Edge Rounding and Polishing of Tools

Process and applicationStraubenhardt, 2 June 2008

Dipl.-Ing. (FH) Martin Bott

OTEC Präzisionsfinish GmbHDieselstrasse 8-1275334 Straubenhardtwww.otec.de

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Contents1.) TOOL CUTTING EDGE system

2.) Process for rounding the cutting edge

3.) Drag finishing 3.1) Process description 3.2) Processing goals

3.2.1) Edge rounding3.2.2) Polishing 3.2.3) Removal of droplets

3.3) Key factors3.3.1) Machine3.3.2) Media3.3.3) Workpiece

3.4) Machine specifications 4.) Outlook

1.) TOOL CUTTING EDGE system

Nowadays tool experts are concerning themselves

with the

TOOL CUTTING EDGE system

consisting of:

tool material

tool cutting edge geometry

preparation of the cutting edge

coating of the cutting edge

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OTEC offers you a process for preparing

the cutting edge of the tool

consisting of

rounding of the cutting edges

and polishing of the cutting

surfaces

VIBRATORY DRAG FINISHING 4

1.) TOOL CUTTING EDGE system

2.) Processes for rounding the cutting edges

- Sandblasting

- Brushing

- VIBRATORY DRAG

FINISHING

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3.) Drag finishing

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3.) Drag finishing

3.1) Process description

Since the workpieces can not come into contact with

each other, the result is a finishing process which is

gentle on the workpiece surfaces. In this process, it is

impossible for the workpieces to collide.

The drag finishing process enables multistage processes

such as fine grinding and polishing to be carried out.

3.2) Drag finishing - processing goals

3.2.1) Edge rounding

achieves the following:

Removes grinding burs Stabilizes the cutting edge Gives uniform surface structure

at the cutting edge Extends tool life Gives better bonding for coatings Reduces jaggedness at the cutting edge Reduces chipping at the cutting edge Reduces build-up edges

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3.2.1) Edge rounding Example of a punching die

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3.2.1) Edge rounding Example of a die

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3.2.1) Edge rounding Example of an end milling cutter

Workpieces: Chip removing tools of all kinds requiring edge rounding.

Material: All materials used, but mainly carbides

Processing

goal:

Rounding of the primary and secondary cutting edges for immediate use

or prior to coating

Media: HSC granulates in the case of required edge rounding of up to 10 µm

SIX granulates in the case of required edge rounding of up to 30 µm

QZ 1-3 in the case of required edge rounding of more than 30 µm

Direction of

rotation:

100% clockwise

Processing

time:

1 – 20 minutes depending on degree of edge rounding required

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3.2.1) Edge rounding Example of an end-milling cutter

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3.2.1) Edge rounding unprocessed cutting edge

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3.2.1) Edge rounding processed cutting edge

3.2) Drag finishing - processing goals

3.2.2) Polishing

achieves the following:

Improves the surface quality Reduces roughness Improves chip flow Improves flow characteristics when drawing Extends tool life Gives better bonding for coatings Reduces cutting forces needed Reduces tendency to cold welding

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3.2.2) Polishing Example of forming dies

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Unbearbeitet

Before processing After initial grinding

After polishing

3.2.2) Polishing Example of a forming tool

unprocessed

processed

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3.2.2) Polishing Example of a forming die

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3.2.2) Polishing Example of a thread-cutting tap

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3.2.2) Polishing Example of a tool holder

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3.2) Drag finishing - processing goals

3.2.3) Droplet removal

achieves the following:

Improves surface quality Reduces roughness Improves chip flow Improves flow characteristics when drawing Extends tool life Reduces cutting forces required Creates microscopic lubricant pockets

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3.2.3) Smoothing of a coated surface

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3.2.3) Droplet removal Example of an end milling cutter

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3.2.3) Example: smoothing of a coated surface

As a result of the PVD coating process, droplets (tiny

balls of material embedded into the surface) often

become lodged in the protective coating.This in turn causes friction.

The drag finishing process removes these droplets.

The miniature “pockets” that remain improve the wetting

properties of the surface.

These “pockets” serve to store lubricant.

