91ÊÓƵÍøÕ¾ÎÛ

Machine shops looking for automation have a variety of options, ranging from long-standing technologies such as bar feeders, pallet changers and industrial robotic arms to newer solutions such as cobots, autonomous robots and various software products. It’s not uncommon for shops to acquire a mix of these technologies over time. Since beginning its automation journey, medical manufacturer rms Machining has assembled automation equipment that represents four distinct phases: traditional automation cells with industrial robot arms, a cell tended by an autonomous guided vehicle (AGV), machines with pallet changers and software to automate tool offsets. With each technology, the team has gained more knowledge and experience with automation, eventually finding its way to the technology that works best for its specific needs.

rms Company is the largest company within Cretex Medical, a family of contract manufacturers in the medical device industry. Its capabilities include machining, additive manufacturing, plastic injection molding, stamping, laser processing and sterile packaging. Within rms, the Pacing business unit makes products for the neural and cardiac stimulation markets. “The Pacing business unit is low-mix, high-volume,” explains Tom Ries, an engineering manager for the Pacing unit at rms. “That's our bread and butter.”

Traditional Robotic Cell

The rms Pacing business unit’s automation journey began in 2015 with three traditional automation cells. Each has two large FANUC industrial robots bolted to the floor that tend two FANUC Robodrills and transfer completed parts to a wash station and then a CMM. These cells are now 10 years old, but they’re still going strong.

The main downside of these cells for rms, according to Ries, is their size. With the necessary caging, they require a lot of floor space in a facility where floor space is at a premium. At the time of our visit, rms had a total of 850 machine tools in its 350,000 square foot facility, with more on order. “It's not going to be long before we’re at 900,” he adds. The Pacing unit alone accounts for about 200 of the company’s machine tools.

Autonomous Robotic Machine Tending

With its first successful automation project under its belt, the team started considering other tasks to automate. This is where the idea for an autonomous robot with a robotic arm mounted on top entered the picture. But Ries says that, at the time, no suppliers were offering what they were envisioning as a fully integrated solution. Then, in 2018, the team found the HelMo system from Staubli. “It was like, ‘Wow, there it is — a pre-packaged solution,’” he says. rms purchased a HelMo in 2019 and started the process of integrating it into its production processes.

The HelMo system consists of an industrial robotic arm mounted on top of an AGV base. Because the base is an AGV and not an autonomous mobile robot (AMR), it does not move completely autonomously, instead following a pre-programmed path. It has three area scanners on its base that detect obstacles in its path during navigation and which can stop it if necessary. The scanners can also slow or stop the speed of the robotic arm if a person is nearby.

rms set up the HelMo system in a cell with eight Robodrills. The cell runs specific part numbers, but that’s because the Pacing team runs low-mix, high-volume work. Theoretically, the cell can run any part as long as it works with the fixturing system. These fixtures, holding incomplete and complete parts, are stored on racks outside each machine tool.

HelMo runs during manned shifts with two operators each running four machines in the cell. It also runs lights-out between second and first shifts, giving the company three hours of extra machining time. “It’s faster than no one being here,” says Abraham Mitchell, an automation engineer at rms.

Although the system was expensive up-front, it actually breaks down to be fairly cost-effective because of how many machine tools it can tend. At the time of our visit, HelMo was tending four machines, but it could tend as many as eight machines at once, depending on demand. According to Ries, it’s cheaper than having a plug-and-play automation system at every machine tool. It also takes up much less space, particularly considering that HelMo doesn’t have a dedicated “home” or charging station. Whenever it arrives at a machine tool, it plugs itself in to charge its battery and hook up to an air supply.

While HelMo was a step in the right direction as far as cost and space savings, rms soon discovered some difficulties in implementing HelMo. Mitchell joined the company shortly after the HelMo system arrived, and it was his responsibility to find the root causes of issues as they occurred and solve them. “There’s been a learning curve that the integrator didn’t see,” he explains.

Many of these challenges weren’t “flat-tire problems,” as Ries describes. If someone notices an issue with their car as they’re driving and they pull over to figure out what’s wrong, a flat tire is easy to spot compared to an issue with, say, the harmonic balancer. When Mitchell arrived in the morning to find something had gone wrong with the HelMo overnight, it wasn’t always immediately clear what caused it. The system keeps a log of when it stops, so he would consult the logs to figure out when the stoppage occurred. Then, he’d piece together what happened using the information from the system and the scene before him. It was “like detective work,” Ries says.

