Manufacture | Machining _____________________________________________________________________________________

Wire erosion dressing for contactless Dressing of Grinding Wheels The precise dressing of Diamond grinding wheels serves two purposes: Generation of the required geometry and manufacturing of the optimum topography. In mechanical processes the wheels are subject to high loads. A new contactless process utilizes the erosion wire for dressing.

Jörg Springmann

Dressing processes are used to profile and sharpen industrially

manufactured grinding wheels

used as machining tools.

Conventional dressing processes

impose mechanical load on the contact area of dressing tool and

grinding wheel. Vibration absorbing dressing units are

therefore required to achieve the

desired quality. _____________ Jörg Springmann is Director and Project Engineer at ITS-Technologies GmbH & Co. KG in 78727 Oberndorf a/N., Germany. Phone (0 74 23) 87 67-35, J.Springmann@its-techologies.de, www.its-technologies.de

ITS wire erosion dressing now

represents a novel dressing

strategy for metal bond CBN and Diamond grinding wheels.

Electric Pulse Dressing and

Profiling in two Steps

On the one hand, dressing shall

sufficiently reduce the grinding

wheel’s binding matrix in order to

achieve high surface quality during

grinding. On the other hand the wheel and dressing tool need to

be cooled in such a way as not to

destroy the abrasive compound by means of micro cracks or heat

strain.

With wire erosion dressing – now

offered by ITS – an erosion wire

serves as the dressing to (illustration 1). This method can

be explained as follows: The rotationally symmetrical grinding

wheels will be clamped into an

additional axis (illustrations 5 and

2). This component is called the

rotational axis and is designated

as ITS-RSI-42. It continuously

turns the grinding wheel. The required speed depends on the

grinding wheel diameter and the

erosion process. In a first roughing pass the desired grinding wheel

geometry using the erosion process will be applied. The

second and final pass will shape

the ideal grinding wheel

topography.

This will be achieved using a contactless electric pulse erosion

process applied to the grinding wheel in continuously cooled

deionised water. The main benefit

of wire erosion dressing: the contact area is not subject to

mechanical load. This contactless

method allows for most precise

concentricity demands of less than 0.002mm at highest profile

accuracy. The process now makes

it possible to manufacture finest contours which could not have

been achieved before. For instance precise inner radii of r ≈ 0.05mm

(illustrations 4 and 7) can now be

manufactured.

Illustration 1:

The Wire Erosion Dressing of Grinding

wheels is a contactless process.

The EDM-Wire act as the dressing tool

Pict. ITS

Manufacture | Machining _____________________________________________________________________________________

Limitations to outer radii only

apply in terms of grit size and the

binding material used. Even highly

tapered grinding wheels with

precise geometry can be created (illustration 3).

A further benefit of this process is the absence of thermal strain to

the binding. Grinding wheels

dressed using this method are

highly open-pored and therefore

offer sufficient chip space.

Additionally there are no chipped

particles in the binding matrix that may lead to poor grinding quality

on the initial workpiece. The

grinding wheels’ load time has proven to increase by several

magnitudes.

It is even possible to

manufacture shaping and

profile rollers. Users of wire erosion dressing

particularly appreciate the

relatively quick and flexible manufacture of novel grinding

wheel profiles, thus generating a substantial competitive edge

compared to conventional

methods. Dressing using this

process can be carried out more

often compared to other methods since only a minimum of correction

will be performed on the grinding wheel. Hence only a small amount

of grinding material will be lost.

Wire erosion dressing makes it quite simple to manufacture form

and profile rollers, which will then

be used as conventional

mechanical dressing tools for mass

production. ITS customers

particularly benefit from quick

reaction times to profile changes and adaptations. New, testing and

special profiles can be

manufactured within shortest time schedules using simple 2D contour

specifications. Profile generation of inner profiles and multiple profiles

as well as complete wheel sets can

be carried out in a single clamping

process.

Continuous miniaturization of

technical components and tools will lead to even smaller grinding

wheels in order to preserve highest machining precision, e.g.

for gear modules with minimum

radii. Conventional mechanical

dressing processes will certainly

reach their limits in such cases.

Automatic holders and robots enhance productivity even

further

ITS wire erosion dressing opens up completely new application

areas. Depending on the grinding wheel characteristics, in particular

in terms of diameter and weight,

the user can choose between various rotational spindle types:

For a wheel diameter of up to

100mm the ITS-MS-24 model can

be used. For wheels with diameters between 100mm and

250mm the ITS-RSI-42 takes over

the dressing process (illustration 5). Both rotational spindles feature

a particularly precise concentricity. The ITS-MS-24 for example offers

a spindle concentricity of ≤

0.001mm at speeds of up to 3000

min -1. The larger ITS-RSI-42

offers a spindle concentricity of ≤

0.003mm at speeds of up to 1500

min-1.

There is also a choice of different

tool holders available. Productivity

can be enhanced further using

automated tool holder systems

and robot loading of the spindle. ITS-Technologies spindles in

combination with the latest

Mitsubishi Electric wire cutting machine series can achieve

optimum feasibility, processing time and quality. Close and

intensive cooperation with

Mitsubishi Electric Europe permits further optimization of quality and

process stability in grinding wheel

profiling.

Illustration 2: cup grinding wheel machining submerged in erosion

fluid.

Illustration 4: Grinding wheel with 0.05mm inner radii.

Illustration 3: 60° tapered CBn grinding wheel.

Pict. ITS

Pict. ITS

Pict. ITS

Manufacture | Machining _____________________________________________________________________________________

Following you will find a short brief

on the features of wire erosion

dressing for metal bond CBN and

Diamond grinding wheels:

▶ Requirements: Binding material

and bonding material of the grinding body must be made of

electrically conductive material.

▶ Application scope: Manufacture

of inner radii down to r ≈ 0.05mm. Outer radii are only limited by

grain size and binding material. Profile generation of inner profiles

and multiple profiles as well as

complete wheel sets can be carried out in a single clamping

process. Miniature components are

machinable.

This results in high profile accuracy in the micrometer range,

high concentric accuracy and

open-pored wheels with finest contours; binding matrix

components do not chip and only the binding material will be

machined; precise geometries and

topographies can be achieved;

higher load times and multiple

dressing operations are possible. Even the manufacture of novel

contours using 2D contour

specifications can be achieved quickly and easily. Productivity

enhancing automation options and flexible tool holders complete the

performance profile.

Illustration 5: Example for use of the rotation spindle ITS-RSI-42.

Illustration 7: Further application example for wire erosion dressing.

Pict. ITS

Pict. ITS

Illustration 6: A grinding wheel on the HSK holder.

Pict. ITS

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