Is the injection moulding machine losing output through downtime or slower cycles?

Two losses worth measuring separately

A machine may produce less than planned because it stopped, because its cycles became longer, or because both occurred. The total part count at the end of the shift cannot distinguish these effects.

To analyse them, identify the planned production time, stoppage intervals and recorded cycles. The ideal cycle time must correspond to the product, mould and number of cavities actually in use.

• Availability: operating time as a proportion of planned production time.
• Performance: actual cycles compared with the number achievable at the ideal cycle time during operation.
• Quality: first-pass conforming units as a proportion of output, where records are available for the same period.

Minimum data for investigating a shift

• Machine, product, mould and planned period.
• Start and end of stoppages; cycle signals where available.
• Ideal cycle time validated for the manufacturing condition.
• Downtime reasons confirmed by personnel and recorded close to the event.
• Conforming and rejected quantities for calculating complete OEE.

KERN IoP can record available signals and accept shop-floor entries through SMARTPRO; MONITOR provides access to the historical data included in the installation.

Explore shop-floor data entry with SMARTPRO

Example: the machine also loses production rate

Assume a shift with 420 minutes of planned production time and 60 minutes of downtime. This leaves 360 minutes of operation. At a validated ideal cycle time of 30 seconds, 720 cycles would be expected during that operating time.

If 660 cycles were recorded, availability would be 360 ÷ 420 = 85.7% and performance would be 660 ÷ 720 = 91.7%. Downtime minutes and cycles lost during operation make different contributions.

Converting cycles to units requires the number of active cavities. Complete OEE also requires conforming quantities from the same interval. This is an illustrative example; the figures are not customer results.

How to quantify capacity losses caused by downtime

Operators provide context beyond the signal

A signal may identify the absence of cycles. Classifying the stoppage requires understanding what happened: set-up, waiting for material, adjustment, maintenance or another condition defined by the plant. Timely recording supports analysis by order, shift and machine.

SMARTPRO and MONITOR can bring this information together when the forms, identifiers and signals are configured for the application.

Continue exploring

• How to calculate OEE in injection moulding
• How to record conforming and rejected parts during the shift
• Return to the production management page

Guide developed from KERN IoP’s earlier articles on productivity and data acquisition. Historical commercial percentages are included only where their measurement conditions are documented.