The original carriage on the crankshaft grinder, after years in storage, shows its damage.Every once in a while a job presents itself to a company that creates quite a challenge. On the one hand, the technology of grinding is not the usual project for the company. However, on the other hand, the job represents an opening for educational growth and potential expansion. So what does a company do?

At KRC Machine Tool Solutions, this is not a rhetorical question or an exercise. “We take the job for both reasons,” says Matt Collins, systems sales manager. “Remanufacturing 50+ year old grinders will make us far more intimately familiar with a technology we, up to now, have not much considered. Working on these machines may very well provide entrée to broader markets.”

When a customer, one of North America’s premiere crankshaft producers, comes knocking on your door, asking about your interest in working with them again on a new project, it is well advised to thoroughly hear them out. The machines in this particular case are cylindrical centered crankshaft grinders, meaning cylindrical type grinders with indexable/adjustable chucks, allowing them to grind the shaft off center to create the throws for the large crankshafts.

The crankshafts are forged and heat-treated steel. The applications for these large cranks include energy, power generation, earth moving, locomotive, mining, engines for marine, large compressors for oil fields, and multi-ton stamping and forge presses that require a crank or eccentric shaft to provide ram movement. These are very large 7m to 11m cranks, and not many companies have the capacity to manufacture them completely.

The Options
Some years ago, the customer bought an English company, and as part of the acquisition came a number of 1950s-era Friedrian Schmalts manual crankshaft grinders. The company put one of the grinders into production and three others in storage. Years later, to facilitate capacity demands, the company needed the machines they had warehoused.

A problem immediately presented itself. The grinders in storage were not intact. They were in complete disarray. The beds were stacked upon each other, stored outside and exposed to years of weather that caused them to warp. Inside the warehouse, scattered about on pallets, were the headstocks, tailstocks, saddles, wiring, attachments, and other mechanisms.

The company contacted KRC to determine if it would be in their best interest to remanufacture the machines from the castings and parts in the warehouse – if they could find a builder who could or would do the job – or scrap out the carcasses and buy new at about $4 million or more per machine.

KRC welcomed the project and even suggested some enhancements to automate the manual machines. That made the customer’s decision much easier. After all, the customer had the carcasses of the machines, wanted to put them to good use, and dimensionally they fit their needs. Furthermore, the remanufacturing package that KRC offered, along with the support of strategic partners, would update the machines from manual to CNC. This would provide the customer with a highly flexible, robust control system configured specifically to meet their unique needs.
The remanufactured package would also replace all components and systems (electrical, hydraulic). In addition, it would add unique features, such as automatic dressing and automatic part gaging. Also offered was an optional feature to automate the chucking and indexing process.

Some of the pieces of the metal puzzle that KRC encountered when they began receiving components that belonged to all three machines, with some appearing to not even belong.The Metal Puzzle
“One of the things that immediately struck us about these cylindrical grinders was that the components and assemblies appeared to be suitable for any of the three machines, even though they were different in size. One grinder was small, in the range of 6m to 8m, and the other two were larger, in the range of 10m to 12m,” Collins says.

Another dilemma was the fact that KRC started receiving parts that belonged to all three of the machines at the same time. The parts were rather scattered, and some of the parts did not seem to belong to any of the machines. Additionally, KRC did not have any prints and, if they would have, they probably would not have helped much after all these decades.

However, in order to get a feel for where the major components belonged, Collins and KRC’s engineers referred to the manual machine in the customer’s plant. After a few visits, the KRC team had a good understanding of the original machine configuration. The next process was to sort castings and components along with parts and assemblies in different areas for all three grinders.

As the metal puzzle for the small grinder began to come together, rework on the pieces began. The bed went to a firm in Cincinnati, OH, for planing and machining, while the carriage had modifications done by a company in Troy, OH. Other components and assemblies were torn down and remanufactured. Some new replacement components were purchased from local strategic suppliers and then altered in-house to suit their particular function.