Some issues were mitigated with physical solutions, such as modifications to the System 3R pull-stud reference system. The robot arm grips two flat sides of the pull stud’s post to move vises in and out of the machine. However, when operators were setting up the job, it was difficult to ensure the flats on the fixture was oriented properly. The team modified the system by adding a pin to ensure that, when the fixture is assembled, the flats are always oriented in the same, correct way. 

Software tweaks also solved some issues. For example, the team realized when the robot arm moved too quickly, the inertia would move the whole AGV base out of position. In order for the system to work, the robot’s positioning needs to be very precise, so if the robot is off by even a few thousandths of an inch, it won’t be able to place fixtures properly into the 3R system or unplug itself so it can move to another machine. Slowing the robot arm down helped mitigate this issue, as well as taking into account whether or not the robot arm was holding a part when it was moving.

The biggest challenge was HelMo’s navigation system. Ensuring HelMo could move, turn and identify obstacles and machine tools effectively required a lot of fine-tuning. One of the biggest navigation hurdles was figuring out why HelMo would stop when there was seemingly no obstruction. Eventually the team realized that HelMo’s sensors would pick up the coolant mist from the machines that was floating in the air and interpret it as an obstruction. “A human doesn't see it, but this nav system sees it,” Ries explains. Now rms has mist collectors on all its machines and is diligent about ensuring they’re all working.

Overall, Mitchell says that within two years, most of these issues were resolved. But he and Ries acknowledge that challenges are to be expected with complex automation integrations such as this. “If a team could sit down and figure out every single failure mode that could possibly ever happen and make sure everything is 100% mitigated before you build it, it would cost you millions and millions of dollars,” Ries says.

Pallet Changers

Despite HelMo’s success, rms has determined that, moving forward, autonomous machine-tending robots aren’t the best solution for its needs. “We've found that integrated automation built into the casting of the machine tool seems to us to be the best bet in the market,” Ries notes.

Around the same time HelMo arrived, RMS was also implementing its first machines with pallet changers. The shop now has 28 Mikron X400U machine tools from GF Solutions. Each system can hold 18 pallets while only taking up a small fraction of the space of a robotic cell or an AGV, which has proved valuable with the density of machines on the shop floor. Instead of having a robot, “I'd rather have a second machine there,” Ries says. “I'd rather have a second spindle making parts.” The space savings, combined with the comparatively low cost and ease of implementation, have led the Pacing unit to settle on pallet changers as its primary form of automation going forward. “We think that's the future,” Ries says.

For now, when deciding which parts work with which machines and automation systems, Ries says the team considers part geometry, as well as the number of tools required. The Robodrill can hold 21 tools each, while the machines with pallet changers have room for 60.

Software

rms’s automation efforts go beyond machine tending. The team implemented Caron Engineering’s AutoComp automated tool wear compensation software in late 2015 and early 2016 with its first FANUC cells. The software calculates tooling adjustments and updates offsets in the machine control automatically based on CMM measurement data. This is useful because “A person will always overcompensate,” Ries says. “A person gets worn out by compensation,” and the temptation to overcompensate to stretch out the time before making the adjustment again is strong. Software can make small, incremental offsets after every part if necessary.

Each of the traditional robotic cells has its own CMM to gather data for AutoComp, and the HelMo cell has one CMM. After a set number of cycles (which is different for every part), the robot or HelMo takes a fixture out of the machine, puts it into a wash station, and then a robot (a separate industrial robot in the case of the HelMo cell) moves it to the CMM for measurement. AutoComp then updates the offsets for the machines based on an RFID chip on the fixture that identifies the machine it came from. The Pacing business unit hasn’t yet deployed AutoComp to its machines with pallet changers, but it’s working on that solution.

This effectively adds an additional layer of automation beyond the machine tending, adding to the complexity of its automation integrations. Ries says, “It’s not for the faint of heart” to have multiple layers of robots communicating and collaborating. This ultimately plays into the Pacing unit’s preference for pre-integrated automation, such as pallet changers.

Automation Success

According to Ries, having a dedicated automation engineer such as Mitchell was key to making this system work. He credits the company’s strong foundation in process engineering for manufacturing complex parts for providing the foundation for HelMo’s success. “Any billionaire could just go buy all these machine tools,” he says. “The keys to our success are guys like Abe, the employees that are engaged.”

Ries also emphasizes having a progressive mindset when it comes to automation technology. “You’ve just got to recognize sometimes as you mature in your career, you have to let old tech go. You’ve got to be forward-thinking and forward-looking.”