DE102008022361A1 - Method for processing a spectacle lens blank - Google Patents

Abstract

The method involves accelerating a milling head (4.1), and accelerating a milling cutter (4) and/or a workpiece spindle (3) in a direction of movement axis (T) in speed. The head and the spindle are drawn near in a direction of the axis with the speed till a distance between the head and a rotational axis (R) of a spindle axle (3.1) is equal to a specific value. The head and the spindle are drawn near with another speed till the distance is equal to another specific value. The latter speed is lowered around 10 percentage at the distance equal to the latter specific value.

Description

The The invention relates to a milling and / or lathe for plastic eyeglass lenses with one Spindle axis and a rotation axis R having workpiece spindle for a blank to be processed or a semi-finished part or semi-finished and having a milling head having Milling cutter and with a movement axis T, where the cutter and the workpiece spindle relative to each other in the direction the movement axis T and in the radial direction to the workpiece spindle are movable, wherein between the milling head and the axis of rotation R of the spindle axis a distance a is provided.

It is already a numerical control unit with a load monitoring function with a load acting on a tool drive source during a machining operation of the DE 60 2004 000 025 T2 known. The control unit further includes a wear detection area and a storage area for various wear-dependent load limits, a calculation area for calculating a current load limit based on the current wear, and a comparison area for comparing the current load with the calculated load threshold. If the load exceeds the load limit, the drive is stopped.

From the JP7-51991A a system for preventing tool breakage is known. Here, a disturbance torque is estimated and compared with a preset reference torque. On the basis of the comparison result, the feed rate of the tool is reduced or the tool is stopped.

From the EP 1 166 960 A2 For example, a processing machine is known which has means for avoiding a collision between the tool and other machine parts. The machine is stopped when the current load exceeds a defined threshold.

Of the Invention is based on the object, a method for operation a spectacle glass processing machine in such a form and to arrange that a fast and safe processing of spectacle lenses is guaranteed.

Solved The object is achieved according to the invention in that the milling and / or lathe the following process steps Completed: accelerating the milling head to an operating speed and accelerating the cutter and / or the workpiece spindle in the direction of the movement axis T to a speed V1 as well Approach of milling head and workpiece spindle in the direction of the movement axis T at the speed V1 to to a distance a = a1. Then reduce the speed V1 by at least 90 to a value V2 and reaching the speed V2 at the latest at the distance a = a1 and approaching of milling head and workpiece spindle at the speed V2 up to a distance a = a2. Then reduce the approach speed V2 by at least 10 to a value V3 at the latest at the Distance a = a2, preferably reaching the approach speed V3 at the latest at the distance a = a2. This will achieve that regardless of the actual size of the inserted and processed blank an elevated Approach speed and thus an uncontrolled blocking of the Blank is avoided despite optimized production times. Of the Starting process between the milling head and the workpiece spindle is subdivided according to the invention into two subregions. The first section, in which at very great speed V1 is approached. The second section, in which with greatly reduced Speed V2 is approached and finally a third section, in which the speed again on a smaller, optimal value V3 is reduced. The respective speed value V1, V2, V3 is a function of the distance a between the milling head and the workpiece spindle selected.

Advantageous It can also be this, if the ratio of V1: V2 between 100: 1 and 30: 1, in particular between 88: 1 and 66: 1 is set. The reduction of the speed to the value V2 ensures also in the presence of a too large blank at the beginning mentioned process reliability despite optimized cutting performance on the blank. Depending on the approach speed in Direction of the movement axis T, of the speed of the milling cutter and the type of materials used for the blank as well as for the block material is also a minor one Lowering the speed to a value within the aforementioned Areas possible.

Further It may be advantageous if the ratio of V2: V3 between 5: 1 and 1: 1, in particular 2: 1 is set. There in this third starting section the best possible surface quality When cutting is to be ensured is a halving the speed V2 to the value V3 desired. With that reached final delay stage ensures the desired surface quality.

It can also be advantageous if the distance a1 between the milling head and the axis of rotation R of the spindle axis is set between 40 mm and 50 mm, in particular 42.5 mm. The raw lenses used for the production of spectacle lenses generally have a maximum diameter of 85 mm and 90 mm, respectively. With the distance a1 according to the invention thus immersing in the Prevented blank with excessive speed. Upon reaching the distance a1, in which, theoretically, a contact between the milling head and a too large blank could already arise, according to the invention a first speed reduction to the speed value V2 is provided.

For the purpose of Reduction of the cutting load acting on the workpiece can be complementary or alternative to speed reduction V1, V2, V3 a speed of the workpiece spindle when reaching the Distance a = a1 and / or a = a2 can be reduced. The reduction can also be initiated before reaching the distance a1, a2 or achieved. Here comes a reduction between 30% and 70% in consideration.

