| 1. |
- Parsian, Amir, 1982-, et al.
(författare)
-
A Mechanistic Approach to Model Cutting Forces in Drilling with Indexable Inserts
- 2014
-
Ingår i: Procedia CIRP. - : Elsevier BV. - 2212-8271 .- 2212-8271. ; 24:0, s. 74-79
-
Tidskriftsartikel (refereegranskat)abstract
- Holes are made in many industrial parts that need screws, pins or channels for passing fluids. The general method to produce holes in metal cutting is by drilling operations. Indexable insert drills are often used to make short holes at a low cost. However, indexable drills are prone to vibrate under certain circumstances, causing vibrations that affect tool life. Therefore, a good prediction of cutting-forces in drilling is important to get a good description of the cutting process for optimization of tool body and insert design. Reliable simulations of dynamic forces also aid in prediction of chatter vibrations that have significant effects on the quality of the manufactured parts as well as the tool life. In this paper, a mechanistic approach is used to model the cutting-forces. Cutting-force coefficients are identified from measured instantaneous forces in drilling operations. These coefficients are used for simulating torque around drill-axis, axial force and cutting-forces in the plane perpendicular to drill-axis. The forces are modeled separately for peripheral and central insert, which results in a detailed description of the cutting-forces acting on each insert. The forces acting on each insert are estimated by dividing the cutting edges into small segments and the cutting-forces acting on each segment are calculated. The total forces are predicted by summation of the forces acting on each segment. Simulated torque and forces are compared to measured cutting-forces for two different feeds. A good agreement between predicted and experimental results, especially in torque and axial-force, is observed.
|
|
| 2. |
- Parsian, Amir, 1982-
(författare)
-
Dynamics of Torsional and Axial Vibrations in Indexable Drills
- 2015
-
Licentiatavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Drilling is widely used in manufacturing of products which need holes, for example for fluid channels, screws or pins. Depending on application, workpiece material, cutting parameters and economic considerations, different types of drills are employed. Indexable insert drills are types of drills which facilitate inserts to make holes. These types of drills can make high pitch noises due to vibrations. The focus of this thesis is to investigate the mechanism behind these vibrations in order to help reducing the generated noise in the future designs. Primary investigations show that the main mechanism which results the mentioned noise is regenerative chatter vibrations due to axial and torsional flexibilities. There is a gap in modeling of chatter vibrations in indexable drills where loadings and geometries are asymmetrical and due to torsional vibrations, delay terms are variable. The first step of simulating regenerative chatter vibrations in the drill is to model static cutting forces in a reliable way. In this thesis, a model is proposed which is capable of predicting static cutting forces through segmentation of cutting edges. Since, using this model, forces can be calculated separately on each insert, it is possible to consider differences of inserts in estimationof the cutting loads. The obtained loads are used in the chatter simulation.A model is proposed to simulate chatter vibrations by considering axialand angular deflections and the coupling between them. The resulted model isa system of delay differential equations with variable delays. Variations in timedelays, tool jump-outs and backward motions of inserts have been included inthe proposed time-domain simulation. A set of experiments is conducted toverify the model.
|
|
| 3. |
- Parsian, Amir, 1982-
(författare)
-
Regenerative Chatter Vibration in Indexable Drills : Modeling and Simulation
- 2018
-
Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- An indexable insert drill is a drill which uses cutting inserts to make holes. Undesirable sound generated by this type of drill has always been considered as a problem in workshops. The focus of this thesis is to investigate the mechanism behind these vibrations, to model it and to provide guidelines for reducing the sound in future drill designs. Primary investigations show that the main sound generating mechanism is a self-induced vibration due to a coupled torsional-axial deformation in the drill which leads to the torsional-axial chatter vibration. The first step of simulating regenerative chatter vibrations in a drill is to model the static cutting forces. In this thesis, a model is proposed to estimate static cutting forces in indexable drills by dividing the cutting edges into small elements. Since, using this model, forces can be calculated separately on each insert, it is possibleto consider insert differences in estimation of the cutting loads. Torsional-axial coupling has been discussed and subsequently a time-domain model is proposed to simulate chatter vibrations. The resulting model is a system of delay differential equations with variable delays. The delay varies with time and is dependent on the state of the system. Variations in the time-delay, tool jump-out and backward motions of inserts have been included in the proposed time-domain simulation. A set of experiments was conducted to verify the model. Finally, a number of different strategies to alleviate the problem of chatter vibration are explored and their feasibilities for use in future products are discussed.
|
|
| 4. |
- Parsian, Amir, 1982-, et al.
