An accurate instantaneous uncut chip thickness model combining runout effect in micro-milling using cutters with the non-uniform helix and pitch angles

As a key factor, the accuracy of the instantaneous undeformed thickness model determines the force-predicting precision and further affects workpiece machining precision in the micro-milling process. The runout with five parameters affects the machining process more significantly compared with macro-milling. Furthermore, modern industry uses cutters with non-uniform pitch and helix angles more and more common for their excellent properties. In this article, an instantaneous undeformed thickness model is presented regarding cutter runout, variable pitch, and helix angles in the micro-milling process. The cutter edge with the cutter runout effect is modeled. Then, the intersecting ellipse between the plane vertical to the spindle axis and the cutter surface which is a cylinder can be gained. Based on this, the points, which are used to remove the material, on the ellipse as well as cutter edges are calculated. The true trochoid trajectory for each cutting point along the tool path is built. Finally, the instantaneous undeformed thickness values are computed using a numerical algorithm. In addition, this article analyzes runout parameters’ effects on the instantaneous undeformed thickness values. After that, helix and pitch angles’ effects on the instantaneous undeformed thickness are studied. Ultimately, the last section verifies the correctness and validity of the instantaneous undeformed thickness model based on the experiment conducted in the literature.

Feasibility Study of On-Machine Inspection of Micro Milling Cutter Runout

During the process of micro machining, the existence of tool runout not only aggravates the wear and breakage of the cutter, but also seriously affects the surface quality of the parts. In order to observe the runout of micro-milling cutter, a detection method based on machine vision was proposed in this paper, which can calculate the tool runout by measuring the maximum value of external fluctuation of the cutter assembly near the tool tip. The proposed method can realize the direct measurement of radial runout of a micro-milling cutter. A dedicated prototype measuring system was established, which includes an on-machine measurement unit, a controller and the software. To obtain the images of maximum profile of the cutter at different angles, the cutter should be perpendicular with the optical axis of camera lens in the on-machine measurement unit. The experiments verified that the proposed method is feasible and the developed measurement system can fulfill the needs of industrial applications.

An Accurate Method for Determining Cutter-Workpiece Engagements in Five-Axis Milling With a General Tool Considering Cutter Runout

Cutter runout is universal and inevitable in milling process and has a direct impact on the shape of the in-process geometry. However, most of the works on the cutter-workpiece engagement (CWE) extraction neglect the cutter runout impact, which will result in a loss of precision. In this paper, an accurate method is presented to obtain CWE boundaries in five-axis milling with a general tool integrating the cutter runout impact. First, each flute's rotary surface is analytically derived. Then, by intersecting the section circle corresponding to the current flute with each of the rotary surface formed by previous flutes, a set of candidate feasible contact arcs (CFCAs) are obtained, and the valid feasible contact arc (VFCA) is defined as the common intersection of these CFCAs. Next, by intersecting the VFCA with the workpiece surfaces, the partial arc which locates inside the workpiece volume is extracted as the engagement arc. Finally, the CWE map is plotted by mapping a set of engagement arcs to a 2D space. To validate the proposed method, the CWE maps with/without integrating the cutter runout impact in five-axis milling of an axial compressor blisk are extracted and compared. The results reveal that the shape of CWE boundaries is changed a lot owing to the cutter runout impact. A cutting force comparison experiment has been carried out to show that the proposed method will lead to higher prediction accuracy especially in the finish milling process with low immersion angle.