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A general algorithm for profiling and dressing grinding wheels when using a grinding spindle on a CNC lathe
Remarkable progress is being made in the technology for grinding complicated geometrical parts. Today, some factories are considering adding a grinding spindle to a turning lathe to save buying an additional expensive new grinding machine. The grinding spindle will be interchangeable with a turning boring bar and it will need two types of software. First is a program and subroutine to control the machine movement during the grinding profile of the work-piece.
Second a program and a subroutine are needed to profile the new grinding wheels according to the grinding profiles of the work-piece, as well as dressing the grinding wheels after usage. In the case of a very small depth of cut, a long program will be required. Each different shape of grinding wheel will require different software. There are no detailed descriptions for this problem in the literature or machine manuals. This paper presents a general algorithm to make the profiling and dressing programs for grinding wheels easier. The programmer will use this algorithm for creating a subroutine suitable for the machine dressing system. This algorithm can be used on grinding machines as well as on an additional grinding spindle on a hollow spindle lathe. This subroutine will be used for profiling and dressing the most common shape of grinding wheels. The programmer will then only need to fill in the parameters which describe the contour53444
of the grinding wheels. This algorithm has been applied on a hollow spindle lathe equipped with a numerical Sinumeric 840C control. Several grinding wheels have been profiled and dressed using the proposed approaches, and satisfactory results were obtained.
1. Introduction
Grinding operations have been necessary for many engineering applications, particularly in parts needing a good surface finish. CNC grinding applications became a challenging job with the increased use of parts with complex geometry. However the cost of machining on CNC grinding machines is high when they are only used for low or medium production runs (Luggan 1983, Groover and Zimmers1984, Siemens 1999a, 1999b).There are several challenges when adding the grinding spindle to a CNC lathe.The main concern is the control software. The ‘add on’ can be very long and complicated(Abbas 2003). Also a different type of software will be needed; i.e. Software for profiling new grinding wheels as well as dressing of old grinding wheels. There are no detailed descriptions in the literature or machine manuals.In this paper a general algorithm has been created and can be applied on any modern CNC machine. It is used to generate a subroutine for profiling new grinding wheels and dressing old grinding wheels, as well as setting zero offsets.This subroutine has been applied on a hollow spindle lathe equipped with a numerical control Sinumeric 840C. A subroutine (SPF49) for different profiles of grinding wheels is created. These grinding wheels are used for grinding the different finish zones in the combustion chamber of large gun barrel.
2. General algorithm
The following is a general algorithm suitable for creating a subroutine for use on any modern type of CNC control. This algorithm and the algorithm addressed by the author (Abbas 2003) represents a complete solution for adding on a grinding spindle on a hollow spindle lathe. The main concept of this algorithm is putting all complicated formula calculations, which are needed in the profiling and dressing operations, as well as machine movements, in parametric form. This algorithm explains in very clear statements the method of creating a subroutine for profiling and dressing taper shape grinding wheels as well as setting offsets in the X and Z axes. In this algorithm the programmer should input the distance from machine centre to the diamond position, as well as the distance from the face-plate to the diamond position. The programmer will input the geometrical parameters for the grinding wheels as well as the cutting condition for the profiling operation,and the subroutine will make all necessary calculations for profiling and dressing operations. The algorithm contains all necessary messages for wrong input to prevent machine crashes. The subroutine can be used for profiling and dressing up to four grinding wheels at the same setting. The programmer can increase the number of grinding wheels by changing the parameters values. These grinding wheels can be used for grinding the different zones in the combustion chamber of large gun barrel