Kevin SekerakClick image to enlargeMaintenance, repair and rebuild tips for machine spindles

by Kevin Sekerak

 

A down machine tool spindle brings production to a screeching halt. And to make matters worse, tack on the hefty cost of a spindle repair that, ironically, could have probably been avoided or minimized by following a few simple maintenance tips.

The easiest tip is to maintain lubricating fluids. They should be clean and kept at safe operating levels. Maintenance of lubrication is critical to both a spindle's performance and its longevity. It is imperative that shops strictly adhere to the machine tool OEM's recommended lubrication schedules.

Many spindles are air/oil types. In addition to keeping up with oil levels, shops must – because these systems also use air – service air-intake filters on a regular basis.

Conversely, larger spindle headstocks, such as those on big turning machines, keep bearings lubricated with oil baths. Shops must periodically check and maintain the oil levels of these baths.

Shops should peridocially check spindle runout via a ground and calibrated spindle test bar. Many shops fail to conduct this test, even after a minor machine crash. OEMs recommend checking a spindle's runout every six months and/or after any crash. Also, workpieces that suddenly trend out of tolerance can indicate that a spindle is running untrue.

In line with monitoring spindle runout, shops should also check a spindle's spring force with a draw bar pull force test. Spring force secures tool holders in spindles, and a sizable drop in that force could lead to tool vibration and runout that can not only damage workpieces, but also the spindle itself.

On turning machines, simply check spindle shafts with an indicator to detect excessive runout. In the event of minor crashes, the tooling or turning machine's turrets often sustain the brunt of damage because spindle headstocks are beefy and to a certain extent crash resistant. But nevertheless, runout tests should be conducted after every crash as well as periodically.

Shops should keep constant watch on spindle vibration levels. While doing so used to be a physical type check, with operators "feeling" more vibration than usual, some of today's machine tools come equipped with vibration sensing technology built in to their controls. These systems will trigger an alarm in the event of unsafe spindle vibration.

Unfortunately, these alarms are often ignored.

Increased vibration indicates worn spindle bearings. Worn bearings, if ignored, can scorch spindle shafts and even cause spindles to seize. Both of these scenarios are costly major repairs that could have been avoided by simply replacing worn bearings at the first sign of excessive spindle vibration.

Addressing high speed spindles equipped with cooling systems. For these, shops must ensure the system chiller units are always operating properly. A good indicator of potential spindle problems is any rise in chiller system output temperature. If this occurs, a certified technician should thoroughly check the system.

Re-install any machine covers that have been removed. Many of today's machine tools have spindle areas sealed off with gaskets and/or some type of covers.

If these are removed for routine maintenance or any other reason, they should be re-installed because contaminants can infiltrate the spindle, spindle motor or other components that should be sealed and protected.

When spindle repairs or rebuilds are needed, tip 6 recommends machine tool OEMs perform the services. This ensures only factory-certified parts are used and specified procedures followed. Shops that attempt to fix or rebuild spindles themselves often end up doing more harm than good.

When evaluating spindle repair services, shops should make sure that OEMs perform these operations.

  • Disassemble, clean, inspect and assess a spindle's overall condition
  • Determine root causes of failure and provide reports that detail those causes, as well as repair quotes and diaries of the specific repairs made
  • Install any needed replacement parts, along with new bearings, O-rings, springs and seals
  • Offer exchange spindle units for immediate deliveries
  • Spindle rebuilds should entail these operations.
  • Precision grind and lap all critical spindle components for flatness and size, both held to tolerances typically within 2 microns
  • Gauge/test spindles at each stage of the rebuild for axial displacement, internal pressure, load settings, tool clamp force and runout
  • Balance spindle cartridges to within no more than 0.5 grams for reduced vibration and improved bearing performance
  • Conduct a progressive runoff for at least 8 hours to gradually work in bearings and monitor temperature

Kevin Sekerak is assistant manager of Spindle Rebuild at Mazak Corp.

Mazak

Get 'Career-Ready' with CTMA Work Program

Program helps match employers with students, recent grads, and/or potential new apprentices

Canada, Ontario support auto investment

The Federal and Ontario governments have created a sub-committee under the Canadian Automotive Partnership Council (CAPC) to promote investments in automotive manufacturing in Ontario.

Cut down your machine buying cycle

by Bryan Jacobs

Be ready to produce production parts prior to machine delivery

New tool holding products mirror modern metalworking demands

In general, tool holding (tooling) equipment has not undergone any fundamental changes for a long time.

Canada's Carrots

by Mary Scianna, Editor

Growth in the manufacturing industry in Canada occurs in two ways—through domestic companies and foreign direct investments.

Cost savings on abrasives: White Paper

Walter Surface Technologies has publsihed a white paper that illustrates how manufacturers can achieve cost savings with abrasives in metal finishing applications.

EMEC adds Swedish machine tool line Modig

EMEC Machine Tools Inc., Mississauga, ON, has added a new machine tool line to its product offerings for customers in Eastern Canada from Modig Machine Tool US Inc., Chicago, IL.

3 Steps to Better Grinding

by Rob Titus

How to improve your cylindrical grinding process

Managing aluminum welds

Assessing when and how to repair aluminum MIG weld defects

by Mike Vandenberg

Due to its low melting point and the presence of an oxide layer on its surface, aluminum can be relatively tricky to weld. It is particularly prone to burn-through and distortion, not to mention it can have a difficult-to-control weld pool.

Free webinar links CAM software to multi-tasking

Topic: Mazak webinar "Process Planning for Improved Multi-Tasking Machining" 

Date & Time: February 18, 2:00 pm EST

Mazak is holding a free webinar on the role CAM software plays in process planning and optimizing of mill-turn operations. 

Canadian firm focuses on additive manufacturing

Nigel Southway, Norman Holesh and David Slimowitz think they have a solution to help Canadian manufacturers become more globally competitive: additive manufacturing.

Important Conversations

by Kip Hanson

The things your machines can teach you

Canadian economy on upswing; challenges remain

The Canadian economy is on course for sustainable, balanced growth, following a setback caused by the drop in oil prices, but it continues to face challenges, according to Stephen S. Poloz, Bank of Canada governor, who spoke to the Greater Charlottetown Area Chamber of Commerce on May 19.

First 3D manufactured bike frame

Renishaw and British bicycle manufacturer Empire Cycles have created what is being called the world's first 3D printed metal bike frame.

Stay In Touch

twitter facebook linkedIn