Quick change is not optional in thermoforming today.

Who can afford to waste several hours or even a full shift to change over from one job to the next? Quick-change systems cost extra, but few thermoformers nowadays can live without them.

Thermoformers of both thick and thin sheet are executing job changeovers with a swiftness these days that would make the pit crew of a racing team blush. With the latest quick-change systems, thermoformers can accomplish machine and tool set-ups in less than half the time of previous methods. As a result, quick-change systems that were regarded as merely an option five years ago are now a virtual necessity that no buyer wants to forego. All major U.S. and foreign builders of either cut-sheet or roll-fed machines offer some types of rapid-changeover features.

Downtime has become too costly in today's competitive market. "If a processor has to run one mold for five hours and another mold for two hours, with a quick-change system he can run them both in one day rather than schedule each run on a different day," says consultant Bill McConnell, president of McConnell Co. Inc.

The scrap savings from getting good parts up and running faster can also be significant. "If you do it right, you can fine-tune your process to run good parts in two or three shots rather than five or 10," says Dick Roe, product manager for cut-sheet equipment at Brown Machine.

The concept of quick change in thermoforming has been around for 30 years, but today's systems feature numerous innovations that make changes even faster, such as quick-connect/disconnect systems, automatic clamp-frame or chain-rail adjustment, more responsive heater elements, and microcomputer controls that can store and recall system set-ups. Quick-change provisions range from simple mechanical devices all the way to "hands-free" automated systems.

Nowadays, quick changeovers can even be made without tools, unlike prior designs in which the mold package was typically bolted onto the machine platens and required considerable time to remove, change, and set-up, says Henk Hoogendoorn, sales manager at Zed Industries.

Processors such as Productive Plastics Inc. (PPI) in Mt. Laurel, N.J., see quick changes as more than just swapping tools. "It is a cultural change from ordinary production methods. Plant layout, equipment, molds, fixtures, scheduling, and planning are all key elements in setting up," says v.p. John Zerillo.

Although the mold may be the first thing one considers when quick change comes to mind, processors note that little will be gained from a fast mold change unless there are provisions for equally prompt changes to the plug assist, ejector device, clamp frame or chain rails, trim tool, oven, material feed, product stacker, and heat exchanger or chiller. Also needing adjustment are process temperatures, pressures, speeds, times, indexing distances, and forming heights.

Mechanical and electrical features can be instrumental in replacing or resetting these components and parameter values. But effective organization of tools and required personnel on the shop floor also make a big difference. Brown's Roe and Dave Morgese, national sales manager at Maac Machinery Corp., say some quick-change systems are designed with staging areas near the machine, where the new mold is preconditioned on a rack with a separate temperature controller. Roe says this alone can shave 10-40 min off job-change time.

How quick is 'quick'?

Processors such as PPI, McClarin Plastics Inc., Hanover, Pa., and Method Associates, Keyport, N.J., say that a cut-sheet forming system today can be converted to its next job in anywhere from 10 min up to an hour or two. Without quick-change features, the process could take an entire shift or even a day. Meanwhile, roll-fed machine changeover can be accomplished in 10-15 min up to an hour, compared with several hours without quick-change readiness. Spokesmen for Sencorp Systems say customers can conduct a complete form and trim tool change in 15 to 30 min, down from 3-4 hr.

And Werner Kruttschnitt, sales manager at Adolf Illig, notes that every increment of time savings can mean a lot to a high-production operation - for instance, a packaging processor that is producing 72,000 units/hr with a 40-cavity mold.

OMV-USA seconds that notion. The firm, which supplies integrated extrusion and thermoforming lines, offers a fast-change program for the entire line "from pellet to product." A processor can shift from production of a 5-oz drinking cup to a 1-lb square margarine container in 2 hr, compared with 8-9 hr previously, says director Kent Johansson. This quick-change system will be on six brand-new lines that feature OMV's new E-76 high-output (1200-1400 lb/hr) machine. These systems must have quick change to take full advantage of the high throughput, says Johansson.

Simple or sophisticated

Quick-change systems vary from a few hundred dollars for a simple system that requires manual manipulation to $60,000-100,000 versions that automatically power the mold in and out of the machine at the touch of a button. "Some processors cannot afford the price of a 10-minute tool change system, and may be satisfied with a 30-minute change," says Brown's Roe. In cut-sheet applications, he says, only 5% of processors use the high-end type of system, and these are large-scale makers of products like pallets and pickup-truck bed liners.

David Cote, sales engineer at Future Mold Corp., says an inexpensive quick-mold-change system for cut sheet may consist of a T-bar mold-locking device, mold-removal wheels, and quick disconnects. A mid-range system includes those features plus tool-removal carts and some sort of mold-locking device to attach the mold to the platen. A high-end system may have drives that locate and lock the mold into the machine and computer controls that set process points.

