Almost everyone has tossed around the phrase “change is hard.” It’s a go-to when the plan is to stick with the status quo. But sometimes, the status quo doesn’t cut it – especially in the competitive manufacturing space.
In the context of a stamping company, the need for change is often tied to a challenge that must be overcome to stay competitive and keep customers coming back. It could be a complex part, deep draws or frequent die changes that are hurting productivity. In these scenarios, substantive change can be facilitated by new technologies and equipment designed specifically for manufacturers.
For these stampers, servo technology can be the type of change that transforms their businesses. As long as it involves thoughtful consideration and a plan to follow it through, a servo press can solve a variety of common operational challenges that will ultimately enhance competitiveness, keep customers coming back and even open the doors to entirely new possibilities.
The servo solution
The big question, therefore, is whether servo technology is the type of change a stamper needs. Ask any press manufacturer, and they will be quick to rattle off the benefits servo presses provide – that they enable complex part forming, reduce scrap rates, significantly extend die life and offer superior control compared to traditional mechanical presses.
Barry Eyre, Northeast regional sales manager at Seyi-America Inc., totally agrees, but he also understands that age-old phrase about change – especially when a higher upfront cost is involved. On average, a servo press could come with a 40 to 50 percent higher price tag. However, he’s seen enough customers quickly offset those costs thanks to the increased output, lower energy use and reduced downtime that servos promise. Regardless, Eyre says that every situation needs to be studied on its own accord.
“Every application has its own special characteristics and challenges,” he says. “And that means that every potential avenue has to be considered. Part complexity is a big factor, and it’s definitely something that servos can tackle.”
When it comes to part complexity, servos can overcome a lot of common stamping issues. And that is due to a servo’s programmability, which truly is its greatest asset.
As the name implies, a servo press uses a servo motor – an electric motor with precise control over speed and position – to drive the ram. Conversely, a traditional mechanical press uses a motor that turns a flywheel to store energy. When the clutch engages, that energy is transferred to the crankshaft, which moves the ram up and down in a fixed, continuous motion. By replacing the flywheel and clutch with a servo motor, a servo press can be digitally controlled, meaning that the motion of the ram can be programmed.
The servo press can be programmed to slow down, pause or speed up at specific points in the stroke, which helps with forming complex parts or working with advanced, high-strength materials. It also improves part quality. Slower forming speeds at the bottom of the stroke reduce springback and tearing.
“A mechanical press is going to have so much springback if you try to work with hard-to-form materials,” Eyre says. “Whereas, with a servo, you can program it go in with a slower profile or slow it down right before you strike to significantly reduce the amount of springback.”
Because servo presses are programmable, the stroke can – and should – be optimized for each part. Additionally, the ram can be programmed to move quickly when not contacting material, reducing cycle times. And once a part has been programmed, its “recipe” can be pulled up quickly for fast setup times.
Finding value
The precise control that can be gained from a servo press offers great value, but getting over the initial sticker shock is still part of the process. Eyre says, “if the decision is left to a plant manager or operation manager who’s heavily involved in production, they’re going to see the benefits and know that they’re going to recoup that money back quickly.” Those benefits add up quickly, he says.
A deep draw is often one of the first examples Eyre gives when explaining the various benefits of servo presses. A mechanical press can handle a deep draw, but it is typically done on a progressive die where the depth of the draw is tackled incrementally. In this scenario, the multiple stations in the progressive die can create undesirable reduction marks and inconsistent wall thickness, which affects quality.
With a servo press, however, precise control over the slide velocity and stroke means the stroke can be slowed down during forming to allow material to flow. In this way, material thinning is prevented and quality, therefore, improves.
Eyre explains that there are actually a couple of different programmable motions that can be leveraged for a deep draw. One option is called a vibration motion where the slide comes down in a way that removes some of the stress as it forms. Instead of a single continuous stroke, the servo press can be programmed to make multiple short, high-frequency steps as it approaches the final press depth. This helps material flow into the die without stressing it, which prevents tearing and distortion and, in turn, reduces scrap.
“Deep draws and highly complicated parts are always going to be better on the servo press, but there are several benefits to producing simple parts on a servo, too,” Eyre says. “By using pendulum motion, you can cut out a lot of wasted motion when forming. Instead of just going in the typical full circular motion, you can cut out the top motion and basically just swing like a pendulum. By doing that, you’re cutting off 50 percent of essentially wasted motion. From an operational standpoint, that could mean 30 percent higher output for a company.”
Further time savings come in the form of the faster setup times thanks to the quick retrieval of part settings or recipes.
“If you know you’re going to be changing your dies a couple times a day, that’s where the servo can really excel,” Eyre says. “With our servo presses, die changes are 30 percent faster than on a mechanical press. With the servo, you can save every die setting, and it’ll automatically change all the important things, such as the shut height and air counterbalance. With a mechanical press, you have to change all of that manually.”
Direct benefits
Reduced maintenance is also a huge time saver. With no clutch or brake to replace, servos basically eliminate one of the primary consumable parts associated with stamping.
“Maintenance is going to be considerably less than on a mechanical,” Eyre says. “That clutch and brake is working every time you start and stop the press. Whoever starts your equipment in the morning gets there at 6 a.m., and then those components run all day long. On a servo, you don’t have a clutch and a brake. You have the one servo motor, and that’s it.”
Because Seyi’s servo motors are a direct-drive design, the servo motor connects directly to the crank, which minimizes vibration and further contributes to the life of the press. It’s also a key factor in extending die life.
“Direct driven basically means the servo motor is going right to the crank, which eliminates the gear reductions needed to transfer energy down to the slide and, in turn, the vibration that’s associated with that,” Eyre explains. “Excessive vibration lessens your tool life, but on the servo, you have a lot less of that, which translates to a lot more die life – around 30 percent, on average.”
Fewer mechanical components also result in quieter operations that are more energy efficient. With a servo press, energy is only used as needed unlike with a mechanical press, which constantly consumes power even when idle.
“Our servo presses also provide the machine’s maintenance history,” Eyre says. “It will tell you, for example, the last time you changed your oil. It will also give you maintenance and fault history: when an error happened and what that error was, which you can then use to resolve the issue directly. It takes out a lot of the troubleshooting. And that’s all available in the servo interface.”
Finding success
Once the decision has been made to invest in a servo press, Eyre encourages new users to identify a couple of staff members to be accountable for it – “knowledgeable operators that can decide things like whether you’re going to run on pendulum motion, vibration motion or freestyle mode or when you need to go from an 8-in. stroke down to a 2-in. stroke.
“Somebody has to do that, and the company has to be willing to allow that to happen,” he says. “You have to make that commitment to give those guys the time they need to go through a part’s settings to make a recipe. Once that recipe is made, they can let the next 100,000 parts be made. The results of giving them the time they need can be amazing.”
Whether it’s adjusting the velocity or the stroke or slowing down the ram to make a certain part, Eyre says the servo’s flexibility is the name of the game. In the mechanical world, there just aren’t as many options available.
“If it’s a 12-in. stroke press, the stroke is going to be 12 in. – period,” he says. “But if it’s a servo press, and you need to run a part at a 5-in. stroke, you can put it in there and run it and be incredibly efficient. When you remove the cost and learning curve scares, the flexibility of the servo justifies everything.”
A servo press will always improve the process of forming a part, but it will also open the doors to different types of work, new customers and new business. Investing in a servo isn’t always about having a problem with a specific part; it’s also about growing a business and branching out.
