A mathematical model for simulating and manufacturing ball end mill
The performance of ball end mill cutters in cutting operations is influenced by the configuration of the rake and clearance faces in the ball component. From the mathematical design of a cutting edge curve, the rake face can be defined by the rake angle and the width of the rake face at each cross section along the cutting edge. We propose the fundamental conditions that must govern the engagement between the grinding wheel and the designed rake face in order to avoid interference while machining a ball end mill. As a result, a new mathematical model for determining the wheel location and a software program for simulating the generation of the rake face of a ball end mill are proposed. In addition, methods for grinding the clearance face in both concave and flat-shapes are introduced. The flute surface generated by a disk wheel during the grinding process is determined on the basis of a tangency condition. The results of the experiment and the simulation are compared to validate the proposed model.
A novel approach to wheel path generation for 4-axis CNC flank grinding of conical end-mills
Conical end-mills are widely used in CNC machining and the flank has a great influence on the performance of the end-mill. However, the complex structures of conical flank make it difficult to grind. The traditional method for conical flank grinding is to control the grinding wheel with a 3-axis archimedes helix motion, which cannot guarantee the accuracy of the desired flank parameters, i.e., relief angle and flank angle. To solve this problem, this paper proposed a wheel path generation method for 4-axis CNC conical flank grinding. In this model, the grinding processes were discretized into a finite of cylindrical end-mill grinding. For each cylindrical end-mill, the machined flank parameters could be calculated within the cross-section through the envelope theory. Additionally, the geometrical constraints to avoid interference and abnormal flank profile were developed based on the cylindrical end-mill. The wheel path was obtained by calculating the wheel’s position and orientation for the discretized cylindrical end-mill section by section. Also, an integral procedure was built to optimize and simulate the conical flank grinding. The simulation results showed that the proposed method had a wide range of applications that could provide a general solution for the conical CNC flanking operations and also could be extended to grind the complex surface of end-mills in the future study.
Submicron polymer structures with X-ray lithography and hot embossing
This article describes the process chain for replication of submicron structures with varying aspect ratios (AR) up to 6 in polymethylmethacrylate (PMMA) by hot embossing to show the capability of the entire LIGA process to fabricate structures with these dimensions. Therefore a 4.7 μm thick layer of MicroChem 950k PMMA A11 resist was spin-coated on a 2.3 μm Ti/TiOx membrane. It was patterned with X-ray lithography at the electron storage ring ANKA (2.5 GeV and λc ≈ 0.4 nm) at a dose of 4 kJ/cm3 using a Si3N4 membrane mask with 2 μm thick gold-absorbers. The samples were developed in GG/BDG and resulted in AR of 6–14. Subsequent nickel plating at 52°C resulted in a 200 μm thick nickel tool of 100 mm diameter, which was used to replicate slit-nozzles and columns in PMMA. Closely packed submicron cavities with AR 6 in the nickel shim were filled to 60% during hot embossing.