An essential component of any mid-range to high-end system is a microprocessor controller with setup storage and retrieval capability for recall and implementation of set-points for vacuum level, indexing speed and distance, tool temperature, and oven zoning pattern. "The limit switches and relay-logic devices of the past made it difficult to set up a new job," notes Roe.

Computer control also paves the way for the use of servo drives. Servo-driven systems can be equipped with encoders for positioning platens, trim press, and auxiliary devices. Programmable servo control eliminates the need for platen stop rods, commonly used with pneumatic drive systems on cut-sheet and roll-fed machines. The rods had to be adjusted by hand during a product change.

Standardize your molds

Every quick-change system will have at its core some mold modifications. "These modifications can be as simple as adding quick connects for water, vacuum, and air to the mold base and pressure box," says Future Mold's Cote. Such preparations cost only $100-500. Arrem Plastics Inc., a custom heavy-gauge former in Addison, Ill., uses a simple quick-change system that does not increase tool cost. "Some customers may have only two production runs a year and they do not want to invest in elaborate quick-change systems," says senior project engineer Ramesh Mehta.

Machine suppliers say the addition of a base or mounting plate affixed to the platens is a must for quick mold changing. "No matter what system you put on, you have to standardize the molds. The idea is to have a standard base-plate size and height so a shallow or deep part can be run," says Brown's Roe. Vacuum, air, and water inlets and outlets should also be positioned in the same place for every tool converted to quick change.

There is some downside to these quick-change arrangements. The presence of the mounting plate could decrease the stroke capability of the machine and could reduce the number of cavities allowed in a mold if a quick-change system is not considered by the machine maker when the forming station is being built. Also, a metal plate may not be a good match with an epoxy and wood mold.

Stanley Rosen, president of Mold Systems Corp., a moldmaker for roll-fed machines, says processors should standardize on several widths of plastic to help reduce setup time, since the pressure box and mold base are designed for easy length adjustments but not width changes.

Provisions for quickly locating and locking the mold in position are also essential features of a quick-change system. Illig sources say positioning tolerances for a quick-change system can run as tight as 0.001 to 0.002 in.

Some machine builders prefer to keep the tasks of mold positioning and locking separate. "Because the tools are big and heavy, we use eight 5/8-in. bolts per tool half rather than a clamping system or hydraulics to hold the mold," says Irwin International v.p. James Naughton. The tool is lined up using pre-positioned dowel pins in the tool. The tool slides along a slot in the machine for alignment and centering.

Several other equipment suppliers, such as Lyle Industries, Modern Machinery, Brown, Maac, Zed, and Sencorp, use quick mold-locking systems developed by Edward D. Segen & Co. Segen's cylindrical locking device replaces bolts or other fasteners and almost instantly attaches a tool to a mold base The device helps locate the mold as well. These locks have been used on machines up to 4 x 6 ft, says Segen president Alain Samson.

Segen also offers quick-lock fasteners for use with plug assists, bottom inserts, mold cavities, and plates. They can be operated manually or electronically.

For processing thin sheet, machine makers such as Sencorp have developed quick-change systems whereby the form or trim tool has fixed retention devices that mate with a quick-change device on the moving platen or bolster plate. The tool is usually lifted on a motorized hoist and deposited on the chain rails (if it's not too heavy) for slide-in installation.

A new machine to be offered by Sencorp's sister company Detroit Tool & Engineering in cooperation with R.I.G.O. Group of Italy is said to change a 1500-lb mold in 5 min. It uses a carriage that carries both the old and new molds. The old mold exits from the rear of the machine while the new mold enters from the front. The old mold is then replaced on the carriage by another new mold for the next tool change.

Another quick-change idea applicable to roll-fed designs is interchangeable mold inserts to run parts of similar diameter but different draw depths. Illig developed a mold-cavity change system whereby each cavity is separated into an inner interchangeable portion and an outer permanent mold portion, which contains the cooling channels. The aluminum inner part is held in place by a bar system. Aluminum inserts for an entire row of cavities are released by removing the bar. Once new inserts and ejector bases are installed, no further adjustment is required, except perhaps of the ejector stroke. If the plugs are motor driven, their stroke and speed, as well as forming-air parameters, can be set on the operator's screen. Illig's Kruttschnitt says a 40-cavity mold can be converted in about 1 hr to handle deeper or shallower parts.

Frank Biller, sales director of moldmaker Marbach Werkzeugbau in Germany says interchangeable cavities are standard on the tools it builds. Naughton says Irwin International also offers cavity-swapping capability on its rotary thermoformer, but he feels it's simpler to exchange the entire mold if there are many individual cavities to replace.

Changing clamp-frame set-ups can be time consuming. Modern Machinery just introduced a new patented four-way adjustable clamp frame that can change width and length without using tools. It eliminates different pin-bar frame sizes and downtime for resizing the clamp frame. A mechanism in each corner of the frame lets an operator unlock and then slide the clamp bars into a new position for different mold sizes. Firms such as Brown, Maac, and OMV also offer fast clamp-frame changes.