In addition to the single tooling, the injection molding machine also offers the option of multiple molds by retrofitting so that the number of molds can be increased from five to six or more. This greatly improves the production efficiency of the injection molding machine, which meets the needs of modern industry for increased productivity. The function of a multi-mold injection machine that uses several molds to work at the same time is called multi-mold injection molding production, which achieves high speed, low cost, and ultimately, increased productivity.

Injection molding is one of the ways we make plastic parts. It’s a process where we melt plastic material, inject it into a mold cavity, and let it cool and harden into the shape defined by the mold. One of the most common questions I get when talking about injection molding is if a machine can run more than one mold at the same time. In this article, I’ll explore running multi mold on an injection molding machine: Is it possible? What are the benefits? What challenges do you face? And what do you need to consider?

Feasibility of Supporting Multiple Molds on an Injection Molding Machine

An injection molding machine’s ability to run multiple molds depends on factors such as the machine’s capacity, the mold size, and the complexity of the parts being produced. Many modern injection molding machines are equipped with multi-molds that can handle more than one refining?These features include a CME, a rotary table, and moldable parts being replaced periodically.

Advantages and Disadvantages of Using Multiple Molds

Advantages

1. Enhanced production efficiency: By using one injection molding machine to produce individual parts, you can optimize the time spent on multi-stage operations, which improves production efficiency. Using a turntable mold allows you to make multiple molds and variations in different positions, which ultimately improves production of multiple models and specifications.

2. Cost savings: By using multiple molds to produce products, you can save the cost of purchasing other injection molding machines, which also reduces capital investment.

3. Reduced production costs: Multi-shot injection molding has the advantage of producing multiple forms at the same time, which saves downtime and the cost of producing defective products, thereby reducing production costs.

4. Improved product quality: The characteristics of multiple molds allow for more uniform friction, which reduces the need for mechanical wear during mold opening and closing, increases the stability of the mold in production, and extends the life of the mold.

5. Reduced requirements for injection molding equipment: Multi-mold injection molding is a process that fully utilizes the production capacity of injection molding machines, shortens production cycles, and extends the life of the machine.

Disadvantages

1. Lengthy mold switching times: When you have different molds, you have to switch between them, and that takes time.

2. Increased failure rates: When you have more than one mold in the injection molding process, you put more pressure on the machines, and that can really mess up your maintenance and repair systems.

Considerations When Using Multiple Molds

1. Skilled operators required: The use of multiple molds in the injection molding process makes the operation of the injection molding machine more complicated, so experienced operators are needed to avoid accidents.

2. Equipment maintenance: Using multiple molds means the mold maker has to pay more attention to the maintenance of the injection molding machine and the normal operation of the mold to avoid frequent production interruptions and increase the service life of the mold.

3. Production planning: In this case, the reason why it is important to use multiple molds to make products ahead of schedule is to make the production plan go smoothly.

4. Machine compatibility: Not all injection molding machines are equipped to use multiple molds at the same time. Manufacturers need to check whether their equipment, such as injection molding machines, can complete all the tasks required for multi-mold operation.

5. Mold alignment and synchronization: The accurate fit and connection of the mold are important for achieving consistent part size, preventing defects such as flash and warpage, etc.

6. Mold costs: The cost of purchasing a set of molds for a complex or high-precision part may be very high. Factories need to consider the main feasibility indicators, mold life, and amortization factors.

7. Maintenance and downtime: Running multiple molds on one machine at the same time increases the likelihood of wear and tear, which can lead to more frequent maintenance needs and potential downtime for repairs and maintenance.

Case Study: Tandem Molding Injection Molding Solution

The Tandem Molding technology is a process that utilizes two identical or similar molds mounted onto one injection molding machine. They basically work simultaneously to achieve the desired outcome. The given time gap between setting products on one mold and the other, is used for the injection molding process of products from the alternate mold, and the machine uses the time in between to balance between the two molds, maximizing productivity per hour of operation.

The efficiency of Tandem Molding technology is usually unmatched, it can increase product output by 40-80% and save 30-40% on equipment and automation investments if the process conditions and equipment configurations are suitable.

Applicable Scenarios

You can use Tandem Molding technology in products with cycle times of 30+ seconds, the same material combinations, and sizing close to one another or paired molecular structures. We’ve done this with “front frame – screw-housing” and “cover-bottom base” parts with symmetric products, system engineering parts that are standardized and involve multiple sets of molds, and flat large frame parts including the hollow structure with easy installation of flow channels. You can combine these parts and molds and produce them efficiently using shallow cavities.