(författare)
-
Sound Analysis in Drilling, Frequency and Time Domains
- 2017
-
Ingår i: Procedia CIRP. - : Elsevier. - 2212-8271 .- 2212-8271. ; 58, s. 411-415
-
Tidskriftsartikel (refereegranskat)abstract
- This paper proposes a guideline for interpreting frequency content and time history of sound measurements in metal drilling processes. Different dynamic phenomena are reflected in generated sound in cutting processes. The footprint of such phenomena including torsional, lateral regenerative chatter and whirling in sound measurement results are discussed. Different indexable insert drills, at several cutting conditions, are covered. The proposed analysis could be used for studying, online monitoring and controlling of drilling processes. © 2017 The Authors.
|
|
| 5. |
- Parsian, Amir, 1982-, et al.
(författare)
-
Time-Domain Modeling of Torsional-Axial Chatter Vibrations in Indexable Drills with Low Damping
- 2015
-
Konferensbidrag (refereegranskat)abstract
- In drills with helical chip flutes the coupling between axial and rotational degrees-of-freedom can cause chatter vibrations. These torsional-axial chatter vibrations can lead to a high frequency and unpleasant noise. It is desirable to design tools which are less prone to chatter vibrations and thus also makes less noise during operation. Dynamics of chatter vibrations in drilling is due to changes in chip-thickness that causes dynamic loads on the structure. These loads in return contribute and sustain vibrations. In this paper a simulation routine is proposed that can be used to model these chatter vibrations in drilling when damping of the drill-body is low. In case of low damping, the drill rotates backward in some instants. The importance of modeling of this phenomenon is emphasized in this paper and a method is proposed to model loads in case of backward rotations. The generated chip is calculated in each time-step and obtained chip-thickness is used to calculate dynamic loads. The structural responses are calculated in form of displacements by loading the drill with predicted dynamic loads based on the calculated chip thickness. Obtained displacements are used to calculate chip-thickness in the next time-step. Spectrum of simulated vibrations is compared with spectrum of measured noise and a good agreement between measurements and simulations is observed.
|
|
| 6. |
- Parsian, Amir, 1982-, et al.
(författare)
-
Time Domain Simulation of Chatter Vibrations in Indexable Drills
- 2017
-
Ingår i: The International Journal of Advanced Manufacturing Technology. - : Springer Science and Business Media LLC. - 0268-3768 .- 1433-3015. ; 89:1-4, s. 1209-1221
-
Tidskriftsartikel (refereegranskat)abstract
- Regenerative chatter vibrations are common in drilling processes. These unwanted vibrations lead to considerable noise levels, damage the quality of the workpiece, and reduce tool life. The aim of this study is to simulate torsional and axial chatter vibrations as they play important roles in dynamic behavior of indexable insert drills with helical chip flutes. While asymmetric indexable drills are not the focal points in most of previous researches, this paper proposes a simulation routine which is adapted for indexable drills. Based on the theory of regenerative chatter vibration, a model is developed to include the asymmetric geometries and loadings that are inherent in the design of many indexable insert drills. Most indexable insert drills have two inserts located at different radial distances, namely central and peripheral inserts. Since the positions of the central and peripheral inserts are different, the displacement and thereby the change in chip thickness differs between the inserts. Additionally, the inserts have different geometries and cutting conditions, e.g., rake angle, coating, and cutting speed, which result in different cutting forces. This paper presents a time-domain simulation of torsional and axial vibrations by considering the differences in dynamics, cutting conditions, and cutting resistance for the central and peripheral inserts on the drill. The time-domain approach is chosen to be able to include nonlinearities in the model arising from the inserts jumping out of cut, multiple delays, backward motions of edges, and variable time delays in the system. The model is used to simulate cutting forces produced by each insert and responses of the system, in the form of displacements, to these forces. It is shown that displacements induced by dynamic torques are larger than those induced by dynamic axial forces. Finally, the vibration of a measurement point is simulated which is favorably comparable to the measurement results.
|
|
