1. DESIGN OF FIXTURE FOR 4-HOLES
OPERATION IN MCV
Department/Company: Production Engineering –
Shanmuga Precision Forging (SPF),
Thanjavur – 613401
Duration: 07/09/2012 – 27/02/2013
Guide: Dr. Raghuraman S
Professor,
School of Mechanical Engineering,
SASTRA University,
Thanjavur – 613401
Submitted By: V N Aravind Krishna – 114009015
III year,
B.Tech., Mechanical Engineering,
SASTRA University,
Thanjavur – 613401

2. 1 | P a g e
Problem Statement:
To improve the quality of the machined product and to increase the productivity by
optimizing the fixture already in use.
Problems Identified:
It was identified by observing the machining process and by interacting with the
machine operators that there were mainly two problems leading to a decrease in quality of
machined products and productivity. They are:
 Misalignment of part placed on the fixture
 Time required to maintain parallelism of part face with fixture component (done
manually using a dial gauge)
 Having to change springs to suit various parts that need to be run on same fixture
It was identified that the misalignment of the part was due to error induced in the milling
process (that occurs before the 4 holes operation) and even if that error is within acceptable
limits, a further error is induced by the spring loaded lever used in the fixture.
Figure 1 - The existing fixture

3. 2 | P a g e
It was further identified that the error from the milling process was multiplied by the spring
loaded lever which had the spring in the central arm and two guide arms on either side. This
error was induced due to the fact that the central arm was of much smaller diameter than
required and the springs used where chosen without due consideration, leading to unequal
distribution of spring tension over the surface of the part, thereby multiplying the error from
milling.
This induced error added with the milling error, crossed the tolerances set in the design
and the operators are forced to use a dial gauge to set the face of the part parallel to that of the
fixture manually in every single operation, thus increasing cycle time and reducing
productivity.
Design Methodology:
The method adopted was to first observe the machining operation and interact with the
operators to find the root cause of the error and subsequent decrease in productivity. Once the
causes for the error was established, it was decided to change the method of clamping the
object.
The first method proposed was to retain the existing fixture and to add a plate moving
on a screw with guide rods on the other side of the object to provide the parallelism, as an
object moving on threads will not be subjected to unequal forces as with a spring. The design
was carried out in SOLIDWORKS and presented for feedback to the designers at SPF.
Figure 2 – The proposed design

4. 3 | P a g e
Based on the feedback from SPF, it was determined that the presence of the spring
loaded lever was not required as a screw operated lever would function both as a setting device
as well as a clamping device. The modified design was again developed using SOLIWORKS
and presented to SPF for review.
Design Justification:
The final design submitted is found to solve the problems encountered due to the
existing fixtures. It can be justified theoretically as follows:
 The clamp is now screw operated and is applied on the larger surface of the part, thus
leading to elimination of misalignment induced by the springs
 The separation between the guide rods is larger and has been designed to match the
ends of the largest part that is machined using this fixture in order to have a uniform
pressure distribution over the face of the part thereby eliminating any chance of further
misalignment
 The screw operated lever provides flexibility in terms of size of parts that can be
machined and also eliminates the need to change any components for use with a
different part
 Finally the screw being designed carefully, with proper cleaning and oiling, will last
longer than the springs
Conclusion:
It can be concluded that on implementation, this fixture will not only increase
productivity, but also the quality of the machined parts and operator comfort. Moreover, when
used over a prolonged period, the proposed fixture would serve as a viable design with lower
maintenance cost and better serviceability.
Figure 3 – The final design