Much seemed routine
Terry Smith, controls engineer, oversaw much of the remanufacturing. “Going to CNC really was not too difficult from the standpoint that motors were used to create the rotation in the first place,” he says. “We changed out standard three-phase motors for new servo motors and integrated the control system. This was pretty much like many of the projects we take on. Most have a control and motor package as part of the job, so from the retrofit aspect of wiring and going from manual to CNC, it was not that huge of an undertaking for us. We gave it an entirely new electrical package.”

The original package was of European power and design, and many of the motors were not going to be reused because of the new servo package. Much of the mechanical remanufacture was also pretty typical of what KRC does on most jobs – building up the wear surfaces, scraping in the hard bed surfaces and grinding them down in some cases.

A central shaft once drove the headstock and the tailstock, and now they are powered by two independent servos running in synchronization. Most of the bearings, mechanical form and function were retained and just adapted to the new motor systems. A large amount of that was a clean, rebuild or disassemble issue, such as changing out worn bearings, seals, etc.

Many components, especially on the carriage, had to be designed and manufactured. In addition, components related to the dressing package and the part gaging system had to be designed and custom built.

The hydraulics were rebuilt and the electrical system is completely new, including the wire, cable tracks, servomotor mounts, spindle drives, and spindle motors.

“We built the entire power track here,” Smith says. “We did all the plumbing and manifolds for the lubrication system. We even built all the way covers. Before, when the machine began to move, operators just made sure there was enough oil poured into the ways to adequately flush them out.”

The gaging package was purchased from Marposs and the wheel dresser was purchased from a company in Michigan – both custom orders. Some of the smaller items, the wire track, and the power track, were fabricated in house; some were purchased from local strategic partners and then modified.

“Basically, the only components not new on the machines are the major castings,” Smith states. “We pieced the metal puzzle into a modern machine. This particular grinder was one of the more challenging machines that KRC has ever remanufactured. This was not a machine that was pulled out in one piece. This was in every way a start-from-scratch project.”

Collaborative Learning
“Most of the learning curve on this project was associated directly with the grinding process. We have had some experience in grinding, but there was just so much to learn about the unique crankshaft grinding process. If we did not get the process steps down right, we would never be able to provide a control that would function in a fashion that would meet the customer’s needs,” Smith says.

“We sat down numerous times with their managers and had them go through and map out all the process pieces so we could put together a robust, flexible control program that embraced all the steps in the correct sequence. We did a step-by-step, hand-in-hand, walk-through process where they told us exactly what the machine should be doing next, and we would say, ‘Ok, that is what we are going to design the machine to do,’ making adjustments as needed. Without having them involved, this would have been a very difficult project. The first few times we went through the process control program with them, we were still missing pieces that were unforeseen to us,” Smith says.

“We had to learn to think like they think. The control package had to reflect their mindset and their anticipations in terms of what happens next. We built in a lot more flexibility than needed because when we would get to a point in addressing a procedure that we really were not too sure of, we designed a way to address the procedure in such a fashion that it could be flexible and easily manipulated.

“One of the things they mentioned during their visits was that they have some pin-chaser style grinders, and they have worked very closely with the manufacturer to develop the ability to do in-process rework when needed to correct an error. On these crankshaft grinders, originally all they could do was load up a raw crankshaft, finish it, and move on to the next. If something happened during the grind, they had no ability to repeat a small piece or a section of the grinding program. Early on they said they wanted the ability to flexibly readdress any small portion of a shaft instead of just doing the whole pass, A to Z. So, we worked a step into the control program that allows them to leave the routine and go back to address a section, rework it, and then proceed with the programmed process.

“Now, all of the operations are performed by using a Siemens 840 D control. All changes were built into the control whether it is depth of cut, dressing cycles, redressing the wheel, the drawback cycle, or changing feeds and speeds. It knows the profile you tell it to use and it reuses that profile. We have graphical screens with data entry fields, so it is a matter of knowing the terms and being able to pick them out of the graphic illustrations.”
 
Positive Results
Basically, when KRC was finished, the company had designed and written multiple custom conversational programming screens, specific for the customer’s crankshaft grinding applications.

