Going beyond mechanical transfers
March 24, 2009
A servo-driven transfer system can help to create a multipurpose press line that expands the number of parts traffic patterns. It also allows stampers to navigate heavy traffic with quick die changes between setups, short run times, and fully programmable setups that can be recalled simply.
In today's ever-changing economic environment, stamping companies are faced with many challenges. Production orders and lot sizes are more varied than ever—and in many cases significantly lower. As they phase out older programs and launch new programs, they must change product and part designs more frequently and shorten program lead-times significantly. In addition, contractual or mandated price reductions and continuous pressure to reduce costs are more prevalent than ever. Contract stampers must be prepared to have the equipment that allows them to quote and manufacture any job that comes along.
Stampers can meet these challenges by automating new or existing presses with servo-driven transfer automation. A servo transfer system can help to create a multipurpose press line in which stampers can feed coil or blanks, in any direction, and using either progressive or transfer dies.
Servo transfers allow quick die changes between setups, short run times, and fully programmable setups that can be recalled simply.
Changing Over Frequently. Small lot sizes require frequent changeovers from job to job. Servo-based transfer systems facilitate quick changeover because they can be set up to change transfer tooling automatically with a button push from the servo transfer human-machine interface (HMI). The part, sensor cables, and pneumatic lines also are automatically disconnected, permitting full automation and hands-free QDC.
Saving Directions. When it's time to change a part or job, the transfer move parameters in the X, Y, and Z axes likely will be different. The servo transfer system stores a part recipe for each job or part that can be quickly and easily recalled. The part recipe is also editable if a product design change has occurred that may affect the transfer travel in a particular axis.
Optimizing Moves. In a servo transfer, all transfer moves for each part can be optimized to achieve optimal performance and productivity, instead of being limited to only one type of transfer move, distance, velocity, and timing. This flexibility expands the ability to process a variety of parts and materials.
Parking Tooling Bars. The automatic changeover feature allows the finger tooling to be "parked," or stored, with the die. This protects the die and maintains its condition so that it is ready to use the next time it is scheduled to run.
Parking Servo. The servo transfer mechanism itself can be parked in an offline position to allow good press bed access for die change and during coil-fed progressive-die production runs when the servo transfer is not required (see Figure 1).
Speeding Deliveries. A servo transfer has fully programmable features that can quickly accommodate end-user design changes.
In addition, because an existing press can be retrofitted with servo transfer technology, this eliminates the need to install a new press, thereby improving deliveries and lead-times by shortening the time frame from program decision to production.
In addition to time savings, retrofitting an existing press can significantly reduce cost and capital outlay compared to purchasing a new press, as well as the associated costs of foundation work for a pit, rigging, assembly, freight, and so forth. In many cases, stampers can reuse their associated ancillary press equipment, such as feed lines, scrap conveyors, and part exit conveyors.
In certain cases, the flexibility of a servo transfer system can reduce the number of presses needed.
Four-way. Traditional transfer dies and mechanical transfer systems require the centerline pitch requirement from die station to die station to be common and long enough to accommodate the largest part and die design. A four-module servo transfer system permits the pitch, or X-axis move distance, to be changed within a multiple die lineup.
In certain situations—most typically in presses with left-to-right bed dimensions 180 inches and longer—a four-module servo transfer system allows the pitch distances to be different in each half of the press bed. This allows the pitch distance, and therefore die spacing, for the first die stations to be spaced further apart, while the pitch distance and die spacing for the final die sets can be shorter and closer (see Figure 2).
This enables a smaller bed press, an additional die in the press for improved part quality, or even elimination of the need for a second press altogether.
U-turns. Die arrangements and part processing can be thought of differently when coupled with a servo transfer system. For instance, dies typically are configured in a straight line, with parts being processed from right to left or left to right.
With a servo transfer system and when part geometry and press bed size allow, the dies and process flow can be configured in a U-turn arrangement (see Figure 3). In this scenario, the part is processed or transferred through a series of dies from left to right. At the end of the first lane of dies, the part is shifted 90 degrees from lane A to the second lane of dies, lane B. In lane B, the part is transferred in the opposite direction, from right to left. With this type of die configuration, the left-to-right press bed dimension requirement is cut in half, allowing the use of a smaller press bed, or eliminating a second press completely.
For example, a traditional, straight-through die setup with 30 die stations and a pitch, or X-axis requirement, of 9.5 in. would require a left-to-right press bed of about 288 in. (or multiple presses). Splitting the dies into two lanes—15 in one lane and 15 in the opposite lane—halves the left-to-right press bed requirement; therefore, production can be processed in a single press with a bed length of only 144 in.
Two Lanes. This arrangement also provides the opportunity to double productivity. Two parts can be transferred through two separate lanes of dies (dual lane), essentially doubling production output (see Figure 4 and Lead Image). For example, transferring two parts at 40 strokes per minute (SPM) equals a net output of 80 parts per minute.
Alternatively, this arrangement allows simultaneously processing a right-hand and left-hand part so each press stroke produces a set of parts (tandem line) for double productivity.
Gripper-type transfer finger tooling is required for both the U-turn and two-out, two-lane die arrangements.
Today manufacturers need to be as versatile and flexible as possible. These attributes are key to long-term viability and success. The parts and geometries processed today are not likely to be the parts or designs produced tomorrow.
The flexibility of the servo transfer system allows manufacturers to think "outside the box" in terms of how they manufacture certain parts using the equipment they have on hand.
A servo transfer system's fully programmable features allow a stamper to solicit nearly every type of press work, from small, round parts to larger, shaped parts.
When a part needs to be rotated for work to be done on its bottom and then rotated back to its original orientation, transfer system tooling can be configured with rotational devices for part rotation and orientation. This can eliminate a secondary downstream process or a second press operation.
These rotation and orientation devices and their programmable operations are easily incorporated into the control and tooling design of the servo transfer.
With servo transfer technology, a flexible, multipurpose press line that can help stampers enhance their pressroom operations is achievable.