New clamping technologies for lathes using high-precision chucks

For machining workshops that manufacture all types of parts, the high-precision chucks from Hainbuch can provide faster changeover, increased grip range, high rigidity in heavy chip removal and reduced maintenance.

Workholding can affect many aspects of the machining process, but often not enough attention is paid to it. Many shops are content to use whatever workholding system comes from the factory with the machine. If they do the work, they don't think about optimising it unless they have to.

But once a shop floor takes a closer look at its hold from the point of view of available manufacturing hours due to downtime, changeovers, breakdowns and waits, or from manufacturing throughput to produce fewer parts per hour, it can lead to serious consideration being given to implementing improvements in several different areas of the parts production process.

One such workholding option for lathes is the high-precision chuck, which is considered an effective clamping solution for machining applications using bar feeders, small diameters and thin-walled, delicate or irregularly shaped workpieces.

Benefits of high precision chucks

• Very rapid format changes

  Almost every workshop that performs more than one job on a machine could benefit from reduced changeover time. Reducing set-up time for part clamping is often overlooked, but it is achievable. One of the reasons many shops have not pushed in this area is related to the fear of losing the accuracy of the parts they make. Increasingly, part tolerances have become tighter and more difficult to achieve.

  For example, with the use of a three-jaw chuck, the changeover process can take 25 to 45 minutes or more, depending on the job and the skill level of the person involved, and have some hope of maintaining a total indicated runout of 0.001 inches. Reducing that time to 10 seconds with a TIR of 0.0004 inches puts the machine in a position to make more parts.

  Hainbuch has a line of high-precision chucks specially designed to provide quick changes. The Chuck TOPlus system offers improved workpiece accessibility with a 25 % plus holding force for increased performance.

  Compared to a conventional chuck, which requires users to thread on a collet and then find a slot to lock it in place with a set screw, the Chuck TOPlus Not only is it faster, but it helps improve repeatability between operators. You don't have the inconsistency of one operator's particular feel and how well it's set up versus another operator coming in later to work with the machine, so any technician can achieve the same results when it comes to set-up time.

• Increased grip range

  The Chuck TOPlus also has a wider gripping range than traditional chucks. For example, shops can take advantage of the wide gripping range by performing two machining operations with the same collet. If the roughed and finished diameters of a part are close enough to grip in the same collet, users can flip the part over and grip the second diameter without having to change the collet. This is how some shops are moving toward single-piece flow versus batch and work-in-process operations.

• Clamping technologies for more precise lathes with guaranteed rigidity

  High-precision chucks can also improve the quality of the parts being produced. These systems have full contact with the workpiece, unlike a three-jaw chuck, which only has three points of contact with the workpiece. These systems provide uniform clamping along the entire length of the workpiece part inside the chuck, this is where greater accuracy and rigidity is achieved.

  Rigid and precise workpiece clamping is essential for most machining processes. Increasing the accuracy of the workholding system not only enables the production of high-precision parts, but can also increase tool life. If the workpiece is more accurately and uniformly positioned in the exact same position, cutting tools have a predictable chip load and can be optimised for longer tool life.

  Increased cutting tool life can reduce tool cost per job. Increased rigidity without sacrificing accuracy also allows users to increase speed, feeds and depth of cut. Increased material removal rates reduce cycle times, which in turn increases throughput.

• High-precision, low-maintenance chucks

  Finally, the chuck system requires less maintenance than a three-jaw chuck. Three-jaw chucks generally require lubrication at least once a day and, depending on usage, up to every six to eight hours of operation. Failure to lubricate a three-jaw chuck can result in a significant reduction in applied clamping force. Most chucks do not require the same level of attention; many come greased and sealed from the factory.

  The other cause of maintenance is chip contamination. Cleaning swarf from most three-jaw chucks can cause significant machine downtime. And this problem is not unique to three-jaw chucks; some conventional chucks are also prone to having chips packed between the nozzle segments.

  When swarf accumulates in the workholding system, the clamping capacity is reduced until the swarf is removed. While nothing is 100 % impervious to swarf on a machine, this system is a significant step above the alternatives when it comes to reducing maintenance.

Practical example in the use of high-precision chucks

A case in point that may be of interest to illustrate the benefits of high-precision chuck as a new clamping technology for lathes is that of an equipment manufacturer with a large workshop.

The company had installed work cells in different parts of its machine shop to produce different components. Within these cells, one employee was responsible for operating various machines, including manual and CNC lathes, robotic and plasma welding, fabrication, horizontal machining centres, vertical machining centres and other machines, along with an assembly department. Approximately 40 employees work in the machine shop of about 6000 square metres in two shifts.

Some of the parts produced by the company required very tight tolerances. These parts must fit with other parts and, in some applications, clearances can be as small as 0.003 to 0.004 inches. Staff burnout was another problem, as it could ruin the functionality of the final product.

All the lathes in the workshop had the same three-jaw chucks. The shop floor operations manager began to notice that the chucks on the two lathes used for finishing operations were starting to wear out and rebuilding them was not an option. Once the company realised that it was going to have to spend money on a new clamping system, it approached its distributor, who recommended the Chuck TOPlus system from Hainbuch.

Initially, some of the company's employees were sceptical about switching to a new clamping technology for their lathes. There was some concern about how the high-precision chucks would affect changeover time. But once the employees saw a video of the quick-change chucks, they were convinced that the system could work for their needs.

The shop started by installing the new workholding system on one of its machines for a three-month study. The company could see that the chuck system was a success, so it implemented it on the second lathe. In the year or so since the company has been using the system, it has seen improvements in several areas.

The biggest benefit the company has seen since switching to the chuck clamping system is the reduced changeover time. Changing a part on the old system required the operator to adjust the jaws and move the tailstock. With the high-precision chucks, the operator simply unplugs the one collet, plugs in the new one and adjusts the tailstock.

Unlike traditional chucks, the new system also requires less maintenance, which has contributed to greater efficiency. Shop floor employees no longer need to turn the lathes» smooth jaws to ensure they stay true, which they described as a »constant battle". The jaw chucks also required greasing every day, which the high-precision chucks do not, and which obviously saves additional time.

In addition to time savings, the company has reported an improvement in part quality. It has also seen fewer repairs and scrap parts since implementing the new lathe clamping system using high-precision chucks.