Study of the influences of rotary table speed on stick-slip vibration of the drilling system

Stick-slip vibration presents one of the major causes of drilling problems,such as premature tool failures,low drilling efficiency and poor wellbore quality.The objective of this work is to investigate the influences of rotary table speed(RTS)on stick-slip phenomenon of the drilling system.In this study,the drilling system is treated as a lumped torsional pendulum model of which the bit/rock interaction is regarded as Coulomb friction.By analyzing cases with different RTS,two types of vibrations on the bit are found:stick-slip vibration and uniform motion.With an increase in the RTS,the stick-slip vibration on the drill bit disappears once the RTS arrives at its critical value.For the cases that stick-slip vibrations occur,the phase trajectories converge toward a limit cycle.For the cases that stick-slip vibration does not appear,the drill bit tends to stabilize at a uniform motion and the phase trajectories correspond to contracting spirals observed in the phase plane.

Rotary axis calculation for five-axis FDM printer using a point-fitting optimization method

This paper presents an optimization method to compute the rotary axes of a 5-axis FDM printer whose A-and C-axes have large deviations relative to the x-and z-directions.The optimization model is designed according to the kinematic model in which a point rotates around a spatial line in the machine coordinate system of the printer.The model considers the A-and C-axes as two spatial lines.It is a two-object optimization model including two aspects.One is that the sum of deviations between the measured and computed points should be small;the other is that the deviations should be uniformly distributed for every measured point.A comparison of the new optimization method with conventional error-compensation methods reveals that the former has higher location accuracy.Using the optimized AC axes,5-axis 3D printing paths are planned for some complex workpieces.Data analysis and printing samples show that the optimized AC axes satisfy 5-axes FDM printing requirements for nozzles with a diameter of 1.0 mm.

Machine vision for drill string slip status detection

Slip status of drill string is system generated binary value computed by comparison of sensor generated real time hook load value with a minimum threshold value of hook load stored in measurement system.This research article describes a novel method of slip status detection by machine vision technology which helps overcome the constraints of slip status detection with legacy measurement method.It also helps improve the real time drilling data quality and optimize and automate drilling operations.A method to detect drill string slip status with high-resolution digital camera installed on mast near rig floor is described along with backend vision processing and communication modules,which generate binary values of slip status.The binary values are transferred in real time to drilling measurement system of rig to compute other drilling parameters like bit depth,hole depth and stand counters.This method includes deploying active optical sensors at the rig floor,obtaining 1-D,2-D,or 3D image data,and processing it to obtain the status of drill string.Reliable measurement of slip status by machine vision helps reduce non-productive time(NPT)by reliable real time surveillance of drilling operations.