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3.3) Key factors

3.3.1) Machine parameters

3.3.2) Media

3.3.3) Workpieces

3.3.1) Machine parameters

3.3.1.1) Speed

3.3.1.2) Processing time

3.3.1.3) Direction

3.3.1.4) Immersion depth

3.3.1.5) Angle of holder

3.3.1.6) Control functions

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3.3) Key factors

3.3.1) Machine parameters

Overview

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Parameter input

3.3.1.1) Speed

Higher speeds give greater rounding values

N.B. The rounding at corners increases more quickly

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3.3.1.1) Effect of speed

Kantenverrundung "unterschiedliche Drehzahlen " HM Bohrer 10.0; Tges= 20 min; Drehricht. 50/50; Granulat: SIX 70/16; DF3 Tools

0,000

0,005

0,010

0,015

0,020

0,025

0,030

0,035

0,040

Zeit [min]

Ka

nte

nv

err

un

du

ng

[µ

m]

25 [1/min]

35 [1/min]

40 [1/min]

30 [1/min]

0 2 4 6 8 10 12 14 16 18 20

3.3.1.2 + 3.3.1.3) Processing time and directionThe processing time and the direction of rotation

can be controlled during the process.

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3.3.1.2) Effect of processing time

Longer processing times give higher degrees of

rounding.

The increase in rounding values is not linear to the

processing time.

N.B. The rounding at the corners increases faster than

at the edges.

Depending on the media, the maximum value can

vary.

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3.3.1.2) Effect of processing time

Kantenverrundung "unterschiedliche Granulate " HM Bohrer 10.0; Tges= 20 min; Drehricht. 50/50; Drehzahl = 25 [1/min]; DF3

Tools

0,000

0,005

0,010

0,015

0,020

0,025

0,030

0,035

0,040

0,045

0,050

0,055

0,060

0,065

Zeit [min]

Ka

nte

nv

err

un

du

ng

[µ

m]

SIX 70/24

QZ 1/3

HSC 1/300

SIX 70/16

0 2 4 6 8 10 12 14 16 18 20

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3.3.1.3) Effect of direction

The choice of direction of rotation affects the flow of media

against the workpiece.

A change of speed is absolutely essential for homogeneous

media flow and uniform processing.

Uneven finishing, which is more pronounced on one side

than the other, is often undesirable.

Differences between the workpiece and the speed or

direction of the rotor affect have an effect on edge

rounding. (Low workpiece rotations give a uniform finish)

(High workpiece rotations give a more pronounced rounding of the

corners)

3.3.1.4) Immersion depth

Different immersion depths can be achieved by

preselecting the operating modes.

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3.3.1.4) Effect of immersion depth

Because of the static pressure, the contact pressure of

the media increases with the immersion depth. In general

we can say that a difference of 100 mm in the vertical

results in a difference of about 25% in the amount of

material removed.

In the case of lightweight media with a low bulk density,

this effect is less pronounced.

3.3.1.5) Effect of the angle of the holder and/or workpieces

An angled position for the holders and/or the

workpieces offers advantages for the processing of

the workpiece face and of large flat areas.

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3.3.1.6) Control functions

In addition to the adjustable machine parameters, the following

additional parameters are monitored:

-Media life for 5 different,

freely selectable, media types

-Workpiece length

(Sensor for avoiding collisions)

-Media level (Sensor for measuring the

level)

Goal: reliable processes

3.3) Key factors

3.3.2) Media

H granulates polishing

HSC granulates gentle edge rounding 15-20 µm

K granulates gentle edge rounding < 15

µm

SIX granulates more pronounced edge rounding up to

30 µm

QZ granulates more pronounced edge rounding over

30 µm

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3.3.2) Media H granulates

- Finishing of HSS tools- Polishing, gentle deburring- Gentle edge rounding- Low rate of chip removal, depending on

grinding or polishing additive

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3.3.2) Media HSC granulates

- Finishing of HSS and carbide tools- Polishing of coated tools and

removal of droplets- Smoothing and polishing of carbide

tools- Edge rounding of carbide materials

up to max. 15 – 20 µm- Removal of solder residues- Rate of chip removal medium to high

depending on grain size- Creates very high surface qualities

(Rz 0.5 for an initial value of Rz 2.5)