The diameter of the grinding wheel is 54" x 5" wide. The 2-axis wheel dresser is cup-shaped, about 0.500" tall. The rim of the cup is impregnated with diamonds, and the diamond dresser then creates the profiles on the wheel. This is a feature that was added to the machine, as was the gaging package. The benefits of automated dressing and gaging are the obvious ones of increased productivity, repeatability, and quality. But the real underlying benefit is operator safety.

Before, wheel dressing on these vintage grinders was done by hand with a carborundum block. This meant the operator had to reach into in the danger zone and dress the radius on the wheel edge with the block. Gaging held the same hazards. Hand gages were physically put in place, and that put the operator in danger. Automating both processes removed the operator from having to reach into the machine. Now they can dress by making a screen selection on the control, and the same goes for gaging.

One of the most in-depth screens is the finishing/gaging process. The gaging system is basically a separate system that provides digital inputs that display the process at known depths. Setting the depth at the gaging screen allows the operator to reduce the feed rate, permitting the wheel to get closer to the part, which ensures a quality finish with no under sizing.

“We put together some screens that are pretty self-explanatory,” Smith explains. “The operator can just look at the descriptions and fill in the blanks. The overall machine has a probing system that establishes coordinate referencing. This allows the operator to define the throw of the crank and grind everything on center to that particular position, thereby making that a coordinate reference.

“Establishing the profile of the wheel often involves corners with radii of different sizes, and the customer wanted to be able to shrink the wheel size. We have created dressing routines based on variables. If the user needs a 4" wide wheel and they have a 5" wide wheel, they will grind down 0.500" on each side or 1" on one side. The control establishes a value for any corner radius they may desire, and every time the wheel gets redressed, it reshapes those corners to the same dimension.

“Another area of interest was angle capability. Sometimes the customer may need to put a taper on a shaft. So we provided the ability to grind an angle on the wheel and then transfer that angle onto a taper-stepping function.

“There are more screens than those above, but in essence the operator simply goes down a course of menus and picks out the functions he wants (come down at this point, do my shoulder, do my corner radius, do my plunge, and address the taper . . . and so on) from those he does not,” Smith says. “Each of these is a selection from the menu. The program and control join it all together.”

The setup for these kinds of cranks has become a matter of plugging the numbers in and pushing start. The software provides the means to store the program, so the operator can recall it and never have to re-enter the data for that particular crank. The grinder reshapes the wheel every time, every job, based on the program data.

The 1950s Friedrian Schmalts crankshaft grinder, fully remanufactured, now has a complete CNC package,
automatic wheel dressing, gaging, and a new electrical package.

The Critical Role
“It took a lot longer than we thought to remanufacture this machine,” Collins says. “When you are doing a special machine, one that has not been done before, much of what you have learned from past experience does not apply because this machine is unique, unlike any that have preceded it. You have got to start all over again. This project was not just a machine challenge but a process-learning, mapping, and program creation challenge as well.

“Initially, we were completely reliant on the customer to walk us through all the aspects of the machine and the process. This took a great deal of time. There were many trips visiting back and forth, countless phone calls, emails, and faxes. However, the longer we worked at it, the deeper we immersed ourselves into a grinding process mindset, the more confident we grew,” Collins says.

“Even though it seemed to take forever, the harder we worked, and the more we talked back and forth, the greater our understanding of their process steps grew. Our ability to map those steps and create a menu of screens that reflected every detail of the process and then build it into a full, conversational program resident right at the machine CNC control – this was quite a journey and accomplishment.

“All said and done, I really believe we have on our floor a top-notch machine tool remanufacture and an exceptional refinement and upgrade of a process in which we had only a limited amount of experience. It is the second half of this result where we had to lean very hard on leadership, direction and education from our customer and from our strategic partners.

“A lesson learned,” Collins concludes, “is to do what you do best and do it better than anyone else. Then, if the water gets deep and murky, seek help from only those who do what they do best.”

KRC Machine Tool Services
Independence, KY
krcmachinetoolservices.com

Marposs Corp.
Auburn Hills, MI
marposs.com

Siemens Industry Inc.
Elk Grove Village, IL
usa.siemens.com/cnc