Indian Patents. 223795:A METHOD FOR PROCESSING WORKPIECES HAVING LOW TOLERANCES BY REMOVING SHAVINGS.

Title of Invention	A METHOD FOR PROCESSING WORKPIECES HAVING LOW TOLERANCES BY REMOVING SHAVINGS.
Abstract	A method for processing products having low tolerances by removing shavings, involving a processing step for finishing the workpiece being processed (2), comprises a step for detecting temperature (T) of the workpiece being processed (2) before or at the same time as the finishing step and a step for adjusting the finishing depths in accordance with the detected temperature value.

Full Text	A METHOD FOR PROCESSING WORKPIECES HAVING LOW TOLERANCES BY REMOVING SHAVINGS Technical Field The present invention relates to a method for processing products having low dimensional tolerances by removing shavings. Technological Background It is known that metal materials are particularly prone to expansion phenomena when heated. It is also known that mechanical production operations for removing shavings, including in particular turning operations, produce substantial heating of the processed workpiece. This leads to the workpiece which is being processed being subjected to greater or lesser expansions. This must be taken into consideration when products having low dimensional tolerances have to be processed. In order to comply with high levels of precision during work cycles, it is known to entrust the evaluation of the dimensional variations resulting from the temperature of the workpiece to the experience of the operator, who is therefore responsible for deciding by estimation any adjustment to the finishing depths of the workpiece. However, this is a source of possible production rejects before the setting of the machine tool is at an optimum level and needs new adjustments each time the temperature of the workpiece being processed is subjected to changes, for example, owing to wear of the tool or for other reasons. As an alternative, it is known from American patent 6.449.526 to provide a machine tool, in particular a grinding centre, with dimensional control means for the workpieces being processed. This dimensional control is preferably carried out by means of an optical control effected by means of appropriate telecameras. In this manner, it is possible to detect the effective dimensions of the part being processed in order to take them into consideration when the machine is programmed or reprogrammed. This system, in addition to being particularly costly, requires at least temporary stopping of the machine in order to carry out the measurements. It is further preferable for the means for taking the measurement, owing to the sophistication thereof, normally to be located outside the machine and to be introduced only at the time of the measurement. This leads to a further increase in the production times owing to the need to position , test and then remove the measurement means. Statement of invention The technical problem addressed by the present invention is to provide a method for processing products having low tolerances by removing shavings, which method is set out so as to allow the disadvantages mentioned with reference to the cited prior art to be overcome. Accordingly.the present invention provides a method for processing workpieces having low tolerances by removing shavings, involving a processing step for finishing a surface of the workpiece being processed, characterized in that it comprises a step for detecting temperature (T) of the surface of the workpiece being processed before or at the same time as the finishing step and a step for adjusting the finishing depths in accordance with the detected temperature value. Preferably, the step for detecting the temperature of the workpiece is carried out in the step immediately before the finishing step. Preferably, the temperature of the workpiece is detected by non-contact measuring means or by optical measuring means. In a preferred embodiment, the processing by removing shavings is a turning process and temperature (T) of the workpiece is detected in the region of a processed diameter. The step for adjusting the finishing depths is preferably carried out by comparing the detected value of temperature (T) with a reference temperature (To, T1) and changing the finishing depths in accordance with the thermal expansion of the material which constitutes the workpiece being processed, taking into consideration the difference between detected temperature (T) and reference temperature (To,T1. Brief Description Of The Accompanying Drawings The characteristics and advantages of the invention will be better appreciated from the detailed description of one preferred embodiment which is illustrated purely by way of non-limiting example with reference to the accompanying drawings, in which: ? Figure 1 is a schematic flow chart showing the method of the invention; ? Figure 2 is a schematic view of a workpiece being turned by the method of the invention. Preferred Embodiment Of The Invention With reference to the appended Figures, a machine tool, such as a CNC turning centre 1 which is arranged for processing a workpiece 2, for example, in order to carry out the finishing processing of the surface 3 thereof, is provided according to the invention with a thermometric device 4, preferably of the non- contact type, such as an optical sensor or laser type sensor of the type know per se. The thermometric sensor device 4, is directed towards the surface 3 (processed diameter) so as to allow temperature T thereof to be detected in the step immediately before the finishing processing. The device 4 is also connected to a unit 5 for processing temperature signal T detected, in which, in addition to processing the signal in order to obtain the temperature value detected, a comparison is carried out between T and the expected nominal temperature for the correct processing tolerances to be obtained. In particular, it is checked as to whether or not detected temperature T falls within a range about the nominal temperature, delimited by lower limit temperature TQ and upper limit temperature T1, respectively. Temperatures To and T1 are defined in accordance with the characteristics of the material being processed, as well as the degree of precision required by the processing operation. When detected temperature T falls within the above-defined range, the processing is considered to be within normal values so that the thermal expansions of the workpiece being processed do not compromise to a significant degree the permissible dimensional tolerances. In this case, no correction is carried out to the processing parameters of the machine with specific reference to the finishing processing of the surface 3. If the result of the temperature comparison falls outside this temperature range, however, the processing unit produces a correction signal which acts on the numerical control of the turning centre 1 in order to change the depths of finishing of the surface 3 so as to compensate for the detrimental thermal effect. In this manner, a substantial level of reproducibility and consistency are obtained in the processing tolerances, even for very precise processing operations, reducing, if not eradicating, rejects owing to dimensional errors. WE CLAIM : 1. A method for processing workpieces (2) having low tolerances by removing shavings, involving a processing step for finishing a surface (3) of the workpiece being processed (2), characterized in that it comprises a step for detecting temperature (T) of the surface (3) of the workpiece being processed (2) before or at the same time as the finishing step and a step for adjusting the finishing depths in accordance with the detected temperature value. 2. A processing method as claimed in claim 1, wherein the step for detecting the temperature of the workpiece is carried out in the step immediately before the finishing step. 3. A processing method as claimed in claim 1 or claim 2, wherein the temperature of the workpiece is detected by non-contact measuring means (4). 4. A processing method as claimed in claim 2, wherein the temperature of the workpiece is detected by optical measuring means. 5. A processing method as claimed in any one or more of the preceding claims, wherein the processing by removing shavings is a turning process and temperature (T) of the workpiece (2) is detected in the region of a processed diameter (3). 6. A processing method as claimed in any one or more of the preceding claims, wherein the step for adjusting the finishing depths is carried out by comparing the detected value of temperature (T) with a reference temperature (To, T1 and changing the finishing depths in accordance with the thermal expansion of the material which constitutes the workpiece being processed, taking into consideration the difference between detected temperature (T) and reference temperature (T0;T1). A method for processing products having low tolerances by removing shavings, involving a processing step for finishing the workpiece being processed (2), comprises a step for detecting temperature (T) of the workpiece being processed (2) before or at the same time as the finishing step and a step for adjusting the finishing depths in accordance with the detected temperature value.

