How many times can a thread grinder be reincarnated? So far, four–but stay tuned. Twenty-eight Jones & Lamson thread grinders at Delphi Automotive have undergone quite a transformation in their 60-plus years of service life. And now, due to complete machine makeovers by Drake Manufacturing, they’re operating as “like-new” machines.
Drake is a mid-sized manufacturer of new and re-manufactured CNC grinders, many of which are used in automotive part, cutting tool, and gearbox production. Its product line includes thread grinders, internal and external grinders, gear grinders, rack mills, hobbers, and piston ring grinders. The company also offers CNC control renewal services for mechanically sound machine tools that are “losing their minds.”
In their first incarnation as manual thread grinders, 28 J&L 6x36s were put to use grinding threads on aircraft propeller shafts during World War II. A typical setup took three hours while operators changed gears, cams, and sine bars in preparation for grinding threads on new parts. (Example 1)
After the war these machines were converted to grind threads on automotive steering components, but used the same mechanical systems originally built into the machines during the war. The hydraulic power steering units in which the ball screws were used were on virtually every rear-wheel drive GM vehicle. (Example 2)
In the mid-1990s, after 50 years of grinding threads, Drake Manufacturing won their first contract to remanufacture and CNC retrofit them. GM Saginaw Steering (now Delphi Automotive) chose Drake for the remanufacturing project because of the company’s experience with automotive steering components and its solid reputation in the grinding industry. The remanufacturing and CNC transformation resulted in like-new CNC thread grinders. (Example 3)
Drake took out the geared transmissions, lead screws, change gears, mechanical dressers, and taper and sine bars and replaced them with precision ground ball screws, servos, CNC controls, and closed loop glass scale feedback. It also added CNC diamond roll dressers for consistent wheel conditioning and process control. The rebuilding process essentially transformed these 50 year-old thread grinders into full-blown CNC machines.
The third-generation Drake J&L grinders started life with a flourish–setup times were reduced from three hours to 15 minutes, part quality and consistency was drastically improved, and throughput increased by 50 percent. Delphi was also pleased with the cost, which was about 25 percent less than the price of the new CNC thread grinders that were commercially available.
The grinders were not just delivered to Delphi. Drake also developed and proved out the entire grind process and programmed it into the Fanuc CNC. As with all of its machines, the controls were programmed with Drake’s PartSmartÅ menu-driven software. No programming knowledge was required by the customer or its operators since they were simply required to enter part-specific parameters.
By 2005, new developments in the power steering market lead Delphi into “e-steering.” With electronic steering, an electric motor drives a worm gear set. This new product called for multi-start worm grinding. Drake was again called on to work its magic–or, more precisely, to re-work it. (Example 4)
Starting with the CNC machines that reduced product, volumes had idled. Drake replaced ball screws, headstock bearings, rebuilt the wheel and dresser spindles, added linear ways, and replaced all cables. In addition to the mechanical refurbishment, Drake also added automated loaders and converted the machines to a front dress from the previous rear dress configuration.
The front dress conversion accomplished two things. It located the dresser and workpiece close to each other, and it put them on the same thermal mass–all but eliminating thermal errors and increasing accuracy. Size, thread pitch diameter Cpk are in the double digits range, with grinding performed in one pass. (Example 5)
The three-start worms arrive at the Drake grinder with threads pre-machined. With no orienting features on the part, centering the wheel in the pre-machined groove would typically present a difficult loading situation. Finding the center of the pre-machined thread is exactly what Drake’s SmartSpindleÅ was designed to do. Smart Spindle utilizes acoustic emission feedback from the wheel to locate the workpiece groove and divide the available stock. This allows equal amounts of stock to be ground from both sides of the thread and assures that the part is cleaned up.
In addition, Smart Spindle technology allows parts to be machined closer to final size before grinding. With a smaller amount of stock to grind, cycle times are further reduced. (Example 6)
The current generation Drake thread grinders are fully enclosed and equipped with mist collectors. The operator has no need to open the door during production, and the machines are believed to meet all present and proposed OSHA safety regulations.
Life is Good
For Delphi Automotive, the economics keep getting better. The 2005 version of Drake thread grinders are a real bargain–priced 55 percent less than a comparable new grinder.
While every machine tool builder wants to sell new machines, Drake realizes that it’s not always in the customer’s budget. Remanufacturing is a smart alternative that minimizes a customer’s capital outlay and maximizes its use of depreciated property. Drake suggests that companies take a hard look at that old iron out in the shop before scrapping it. Underneath the dirt, there may be hidden gold. (Example 7)
Not every machine needs to be completely rebuilt. Sometimes they just need new controls. For example, a typical Drake Control Renewal project is about one-third the cost of a new machine and half the cost of a complete remanufacture. For machines that have failure-prone controls, this is an ideal solution.
Because Drake builds both new and remanufactured machines, it can outfit older machines with its latest grinding wizardry and CNC programming at a fraction of the cost of new. In fact, Drake’s expertise in control system renewals has earned it recognition as a certified GE Fanuc 5-Star retrofitter.
Customers around the world are getting the message. Drake recently exhibited at the China International Machine Tool Show and is aggressively pursuing the Asian automotive and cutting tool parts market. Its new and remanufactured grinders are operating all over the world, including China, Korea, and Australia as well as Eastern Europe and the Americas.