For manufacturers, CNC machine tool spindles are critical to any drilling, milling, boring, grinding, routing, cutting or sawing process. However, when these systems deteriorate and fail due to contaminants, human error, improper maintenance, lubrication issues or poor spindle design, a quality rebuild is often required.
Despite the availability of spindle rebuilders nationwide, not every firm provides the same level of quality. Even if a rebuilder has the equipment, they may not have the experience, technical knowledge or attention to detail necessary to rebuild a spindle that performs reliably for many years.
“After one spindle rebuild, I had to pull the machine out of production within a short time for additional repair,” said Tom Collins, maintenance supervisor at Edro’s Engineering’s Walnut, Calif. facility.
Edro Engineering, which serves North America and Europe, is a one stop tooling solution shop for machining services, special materials, custom mold bases, PVD/DLC coatings and additive manufacturing.
“Any time these CNC machines are down it costs us money, so we never want them down,” explained Collins, who is responsible for more than 50 milling machines, jig borers and surface grinders. “Because we run our spindles often at high speeds and we do surface grinding of stainless steel and specialty materials, frequent rebuilds are necessary – even expected.”
Morgan Stipp, who supervises a grinding operation for Embee Processing in Santa Ana, California, agrees that minimizing downtime is essential.
Stipp oversees about 20 precision grinders at Embee Processing’s 124,000 square foot metal finishing campus facility in Santa Ana, Calif. This includes Studer CNC grinders, Okamoto NC OD grinding machines, centerless grinders and other equipment with thread, surface and superfinish grinding abilities.
“We are extremely picky with our precision grinding because it has to be essentially perfect for our customers,” Stipp said. “Without the right equipment and properly maintained spindles, we would not be able to stay in business.”
In this regard, Stipp believes the thoroughness of the initial inspection performed by the repair/rebuild shop not only impacts the longevity of the spindle after it is rebuilt, but also the accuracy of the price quote.
Both Stipp and Collins found the precision and attention to detail they required when they contacted an experienced machine tool spindle rebuilder with a complete process to supply customers with a fast way back to maximum productivity.
While most spindle rebuilders only take minimal time to wipe parts before inspection, during disassembly, the rebuilder cleans and polishes each component with emery cloth to clearly reveal even minute imperfections. Even the nuts are removed, polished and then tested to ensure proper fit.
The next step is detailed measurement and documentation of every part of the spindle’s shaft and housing geometry. Micrometers are used to take detailed size measurements.
Runout is checked using 50 millionths of an inch dial indicators. The shaft bearing shoulders are then checked to see that they are true and perpendicular. The housing bores are checked for size, alignment and shoulders squareness. The spindle rebuilder also takes video, followed by digital photographs of each part during the disassembly process.
“If I have anything go wrong with our spindles, I will call them before the manufacturer,” Stipp said. “They will diagnose the spindle at no cost and send me a detailed quote, which has been down to the penny on everything. I have never had a surprise charge.”
According to Edro Engineering’s Tom Collins, the quality of the repair is also impacted by the expertise of the rebuilder and level of communication, traits he also found in the spindle rebuilder.
“Communication is important, and it is a two-way conversation,” Collins said. “The company wants to understand how the spindle is run, the conditions, the types of parts being made, what metals are cut, the depths of cuts, etc. so the rebuild can be tailored to my application. When I have a question, they answer it quickly.”
Collins also appreciates the spindle rebuilder’s use of only high-grade replacement components and bearings, which help to increase equipment reliability and lifespan.
“I have found their rebuilds to be as good as OEM and sometimes better,” Collins said. “The spindles have run perfectly so I expect them to last a long time.
While spindle rebuild reliability and lifespan is essential, quick turnaround is also important since equipment downtime must be minimized.
“The turnaround for our spindle rebuilds has to be timely to keep our production on track,” Collins said.
Although spindle rebuilds are available from various sources, for manufacturers that seek greater production reliability, uptime and lifespan out of their CNC equipment, working with an expert spindle specialist is usually the best option.
Ed Zitney is President of MZI Precision, a Southern California manufacturer specializing in machine tool spindle rebuilding with a complete process to supply customers with the fastest way back to maximum productivity.