Conditioning of a superabrasive grinding tool
In a method of machining workpieces in a gear grinding machine with a grinding tool having vitrified-bonded abrasive grains made of a superabrasive material. The grinding tool is first dressed. Subsequently, the dressed grinding tool is conditioned such that a desired wear condition is produced. Thereafter, pre-toothed workpieces are machined using the dressed and conditioned grinding tool. Conditioning prevents undesirable grinding-in behavior of the grinding tool, which can cause thermal damage to the edge zone of the workpiece. Conditioning is performed with a conditioning kinematics, which is different from the machining kinematics and may correspond to a dressing kinematics. For conditioning, a conditioning tool is used which has a basic shape that is different from the basic shape of the workpieces.
1 . A method for machining pre-toothed workpieces in a gear grinding machine using a grinding tool, comprising the steps of:
a) dressing the grinding tool using a dressing tool, wherein the gear grinding machine executes a dressing kinematics for moving the dressing tool relative to the grinding tool during the dressing of the grinding tool, wherein the grinding tool comprises vitrified-bonded abrasive grains made of a superabrasive material having a Vickers microhardness at room temperature that is higher than for corundum, wherein a geometric shape of the grinding tool is produced or restored by the dressing of the grinding tool;
b) conditioning the dressed grinding tool using a conditioning tool, wherein the geometric shape of the dressed grinding tool is not changed by the conditioning of the grinding tool, wherein the gear grinding machine executes a conditioning kinematics for moving the conditioning tool relative to the dressed grinding tool during the conditioning of the dressed grinding tool; and
c) machining the pre-toothed workpieces using the dressed and conditioned grinding tool, wherein the gear grinding machine executes a machining kinematics for moving the dressed and conditioned grinding tool relative to the pre-toothed workpieces during the machining of the pre-toothed workpieces,
wherein the conditioning kinematics is different from the machining kinematics.
2 . The method of claim 1 , wherein the conditioning kinematics corresponds to the dressing kinematics.
3 . The method of claim 1 ,
wherein the gear grinding machine comprises a dressing spindle on which the dressing tool is clamped in step a);
wherein the gear grinding machine comprises a conditioning spindle on which the conditioning tool is clamped in step b),
wherein the gear grinding machine comprises a workpiece spindle on which the workpieces are clamped in step c), and
wherein the conditioning spindle is different from the dressing spindle and from the workpiece spindle.
4 . The method of claim 3 , wherein the conditioning tool has a basic shape that is different from a basic shape of the workpieces.
5 . The method of claim 4 , wherein the basic shape of the conditioning tool corresponds to a basic shape of the dressing tool.
6 . The method of claim 1 , wherein during the conditioning the grinding tool is in direct contact with a metallic portion of the conditioning tool.
7 . The method of claim 6 , wherein the metallic portion of the conditioning tool that is in direct contact with the grinding tool during the conditioning is made of steel.
8 . The method of claim 1 , wherein the grinding tool rotates during the step of conditioning and the conditioning tool is stationary during the step of conditioning.
9 . The method of claim 1 , wherein the grinding tool rotates during the step of conditioning and the conditioning tool rotates during the step of conditioning.
10 . The method of claim 1 , wherein the conditioning tool is in line contact with the grinding tool during the step of conditioning.
11 . The method of claim 1 , wherein the conditioning kinematics comprises a relative movement between the grinding tool and the conditioning tool such that a contact position between the conditioning tool and the grinding tool changes along a profile of the grinding tool during conditioning.
12 . The method of claim 1 , wherein the step b) of conditioning is carried out several times with the same conditioning tool.
13 . The method of claim 1 , wherein the grinding tool is a grinding worm.
14 . The method of claim 1 , wherein the conditioning tool corresponds to a metallic base body of a dressing roll, the conditioning tool being devoid of any hard material coating in a region that is in direct contact with the grinding tool during the conditioning.
15 . The method of claim 1 , wherein the conditioning tool is in point contact with the grinding tool during the step of conditioning.
16 . The method of claim 1 , wherein the grinding tool is a profile grinding wheel.
17 . The method of claim 1 , wherein the conditioning comprises removing a bonding agent between the abrasive grains of the grinding wheel to partially expose the abrasive grains.
18 . The method of claim 1 , wherein the superabrasive material is cubic boron nitride.
19 . A method for machining pre-toothed workpieces in a gear grinding machine using a grinding tool, comprising the steps of:
a) dressing the grinding tool using a dressing tool, wherein the gear grinding machine executes a dressing kinematics for moving the dressing tool relative to the grinding tool during the dressing of the grinding tool, wherein the grinding tool comprises vitrified-bonded abrasive grains made of a superabrasive material;
b) conditioning the dressed grinding tool using a conditioning tool such that a desired wear condition of the grinding tool is produced, wherein the gear grinding machine executes a conditioning kinematics for moving the conditioning tool relative to the dressed grinding tool during the conditioning of the dressed grinding tool; and
c) machining the pre-toothed workpieces using the dressed and conditioned grinding tool, wherein the gear grinding machine executes a machining kinematics for moving the dressed and conditioned grinding tool relative to the pre-toothed workpieces during the machining of the pre-toothed workpieces,
wherein the conditioning kinematics is different from the machining kinematics,
wherein all workpieces in step c) are machined with identical machining parameters,
wherein the machining parameters are selected such that thermal edge zone damage would occur during machining of at least a first workpiece in step c) if step b) were not performed, and
wherein in step b) the conditioning is carried out in such a way that no thermal edge zone damage occurs during the machining in step c).
20 . A gear grinding machine, comprising:
a tool spindle;
at least one workpiece spindle;
a dressing spindle;
a conditioning spindle;
a plurality of machine axes for driving the tool spindle, the workpiece spindle, the dressing spindle, and the conditioning spindle, and for moving the tool spindle, the workpiece spindle, the dressing spindle, and the conditioning spindle relative to each other; and
a control unit for controlling the machine axes, the control unit being configured to control the machine axes such that the machine tool performs a method comprising:
a) dressing a grinding tool while the grinding tool is clamped on the tool spindle, the dressing being carried out with a dressing tool that is clamped on the dressing spindle, wherein a geometric shape of the grinding tool is produced or restored by the dressing of the grinding tool, wherein the gear grinding machine executes a dressing kinematics for moving the dressing tool relative to the grinding tool during the dressing of the grinding tool;
b) conditioning the dressed grinding tool while the dressed grinding tool is clamped on the tool spindle, using a conditioning tool clamped on the conditioning spindle, wherein the geometric shape of the dressed grinding tool is not changed by the conditioning of the dressed grinding tool, and wherein the gear grinding machine executes a conditioning kinematics for moving the conditioning tool relative to the dressed grinding tool during the conditioning of the dressed grinding tool; and
c) machining pre-toothed workpieces clamped on the at least one workpiece spindle using the dressed and conditioned grinding tool while the dressed and conditioned grinding tool is clamped on the tool spindle, wherein the gear grinding machine executes a machining kinematics for moving the dressed and conditioned grinding tool relative to the pre-toothed workpieces during the machining of the pre-toothed workpieces,
wherein the conditioning kinematics is different from the machining kinematics.