Automating the Grinding Process
Resurgent US manufacturing spurs demand for automation
By Jim Lorincz
Whether the process is cylindrical or profile grinding, automation, which can increase cycle time, throughput, consistency of part quality and taking real-time in-process measurements, is once again in demand. The reasons can be found in the benefits found in typical applications and the innovative and effective forms of automation available from machine builders like United Grinding Technologies Inc. (UGT; Miamisburg, OH), and their automation integrator of choice, Matrix Design Inc. (Elgin, IL).
“Automation was very popular in the 1980s, when the aerospace world was driven by large government contracts,” said Larry Marchand, vice president of UGT’s Profile Division, “then automation faded away in the profile business with the transition to lean manufacturing. In the last 12 years, we delivered a single automation project and that was for steering racks. However, in the last year we’ve booked five automated projects. There has been a resurgence in US manufacturing, and all the alarm about there being a labor shortage appears to have some validity. Companies are looking to automate now to fill the labor gap, while in the past they would have relied on manual loading and unloading. For example, three of the five projects we’ve automated in the last year include a steering rack project, a hydraulic pump project and a plastic injection molding project,” said Marchand.
Automate to Improve Productivity
“Manufacturers are turning to automation as the only option to get productivity up and maintain it, to have machines running consistently, and to have one person run three, four and five machines as a machine tender,” said Marchand. “They can keep the robot loaded with queues of parts so that the robot can feed the machine at a steady pace. I’d add further that with our machines automation is almost exclusively via multiaxis robots, because most of our parts are odd-shaped, may be imbalanced and they’re usually produced in low volume.”
Just about everything UGT has automated requires a multiaxis robotic system, and the automation is always sourced to a dedicated automation supplier. “We use only Matrix Design Inc. [Elgin, IL] as an integrator, and the reason for this is simple: the president, Ryan Berman, and founders of the company came from the grinding industry, so they know grinding machines and the grinding process,” said Marchand. “Matrix specializes in one-of-a-kind jobs, and their business model fits very nicely into our business model of customized solutions. These guys know grinding; they speak the language, and finding an automation supplier with that kind of process knowledge is crucial to successfully automating what we do,” said Marchand.
“I’d like to think there’s a pattern in automating profile/creep-feed machines. The economics are there and it’s easier to automate profile machines, primarily Blohms and Mägerles, because today’s robots are easier to use and easy to program, as well as more widely accepted. The skill levels required to maintain robots aren’t that great, so the technology fits nicely into our typical applications as well as meeting our customers’ expectations. When we do an automation job, we do a turnkey, because every job is going to have its own unique set of requirements–different grippers, some inlet and outlet delivery systems with trays, conveyors and whatnot and usually a lot of engineering on the robot side, and that’s where the system integrator must be very strong,” Marchand said.
Systems May be Simple or Complex
“In the last five to 10 years, we’ve seen a steady rise in automation requests, from simple, straight-forward pick-and-place systems to highly sophisticated, full-blown automated flexible grinding cells,” said Hans Ueltschi, vice president, UGT’s Cylindrical Division. “Traditionally, as you might expect, we’ve seen automation in high-volume jobs, such as automotive applications. Lately, however, we’re seeing more and more requests for automation in low-volume jobs—automation demanding greater flexibility. This trend for more flexibility is spilling over to higher volume jobs as well. Automotive and Tier suppliers in particular are asking for this flexibility when it comes to changing over from one model year to another, one part to another, or from one version of a part to another. In the past, this wasn’t a high priority for them, because their major concern was the issue of high volumes,” said Ueltschi.
Many companies are requesting more than just part loading and unloading. “Automating grinding is becoming very complex because it often involves integrating measuring systems, for example, and data management. In addition, automating a grinding machine is far more difficult than automating a turning machine. You have to have great workholding, which requires much more precise part loading than is required in turning applications. This requires a superior loading system and the ability to handle the data flow from the post processor. In essence, the loader is in charge of the cell or process, and the loader dictates when the machine can start, when the data flows and so forth,” said Ueltschi.
“We have a number of variations of what we call simple loading systems. There is the Studer easyLoad, the Studer echoLoad and the Studer smartLoad. These are pretty low-cost, basic approaches to automating the grinding process, specifically designed to allow the machine to run unmanned for one to two hours. The machine control operates the loader in these cases, but they aren’t designed to allow the machine to run unmanned over a weekend or all night, lights out. Basically, the operator can take an hour or two out, to tend to another machine or to take a break, and then come back and load or unload the loading system, the baskets or trays,” Ueltschi said.
