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Design
Validation
Normally, stresses are of primary concern when evaluating
failure modes and life. However, stiffness plays a major role in
deflections and response to vibratory input. This example
highlights design considerations in the design of Gear Box Cover.
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Gear
Box Cover Design
In this example the
design of a gear box cover is taken as an example to illustrate the
design process that includes among other considerations, the estimation
of stiffness. This cover mates with a gearbox housing containing
all mating gears in oil-immersed condition. Every design involves
consideration of numerous
aspects in terms of Fit, Form and Function in addition to
Manufacturability, Assembly and Service. Needless to say, a
design evolves over a period of time while addressing these
aspects. Carefully considered designs, when produced, reflect
maturity in thought process, assessment of criticality of functions and
incorporation of technology that establishes the success or the lack of
it, for the organization involved. This article is by no means
comprehensive. It is a perspective that could also be considered
as a part of the design process.
Gear Box Views
Following aspects are considered as a part of the Gear Box Cover design:
- Least cost
- Acceptable Factor of
Safety
- Acceptable Stiffness
- Manufacturing and
Assembly considerations
- Tolerance allocation
for meeting Assembly Stack-up requirements
Based on economy of
volume, weight consideration and performance Aluminium Casting made of
material grade 356 T6 is considered in conjunction with High Pressure
Die Casting (HPDC) process. Let us evaluate each
aspect in detail.
Least Cost
Considerations:
Cost of a product is influenced by many factors such as mass,
manufacturing process, number of machining operations, cost to achieve
specified tolerances, assembly time, number of parts going into
assembly. A detailed review of the contributors will enable us to
understand that
Design influences profitability. By over 85% the cost of a
product is dictated/ influenced by Design.
Some of the considerations could be:
- Minimum Wall Thickness
- Minimum number of
features
- Least number of
fasteners to meet the functional requirements of assembly
- Minimum material
removal by machining
- Adequate functional
tolerance taking into consideration achievable manufacturing tolerance
based on Process Cp and Cpk
- Minimum number of
operations to product the part cost-effectively
Acceptable Factor of Safety:
Factor of Safety
(FOS) calculations are the first steps to be taken to assure product
design performance. They do not guarantee 'adequate' life.
Acceptance criteria for FOS depends on material (isotropic,
orthotropic, an-isotropic) and modes of failure (brittle, ductile among
others) and mode of failure expected (bending, torsion among
others). SolidWorks Simulation provides FOS plots enabling the
design engineer to evaluate designs and strengthen appropriately.
This justifies material usage as required.
Note: All FEA strength calculations should be done for LMC
conditions of the design. This can be accomplished in SolidWorks
using Configuration Manager. MMC considerations would also be required for dynamic
calculations involving natural frequencies and vibration response.
Gearbox
Casing Factor of Safety Plot
SolidWorks Simulation performs true Assembly level Stress analysis
involving contact between parts for realistic load transfer.
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Our Mission
Engineering
Development Through Effective Partnership
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Contact: SolidWorks
Reseller Chennai, Coimbatore, India
EGS Computers
India Private Limited
342/ 90 Arcot Road I Floor Kodambakkam
Chennai 600 024
Branch: 1/1 B.R.
Nagar Trichy Road Singanallur Post
(Opp. Coimbatore Stock Exchange) Coimbatore 641 005
Corporate:
+91-44-2480 3370
Corporate fax: +91-44-2484-4227
Coimbatore: +91-422-2310 268 / 2314 653
E-mail: info@egs.co.in
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