| 1. |
- Pettersson, Linus, et al.
(författare)
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Active Control of Boring Bar Vibrations in Cutting Operations
- 2002
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Konferensbidrag (refereegranskat)abstract
- Internal turning or boring operations have a history of being a cumbersome manufacturing process. The manufacturing industries are facing tougher tolerances of their product surfaces and a desire to process hard to cut materials and therefore the vibrations must be kept to a minimum. An increase in the productivity is also interesting from a production point of view. When cutting in pre-drilled holes the boring bar is usually long and slender and is thereby inclined to vibrate destructively concerning the machining result. The knowledge of the vibrations involved in boring operations and active control of external turning operations, have given a good basis for the active control solution in boring operations. The active control solution is based on a standard boring bar with an embedded piezo ceramic actuator placed at the peak modal strain of the boring bar. An accelerometer is also included in the design, mounted as close as possible to the cutting tool. The control algorithm is a filtered X LMS algorithm built on a feedback approach since the original excitation, the cutting process, cannot be observed directly. Preliminary results show reduction of the vibration in the boring bar by up to 30dB.
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| 2. |
- Pettersson, Linus, et al.
(författare)
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Active Control of Internal Turning Operations Using a Boring Bar
- 2002
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Konferensbidrag (refereegranskat)abstract
- Vibrations in internal turning or boring operations are usually a cumbersome part of the manufacturing process. The manufacturing industries are having problems with these kinds of cutting operations. When cutting in pre-drilled holes the cross sectional area of the boring bar is limited at the same time as it is long. Since a general boring bar is long and slender it is sensitive to external excitation and thereby inclined to vibrate. The vibration problem affects the surface finish in particular. The demand for smaller and smaller tolerances of the surface finish leads to that the manufacturing industry seeks for a solution to the boring bar vibration problem. The tool life is also likely to be influenced by the vibrations involved in a cutting operation. Another problem in boring operations is the high noise level in the cutting process. The noise level in the environment of the operators is today more and more regulated, especially in the western world. Active vibration control will reduce the amount of vibrations in the cutting operations. Since the noise is induced by the vibration of the boring bar, the noise level will also be reduced due to the cancellation of the noise source. Preliminary results show reduction of vibrations in the boring bar by up to 30dB.
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| 3. |
- Pettersson, Linus, et al.
(författare)
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Active Control of Machine-Tool Vibration in a CNC Lathe Based on an Active Tool Holder Shank with Embedded Piezo Ceramic Actuators
- 2001
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Konferensbidrag (refereegranskat)abstract
- In the turning operation chatter or vibration is a frequent problem affecting the result of the machining, and, in particular, the surface finish. Tool life is also influenced by vibration. Severe acoustic noise in the working environment frequently occurs as a result of dynamic motion between the cutting tool and the workpiece. These problems can be reduced by active control of machine-tool vibration. However, machine-tool vibration control systems are usually not applicable to a general lathe and turning operation. The physical features and properties of the mechanical constructions or solutions involved regarding the introduction of secondary vibration usually limit their applicability. An active control solution for a general lathe application has been developed. It is based on a standard Industry tool holder with an embedded piezo ceramic actuator and an adaptive feedback controller. The adaptive controller is based on the well known filtered-x LMS-algorithm. It enables substantial reduction of the vibration level by up to 40 dB at 3.4 kHz.
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| 4. |
- Pettersson, Linus, et al.
(författare)
-
Active Control of Machine-Tool Vibration in Cutting Operations in a General Lathe
- 2001
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Konferensbidrag (refereegranskat)abstract
- In the general lathe the turning operation chatter or vibration is a frequent problem affecting the result of the machining, and, in particular, the surface finish. Tool life is also influenced by vibration. Severe acoustic noise in the working environment frequently occurs as a result of dynamic motion between the cutting tool and the workpiece. These problems can be reduced by active control of machine-tool vibration. In a general lathe the physical features and properties of an ctive control system usually limit their applicability. By using piezo ceramic actuators some constraints regarding the mechanical construction of the active tool holder can be circumvented. An active control solution for a general lathe application has been developed. It is based on a standard industry tool holder with an embedded piezo ceramic actuator and an adaptive feedback controller. The adaptive controller is based on the well known filtered-x LMS-algorithm. It enables substantial reduction of the vibration level by up to 40 dB at 3.4 kHz.
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| 5. |
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| 6. |
- Pettersson, Linus, et al.
(författare)
-
Adaptive Control of Machine-Tool Vibration Based on an Active Tool Holder Shank with an Embedded Piezo Ceramic Actuator
- 2001
-
Konferensbidrag (refereegranskat)abstract
- In the turning operation chatter or vibration is a common problem affecting the result of the machining, and, in particular, the surface finish. Tool life is also influenced by vibration. Severe acoustic noise in the working environment frequently occurs as a result of dynamic motion between the cutting tool and the workpiece. These problems can be reduced by active control of machine-tool vibration. However, machine-tool vibration control systems are usually not applicable to a general lathe and turning operation. The physical features and properties of the mechanical constructions or solutions involved regarding the introduction of secondary vibration usually limt their applicability. An adaptive active control solution for a general lathe application has been developed. It is based on a standard industry tool holder shank with an embedded piezo ceramic actuator and an adaptive feedback controller. The adaptive controller is based on the well known filtered-x LMS-algorithm. It enables substantial reduction of the vibration level by up to 40 dB at 3.4 kHz.
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| 7. |
- Pettersson, Linus
(författare)
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Vibration Analysis of a Boring Bar
- 2002
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Rapport (övrigt vetenskapligt/konstnärligt)abstract
- In boring operations the vibrations are a cumbersome part of the manufacturing process. This report puts the vibrations under scrutiny and the vibrations were measured both in the cutting speed direction and the cutting depth direction. The cutting process seems to be a time varying process and contains nonstationary as well as nonlinear parameters that are not under control. The experiments showed that the vibrations were usually dominated by the first resonance frequency in either of the two directions of the boring bar. Sample probability density estimates of the vibration records points to that the probability densities are varying from sinusiodal probability shape to gaussian shape. They also indicate that shape of the two directions could be of different probability density function from the same vibration record. Stationarity tests show, besides that the processes usually are nonstationary, that it is possible to extract short time stationary segments within a vibration record. The problem with force modulation in rotary machinery, which appears as side band terms is the spectrum, is also addressed. Furthermore, the resonance frequencies of the boring bar are correlated to an approximate theoretical beam model. The theoretical calculation of the boring bar deflection corresponds well with the experimental results from the modal analysis and the operating deflection shape analysis.
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| 8. |
- Pettersson, Linus
(författare)
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Vibrations in Metal Cutting : Measurement, Analysis and Reduction
- 2002
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Licentiatavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Vibration and noise in metal cutting are ubiquitous problems in the workshop. The turning operation is one kind of metal cutting that exhibits vibration related problems. Today the industry aims at smaller tolerances in surface finish. Harder regulations in terms of the noise levels in the operator environment are also central. One step towards a solution to the noise and vibration problems is to investigate hat kind of vibrations that are present in a turning operation. The vibrations in a boring operation have been put under scrutiny in the first part of this thesis. Analytical models have been compared with experimental results and he vibration pattern has been determined. The second part of the thesis deals with active vibration control in external turning operations. By embedding a piezo-ceramic actuator and an accelerometer into a tool holder it was possible to obtain a solution that can be fitted in a standard lathe. The control system consists of the active tool holder, a control system based on the filtered-X LMS algorithm and an amplifier designed for capacitive loads. The vibration level using this technique can be reduced by as much as 40 dB during an external turning operation.
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