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Process Parameters

Parametric Analysis

1) Amar Kumar Behera & Joost R Duflou 2013, Too

path compensation strategies for SPIF using

multivariate adaptive regression splines, Computer

Aided Design, vol.45, pp.575590

2) Kurra Suresh, Arman Khan & Srinivasa Prakas

Regalla 2013, Tool Path Definition for Numerica

Simulation of Single Point Incremental Forming

Procedia Engineering, vol.64, pp.536545.

3) Skjoedt & M.Silva, 2007,Single point incrementa

forming using a dummy sheet, Proceedings of th

Second ICNFT Bremen, Germany, pp.267276.

Hardik Shah1, Prof. S.C. Chaudhary21M.E. Production Engineering student (En No.140390728006),

2Assistant Professor, Mech. Dept. S.P.B. Patel Engineering College, Linch - Mehsana

Introduction

Conventional Sheet forming process is very costly as

higher costs are involved in hydraulic punch-press &

die.

Incremental sheet forming eliminates major cost of die

and hydraulic punch press. Also called die-less forming

CNC motion with pre-defined tool path and CAD design

of desired product are main components of process

which utilizes round ball ended tool to form sheet into

desired product.

Process parameters like step depth, Wall angle &

spindle speeds are optimized for ISF process.

Basic arrangement for ISF process

NC motion control

Predefined tool path

Roundball ended tool

Blank holder

Forming sheet of required

thickness.

INPUT PARAMETERS OUTPUT PARAMETERS

SPINDLE SPEED (IN RPM) SURFACE ROUGHNESS

WALL ANGLE (IN DEGREE) WALL THICKNESS

STEP DEPTH (IN MM)

Experimental Specification

A square blank of approx. 100 mm X 100 mm X

1.22mm size is used on 3-axis CNC milling machine.Fixture is used to hold blank made from mild steel.

Hemispherical tool used is 10 mm in diameter and

length will be 150 mm made from SS304.Varying wall angle pyramidal frustums are formed.

Sample pyramidal geometries are modelled with top

base is a square of side 100 mm and 30 mm depth withdefined wall angle

Experimental procedure

In Incremental sheet forming process, 3D shapes are

formed from sheet metal using simple rotating tool

moving downwards along defined path on the sheet

surface by progression of localized plastic deformations

The process starts from a flat sheet metal blank,

clamped on a sufficiently stiff blank holder and

mounted on the table of a CNC

Hemispherical tool is inserted in tool holder. Tool

moves on the predefined tool path by CNC to form

desired shape with progressive increment of step

depth.

Sr. Parts Size

1. Frame 300 x 300 x 10mm

2. Baseplate 300 x300 x 10mm

3. ColumnHeight 150 mm

Width 10mm

length 200mm

4. Bolt M12

No. Dia. Material

1. 8 mmSS304

length:

150 mm

2. 10 mm

3. 12mm

PROCESS PARAMETERS RESPONSE

Sr.

No.

Wall Angle

(degree)

Step

Depth

(mm)

Spindle

Speed

(rpm)

Surface

Roughness

(m)

Thickness

(mm)

1 45 0.2 800 4.87 1.16

2 45 0.5 1000 4.36 1.17

3 45 1 600 6.69 1.19

4 55 0.2 1000 4.11 0.73

5 55 0.5 600 4.76 0.77

6 55 1 800 5.02 0.75

7 65 0.2 600 4.02 0.98

8 65 0.5 800 4.18 0.97

9 65 1 1000 5.54 0.99

Design of Experiment & Results

Literature Review

Filice & Park (2002) concluded that the crack occurs

mostly at the corners, since the deformation at the

corner is greater than that of along the sides.

Jeswiet (2006) studied incremental forming of AA3003.

Faster spindle rotation speeds improved the sheet

formability significantly. Tool diameter has negligible

effect on the likelihood of forming a part.

Durante (2009) in an investigation on spindle speed

evaluated the surface roughness of the formed sheets.

ANOVA tables were observed to be satisfactory to

identify whether a process variable exerts significant

influence on the process or not.

Kurra Suresh (2013) reported that the tool path has a

significant effect on dimensional accuracy, surface

roughness, processing time and thickness variation.

Arfa (2013) in his investigation on the tool forces

required to deform plastically the sheet concluded that

the numerical simulation might be exploited for

optimization of the incremental forming process

Harshal & Deshmukh (2014), in a review on

optimization techniques during sheet metal forming,

have stated that one of the most widely used methods

is Gray RelationalAnalysis (GRA)

U

Analysis of variance for Surface Roughness

No.PROCESS

PARAMETER VARIANCE F TEST% OF

CONTRIBUTION

A Wall Angle 0.9884 1.57 16.97%

B Step depth 3.7506 5.96 64.40%

C Spindle Speed 0.455 0.72 7.81%

Error 0.6295 1 10.81%

Analysis of variance for Wall Thickness

No.PROCESS

PARAMETERVARIANCE F TEST

% OF

CONTRIBUTION

A Wall Angle 0.26948 173.243 99.46%

B Step depth 0.00062 4 0.23%

C Spindle Speed 0.00068 4.43 0.25%

Error 0.00015 1 0.06%

WallthicknessSurface Roughness

In multi response optimization the optimum paramete

combination for incremental forming is meeting aexperiment 6 and its parameter value is 600 rpm/mi

spindle Speed and 0.5 mm depth of cut, for a wall angleof 450.

Force Calculations & FLDForming Limit Diagram

Major strain = (major axis length original circle dia.) x100

Original circle dia.

Minor strain = (minor axis length original circle dia.) x100Original circle dia.

Conclusion

Surface roughness:

Wall angle and Step depth are found the mos

significant effect on surface roughness. Increase in

spindle speed rate, value of surface roughness is

decreases up to 0.2 micron after that it increases.

Spindle speed are found to have very least effect on

surface roughness.

Wall thickness

The volume of material deformed can be achieved

better when machining was done at medium Step

depth and small wall angle. Wall angle is found the most significant effect on Wa

thickness. Increase in wall angle value,Wall thickness

increases in between and after that Wall thickness is

decreases with increase in wall angle.

References