Grinding versus Hard Turning review - United Grinding and Studer - featured in Shop Metalworking Technology Magazine - February, 2015 edition

1. Frank Pfeiffer: How have customers’
behaviours changed the competition
between hard machining with a
geometrically defined cutting edge
and grinding?
Frank Fiebelkorn: It has led to a
relativization of the previously strict
positions held by the advocates of both
processes. Fifteen or twenty years
ago there were many publications
which predicted that, due to the
increasing potential of hard turning, the
requirement for grinding would be much
reduced. Precision tool manufacturers
reinforced this with references to the
increasing capability of their cutting
materials. However, at the same time
there was also an increase in customer
requirements, which could best be met
by means of grinding. Today these two
processes coexist happily.
Mathias Gerber: As you can see from
our business development, cylindrical
grinding has anything but disappeared,
as some people predicted. On the
contrary, it is in demand as never before.
FP: What are the requirements that have
given grinding a new impetus?
FF: In the first instance, one surprising
fact should be mentioned: precision tool
manufacturers have been processing
increasingly efficient cutting materials,
such as carbides or cermets, which are
almost exclusively machinable using
grinding. And we have been helped by
an increase in the consumption of these
cutting materials of around 40 per cent
between 2010 and 2015. More and
more materials must also be precision-
machined for medical technology,
especially ceramic materials. Once again,
grinding is virtually the only possibility
here. Sources for North America show
an increase of more than 20 per cent in
this field from 2010 to 2016.
FP: What role is played by the users’
requirement for higher precision?
FF: The tolerances for precision
components have become ever
tighter. When manufacturing high
precision toolholders, for example,
today, an ATI tolerance class is
often used instead of AT3 for a
standard toolholder. This means
that roundnesses and straightnesses
of less than 0.5 micron must be
achievable at the toolholder cone.
MG: In principle, it is possible to
precision-turn these tolerances, but
process reliability can not be attained
cost-effectively. Often, the absolute
tolerance of the customer part has
remained the same, but the process
capability and machine capability have
increased, so the window in which you
may utilize the tolerance has become
smaller. Here too, grinding is the
user’s first choice.
Reprinted with permission from Shop Metalworking Technology | www.shopmetaltech.com February 2016
CUTTING TOOLS | Turning
Grinding vs Hard Turning
Which process has the edge?
When it comes to precision machining, classic grinding and machining with a
defined cutting edge have always been neck and neck in the market. There have
been plenty of discussions about the pros and cons. Dr. Frank Fiebelkorn, head
of product development, research and technology, and Mathias Gerber, precision
machining product manager at Swiss Fritz Studer AG, a United Grinding Group
company, discuss the subject in this Q&A, conducted by Frank Pfeiffer.
FP: Is grinding always preferred in cases
where high precision is required?
FF: Despite what has already been
said, this should not be our message.
Whatever benefits the customer is
preferable. And if hard turning is the
best process for the application, then
that’s what we recommend. We have
sufficient experience in both areas
to make a neutral assessment of the
respective manufacturing task. Our
starting point is the advantages of the
process group.
FP: Which processes in particular?
MG: Well, machining with a
geometrically defined cutting edge is
very fast, can produce contours very
flexibly and requires only little set-up
effort, if you need to perform a number
of operations. However, as the cutting
edge wears you get a gradual loss of
precision, culminating in complete
replacement of the cutting edge, with
the inevitable interruption of production.
This also brings disadvantages for
production with reduced staff. The
situation with grinding is different.
Here, as we have mentioned, you can
permanently ensure the values for
diameter, length, surface and shape.
You always have an easy-cutting,
geometrically accurate tool available,
which can be dressed in an autonomous
and process-integrated manner, so that
it once again resumes it initial state.
With a 500 grinding wheel for example,
this can be done up to 15 000 times.
And it should also be borne in mind that
grinding is less susceptible to material
in homogeneities such as hardness
fluctuations or inclusions, than hard
turning or milling. SMT
ThisarticleisaneditedversionofaQ&A
suppliedbyUnitedGrindingGroup.
www.grinding.com
Mathias Gerber, left, and Frank Fiebelkorn from
Swiss Fritz Studer AG, a United Grinding Group.