Page 41 - MetalForming February 2019

tonnage at 350 or 400 tons. Surpassing needed tonnage, then traveling to a hard stop, affects cycle time. Exceeding needed tonnage means waiting for the press to compress the oil, extend all of that steel and build to that tonnage, then decompress all of that and reverse that extra distance. If the ram travels only to the position needed, you may find that forming only requires 275 to 300 tons, below the normal setpoint of 350 to 400 tons. That’s easier on the press. We see a night-and-day change in cycle time when transferring to a position setpoint as opposed to a par- ticular pressure with a hard stop—as much as 1 to 2 sec./cycle.
MetalForming: Can metalformers actually add speed to the press?
Wilson: We often hear from metal- formers about wanting to close daylight as rapidly as possible, but they’ll hit certain limitations in this effort. The main limitation is cost. Adding pump flow, a primary method for increasing press speed, may require adding an entire circuit to the press. The key: Examine the applications—specific requirements may be more important than speed. When buying a new press, merely jumping from one frame size and motor to the next brings a signifi- cant cost jump with little correspon- ding increase in speed.
Know the application, and don’t specify a press to fit every possible application if all you really need is a dedicated press for one specific appli- cation. A one-size-fits-all approach can become very costly. Pre-design meet- ings with press manufacturers help specify your needs and fine-tune an ideal solution. Such conversations can get to the heart of what’s really impor- tant, which may not be addressed properly in a request for quote.
MetalForming: Can adding automa- tion help reduce cycle time?
Wilson: Yes. If loading and unload- ing result in bottlenecks, a robot can greatly increase throughput. Hydraulic presses have become much more sophisticated in just the past 10 years, with robot integration now a simple task—and robots solve a lot of prob-
Manufacturers are recognizing the dangers surrounding equipment, and robots mitigate that, reducing cut risks due to handling sharp sheetmetal and other health risks from handling bulky, heavy and awkward parts.
www.metalformingmagazine.com
MetalForming/February 2019 39
lems. Just manipulating a part to pull it out of the press may require greater press daylight for an operator than for a robot arm, maybe a few feet as com- pared to a few inches, and robots make the process much safer.
Manufacturers recognize the dan- gers surrounding equipment, and robots mitigate that, reducing cut risks due to handling sharp sheetmetal and other health risks from handling bulky, heavy and awkward parts. We recently integrated robots into one application where an operator easily loads a flat blank, but has difficulty removing the resulting awkward part. Previously, the press would open, the operator would manipulate the part out of the press and walk it over to a stack, then walk over to pick a blank, and walk it over to the press to load—so many steps here. Now, a robot pulls the part through the back of the press while the operator feeds the next blank. Robot integration brought huge cycle-time reductions.
Heavy blanks and parts also become candidates for robot integration and resulting cycle-time savings, while reducing ergonomic risks and combat- ing operator fatigue.
MetalForming: Can hydraulic press- es communicate with other line equip-
ment and effectively mesh to help reduce cycle time?
Wilson: Handshaking with auxiliary equipment—optimizing initiation of a feeder, robot or other equipment for press entry and exit—offers plenty of opportunity to cut cycle time. Espe- cially with older equipment and retro- fits, we see exaggerated motion. A press ram may travel all the way up and stop, and then trigger a robot or some other equipment to feed—a lot of wasted motion. A mid-stroke setpoint versus waiting until a press top-stop provides a simple fix here.
With modern equipment, we know exactly where the platen locates at all times. We know when space is free to feed while the platen is still moving, and don’t have to wait for a relay. Pro- gramming and controls will start the robot moving toward a part grab, which saves time. Or, during a blank feed, the line knows when the operator has cleared the work area, enabling safe equipment movement. Light-curtain technology senses the number of breaks and the press and auxiliary equipment can act accordingly to quicken the cycle.
With hydraulic presses, taking advan- tage of all of these things add up to significant cycle-time savings. MF