This article describes the essential components of a stamping-press line, including the stamping press; coil-handling equipment; feed equipment for coil, strip and blanks; part-transfer machinery; delivery systems for stamping lubricants, die-change equipment including QDC apparatus; and more. Also described is the typical layout of a stamping-press line.
For a metal-stamping business to remain competitive, stamping presses, related equipment and the people that tend them must perform to their full potential. A stamping press, surrounded by the right complementary equipment, will stamp quality parts efficiently. That means less scrap, fewer bad parts and more productive use of manpower. Here’s a rundown of what you’ll find in a stamping-press line, and what considerations are made when putting one together.
This robotic destacker and blankloader automatically feeds blanks into stamping presses, with safeguards installed to prevent blank misfeeds.
Photo courtesy of Shuler Inc., Canton, MI.
Coil, strip and blank handling
A stamping-press line typically begins with apparatus designed to feed sheetmetal, in the form of coil, strip or individual pieces, into a press. The material must be fed steadily and at a rate that matches the production speed of a particular stamping job. Besides matching feed speed to press speed, the material must enter the press in the correct orientation and must be of sufficient flatness. Various types of equipment are available to ensure such requirements.
Coil, strip and blanks are delivered to the stamping press by some form of material-handling equipment. Blank feeding may be as simple as a shopfloor worker loading a blank, an individual piece of sheetmetal, into the press by hand. For high-volume jobs or those involving large-sized blanks, robotic destackers stage blanks, and then pick them up and place them into the press. Related equipment such as fanners separate blanks to prevent double-blank feeding, which can harm the stamping press and its tooling, or at the very least create scrap and waste production time as the offending material is cleared. Sensors can be placed to detect blank misfeeds.
A plethora of equipment is available to hold strip and coil in place at the front of the line, and successfully deliver it into the press. Coil-handling equipment such as coil reels hold the coil and strip. Strip is regarded as coil with a narrower width, typically less 12 in. or less, while coil can be as wide as 72 in. and weigh 6,000 lb. or more. Coil- and strip-handling equipment is selected based on the width of the material. A coil reel may be powered to unwind the coil or strip, or power may be provided by a feed unit, powered material straightener or by the stamping press itself. In many cases the feeder, which provides power and guiding for material delivery into the press, is combined with a straightener. The straightener removes imperfections from the material after it unwinds from the coil and before it enters the press. Recent years have seen the advent of servo feeds, which power material movement via servo drives. Servo drives permit more accurate feed lengths (the length of material fed into the press for each press hit) and quicker starts and stops than previous powered-feed methods. Coil-handling equipment may also include coil-end welders that attach the end of one coil to the next, and stations that apply forming lubricant—via rollers or spray nozzles—to the material.
As space is at a premium on many stamping-plant shopfloors, a compact coil line may be specified. Such lines typically are at least 50 percent shorter than standard lines. Compactness is accomplished by combining coil-handling equipment such as the feeder and straightener, and by eliminating a long coil loop that traditionally has handled sheet slackness and tautness after coil unwind and prior to its entry into the press.
A typical small-part metal-stamping line includes, from left, a coil unreeler, a straightener and the stamping press. The control panel in foreground manages the entire operation, including monitoring of in-die sensors that ensure part presence and proper part orientation.
A press line may contain one or more stamping presses. Should a line contain multiple presses, the parts must be passed from press to press. Robots or special automated machinery are placed between the stamping presses to accomplish this. Sometimes parts must be moved from station to station in a press. With progressive dies, the carrier strip holds the parts and provides the means of support and movement throughout the press stations. In the case of transfer dies, apparatus attached to the press raises, indexes and loads parts into successive stations.
Stamping-press lines may incorporate the means to quickly place dies for a job and remove them promptly upon completion to make room for tooling for the next job. In such quick-die-change (QDC) environments, die carts or towmotors retrieve tooling for a job, staging it next to the press. Rolling bolsters quickly move tooling into and out of the press, making way for quick insertion of staged dies. A control system sets up parameters for an upcoming job to help ensure rapid job changeover. Without QDC capability, job changeover may take as long as half a shift. QDC capability can cut that wasted time—when the press idles—to less than half an hour.
Plenty of work performed in the tooling
To save on costly secondary processes that require material to be transported from the press to another area of the plant or even to an outside source, stampers try to perform as many part-making tasks within the press line. Some actions, such as tapping and welding, may take place within the tooling itself, or at least via machinery attached to the tooling or stamping press. Sometimes nuts or other hardware must be attached to parts. Here, specialized machinery feeds these items into a location where stamping-press action then provides the means of attachment. To ensure proper item placement and orientation, and to ensure that attachment has occurred, sensors may be placed into the press or onto the tooling, a setup referred to as in-die sensing. The sensors relay information to a press-control unit that monitors the part job and if need, be, stops the press should a sensor detect a problem.
Forming lubricant may also be applied within the press bed. Here, lubricant-storage tanks—located remotely or adjacent to the press, feed spray nozzles that apply stamping fluid in a mist to parts and tooling to ease forming and reduce heat and friction. In some cases, the press bed is enclosed to allow forming fluids to flood the work area. In any case, barriers, doors and other apparatus prevent lubricant from reaching the shopfloor environment. For economic and environmental reasons, stampers may employ equipment to capture and reclaim forming fluids for proper disposal or reuse.
Metal stampers must evacuate scrap efficiently from the stamping-press work area to prevent damage to the press, parts and tooling. One method is the use of a press-mounted conveyor that agitates to collect and move scrap out of the way.
Photo courtesy of Mayfran International Inc., Cleveland, OH
Press operation creates scrap, though much thought goes into tooling design to minimize costly scrap generation. Scrap, such as slugs from punching operations, must be evacuated from the stamping-press work area to avoid jamming and damage to the tooling or press. Tooling may be designed to eject scrap from a punch head as the press ram lifts. In any case, scrap collects in the work area and must be discharged. Stamping presses and tooling are designed to help clear scrap to trays or collection areas outside of the work area or underneath the press. This scrap may be transported via conveyance to hoppers. Some stamping-press lines include automated scrap-handling systems that collect scrap and transport it to dumpsters outside of the pressroom. Press lines may make use of technology that senses creation of a bad part, then ejects it into the scrap stream.
End-of-line part capture
Once parts complete the stamping process, they must be collected. In some cases, parts are manually removed and placed in trays, bins or special packaging. Large parts may require end-of-line automation such as robots that grasp parts and place them on racks. Material-handling equipment such as conveyors inhabit the end of press lines to evacuate finished parts.
Press controls tie the line together
As we can see, stamping-press lines contain multiple pieces of equipment, each with a specific function. Press controls tie this myriad equipment together, setting up a line and identifying the correct tooling based on a job number, then managing the processes and providing warnings or even stopping production should faults be detected.
Thought goes into pressline placement
Full stamping-press lines are ideal for production of a similar family of parts or when high part volumes are required. Many large stamping operations employ rows of press lines. For maximum productivity, press lines are arranged so that entry ends are located near part-material storage areas and exit ends are near packaging and shipping areas.
- How much attention does your stamping business pay to how a pressline is setup?
- Is the pressline situated to allow simple access for moving coils to the press, and moving parts to secondary operations or the shipping department?