Method and test assembly for determining machine parameters

Patent metadata

Field	Value
Publication number	US-10675725-B2
Application number	US-201615045905-A
Country	US
Kind code	B2
Filing date	Feb 17, 2016
Priority date	Feb 18, 2015
Publication date	Jun 9, 2020
Grant date	Jun 9, 2020

Abstract

The invention pertains to a method for determining machine parameters of a mechanical device in which a first element and a second element are mutually movable in settable patterns of movement, the method comprising placing a measuring arm between the first and second elements, displacing the first and second elements mutually in a predetermined intended movement path, applying a predetermined force between the first element and the second element substantially in the longitudinal direction of the measuring arm, recording the resulting actual movement path by means of the measuring arm, thereby determining a difference between the intended movement path and the actual movement path, and deriving, based on the determined difference, machine parameters indicating a condition of the mechanical device, characterized in that the predetermined force comprises a dynamically varying portion. The invention furthermore pertains to a test assembly for performing said method.

First claim

What is claimed is:

1. A method for determining machine parameters of a mechanical device in which a first element and a second element are mutually movable in settable patterns of movement, the method comprising:
placing a measuring arm between the first and second elements,
displacing the first and second elements mutually in a predetermined intended movement path,
applying a predetermined force between the first element and the second element substantially in a longitudinal direction of the measuring arm,
recording, while the predetermined force is applied, a resulting actual movement path by means of the measuring arm,
determining a difference between the intended movement path and the actual movement path, and
deriving, based on the determined difference, machine parameters indicating a condition of the mechanical device,
wherein the predetermined force is generated by a power unit and comprises a dynamically varying portion and a static portion that are generated separately, wherein the dynamically varying portion is generated at least partially by a piezo actuator of the power unit,
wherein:
the predetermined force is applied in various mutual positions between the first and second elements, the dynamically varying portion being position dependent, and
recording the resulting actual movement path comprises dynamically determining a current length or a length difference of the measuring arm while the predetermined force is applied.

2. The method according to claim 1 , wherein the dynamically varying portion is sinusoidal, subject to an analytic function or subject to a step function.

3. The method according to claim 2 , wherein the dynamically varying portion is position dependent and sinusoidal.

4. The method according to claim 1 , comprising:
at least one measurement operation comprising moving the first and second elements mutually in a settable pattern of movement and recording the resulting actual movement path, the predetermined force applied during each measurement operation comprising the dynamically varying portion, so that an applied force varies dynamically during each measurement operation, wherein the applied dynamically varying force is different for each measurement operation.

5. The method according to claim 4 , wherein the at least one measurement operation comprises a plurality of subsequently performed measurement operations.

6. The method according to claim 1 , wherein
the predetermined force is defined as
F=F 0 +F ( t ),

where F is the predetermined force, F 0 is the static portion of the force and F(t) is the dynamically varying portion of the force.

7. The method according to claim 1 , wherein the machine parameters comprise at least one of the following:
stiffness in at least two directions based on an applied force vector and on a deflection vector;
displacement in dependence of a direction of movement;
hysteresis;
recti linearity; and/or
damping.

8. The method according to claim 7 , wherein the stiffness comprises a dynamic stiffness value.

9. The method according to claim 1 , wherein
the mechanical device is a machine tool, wherein the first element is adapted to support a machining tool, and the second element is adapted to support a workpiece,
wherein the second element is adaptive to provide a fixation for holding the workpiece in its place, and
wherein the machine parameters comprise a stiffness of the fixation.

10. The method according to claim 1 , wherein the second element is adapted to provide a fixation for holding a workpiece or an object to be measured, respectively, in its place, by means of clamping.

11. The method according to claim 1 , wherein the mechanical device is a machine tool, and the method comprises a tooling simulation of a specific tooling operation of the machine tool, in the course of which
mutual movements between the first element and the second element are performed that are typical for the tooling operation, and
the dynamically varying portion is applied according to forces typically occurring during the tooling operation.

12. The method according to claim 1 , wherein the first element is a spindle and the second element is a worktable.

13. The method according to claim 1 , wherein the measuring arm is telescopic.

14. The method according to claim 1 , wherein the mechanical device is a coordinate measuring machine, wherein the first element is adapted to support a measuring head, and the second element is adapted to support an object to be measured.

15. An assembly for determining machine parameters of a mechanical device in which a first element and a second element are mutually movable, the assembly comprising:
a measuring arm which has at its ends fastening devices for articulated fixing to articulations of the first element and the second element respectively, the measuring arm comprising a telescopic element that links the articulations and measuring equipment for recording changes in the distance between the articulations to make it possible to measure positional change between the first element and the second element while a predetermined force is being applied, and
a power unit that is arranged to apply the predetermined force substantially parallel with the measuring arm to the first element and the second element, the power unit being arranged to apply the predetermined force that comprises at least a dynamically varying portion and a static portion, wherein the dynamically varying portion and the static portion are generated separately by the power unit, wherein the power unit comprises at least one piezo actuator that is adapted to generate the dynamically varying portion,
wherein:
the power unit is arranged to apply the predetermined force in various mutual positions between the first and second elements, and to apply the dynamically varying portion dependent on the position, and
the assembly is arranged to record a resulting actual movement by dynamically determining a current length or a length difference of the measuring arm while the predetermined force is applied.

16. The assembly according to claim 15 , wherein the dynamically varying portion is sinusoidal, subject to an analytic function or subject to a step function.

17. The assembly according to claim 15 , wherein
the power unit is provided with a first bracket for fixing to the first element and with a second bracket for fixing to the second element, wherein the first and second brackets are each provided with a bearing allowing rotation of the power unit, wherein the second bracket is provided with devices for fixing one end to the measuring arm.

18. The assembly according to claim 15 , wherein the first element is a rotating spindle, wherein the assembly
is adapted to measure a stiffness of the spindle, the stiffness varying with a rotational speed of the spindle.

19. The assembly according to claim 15 , wherein the assembly is adapted to be operated cordless.

Assignees

• Hexagon Technology Ct Gmbh

Inventors

• Pettersson Bo
• Archenti Andreas

Classifications

• G01B21/042 Primary

  Calibration or calibration artifacts (G01B3/30, G01B9/02072 take precedence) · CPC title

• G01B7/14

  for measuring distance or clearance between spaced objects or spaced apertures (G01B7/30 takes precedence) · CPC title

• B23Q17/22 Primary

  for indicating or measuring existing or desired position of tool or work {(B23Q16/005 takes precedence)} · CPC title

• B23Q17/00 Primary

  Arrangements for {observing,} indicating or measuring on machine tools (for automatic control or regulation of feed movement, cutting velocity or position of tool or work B23Q15/00) · CPC title

• B23Q17/2233

  for adjusting the tool relative to the workpiece · CPC title