We started this series a couple of months back, and, as a refresher, we thought it might be fun to, from time-to-time, revisit some old pieces of content that have lived in the pages of the Gateway Magazine at some point in the last 20+ years of the periodical’s existence. This will also serve as a welcome departure from all the pandemic prose we seem to have been typing up for the past nine-months… With that departure in mind and in the spirit of taking “a look back,” let’s move forward (as best we can)! In many ways, the industry has changed greatly, while, in others, it’s “business as usual”, where we’re simply looking to continue the grind and get ourselves from point A to point B in a job cycle.
Today we’re going back nearly 15 years to October of 2006 to have a look at “A Gateway Educational Enlightenment Article” that we used to run as space permitted. The pieces were submitted by our readers and invaluable advertisers. The spotlight in October’s issue 15 years ago was on Machine Tool Spindles and was originally submitted by Michael Gunski Jr. of Spindle Parts and Services, LLC. So, without further ado, here’s the text verbatim (with some minor formatting changes…)
Einstein’s Corner: A Gateway Educational Enlightenment Article – Machine Tool Spindles
Many people agree that the spindle is the most important component of the machine, and is often considered the heart of said applicable machine. For those who don’t know what a machine tool spindle is, it is more than just a basic motor, or even a shaft with bearings. Instead, it is an extremely precise mechanical assembly consisting of a shaft and housing, tool holding systems, and ultra-precision class ball bearings. The quality and sophistication of the spindle assembly directly impacts the capabilities of the machine tool. With such an important component, it only makes sense that great care would be put into the prevention of failure, and the service of the spindle should an unfortunate failure occur.
Spindle failures on machine tools cannot always be prevented, but some of the following steps can be taken to minimize the amount of failures.
Visual inspection of machine system: Periodic inspections of the lubrication system and air supply can prevent over (or under) lubricating, as well as internal contamination. In the case of oil lubrication, maintain a clean lube supply. This, along with the application of the appropriate delivered amount of lubrication can have positive lasting effects on the life of the spindle (or negative if you’re not monitoring things carefully). Machine air supplies should also be filtered and dried for best results.
Spindle taper inspection: Monitoring of the taper concentricity, surface contact, and gauge line will give you warning of any change to the tool holding surface. A poor taper surface will affect the machine accuracy and ultimately the quality of the manufactured part.
Retention force: Maintaining the proper retention fore on a machine drawbar is often overlooked by many shops. The fact is, low drawbar pull force because of broken or worn Belleville washers can be detected with a dynamometer before it affects other components in the spindle. Low clamping pressure can cause premature wear of the spindle taper resulting in decreased spindle accuracy and poor part quality.
Vibration analysis: The paper and power industry have had tremendous results using this technology to predict failure. This type of technology is not as well recognized in the machine tool industry, but it does have its advantages. Several large U.S. manufacturers have used vibration analysis programs to establish baseline information on their machinery. They then make periodic measurements over time and monitor the change to help them prevent catastrophic failure and unnecessary downtime. SPS has simplified this technology to assist smaller shops with implementing basic vibration programs to assist maintenance efforts.
Taking steps to prevent failures on your machine tool spindles can ultimately lead to significant cost savings for the company. The advantages of a comprehensive preventative and/or predictive maintenance program can be tremendous for the manufacturer as long as you clearly define your expectations. Too often companies try and implement a program where they want to shoot for the stars, but don’t want to invest fully into the program, or they don’t have the support of all the individuals involved. Most people in manufacturing understand there is a fine line between machine maintenance and production. Understanding where that line is in your shop will determine what types of programs work best for your company. Whether you perform periodic retention force measurements or condition trending through ca complete vibration analysis program, the goal with any plan is to try and limit catastrophic failures, control excessive repair costs, and reduce the total downtime of your precision machine tool spindle.
In summation of the look back (which is still true today), you can have the greatest tool on planet earth in your possession, primed and ready for production go-time, however, if you’re spindle is “wonky,” the tool is going to produce parts that will have you scratching your head and putting holes in the drywall. Your tool is only as good as the spindle it’s on in the working confines of your machine. If it’s off axis, you’re going to get some undesirable results. If it’s suffering from some corrosion or other signs of wear, you’re going to get some undesirable results. If the motor that fires the spindle isn’t being tested and treated, it’s not going to drive the spindle correctly, and thus, that other-worldly tool you’ve had developed and delivered is nothing but a fancy paperweight.
When downtime is not an option, think ahead. It’s safe to say we learned a lot of lessons with this very sentiment in mind (from myriad vantage points) in 2020!
As we enter 2021, plan for routine, plan for some annual machine maintenance, be proactive about the operative health of your organization from both human and machine resource vantage point. There are also all kinds of tools/solutions out there that are analytical, and give you real time machine health analysis right on your handheld device. You can also Google it and get a mile’s worth of results for yourself. The trick is finding the right solution that works for your unique need(s).
As it relates to spindle health, SPS (the kind folks that wrote the original piece above) is a company packed with knowledgeable, spindle sharp people that do not consider downtime as an option. They, of course, rebuild spindles that fail, will go onsite to remove or install spindles, and they can do onsite inspection with vibration analysis, among other things. Their real claim to fame is to educate and train customers to keep the spindles you have running right. Their goal is to help reduce the total cost of ownership of customers’ equipment.
For more information visit them at: www.spsspindle.com.