Requirements for Molds

In Tandem Molding, the mold has two parts: one is the hot runner system that alternates shots between the front and rear molds, and the other is the locking system that alternates the opening and closing of the molds. On the other hand, Tandem Molding design is based on two molds that share the injection. The easiest way to alternate between the front and rear molds is to use a front and rear hot runner system.

Today, most hot runner manufacturers design their products for Tandem Molding and also for low-cost cold runner molds that can do Tandem Molding or even for existing two molds that can be retrofitted for combined use. All in all, the complexity is not in the molding, it is mostly in the hot runner.

Requirements for Injection Molding Machines

With Unilateral Molding, you don’t have to make any complex adjustments to the mold making machines. You just insert a plate in the hydraulic mold that increases the thickness of the clamping part of the molding machine so that the overlapping molds fit. Typically, this means increasing the clamping thickness of the mold by about 20-25% more than the standard equipment mold capacity.

With Tandem Molding, you have to use control software where the injection molding machine control system includes this software to accommodate the variables used in processing Mold A and Mold B to produce different products. Stopping and starting the melt and the amount or volume of melt are the key features to improving production efficiency.

If you don’t have enough melt capacity, you can use independent holding pressure devices or close the nozzle valves to start the plastification process earlier during holding pressure. Typically, these applications don’t require the most expensive equipment, and the subsequent improvements usually only increase the cost of the equipment by 5-10% over what you had before. When the single machine can run at the same productivity as two machines, all you get is a cost savings as soon as the molds can keep up.

Differences between Tandem Molding and Stack Molding

When people first start using stack molds instead of single-face molds, they often ask me about the difference in what you can make with them. The simplest form of stack molding is just taking turns making parts in mold A and mold B. This is mainly used for technical parts that need to be thick. It’s not like flash molding, where you make a complicated part (and it takes longer to make it). Stack molding is used to make thin parts or parts with a lot of cavities, where the cycle time is short (less than 10-15 seconds) and the cooling time is less than 5-6 seconds.

So, stack molding is a process that requires opening molds A and B simultaneously, suspending the center mold while the molds open, and then dealing with issues like positional stability, support, and synchronization when you’re dealing with mold structure. The main problem is the need for strength, precision, and durability in the mechanical parts used to produce parts under high-speed production conditions. Molders who can produce high-quality, reliable, precision molds are not like other mold shops. They usually charge more for their molds than the average mold.

As the number of cavities increases, the cost increases. The fast production speed results in extremely high costs due to flow balance and sequential valve control. In order to consider the quality and production stability, the mold factory usually chooses the hot runner brands like Moldmaster or Husky, which cost more. In the end, the high cost of molds will affect the company’s competitiveness in a project. The tandem molding process allows only one mold parting surface to be opened at a time during each cycle, while the other half remains relatively permanently locked in position. What makes this method valuable is that the mold layout is similar to a conventional mold, so it does not have the problem of high complexity of the mold structure.

The stack molding process requires higher acceptance criteria for precision and machining, longer molding cycles, and slower production speeds compared to the cost-effective and more forgiving molding process. In addition, Tandem Molding does not prefer using high-cavity designs, so it relies on more common hot runner brands in the market.

Tandem molding, by having only one mold parting surface, opens only one parting surface at a time and a single parting surface, unlike stack molding where you have to open and inject into two parting surfaces at once. So, you need the machine to have a minimum of loading space within the mold clamping (parallelism) and a melt and injection capacity in the injection molding portion.

The injection molding machine normally used in stack molding is, in most cases, 1-2 specifications higher than the one used in Tandem Molding for the same number of cavities. The fact that Tandem gravity molding has a longer cycle length but uses lesser load on equipment at the same time than stack molding makes it quite ideal for domestic products while the quick-speed stable production of stack molding presents great challenges to domestic brands.

Tandem Molding production is more flexible. A and B half molds can make different products with different injection molding processes, while stack molding usually produces a single product with the same mold cavity numbers and injection conditions. In comparison, Tandem Molding is in a lesser position to the stack molding by the differences in the production equipment, the molds and the production processes. Therefore, this method is simpler, more economical and more practical way of improving productivity.

Conclusion

In summary, whether or not it is feasible to have an injection molding machine that can handle multiple molds depends on several factors including the capability of the machine, the design of the mold, and the production requirements. There are many benefits to running multiple molds: it saves time and labor, it makes the process more cost-effective, and it allows you to change the finished product. However, this machine is also complicated to run, it takes time and a little bit of skill to get it lined up, and lastly, you have to think about maintenance. Basically, machine manufacturers have to think about what they need and what they can do to see if a dual purpose machine is a good option for them to have a more optimized manufacturing process.