In addition, it can be advantageously provided that a diameter D of the blank used and to be processed ( 2 ) and as a value for the distance a2 between the milling head ( 3.1 ) and the axis of rotation R of the spindle axis ( 3.1 ) Half the diameter D is used or a value for the distance a2 is used, which deviates more than 10% from half the diameter D. As soon as the milling head has approached the blank with the diameter D, the last time the approach speed is reduced to the process speed in order to ensure a desired surface quality. If the actually present diameter D of the blank coincide with the diameter set in the machine, the milling head, when reaching the distance a2, engages the blank in the radial direction relative to the blank. Edge processing is done as usual.

Should a blank used in the machine whose diameter D is greater than the one set in the machine, The milling head occurs when reaching the distance a1 or a smaller distance between a1 and a2 with the blank in contact. The processing takes place at increased speed V2. However, the speed V2 still guarantees one Chip process with a sufficiently good surface quality, in particular, the blocking of the blank or a disadvantageous Impairment of the storage of the blank is prevented. Also in this case, when the distance a2 reaches the speed V2 reduced to the value V3 to the ultimately desired To ensure surface quality.

alternative For this purpose, it may be provided that an actual value Li of a drive current and / or a drive power of the milling head, the movement axis T and / or the workpiece spindle or a reference value Li recorded and monitored for the actual cutting load and that a reference value Lf of the drive current and / or the Drive power for the freewheel available is made and that the actual value Li compared with the reference value Lf is, with the spacing used as the distance a1 at the ratio of the amount of the actual value Li to the Amount of the reference value Lf is greater than one. Once the rotating milling head on the rotating workpiece engages, there is an increase of the actual value Li, by Comparison with a free-wheeling value Lf can be detected.

To This time can before the actual distance a2 the speed is reduced, if necessary reduced to the value V3 become. Alternatively, the speed of the workpiece spindle be reduced. In both cases, the on the workpiece reducing cutting load is reduced.

Of the Distance a2 is redefined here. The possibly desired Speed reduction from V2 to V3 occurs in this case only after reaching the new distance a2. Because when using the speed V2 for the movement axis T damage of the workpiece is usually prevented, is the presence the speed V2 at the time of reaching the newly defined distance a2 almost uncritical.

A further protection of the workpiece can be achieved if a maximum value Lm of a load L, ie the drive current or the drive power of the milling head, the movement axis T and / or the workpiece spindle arising during a previous standard machining of a corresponding blank is detected and stored and if the speed V2 or V3 and / or a speed of the workpiece spindle is reduced by at least 10% or 20%, when the actual value Li reaches a critical value Lk in the first 1 s to 3 s after reaching the distance a = a2, the value Lk is between 50% and 110% or between 80% and 100% of the maximum value Lm. At the beginning of the processing of a blank is the edge processing. This is followed by the machining of a first side or the optical surface of the blank. The load L produced during the edge processing is less than the load L during the processing of the first side. During the processing of the first page, a maximum value Lm of the load L is to be expected. Should an increase in the load L to the value Lk occur during the processing of the edge, which usually takes place in the first 1 s to 3 s after reaching the distance a2, that is to say after the contact between the cutter and the blank, then this can be reduced by lowering the feed. The feed is determined in the edge processing by the speed V2 or V3 of the movement axis T and / or the speed of the workpiece spindle. The maximum value Lm is determined from a previous standard processing of a corresponding blank. He represents a comparison value for the material used. The state or the operating time of the tool is an uncritical variable when processing plastic lens blanks or when determining the load, so that it is possible to use a comparison value from an earlier machining.

Further Advantages and details of the invention are in the claims and explained in the description and shown in the figure.

An in 1 illustrated turning and milling machine 1 has a machine bed 1.1 on which a workpiece spindle 3 with a blank recorded in it 2 as well as a router 4 with a milling head 4.1 are arranged. The workpiece spindle 3 has a spindle axis 3.1 with an axis of rotation R on which the blank 2 is driven in rotation. The machine bed 1.1 has a position relative to the horizontal by the angle α.

The workpiece spindle 3 is via a linear drive 3.2 in the direction of a translatory movement axis T relative to the cutter 4 traversable. About the movement axis T is a distance a between the milling head 4.1 and the rotation axis R variable.

Starting from the position shown is for the purpose of processing the lens blank 2 the milling head 4.1 to a loading operating speed and the workpiece spindle 3 accelerated in the direction of the movement axis T to a speed V1. After the milling head 4.1 and the workpiece spindle 3 have reached a distance a = a1, the speed V1 is lowered to a value V2. After the milling head 4.1 and the workpiece spindle 3 After approaching a distance a = a2 have reached, the speed V2 is further lowered to a value V3. The speed V1 has about 666 mm / s, the speed V2 about 7.5 mm / s and the speed V3 about 3.75 mm / s. The distance a1 is about 42.5 mm and the distance a2 about 32.5 mm.

