The value of injection molding cycle time optimization and monitoring

M-Box monitors Cycle Time and Mould Closed Time of injection moulding machines

Instantly increasing your productivity in injection molding is easy if you pay attention

Production departments (including our own) and their management can grow complacent and fail to be critical on the results. This particularly applies to injection molding cycle time settings and the performance on this KPI.

The company is footing the bill through overtime pay and revenue loss, and even considers investment in additional production capacity. Meanwhile, a simple output increase could be realized by just being critical of the productions at hand.

What is the Cycle Time in Injection Moulding?

The cycle time in injection molding is the total time needed to complete the stages of the molding process:

  1. Closing the mould
  2. Material injection
  3. Holding stage to fill and cool and avoid sink marks
  4. Opening the mould
  5. Eject or release the part

Use M-Box to monitor the cycle times in production

M-Box helps you to monitor:

  • Total cycle time (stage 1-5)
  • Mould closed time (stages 2 and 3).

You just set the optimized target times (following the optimization steps below) for each mold configuration to the system.  When the mould appears on the machine, the corresponding RFID card (unique per mould configuration) is set to the M-Box. Then, if during the production either the cycle time or mould closed time deviates from the target, an instant notification is issued to the supervisor. If it goes unattended, a ticket is generated for handling by the production manager.

Cycle time deviations no longer go unnoticed and are addressed immediately to make sure you produce at optimal output speed. 

Our recommended approach to reduce the cycle time in production

Step 1. Decrease cycle time by reducing time for opening/closing the mold and part ejection

Particularly stages 1, 4, and 5 deserve scrutinization and may be subject to improvement as they have zero to none impact on the outcome of the process. You may be able to start the ejection stroke before the mould is completely opened and save additional time (only possible when the machine program allows this). The mould open/close runway may be set too long, this will cost time. (Be careful with setting the speed of the mould closing, as a forceful impact on closing may damage the mould parts.)

Step 2. Reduce cooling time in injection molding

The cooling step can often be shortened by a bit with an acceptable loss of additional shrinkage (within specified limits) and by optimizing the cooling process (chilled water) and cooling channels through the mould.

Step 3: Experiment with slightly shorter holding times to check its impact on quality

Verify the part weight after each reduction of the holding time. As long as the weight remains the same, the reduction of holding time did not impact the quality of the part produced.

In our own factory we went through the process of finding the optimal setting for each mold configuration (in combination with the different machines) by simply twisting and tweaking these parameters. We found out that on average the cycle times could easily be reduced with 5-10%, with outliers of up to 25%. Then, on the floor we found that machines often were running up to 50% above the optimal time.

Root causes of the deviations were either sub-optimized processes, insufficient cooling (operators will not address the root cause but simple increase the holding time) or bad operator morale (set the mould open/close runway excessively long and have an easy job).

What is the value of a reduction of 5% in cycle time?

If the machine hours can be “sold” at typical gross margin levels, a reduction of 5% can yield the following:

Machine Type (Tones)Typical Gross Margin per hour

Additional Productive hours/year

5%

Added Value
50$10.00350$3,500.00
150$25.00350$8,750.00
350$50.00350$17,500.00
1000$140.00350$49,000.00

Reducing cycle time in manufacturing is easy

Well, the cycle time is easy to optimize with a critical approach. To ensure that your machines are always running at the optimal cycle time, use a real-time production monitor