The Sharpest Knife in the Drawer—OEM Re-Conditioning Expertise
by Jack McGuinn, Senior Editor
Setup of a tool grinding machine at Gleason Cutting Tools.
Since time began—man's time, more specifically—there has been a need for sharp instruments to cut things. Whether for skinning a saber-tooth tiger or defending one's cave, cutting tools have been around awhile.
Today, not much has changed-sharp implements are needed-but now for a myriad of other applications. And cutting tools-the "razor blade" component of the "razor"—i.e., hobbing, shaping, milling, broaching and, yes, shaving machines—are among the most important and sophisticated ones.
Another thing that hasn't changed since the Fred Flintstone days is that sharp instruments don't stay sharp forever. When dulling sets in, it's time for re-sharpening or, in gear industry parlance, reconditioning and recoating. And both processes have a symbiotic relationship in that a sharp tool is only as good as its coating, and the tool coating can be compromised by a dulled or nicked blade.
All of which is prologue to the fact that cutting tool re-conditioning and re-coating is a key service provided to its customers by any cutting tool manufacturer of note. The equation is simple—no razor blades, no razor (and, promise, that is this article's last allusion to that workhorse metaphor).
We talked to two companies with a global presence that know a thing or two about tool reconditioning—U.S.-based Gleason Tooling Products/Gleason Cutting Tools Corp. and Germany's LMT-GmbH and Company (LMT-Fette).
It is useful to first determine who in fact performs the reconditioning—the OEM or a sub-contractor? Back in the day, end-users did the work themselves, to a large extent. But today, given the hi-tech sophistication—and considerable cost—built into these machines, not so much. Just what is meant by "re-conditioning" is also a factor.
"Tool re-conditioners can mean anything from an independent that specializes in a narrow product range with limited capabilities to large, original tool manufacturers that cover a broad range of products with extensive capabilities and capacity," says Gleason's Robert P. Phillips, Sr. VP, Tooling & Products Group. "It is safe to say (that) an extremely critical requirement is that the company performing the re-conditioning be qualified and reliable, relative to the processes utilized and the quality of the re-conditioning work.
"The general consensus is that (gear makers) would rather focus on their core competencies of gear manufacturing than investing in servicing their tools. In today's industry, most likely the tools are sent out to have them recoated. As an original manufacturer, our customers are confident that we understand the tool and the process of reconditioning. It also puts the total liability of sharpening accuracy and coating integrity within a single source."
And just how big a universe is the tool re-conditioning market? There's no black-and-white answer, according to Phillips, but the arrow is definitely pointing upward.
"This is very difficult to quantify," he says. "What can be said, however, is that it is a growing market. More and more end-users are opting to have their tools re-conditioned outside of their own operations."
Close-up of a hob tooth edge before reconditioning (courtesy Gleason).
That said, how often does a tool need to be re-conditioned? And, how many "lives" does a tool possess?
"Its application-driven, but for round tools we say 5-10 times; for hobs 10-15 times," says Jurgen Freund, head of Service International at LMT."
Gleason's Phillips concurs, adding that the situation "is closely impacted by how aggressively the tool is being applied and the machinability of the part material." Relying on Gleason customers' input is also important, says Phillips, in that "End-users have a good idea of how many parts or how many lineal meters can be cut before the tool needs to be sharpened. Generally-again, depending on the tool-the amount of wear for gear tools is kept in the range of 0.013-0.025 mm. The design of the tool also has a large impact on the number of sharpenings. There are some tools that are designed to have limited numbers of sharpenings, say 8-10. There are other tools that may have as many as 30 sharpenings available."
Adds LMT's Freund, "Customers that use particularly valuable tools are the ones that benefit hugely from (re-conditioning). They simply need to purchase fewer new tools if the ones they already have in the production process can be re-used several times. And the re-conditioning of worn out tools is possible in many application areas.
All re-conditioners—standalones and OEMs—guarantee "like-new" results from their work. But does that apply to trickier, more standards-demanding applications such as aerospace and wind turbines?
"If the tool has been reconditioned correctly, it is returned to the original quality and performance level as the new tool," Phillips affirms. "Again, this further supports the earlier comments relative to the importance of utilizing a quality re-conditioning source. These tools definitely have higher quality requirements and typically are producing very expensive gears."
Close-up of a hob tooth edge after reconditioning (courtesy Gleason).
Or, as Freund puts it, "Yes, sure, same performance. Like new!"
Taken a bit further, if you are wondering whether one application over another lends itself to tool re-conditioning success, the answer is pretty straightforward.
"Applications with a linear wear and no or little build-up material," are key candidates, says Freund.