The distance a is determined between the axis of rotation R and a circumferential line of the milling head 4.1 in which a cutting tooth first comes into contact with the blank due to the movement in the direction of the movement axis T.

With respect to the distances a1, a2 are the blanks 2 dashed and with the reference numerals 2 ' . 2 '' marked shown. The blank 2 ' has the distance a1, while the blank 2 '' has the distance a2.

1

rotary and milling machine

1.1

machine bed

2

Spectacle lens, Blank, lens blank

2 '

blank

2 ''

blank

3

Workpiece spindle

3.1

spindle axis

3.2

linear actuator

4

milling cutter

4.1

milling head

a

distance

a1

distance

a2

distance

D

diameter

R

axis of rotation

T

motion axis

V1

speed

V2

speed

V3

speed

α

angle

QUOTES INCLUDE IN THE DESCRIPTION

This list The documents listed by the applicant have been automated generated and is solely for better information recorded by the reader. The list is not part of the German Patent or utility model application. The DPMA takes over no liability for any errors or omissions.

Cited patent literature

• - DE 602004000025 T2 [0002]
• - JP 7-51991 A [0003]
• - EP 1166960 A2 [0004]

Claims (8)

Method for processing a spectacle lens blank ( 2 ) made of plastic by means of a milling and / or lathe ( 1 ) with a spindle axis ( 3.1 ) and a rotation axis R having workpiece spindle ( 3 ) for a blank to be processed ( 2 ) or a semi-finished part and with a milling head ( 4.1 ) having cutters ( 4 ) and with a movement axis T, wherein the milling cutter ( 4 ) and the workpiece spindle ( 3 ) relative to each other in the direction of the movement axis T and in the radial direction to the workpiece spindle ( 3 ) are movable, wherein between the milling head ( 4.1 ) and the axis of rotation R of the spindle axis ( 3.1 ) a distance a is provided, characterized by the following method steps: - accelerating the milling head ( 4.1 ) to an operating speed; - accelerating the milling cutter ( 4 ) and / or the workpiece spindle ( 3 ) in the direction of the movement axis T to a speed V1; - approach of milling head ( 4.1 ) and workpiece spindle ( 3 ) in the direction of the movement axis T at the speed V1 up to a distance a = a1; - Lowering the speed V1 by at least 90% to a value V2 and reaching the speed V2 at the latest at the distance a = a1; - approach of milling head ( 4.1 ) and workpiece spindle ( 3 ) with the velocity V2 up to a distance a = a2; - Lowering the speed V2 by at least 10% to a value V3 at the latest at the distance a = a2. Method according to claim 1, characterized in that that the ratio of V1: V2 between 100: 1 and 30: 1 or between 88: 1 and 66: 1. Method according to claim 1 or 2, characterized that the ratio of V2: V3 is between 5: 1 and 1: 1, in particular set to 2: 1. Method according to one of claims 1 to 3, characterized in that the distance a1 between the milling head ( 4.1 ) and the axis of rotation R of the spindle axis ( 3.1 ) is set between 40 mm and 50 mm, in particular to 42.5 mm. Method according to one of claims 1 to 4, characterized in that a rotational speed of the workpiece spindle ( 3 ) is reduced when the distance a = a2 and / or a = a3 is reached. Method according to one of claims 1 to 5, characterized in that a diameter D of the inserted and to be processed blank ( 2 ) and as a value for the distance a2 between the milling head ( 3.1 ) and the axis of rotation R of the spindle axis ( 3.1 ) Half the diameter D is used or a value for the distance a2 is used, which deviates more than 10% from half the diameter D. Method according to one of claims 1 to 5, characterized in that an actual value Li of a drive current or a drive power of the milling head ( 4.1 ), the movement axis T and / or the workpiece spindle ( 3 ) is detected and monitored, and that a reference value Lf of the drive current and / or the drive power for the freewheel is provided and that the actual value Li is compared with the reference value Lf, wherein as distance a2 the distance is used, in which the Ratio of the amount of the actual value Li to the amount of the reference value Lf is greater than one. Method according to one of claims 1 to 7, characterized in that in the standard processing of the blank ( 2 ) resulting maximum value Lm of the drive current or the drive power of the milling head ( 4.1 ), the movement axis T and / or the workpiece spindle ( 3 ) is detected and stored and that the speed V2, V3 and / or a rotational speed of the workpiece spindle ( 3 ) is lowered by at least 10% or 20% when the actual value Li reaches a critical value Lk in the first 1 s to 3 s after reaching the distance a = a2, wherein the value Lk is between 50% and 110%, or between 80% and 100% of the maximum value Lm.