MINIMIZATION OF BURR IN DRILLING

Under The Guidance of Prof. N. S. Das

• To become familiar with burr formation in drilling

• To study the variation heights of burr in drilling of Aluminum and Mild Steel work-pieces with different feed, spindle speed for and three different diameters

Objective of Project

• Burrs are defined as undesirable projections of materials beyond the edge of the work-piece arising due to plastic deformation during machining.

• Burrs can cause many problems during inspection, assembly, and automated manufacturing of precision components. Therefore, it is desirable for precision parts to be free from burr. This project considers burr assessment in drilling operations.

Background

The burr height depends on many variables. They are:

– Drill Geometry, Drill Sharpness, Drill Diameter

– Drill machine conditions – Vibration and Deflection

– Work material geometry and its properties– Drilling Conditions – Spindle speed and Feed– Cutting Fluid composition, flow rate and

method of application

Experimental Parameters

For this project the effect of feed, spindle speed, drill diameter and work material will be used as input parameters

Scope of our Project

• Aluminum alloy (bright aluminum) blocks of size 60mm x 30mm x 16mm.

Materials

• Mild steel blocks of size 60mm x 30mm x 16mm

• R. K. Engineering Radial Drilling machine with 2HP. The drilling machine allows three discrete variations in the spindle speed and three discrete variations in feed.

• High speed steel (HSS) drill bits of diameter 6mm, 8mm and 10 mm

Machine tool and Tools

• Meter M Horizontal Floor Profilometers with 10 x lens, 20x lens, 50x lens,

• Magnification accuracy ±0.1% and surface ±0.15%, with least count of 0.01 mm

Measuring Instruments

• Determine the spindle speed and feed rate at different settings of the drilling machine

• Drill holes in both Aluminum and Mild Steel work pieces with all combinations of feed, spindle speed and diameter

• Determine the heights of burr using Profilometer

• Record the observations and plot the graphs

Experimental Procedure

• The drilling machine allows three discrete variations in the spindle speed and three corresponding discrete variations in the feed

• But the values of these feed and spindle speed are measured individually and has been tabulated

Determination of spindle speed and feed rate

SPINDLE SPEED MEASUREMENT:

• Fix a counter sunk shaft in the drill spindle

• Values of spindle speed are measured with the help of a Tachometer

• Feed values are measured by recording the distance traversed using graduations on the quill

• Time to move a certain distance for all the feeds are recorded using a stop watch

• And finally the feed is calculated

FEED MEASUREMENT:

Spindle speed RPM value Feed

Feed value(mm/sec)

A 285

a 0.84

b 0.805

c 1.59

B 554

a 1.02

b 1.53

c 2.87

C 1022

a 2.81

b 2.87

c 4.87

• Three holes are drilled in each block with same spindle speed & diameter and three different feed rates.

• This process was repeated for other two spindle speeds and other drill diameters also

To drill holes in work pieces

• The Profilometer enlarges a two dimensional shadow of the work piece on the projection screen

• Work piece kept on the table is moved by rotating the micrometer so that the cross hair line moves from metal surface to highest tip of the burr

• Burr height is the difference between initial and final micrometer reading

To determine the burr height

• The Results obtained from Profilometer are tabulated and then plotted graphically for easier interpretation and understanding

• BURR HEIGHT VS FEED: These graphs show the burr height against feed for different values of RPM for both Aluminum and Mild Steel for all three diameters

• EFFECT OF DRILL DIAMETER: These graphs helps us in comparing how burr height is influenced by Drill diameter

• EFFECT OF WORK MATERIAL: These graphs helps us in comparing how burr height is influenced by work material and its properties

Burr Observed in Drilling Process

• The first set of graphs plotted are Burr Height against Feed for different values of RPM for both Aluminum and Mild Steel for all three diameters

• So there are three graphs each for Aluminum and Mild Steel (one for each diameter 6mm , 8mm, and 10mm)

Burr Height vs. Feed

• Aluminum, 6mm diameter

• Aluminum, 8mm diameter.

• Aluminum, 10mm diameter.

• Mild Steel ,6mm diameter.

• Mild Steel, 8mm diameter.

• Mild Steel, 10mm diameter.

• These graphs plot burr height against nine different combinations of feed and RPM for each Drill diameter.

• So there are two graphs one each for Aluminum and Mild Steel

• These graphs help us in comparing how burr height is influenced by Drill diameter

Effect Of Drill Diameter

• Aluminum

• Mild Steel

• These graphs plot burr height against nine different combinations of feed and RPM for each Work material

• So we will three graphs one for each Drill diameter

• These graphs helps us in comparing how burr height is influenced by Work material

Effect of Work Material

• Drill diameter 6mm

• Drill diameter 8mm

• Drill diameter 10mm

FEED vs. BURR HEIGHT

• The first three graphs are of aluminum we observed that at low rpm on increase of feed rate, the burr height increases

• We further observed that at medium rpm on increase of feed, burr height tends to a constant value

• At highest rpm there is no such pattern

• The same pattern can be observed in mild steel but with a few exceptions

Conclusion

EFFECT OF DRILL DIAMETER ON BURR HEIGHT

• In aluminum we observed that the average burr height is maximum with 8mm drill whereas in mild steel 6mm drill gives the largest burr

EFFECT OF WORK MATERIAL ON BURR HEIGHT

• We observed that in the two graphs of 8mm and 10mm drill diameter, the burr heights of aluminum is less compared to mild steel. Which is true as per the theory but in the graph of 6 mm there is an exception where burr height is more in mild steel than aluminum

Conclusions contd..