Says Phillips: "Any tool that is going to be sub-contracted for re-coating is an ideal candidate for re-conditioning. Having the ability to perform both the re-sharpening and re-coating within a single source has logistical benefits and can minimize the time that the tool is out of the customer's plant."
What is the A-to-Z course of a tool in need of re-conditioning? In a nutshell:
- Tool and material/coating identification.
- Definition of technical specifications.
- Pre inspect the amount of wear or damaged areas observed using a magnification system. Determine the amount that must be removed vs. the amount of life remaining.
- Sharpen the tool to remove the prescribed amount of wear.
- Visually inspect to confirm the wear has been removed from the sharpened tool.
- Inspect the features of the sharpening to confirm that they conform to the original specifications for the class of tool.
- Edge preparation and grinding burr removal.
- Cleaning process prior to coating.
- Coating process.
- Coating adherence inspection and coupon load verification.
- Packaging and shipping.
The above steps indicate a needed skill level beyond the norm. Just how skillful must an operator be in order to re-condition a tool? In a word—very.
"You need the best operators and grinders," says Freund, "because you have thousands of different tools-your own and competitor tools. Process time and costs are driven mainly by machine set-up time and this is directly linked to operator skill."
Phillips seconds that response, and more.
"The operators doing the re-sharpening process need to understand the critical factors with respect to the performance of the tool. Assessing the amount of stock removal is an important aspect of the process. The operator must also be experienced in the grinding parameters to effectively remove the worn area and yet not damage the tool by grinding too aggressively.
"Burr removal is critical prior to recoating," he states. "Typically, the operators need to be fully capable within the CNC machine operation. The skill level of the operator is also dependant on the type of tool being reconditioned. If the tool is a high-spiral gashed worm gear hob with tight outside diameter tolerances, it is much more difficult to sharpen than a standard straight-gashed hob."
And as for the re-coating step in the process, "As far as the skill level of the operators and technicians in the coating process, the individual needs to fully understand the critical aspects of the process itself in addition to the proper tool preparation process," Phillips says. "The individual needs to be capable of running full CNC equipment and understand the importance of minimizing possible contamination of the tools prior to loading in the coating unit. The coating process is very sensitive to proper loading of the unit relative to the type, configuration and number of tools per load."
Given the importance of the tools being re-conditioned, how large a role does R&D play in the re-conditioning process? A leading one, as it happens—and with crucial issues to address.
"Both (research and development are important)," Freund says, "because you must include in R&D the issues of reconditioning. (Customers are looking to determine the cost) for the whole process. Micro-geometry and coatings are very important. From my view, it's equal—tool development and coating side."
Speaking of coatings—and R&D—who develops them?
"Normally, re-conditioning shops are too small to do their own coating development, and it is a very big investment," Freund points out. "Coating developments are mainly done by the toolmaker and/or big coating companies."
Adds Phillips, and not unlike the machinery OEMs and their sharpening expertise, "The actual coating development is generally done by the companies developing and building the coating equipment. This is normally done in collaboration with the tool manufacturers and driven by the industries ongoing quest to reduce the total cost to produce gears."
A basic question regarding coatings asks how is the "best coating" determined for a particular need? The answer is anything but basic, as the following responses demonstrate.
(The correct coating) "is typically application driven," says Phillips. "Desired feeds and speeds—balanced with the amount of wear expected—will impact the decision as to the coating to be used. Whether a tool is applied with or without coolant will also determine which coating it recommended. At the same time, the part material being cut and the material the tool is made of are considerations when identifying which may be the best coating to be utilized."
"This I can't answer," Freund frankly states, but he gives it a good try, nevertheless. "(The coating chosen) is tool and application driven. You need (to know the) different conditions, coatings and coating properties; for example-(is it) tapping or drilling; dry or wet; solid carbide or HSS; milling or hobbing; different materials. You can get some universal coatings on the market, but if (it's for) high-performance cutting you will find special coatings like Nanosphere (that) are designed for hobbing, or Nano Red, designed for hard-machining.
And what is the price to the customer and how soon can he expect to get his part back?
"The normal market demand is around two weeks," says Freund. "(Price) depends on the complexity of the tool and coating. For standard round tools we can say (the price is) between 20 and 33 percent of the new-tool price. Special (custom) tools have no rules."
Phillips points out that price and turnaround time are "dependant on the type of tool and (what is) negotiated with the customer. Typically, the turnaround time for re-sharpening is 2-5 days. If the tool is to be stripped and re-coated as well, this can add an additional week.
"The re-sharpening cost is generally calculated by an hourly rate times the amount of time to remove the wear, and the size and complexity of the tool being sharpened. This cost can be anywhere from $50 to $500. Likewise, the coating cost is totally dependent on the size of the tool being coated and can vary widely."