TA 201-mE

PROJECT REPORT

“Mechanical Iris”

INSTRUCTOR: -Dr. J. RamKumar

LAB INCHARGE:- Mr. P. C. Gond

PROJECT GUIDE: - Mr. D. K. S. Chauhan

SECTION: - M1 & M2

GROUP NO. 9

Amit Kumar Y9073

Kumar Kislay Y9294

Mattam Pratap Naidu Y9327

Mohit Singh Y9343

Rohit Kumar Sinha Y9493

CONTENTS

Acknowledgements

General Description

1. Motivation

2. Innovations

Isometric Drawing

Procedure

Processes Involved

Cost Estimation

Difficulties Faced

Scope for Improvement

ACKNOWLEDGEMENTS

We sincerely express our gratitude to our project guide Mr.

D.K.S. Chauhan, our ME laboratory in charge Mr. P.C. Gond,

and all the other guides of the TA 201 ME lab for their valuable

support and advice in making this project possible. Without

their moral and technical support we would not have been able

to complete this effortful task. Overall we thank our instructor-

in-charge Dr. J. Ramkumar for providing us with the

opportunity to make something creative along with gaining

hands-on-laboratory experience.

THANK YOU

GENERAL DESCRIPTION

A Mechanical Iris is a mechanism that is used as a compact

solution to close and open holes. It is made up of usually a

series of metal plates that can fold in on each other or expand

out. Iris mechanisms are commonly found in optical shutters

(diaphragms), and also in various kinds of valves. Irises are

sometimes used in science fiction as doors.

MOTIVATION

The motivation for making this project was drawn from the iris

mechanism operating behind various optical devices, primarily

our eyes and others like camera, spotlight, optical shutters, etc.

We also saw its real time application in valves controlling flow

of material as well as light.

INNOVATIONS

We did some slight modifications in the original model to

complete the project effectively using the available lab facilities

and in constrained time.

Instead of using large number of blades, we reduced them

to only 5 and shaped them appropriately.

We used spur gear system to provide motion to the

blades.

Diverting away from the conventional way, we provided

axis to the main setup using external hold at the periphery.

We devised a mechanism to convert circular motion to

radial motion.

PROCEDURE

We started with making the outer ring, which was cut in

the 4i lab.

Simultaneously we machined the smaller spur gear.

We then turned and faced the inner ring to required

dimensions.

We also made the strips and blades of required shapes

using sheet metal.

We then machined the outer ring to give proper finishing

and made the gear.

After that we started the initial assembling of small spur

gear and handle on the base plate.

Then the positions of all other parts were marked

accurately on the base plate.

Finally we assembled the gears, rings, blades and strips

which lead to realisation of our concept.

PROCESSES INVOLVED

Lathing:

Turning and facing of the discs which were later bored to

rings (inner and outer) were done on Lathe.

Gears were initially turned and faced on Lathe.

The peripheral holds were also turned on Lathe to fix it rigidly

on base plate.

Milling:

The teeth for spur gear were cut on Horizontal milling machine.

Gear Diameters(Large, small) = 201, 63 mm

Gear cutter module = 1.5

Depth of cut = 4.314mm

Drilling:

Through and blind holes of various diameter were drilled on the

parts wherever required.

Filing and Tapping:

Filing of blades and strips was done for proper fitting.

Tapping was done in holes where screws were to be fitted.

COST ESTIMATION

ITEM RATE QUANTITY AMOUNT

Thermocole ` 15 per sq feet

0.50 sq feet ` 7.50/-

Fevicole ` 5/tube 1 tube ` 5/- Pig Iron ` 50/kg 4.5 kg ` 225/-

Electricity used

` 4.80/unit 2 units ` 9.60/-

Mild steel sheet (upto

3mm)

` 40 per sq feet

0.28 sq feet ` 11.40/-

Lathe ` 65 per hr 8 hr ` 520/- Milling ` 85 per hr 3 hr ` 255/- Drilling ` 50 per hr 2.5 hr ` 150/-

Unskilled Labour

` 200 per 8hr 17 X 5 hr ` 2125/-

Skilled Labour ` 250 per 8hr 5 hr ` 156/- Total ` 2080/-

Overhead charges: 10% = ` 208/-

Gross total = ` 2288/-

DIFFICULTIES FACED

Our project demanded cutting of a large diameter ring which is not possible on Lathe.

Solution: We got it cut in 4i lab.

In our original design, we wanted to provide axis via holds placed in slots working as guide ways. But the slots could not be made either by drilling or milling. Solution: We modified our design and provided

peripheral holds.

Initially we ignored the depth of teeth on the outer ring due to which there was a chance of bending near the gear . Solution: We increased the ring widths and

appropriately changed the strips.

SCOPE FOR IMPROVEMENT

Increasing number of blades and overlapping the blades

on one another would give a better aperture shape.

Making the strips curved would provide uniform motion to

the blades.

Providing holders to the outer ring would allow the project

to be held in any orientation.

Increasing the number of peripheral holds would give a

smooth motion to outer ring.