Quick on the draw
- Created: 2018-08-06
To produce a variety of deep-contour auto components, OEM suppliers rely on hydraulic presses for accuracy, flexibility
by Abbe Miller, editor-in-chief
According to Toyota – and most likely agreed upon by all automakers – a car is comprised of “30,000 parts, counting every part down to the smallest screws.” To produce these complex machines, the role of suppliers to the automotive supply chain is crucial.
Just as auto OEMs are fully reliant on their Tier 1 suppliers, Tier 1 suppliers are reliant on their Tier 2 partners and so on. To put full faith into this chain of parts suppliers, companies are subjected to comprehensive quality assurance tests. To adhere to these rigorous quality requirements, the equipment and processes used to produce each part are carefully vetted.
Greenerd designed and manufactured this custom, complex double-moving platen deep-draw hydraulic press, which is fully integrated with two 6-axis Fanuc robots to produce a heavy-duty high-pressure cylinder tank for one of the company’s automotive customers.
Hydraulic vs. mechanical
Great lengths are taken to produce vehicles that are comfortable, fuel-efficient and most importantly, safe. When considering the purchase of manufacturing equipment, an understanding of the parts the equipment will make is critical.
The hood of a car, as just one example, requires automakers and Tier suppliers to seek out and formulate the best material and equipment available today. Likewise, to produce transmission housings, connectors or mounting assemblies, Tier suppliers must compare the capabilities of mechanical or hydraulic presses to determine which option is best for the deep-draw requirements of those parts. Any component containing a feature where the depth of draw exceeds the diameter at the narrowest point is considered a deep draw.
“Modern hydraulic presses enable the manufacture of demanding part geometries more so than on traditional mechanical presses,” says Mike Josefiak, mechanical engineer, Greenerd Press & Machine Co. “They offer the ability to apply maximum tonnage and can control the speed of the slide at any point in the stroke. This is particularly useful with difficult materials where a range of cycle parameters must be changed throughout the stroke to accommodate changing part geometries. This reduces scrap rates that result from wrinkling or tearing and overall, improves finished part quality.”
Deep-drawn parts, such as a transmission housing, need sufficient force to be able to carry the draw all the way through to the bottom of a part’s deep contour.
Any time that there is a feature in a part that's considered a deep draw, there is a high load at the beginning of the moving of the material that must be maintained over a long distance. “And that's where hydraulic shines,” Josefiak says.
Identifying hydraulic presses as the best choice for the deep drawing of automotive parts is based on years of manufacturing experience. It’s also based on the understanding of how mechanical presses work versus hydraulic presses.
In a traditional mechanical press, a toggle mechanism provides a large amount of force at the last portion of the stroke. Inherently, however, a deep-drawn part requires an ample amount of force that can carry the draw all the way through to the bottom of the part’s deep contour. Although a mechanical press can do a deep draw, it would need to be four or five times larger than a hydraulic press – even for relatively small parts.
Recently, Greenerd designed and built this transfer line for an automotive company. The line features three stations, which draw, re-draw and punch the component. The draw presses have 250-ton capacities, and the punch press is a 150-ton capacity machine. Speeds on the line exceed 2,000 ipm, providing an ideal high-volume automotive solution.
“It isn't just a simple up and down stroke movement on the hydraulic press,” says Tom Lavoie, applications engineering manager at Greenerd. “With a hydraulic press, the stroke can be interrupted. Pressure can be applied or reduced. A load can be taken off, a part can be repositioned and the load put back. It really comes down to the flexibility of hydraulics and hydraulic presses verses other press systems.”
Dual pumps are commonly used in hydraulic press applications where the first pump would be a high-flow low-pressure pump that enables rapid movements, while a secondary pump provides high pressure at a lower flow. Maintaining a consistent strain on the part as it is being formed creates the most uniform surface tension and reduces the risk of tearing. To accomplish this, a hydraulic press will switch into a lower speed that can be tightly controlled while forming the part. The appropriate forming speed will vary with material, lubrication and the geometry being drawn.
Therefore, the key factors in the design of a hydraulic system are the speed, force and control: The force required to move the material, the appropriate speed to create smooth uniform surfaces and the control of the machine that enables flexibility to adjust for demanding components.
Greenerd’s 4TA-900 straight-side open-gap hydraulic press is a robust piece of equipment for a multitude of industries. For automotive manufacturers, it’s capable of producing a variety of drawn components, such as oil pans and more.
In addition to delivering on strict quality requirements, hydraulic presses also serve as a flexible, affordable and space-saving equipment choice.
“Anytime you’re dealing with a deep-draw application, it's worth looking into a hydraulic press, just from an economic standpoint,” Josefiak says. “The capital expenditure up front is going to be significantly lower.”
Affordability is also part of the equation in regard to the dual pumps featured on hydraulic presses. In addition to providing smooth movements during the stroke, these pump arrangements reduce overall horsepower demand – an economical way of increasing the speed of the press.
The return on investment for a hydraulic press is also faster, thanks to the variety of processes it is capable of performing. Hydraulic presses are used in a wide variety of manufacturing processes, including drawing, coining, compression molding and hot forming, to name a few.
“For the team at Greenerd, we find ourselves in so many applications that benefit from flexibility,” he says. “The customer may have a large range of tooling, a long stroke with high tonnage demand throughout, or a cycle that needs dynamic force and speed control. Hydraulic systems can meet all of these challenges.”
For most automotive suppliers, flexibility is the name of the game. Where one hydraulic press may be sufficient, multiple mechanical presses would be required.
“A big thing that we see with a lot of our customers, especially the smaller automotive suppliers, is as you get down to Tier 2 or 3, they may not be making tens of millions of parts,” Lavoie explains. “They may be producing a million parts or a half a million parts that requires them to regularly switch over between different die sets. Having one piece of equipment that can run a range of dies is important to them.
“With a hydraulic press, it's much easier to program multiple recipes on the electronic control system,” he continues. “Instead of having two or three dies that can only run on one machine in their facility, they have one piece of machinery that they can adapt to run any of their dies. That's something our customers value.”
In addition to requiring fewer machines, the footprint of a hydraulic press is much more desirable when square footage is at a premium. As a reminder, even though a mechanical press might be capable of performing a deep draw, it would need to be multiple times larger than the hydraulic press that could do the same job better.
The triple-action draw press from Greenerd has a 600-ton capacity main ram/punch, 300-ton capacity blankholder platen and 125-ton capacity cushion.
To get even more productivity from a hydraulic press, automation is an option. As can be assumed, this is the case in most large manufacturing facilities where high-volume, repetitive work is prevalent. According to Josefiak, many of Greenerd’s auto manufacturers opt to go in the direction of automation.
“We do all of our own in-house controls work,” he explains. “We'll bring in the robotics, the end-of-arm tooling and all of the automation features that the customer requires and integrate all of that right into the press control station.”
In addition to high-volume requirements, automation is often employed based on ergonomics. Some parts can be large and awkward to remove from the press, sometimes requiring more than one operator. So not only will a manufacturer get more productivity out of the machine, their employees will be more productive, too.
“Beyond the Tier suppliers, that type of automation is something that you could expect to see at a Ford or GM plant – where most of the work is hands off,” Josefiak says. “Just bring the materials to the machine and it takes care of the rest.”
For manufacturers or fabricators that are still in the vetting process, Greenerd can offer assistance in choosing the right equipment for the application. That goes for the presses and the ancillary automation, too.
“When it comes down to it, modern hydraulic systems can achieve superior results with more flexibility, higher speeds and smoother movements,” Josefiak concludes. “And with high-speed monitoring and control, they can achieve repeatable depths of ±0.001 in.”