Full Text

A METHOD FOR PROCESSING WORKPIECES HAVING LOW
TOLERANCES BY REMOVING SHAVINGS
Technical Field
The present invention relates to a method for processing products having
low dimensional tolerances by removing shavings.
Technological Background
It is known that metal materials are particularly prone to expansion
phenomena when heated. It is also known that mechanical production
operations for removing shavings, including in particular turning operations,
produce substantial heating of the processed workpiece. This leads to the
workpiece which is being processed being subjected to greater or lesser
expansions.
This must be taken into consideration when products having low
dimensional tolerances have to be processed.
In order to comply with high levels of precision during work cycles, it is
known to entrust the evaluation of the dimensional variations resulting from the
temperature of the workpiece to the experience of the operator, who is therefore
responsible for deciding by estimation any adjustment to the finishing depths of
the workpiece.
However, this is a source of possible production rejects before the setting
of the machine tool is at an optimum level and needs new adjustments each time
the temperature of the workpiece being processed is subjected to changes, for
example, owing to wear of the tool or for other reasons.
As an alternative, it is known from American patent 6.449.526 to provide a
machine tool, in particular a grinding centre, with dimensional control means for
the workpieces being processed. This dimensional control is preferably carried
out by means of an optical control effected by means of appropriate
telecameras. In this manner, it is possible to detect the effective dimensions of
the part being processed in order to take them into consideration when the
machine is programmed or reprogrammed. This system, in addition to being
particularly costly, requires at least temporary stopping of the machine in order
to carry out the measurements. It is further preferable for the means for taking
the measurement, owing to the sophistication thereof, normally to be located
outside the machine and to be introduced only at the time of the measurement.
This leads to a further increase in the production times owing to the need to
position , test and then remove the measurement means.
Statement of invention
The technical problem addressed by the present invention is to provide a
method for processing products having low tolerances by removing shavings,
which method is set out so as to allow the disadvantages mentioned with
reference to the cited prior art to be overcome.
Accordingly.the present invention provides a method for processing
workpieces having low tolerances by removing shavings, involving a processing
step for finishing a surface of the workpiece being processed, characterized in
that it comprises a step for detecting temperature (T) of the surface of the
workpiece being processed before or at the same time as the finishing step and
a step for adjusting the finishing depths in accordance with the detected
temperature value.
Preferably, the step for detecting the temperature of the workpiece is
carried out in the step immediately before the finishing step. Preferably, the
temperature of the workpiece is detected by non-contact measuring means or by
optical measuring means. In a preferred embodiment, the processing by
removing shavings is a turning process and temperature (T) of the workpiece is
detected in the region of a processed diameter. The step for adjusting the
finishing depths is preferably carried out by comparing the detected value of
temperature (T) with a reference temperature (To, T1) and changing the finishing
depths in accordance with the thermal expansion of the material which
constitutes the workpiece being processed, taking into consideration the
difference between detected temperature (T) and reference temperature (To,T1.
Brief Description Of The Accompanying Drawings
The characteristics and advantages of the invention will be better
appreciated from the detailed description of one preferred embodiment which is
illustrated purely by way of non-limiting example with reference to the
accompanying drawings, in which:
? Figure 1 is a schematic flow chart showing the method of the invention;
? Figure 2 is a schematic view of a workpiece being turned by the method
of the invention.
Preferred Embodiment Of The Invention
With reference to the appended Figures, a machine tool, such as a CNC
turning centre 1 which is arranged for processing a workpiece 2, for example, in
order to carry out the finishing processing of the surface 3 thereof, is provided
according to the invention with a thermometric device 4, preferably of the non-
