Work Holding Method for Cylindrical Grinding
If you do not know what a cylindrical grinder is, it is actually a type of grinding machine that is commonly used to shape the outside of an object, specifically metal objects. This kind of grinder can work with different shapes and sizes.
But the only down side is that the object must have a central axis of rotation to make it easier on the grinder. Usually it will grind objects that are shaped in cylinders, ellipses, cam or a crankshaft.
As the age of technology starts to advance, grinding technology as has also been taken to the next step, and is actually considered now a day as a “black art.” There have been some advances in terms of the technology of the wheels; temperature control and precision drive system that can be found in the machines.
Also Read: Use chuck system for cylindrical grinder
These systems have been significantly starting to develop over the last couple of decades, and improving continuously to make grinding better and faster.
Though we may want to believe that when there is an advancement it will continue to be better, there will always be a weak point that will end up surfacing one way or another.
One of the possible weak links that can be found in cylindrical grinding is the work holding. With the drastic exception of craftsmanship, the work holding in cylindrical grinding has not changed much in the last decade.
- Center less grinding process for cylindrical grinder
When it comes to work holding, the most commonly understood and sometimes least understood methods of cylindrical grinding is the centerless grinding process. This process is known primarily for its grinding stock into precise rounds.
The centerless grinding process is usually accomplished by feeding stock between a fixed blade and a rotating roller that regulates as well as a grinding rotating wheel. The roller that is regulated is used to control the part’s rotation.
The action, which is to feed the stock, is advanced by skewing slightly the blade axis in relation to the roller regulation, causing the roller to pull across the face of the grinding wheel. Gravity comes into play by holding the work piece, guide blade and roller together.
When moving the wheel, you must remember to move it toward or away from the guiding blade and roller regulator. The regulating roller will control the precise diameter. Once the spots are on a round, the diameter will be reduced to the preferred range.
This process is fairly simple to establish, and even though the parts have to be consumed through the grinder for a number of times to achieve the roundness you prefer, it can be very efficient, especially when you see the increase in volume.
Dissimilarity with the process can produce parts in the profile. Instead of the work piece being fed through the grinder, the located part against a specially stopped dress wheel is crisscrossed into the part, while the profile is crushed and grinded into the work piece.
Higher volumes is better for this process in general, because as the wheels that are used to grind is expensive and large, it can often be too time consuming If you were to custom the dressing.
To achieve a perfect roundness that is best desired, you will usually require the stock to be centerless and ground before grinding.
Collets and Chucks
These two items are usually used for grinding work pieces that are either too small or require one end to be featured or profiled. Unlike centerless set ups where the most of the set ups are stationary; the work pieces will move the collet with the chuck.
Which means, that inaccuracies will suffer in terms of the quality and balance of the drive system that is used to maintain the overall stability of the workpiece holding. The most accurate of the two methods uses a four jaw chuck.
The workpiece can usually be indicated to align precisely the center lining of the specific part with the centerline of the chuck and spindle.
There will usually be an indicator that can be used to slide into position along the length of the blank. Any run out can be turned into the adjustments of the jaws and the chuck.
Usually the indicated time used to adjust each part can be excessive. System collets are faster to load than to unload. These usually consist of a barrel that is tapered and an expandable type of collet that can be inserted to the workpiece diametrically, as the insert is pulled into the tapered barrel.
When indicating the setup for the collet system, the aligning of the collet’s tapered barrel must be at the centerline of the work head. Once that is completed, the operator must consider the accuracy of the collet system.
When it comes to ultra precision collets, the accuracy of the 4 microns must be accurate when they are new. Some even have 2 microns.
For some more common jobs, 2 microns may be accepted, and the accuracy compromise is accepted to save the time that it takes for the machine to load. Two microns, can sometimes be unacceptable because the machine manufacturing tools are used to create very precise features.
Especially for smaller tools, this can be true. Inaccuracy in the collet moves the centerline of the tool shank, which results in the ground features to run out on a grounded machine features.
Swarf contamination can be another possibility, or any compliance in the grinding spindle wheel or bearing assemblies in the collet or chuck, sometimes even the software and drive system can be completely compromised.
The cylindrical grinder is one a very useful piece of machinery, and you should always make sure to know the basics before you can use it personally. Always make sure to be careful, because these can be very dangerous when not handled properly.
This piece of machinery is recommended more for those who are professionals. Always make sure to be careful when using it.