Thread whirling is essentially a thread milling process to which the thread cutters are mounted on the inside of a cutting ring, or the cutter holder, instead of on the outside of the cutting tool. A thread whirling unit refers to the cutting tool unit that applies the thread whirling technique to create a thread on a work piece. A thread whirling unit comes in with the configuration of a ring-like device which gets hold of a series of cutting tools used to create a thread. During a thread whirling process, the work piece is positioned in the middle of the thread whirling unit to be machined.
The other crucial component of a thread whirling unit is the power machine. In order to perform a thread whirling operation, the unit is mounted onto the power machine which drives the cutter to rotate. As the cutter is rotating, it cuts thread onto the workpiece when the cutter engages with the work piece. The whirling ring and the power machine together make a thread whirling unit. The thread whirling unit is implemented to manufacture large worm gears and threaded parts for the automotive industry.
There are several advantages that thread whirling has. The most important benefits of this process are that it can create long length to diameter threads and the threads that are cut by the thread whirling unit are deep. Other advantages include fast setup, increased productivity and prolonged tool life, etc. These advantages make thread whirling preferable over other threading techniques in particular applications.
The capability to cut long length to diameter threads is considered the most important feature a thread whirling process has. When using the thread whirling unit to make threads, the thread whirling spindle works close to the guide bushing for an extra support and increased rigidity on a long length to diameter screw. This process is typically conducted in a single pass from the workpiece so that a constant material support can be maintained.
By means of applying thread whirling, deep threads can be cut within a shorter period of time compared to other threading processes. The thread whirling unit is able to machine deep threads on a material such as bone screws, worm gears and the devices with Acme thread forms. Acme thread form is also called trapezoidal thread form. It is the thread that has a higher thread angle with the thread height half of the pitch and the apex and valley of the thread are flat instead of sharp.
The setup of a thread whirling unit is simpler and faster because the need to match rough and finish insert is no longer required. Therefore, the thread whirling unit can be put into operation in a shorter given time. With shorter machine downtime, the production time is increased in general and that leads to an improved productivity. In addition, the productivity is improved because the machining process is simplified. It takes a single pass from stock diameter rather than multiple passes. This way, the cycle is reduced.
The inserts on a thread whirling unit generally have a stronger cutting edge than the single point cutting tools. The reason is that the side clearance of the cutter is achieved by rotating the whirling spindle instead of relieving material under the cutting edge. With a stronger cutting edge, the wear of the cutting tool is reduced and hence the tool life is increased.
Besides easier setup and increased productivity, the thread whirling process is also able to manufacture products with better quality. The surface finish is better because of the tangential cutter path and the increased rigidity. The tangential radial entry and exit of the cutter leaves a uniform pattern on the surface of the thread and therefore the finish pattern is improved. In a thread whirling process, the cutter enters and exits the work piece in a radial arc which is similar to the thread radius direction; as a result, the finish is improved and the burrs are minimized.
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