contact type, such as an optical sensor or laser type sensor of the type know per
se. The thermometric sensor device 4, is directed towards the surface 3
(processed diameter) so as to allow temperature T thereof to be detected in the
step immediately before the finishing processing. The device 4 is also connected
to a unit 5 for processing temperature signal T detected, in which, in addition to
processing the signal in order to obtain the temperature value detected, a
comparison is carried out between T and the expected nominal temperature for
the correct processing tolerances to be obtained. In particular, it is checked as to
whether or not detected temperature T falls within a range about the nominal
temperature, delimited by lower limit temperature TQ and upper limit temperature
T1, respectively.
Temperatures To and T1 are defined in accordance with the characteristics
of the material being processed, as well as the degree of precision required by
the processing operation.
When detected temperature T falls within the above-defined range, the
processing is considered to be within normal values so that the thermal
expansions of the workpiece being processed do not compromise to a significant
degree the permissible dimensional tolerances. In this case, no correction is
carried out to the processing parameters of the machine with specific reference
to the finishing processing of the surface 3.
If the result of the temperature comparison falls outside this temperature
range, however, the processing unit produces a correction signal which acts on
the numerical control of the turning centre 1 in order to change the depths of
finishing of the surface 3 so as to compensate for the detrimental thermal effect.
In this manner, a substantial level of reproducibility and consistency are
obtained in the processing tolerances, even for very precise processing
operations, reducing, if not eradicating, rejects owing to dimensional errors.
WE CLAIM :
1. A method for processing workpieces (2) having low tolerances by
removing shavings, involving a processing step for finishing a surface (3) of the
workpiece being processed (2), characterized in that it comprises a step for
detecting temperature (T) of the surface (3) of the workpiece being processed (2)
before or at the same time as the finishing step and a step for adjusting the
finishing depths in accordance with the detected temperature value.
2. A processing method as claimed in claim 1, wherein the step for detecting
the temperature of the workpiece is carried out in the step immediately before
the finishing step.
3. A processing method as claimed in claim 1 or claim 2, wherein the
temperature of the workpiece is detected by non-contact measuring means (4).
4. A processing method as claimed in claim 2, wherein the temperature of
the workpiece is detected by optical measuring means.
5. A processing method as claimed in any one or more of the preceding
claims, wherein the processing by removing shavings is a turning process and
temperature (T) of the workpiece (2) is detected in the region of a processed
diameter (3).
6. A processing method as claimed in any one or more of the preceding
claims, wherein the step for adjusting the finishing depths is carried out by
comparing the detected value of temperature (T) with a reference temperature
(To, T1 and changing the finishing depths in accordance with the thermal
expansion of the material which constitutes the workpiece being processed,
taking into consideration the difference between detected temperature (T) and
reference temperature (T0;T1).
A method for processing products having low tolerances by removing
shavings, involving a processing step for finishing the workpiece being
processed (2), comprises a step for detecting temperature (T) of the workpiece
being processed (2) before or at the same time as the finishing step and a step
for adjusting the finishing depths in accordance with the detected temperature
value.

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Patent Number

223795

Indian Patent Application Number

01613/KOLNP/2005

PG Journal Number

39/2008

Publication Date

26-Sep-2008

Grant Date

23-Sep-2008

Date of Filing

11-Aug-2005

Name of Patentee

MAUS S.P.A.

Applicant Address

VIA CALTANA, 28, 35011 CAMPODARSEGO (PD)

Inventors:

#	Inventor's Name	Inventor's Address
1	SAMMARTIN, ROBERTO	VIA AQUILEIA, 4, 35030 SELVAZZANO DENTRO (PD)

PCT International Classification Number

B23Q 11/00

PCT International Application Number

PCT/IT2004/000075

PCT International Filing date

2004-02-20

PCT Conventions:

#	PCT Application Number	Date of Convention	Priority Country
1	PD2003 A000039	2003-02-28	Italy