Data Control Measurement in Cells
Other types of automation used in the Cylindrical Division include gantry-type or robot-type loading systems. These do more than just load and unload but provide stacking capabilities, which permit many more parts to reside in the system, facilitating lights-out operation. “We use a lot of robots that not only can stack but do other tasks as well. They can load the part into post-measuring systems or pre-measuring systems. Sometimes this is all in one cell. The most complex cell is a match-grinding cell where the loader loads the female part into a pre-measuring station where the ID is ground and provides the data to grind the OD of the male part. Then the part goes into a post-measuring station where data are compared from pre-measuring to post-measuring and are evaluated as a clearance between the two. In this cell, we aren’t looking at grinding the part precisely to size, but rather grinding the part to achieve a precise clearance,” said Ueltschi.
“These can be very complex systems, because the loader is not only loading the machines but handling other tasks like pre- and post-measuring, deburring and cleaning while the machines are grinding. You also have the capability to have the loader use the master gages to calibrate the gages automatically every so often. So, say you want to calibrate the gage every two hours, the loader will do that. You can also calibrate the pre- and post-gages, and it can also calibrate any in-process gage. Loading, unloading, measuring, deburring, cleaning, acquiring data, and calibrating gages all automatically make this is a really complex cell,” Ueltschi said.
Automation Provides a Competitive Edge
“Automation in this country is getting more and more essential to keep us competitive, labor-wise,” said Ryan Berman, president, Matrix Design. “When it comes to automating grinding systems, we’ve seen numerous applications on the cylindrical side, mainly because of the cycle times. Cylindrical grinding processes can have very fast cycle times. We did a job not too long ago with an 8.2-second cycle time. We see more automation on the cylindrical side, because of the very fast cycle times, than we have on the profile or creep-feed grinding side. Creep-feed cells seem to be larger and more expensive than cylindrical cells. The parts tend to be heavier and oddly shaped and the volumes much lower than cylindrical cells. Cylindrical parts tend to be lighter, shaft-like parts and require smaller robots and smaller cells,” said Berman.
“However, lately we’ve seen some advances on the profile grinding side. We’ve started to look at creep-feed jobs where they’re running a cycle time of less than a minute. Any time you get under that one-minute processing range, operator load and unload time becomes a big factor because it’s a lot faster to load and unload a machine robotically. Loading manually, you’re usually in the 65–75% efficiency range. You have to take into consideration breaks and lunches and just the inefficiencies of getting the door open and the parts in and out. When you do it robotically, you can figure around 85% efficiency on the low-end, and we’ve seen jobs where you can actually get up to 95% efficiency. So you get a lot more parts in and out of your machine robotically as opposed to manual loading,” Berman said.
Berman said he prefers robotic automation to hard automation, like gantry loaders. “Smaller shops don’t necessarily have long-term contracts with their customers on the parts they are supplying, so they like to take into consideration what happens in two, three, or four years and if the contract goes away. What do these shops want to do? They want to run something different through the machine. It’s a lot easier to repurpose a robot, and it’s a lot less expensive than it is to redesign some sort of hard automation,” said Berman. For Matrix, the robot is just a tool, no different than a gripper or a solenoid valve. It’s just a tool they purchase, but one that allows them to bring flexibility to a cell and make it cheaper for the customer in the long run to change parts if he has to.
The grinding process involves a lot of unusual considerations you wouldn’t ordinarily think of. “On today’s cylindrical grinding there is a lot of post-process gaging, where the customer wants to measure the part after it leaves a cell and send that data back to the machine,” Berman said. “We’re starting to see a lot more intelligent systems come through today—not just loading and unloading the machine, but also measuring the parts and controlling the process. There’s much more nuance involved in automating the grinding process than there is in turning or milling,” said Berman. “Basically, what grinding comes down to is this: You take all the mistakes that are put into the parts on the green-side processes like milling and turning, as well as anything that can happen to the part in heat-treat, and you’ve got to fix all that in the grinding machine so that you can ship a good part,” said Berman. ME
This article was first published in the June 2013 edition of Manufacturing Engineering magazine. Click here for PDF.