E-Sharp News October 2022

 
Capable of achieving runout of less than 2 microns, the four axes CPX Linear grinder is the solution for grinding tool blanks. The CPX Linear has a large working envelope and powerful grinding spindles to achieve the highest precision and productivity for blank preparation in the market. High material removal rates form as the primary function of the machine without compromising on dimensional accuracy and surface finish of <0.2Ra.

The grinder utilises the peel and the pinch-peel grinding methods. The peel method of grinding is associated with the roughing wheel and the capability of high material removal rates (MRR). This is all made possible with the advancement in grinding wheel technology with its grain structure, bonding, and construction. From a process perspective these advancements give higher aggressiveness numbers, where grinding aggressiveness refers to the depth that the grit can penetrate the material.

High material removal rates in grinding cannot be achieved just with high performance grinding wheels. It requires the machine, grinding spindle, stiffness of different machine elements and the grinding coolant system to be carefully designed to extract the wheel performance. The blank stiffness and the setup to present it to the grinding wheel is another important condition to achieve higher material removal rates.
Let’s look at two different cylindrical grinding methods and how this condition affects the grinding stiffness.

 

Grinding with Centre support

In one of the conventional cylindrical grinding methods, the blank is supported with centres at each end of the blank. The blank is then ground as the wheel plunges and traverses between centres as shown in the image below.
 
The grinding process and the material removal is efficient closer to the centres as the blank is stiff at the ends and less stiff towards the middle of the blank. For long and slender grinding applications, an additional steady support is introduced at the middle of the blank with an option to choose a fixed or a travelling support system. This makes the method suitable for low material removal rates and to finish grinding applications.
   

Grinding with Fixed Grind Point Support

 
The CPX blank grinder uses the peel method of cylindrical grinding. In this method, the grind point and the support are at a fixed distance and the blank slides longitudinally while the blank is ground to a required shape. The image below is a top view of the setup on a CPX blank grinder, where the green shape depicts the roughing wheel, and the orange is the finishing wheel.
 
The fixed distance of 1-2mm between the wheel and the support removes the weak stiffness zones on the blank that was discussed in the conventional cylindrical grinding. This enables the process to utilise the higher aggressiveness numbers of the grinding wheels.
 
The CPX Linear is an effective solution to deliver higher material removal rates and reduced grinding times, leading to higher productivity.
 
   
In the next article we will discuss another support system on the CPX blank grinder that will further expand grinding applications and productivity.
 
 
 

3 October 2022