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3.3.2) Media K granulates

- Finishing of HSS and carbide tools

- Polishing of coated tools and removal of droplets

- Smoothing and polishing of carbide tools

- Edge rounding of carbide materials up to max. 10 – 15 µm

- Natural granulate bonded with PP1 polishing powder

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3.3.2) Media SIX granulates

- Finishing of carbide tools- Deburring and edge rounding of HSS

tools- Smoothing and edge rounding of chip

removing tools in carbide up to max. 30 µm

- Finishing of inserts- High rate of chip removal- Creates high quality surfaces

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3.3.2) Media QZ granulates

- Finishing of carbide tools- Gives especially high degree of edge

rounding over 30 µm- Rate of chip removal approx. twice as

high as with SIX granulates- Carborundum with grain size of 1-3 mm- Very high rate of material removal- In the case of small edge radii under

30 µm; gives rougher surfaces than SIX or HSC granulates.

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3.3.2) Media - Changing the media

It is a quick matter to change the media by simply

changing the process container. This makes it possible to

carry out multi-stage processing very efficiently.

The drag grinding or drag finishing process is the only type

of vibratory grinding that enables targeted surface

finishing such as deburring, grinding, polishing and

targeted edge rounding – all from the same machine.

3.3.2) Media - Changing the media

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3.3) Key factors

3.3.3) Workpiece

3.3.3.1) Workpiece size

3.3.3.2) Workpiece geometry

3.3.3.3) Workpiece materials

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3.3.3.1) Effect of workpiece size

In the case of single-drive DF machines, the transmission ratio between rotor and workpiece can not be adjusted. Here the diameter accounts for only about 10% of the effect.

In the case of dual drive versions with two motors, the satellite speed can be set independently of the rotary speed.

Areas of application:Thread-cutting taps high satellite speed, low rotor speedCarbide drills low satellite speed, high rotor speed

In the case of high satellite speeds, the diameter of the workpiece has a much greater effect than it does with low satellite speeds.

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3.3.3.2) Effect of workpiece geometry

Larger workpieces displace more media, which ‘glides’

over the edges and removes more material.

The processing has little effect on the central areas of

large, flat workpieces.

“Scooping” workpieces push the media away from

themselves.

This reduces the effect of processing.

Inner surfaces can be processed to a limited extend. With

small bore holes, the media grain size should not be too

large.

3.3.3.3) Effect of workpiece materials

Workpieces made from hard materials can be rounded

more accurately than soft ones.

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3.4) Machine specifications

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DF-3 DF-4 DF-5 DF-6 DF-10Maximum immersion depth

250 mm 250 mm 250 mm 250 mm 250 mm

Holder connections 3 4 5 6 10Maximum workpiece diameter

250 mm 210 mm 250 mm 210 mm 200 mm

Maximum holder weight 15 kg 15 kg 15 kg 15 kg 15 kgAdapter interfaces for 4-way / 6-way holders

12 / 18 16 / 24 20 / 30 24 / 36 40 / 60

Maximum workpiece diameter with 4-way / 6-way adapter

85 mm 55 mm

82 mm55 mm

85 mm55 mm

82 mm55 mm

65 mm55 mm

Maximum workpiece weight with adapter

0.5 / 2 kg

0.5 / 2 kg

0.5 / 2 kg

0.5 / 2 kg

0.5 / 2 kg

Extra drive optional optional optional optional optionalConnection voltage 400 V 400 V 400 V 400 V 400 V

Power requirement depending on configuration

2-3 kW 2 -3 kW 3 – 5 kW 3 – 5 kW 3.5 – 7 kW

3.4) Machine specificationsIndependently rotating holder systems

Holder type 4-way 2B up to 500 g

Holder type 6-way 2B up to 500 g

Holder type 4-way 2B up to 2 kg

Holder type 6-way 2B up to 2 kg

Holder type 4-way 2B SL

Holder type 6-way 2B SL

Special types on request

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4.) Outlook

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DF-3/4 and DF-5/6 available with additional drive

unit

4.) Outlook

DF-3/4 and DF-5/6

with angled holders

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4.) Outlook

DF-6 Automation

4.) Outlook

DF-6 Automation

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4.) Outlook

DF-6 Automation

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Thank you

for your attention !