Sponsored By

Current industry buzzwords abound, and one of the most repeated ones is “green.” One way to take advantage of the green wave is to incorporate quick mold (QMC) change procedures into your molding facility.

QMC can cut waste and increase mold change efficiency. Through standardization of the process, safety and improved press utilization are additional benefits. A QMC system will quickly pay for itself when additional press capacity and reduced changeover overhead are needed.

Michael Ray

August 31, 2009

7 Min Read
Mold changing options will make you green

Current industry buzzwords abound, and one of the most repeated ones is “green.” One way to take advantage of the green wave is to incorporate quick mold (QMC) change procedures into your molding facility.

QMC can cut waste and increase mold change efficiency. Through standardization of the process, safety and improved press utilization are additional benefits. A QMC system will quickly pay for itself when additional press capacity and reduced changeover overhead are needed.

When using QMC, the mold can be moved either from the operator side or the nonoperator side of the molding machine. Molds are generally pushed in or pulled out of the press using the vertical space between the strain rods.

Press setup

QMC1.jpg

Figure 1: Mold base with back plates attached.

Each press will need to be set up for QMC side mold changing. To change molds with standard back plates quickly, the press will need a quicker means of clamping the tool onto the platen, rollers to support the mold during the transition from cart or table to the press platen rollers, and a mold handling/exchange device to support the “new mold” and the removed mold.

The common back plates will be used to create a common attachment point and a common transfer surface for rolling the molds into and out of the press. This back plate also serves as a common clamping point for retaining molds to the platen of the press (see Figure 1).

Clamping
Although manually clamping the molds to the platen is still an option, this wastes time. A better option is to incorporate a type of automatic clamping. This, in conjunction with common back plates, can strip minutes from your mold change times.

Two different types of automatic clamping are in use throughout numerous injection molding plants today: magnetic or hydraulic. Each method has a drawback and it is up to your individual case as to which method you should select.

Magnetic clamping requires the purchase of magnetic plates that are attached to the moving and stationary platens. The drawback is a loss of daylight in the press. You will have to subtract two times the thickness of the magnetic plates from the maximum mold shut height for your particular press. Still, magnetic clamping provides a safe and efficient way to attach your molds to the platens.

Hydraulic clamping can be used to attach your common back-plate-mounted molds into the press. This generally involves adding four to six hydraulic clamps to each of your press platens and controls for the same. The drawback is they are not as quick as magnetic clamps and hydraulics could eventually lead to system leaks. But there is no loss of daylight. 

The cost of clamping, whether magnetic or hydraulic, is a key consideration. Hydraulic clamping can be expensive to install aftermarket and is usually more cost-effective if installed by the press manufacturer.

Rollers

QMC2.jpg

Figure 2: Platen rollers and prerollers mounted to the press platen bridge the gap from the safety gate to the cart or table

Rollers need to be installed on each platen to provide a means of rolling the molds into and out of the press. The press manufacturer can provide these rollers with the molding machine or they can be incorporated into either clamping method. They can also be purchased aftermarket.

Prerollers are needed to bridge the gap between platen rollers and the press safety gate and your mold changing apparatus (cart or table). Generally, this gap is too large to span without the aid of extra rollers (see Figure 2).

The prerollers can be mounted to the edge of the stationary and moving platens using holes that are premachined by the press manufacturer or match-drilled in place by a competent mechanical contractor.

Mold handling/exchange device
There are several options for a device to handle your back-plate-mounted molds. Carts are available that use different types of power sources to move around in your facility. Free-ranging carts can be designed and built to handle loads up to 100,000 lb and greater.

These carts can be single- or dual-station. Single-station carts can remove one mold from the press and take it to a rack or mold storage area, followed by taking the new mold to the press and inserting it. Dual-station carts are designed to take advantage of the remove-one/add-another style of mold changing. A new mold or “ready” mold is placed on the cart before the change process. When the mold change is initiated, the operator removes the existing mold from the press and inserts the ready mold in a matter of minutes. These free-ranging carts can be used to service several presses with optional lift capabilities (see Figure 3).

QMC3.jpg

Figure 3: A two-station, 20,000-lb mold cart services many presses.

QMC4.jpg

Figure 4: Typical two-station mold shuttle table.

Depending on your facility’s requirements, your company may opt to provide each press with a shuttle-style table that’s capable of storing one or several molds to be inserted into the same press. The shuttle tables are permanently mounted to the floor parallel to the injection machine and act as a staging area for the “next up” mold. When it’s time to change molds, the existing mold is pulled from the press and the ready mold is shuttled into position and inserted into the press (see Figure 4).

Some facilities opt for using rail-mounted carts that are lined up to service presses on either side of the rail. The capacities of such systems are virtually unlimited but the drawback is that it is difficult to incorporate after a facility has already been constructed and presses are in place. This type of arrangement must be incorporated during the building structure phase to be feasible.

All of these options require an investment from the molding facility. Depending on the degree of automation required and options available, the QMC upgrade to your facility could cost several hundred thousand dollars, depending on mold sizes and the number of presses. The return on investment can generally be within the first year based on improved efficiency, safety, and product output.

QMC5_sb.jpg

Figure 5: A press setup for side QMC with platen rollers and prerollers installed. The molder uses a free-ranging DC cart to service several presses from 65-300 tons.

QMC: Even for small machines?
Quick mold change can generally be applied to nearly any size press due to the increased safety factor. Mold weights that customers have successfully changed using QMC range from 1000-100,000 lb. One of our customers, a molder in Mexico, has QMC for presses as small as 65 tons (see Figure 5).

This molder is changing out molds in 6 minutes or less, shot to shot. It uses rollers and a manual quick clamping system to achieve its desired results. This eliminates the need for an overhead crane and improves overall safety. The mold techs do not have to deal with a heavy swinging load on an overhead crane and there is less chance of damage to the press due to banging into press components or strain rods during the mold changeover process.

Calculate the cost
There are several items to consider when transitioning to QMC, so before jumping in, create a budget to incorporate QMC into your molding operations. Use our cost justification ROI calculator to assist you in calculating return-on-investment numbers.


Author Michael Ray is senior application engineer with Green Valley Mfg. Inc. (Mt. Zion, IL), a manufacturer of quick mold and die change equipment.

Sign up for the PlasticsToday NewsFeed newsletter.

You May Also Like