: It is actually a fixture plate or plate fixture on which with fixture aid any part can be held.
In the book of Halevi, an algorithm is given to decide the fixture required.
Introduction to Fixture Design
_____________
https://www.youtube.com/watch?v=Kei2OTc8xr0
Download slides from
https://cadxdesigns.files.wordpress.com/2020/02/design-of-workholding-fixtures.pdf
_____________
Fixture Design - Playlist (9 Videos)
https://www.youtube.com/watch?v=Kei2OTc8xr0&list=PLs7bBpjS0n0G_LYl0-b9YQ4uzu7ufDy8s
1 Group technology methods (GT)
Chuck related issues
Three jaw chuck: Only cylindrical segments can be placed in the three jaw chuck. Length of contact between the jaws and the length of the chucked segment has to be at least 1.2 times the segment diameter. The minimum length in the chuck has to be at least 5 mm. If for any reason the length is less, the free end has to be checked for concentricity and adjusted. The three jaw chuck holding without any other support can be used up to ratio of length to diameter of 3.5.
Three jaw chuck with support is to be used when length to diameter is greater than 3.5 to 6.
Collet gives more accuracy but the part to be chucked in collet must have smooth surface.
Four jaw chuck: it is used for nonsymmetrical parts that must be adjusted for a centerline on the part.
Face plate: It is actually a fixture plate or plate fixture on which with fixture aid any part can be held.
In the book of Halevi, an algorithm is given to decide the fixture required.
Introduction to Fixture Design
_____________
https://www.youtube.com/watch?v=Kei2OTc8xr0
Download slides from
https://cadxdesigns.files.wordpress.com/2020/02/design-of-workholding-fixtures.pdf
_____________
Fixture Design - Playlist (9 Videos)
https://www.youtube.com/watch?v=Kei2OTc8xr0&list=PLs7bBpjS0n0G_LYl0-b9YQ4uzu7ufDy8s
Conclusions - Economic Considerations in Fixture Design
1 Group technology methods (GT)
For a group of components master jig can be developed and adapters can be used for dealing with variations in the components in size and location of some features.
2 Modular Fixturing
The fixture is made up of standard building blocks assembled in a suitable manner. The blocks are disassembled after use and they are used in different fixtures.
3 Set up time reduction
Setup time reduction is important and certain design guidelines for fixture can decrease setup time. Rotary tables allow machining of the four sides of a cube in one setup. Quick clamping devices, special eccentric cams, slotted bolts and hydraulic or pneumatic clamping etc. are available to design fixtures that reduce setup time.
2 Modular Fixturing
The fixture is made up of standard building blocks assembled in a suitable manner. The blocks are disassembled after use and they are used in different fixtures.
3 Set up time reduction
Setup time reduction is important and certain design guidelines for fixture can decrease setup time. Rotary tables allow machining of the four sides of a cube in one setup. Quick clamping devices, special eccentric cams, slotted bolts and hydraulic or pneumatic clamping etc. are available to design fixtures that reduce setup time.
Further Reading
Boerma, J.R., (1990); The Design of Fixtures for Prismatic Parts, PhD Thesis, University of Twente
Lin, L., Zhang Y.F., Nee A.Y.C., (1997); An Integrated Setup Planning and Fixture Design System for Prismatic Parts.
Master Jig and Adapters
Interesting
Case Studies on Work Holding
Modular Fixtures
5/15/2002
Making The Most of Modular Fixturing
Modular fixturing makes sense for this manufacturer, whether it's machining one- or two-of-a-kind parts for its custom machine tools or larger quantities for its contract machining business.
LEO RAKOWSKI, Editor
https://www.mmsonline.com/articles/making-the-most-of-modular-fixturing
https://www.amf.de/en/products/clamping-technology/modular-fixture-systems.html
https://www.ctemag.com/news/articles/modular-fixturing-pros-and-cons
https://www.carrlane.com/engineering-resources/technical-information/manual-workholding/modular-fixturing/introduction
Fixlogic CMM Modular Fixture Building
Dan Smith
_______________
https://www.youtube.com/watch?v=EA5n89Rab98
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Two more fixlogics videos
https://www.youtube.com/watch?v=y9d7uIG4Rdk
https://www.youtube.com/watch?v=F_jG2Gkllf4
A systematic conceptual design of modular fixtures
Cheng-liang Liu
The International Journal of Advanced Manufacturing Technology volume 9, pages217–224(1994)
https://link.springer.com/article/10.1007/BF01751119
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