What is Closed-Loop Manufacturing ?

Closed-Loop Manufacturing is a concept developed under the supervision of Professor Maurice Pillet by the SYMME research laboratory at the University of Savoie Mont Blanc in France. Closed-Loop Manufacturing is an evolution of SPC (Statistical Process Control) and involves using digital tools to control a production process in order to achieve better quality results than with traditional SPC.

Today, Closed-Loop Manufacturing is used industrially across multiple fields, and its benefits are well established. In the case of machine tools, Closed-Loop Manufacturing has reduced changeover times by a factor of three or four and divided scrap rates by ten. More recently, it has been applied to other types of processes such as bending, injection molding, extrusion, etc…showing equally impressive results.

Closed-Loop Manufacturing is implemented through software available to the operator, which calculates the necessary process adjustments based on the measurement of one or several parts.

Closed-Loop Manufacturing is based on two fundamental principles:

• Controlling complex processes by managing the simultaneous correction of dozens of control parameters

• Correcting process drift through a damping function

When monitoring complex processes that involve multiple interdependent measurements, such as the machining of complex parts, machine setup is often a difficult task. For example :

You want to correct measurement A because at a value of 10.2, it is out of tolerance.

To correct it, you need to modify the position of tool C3; however, doing so will also affect dimension C, which is currently within tolerance.

Therefore, you must also adjust tool C2—but that will in turn affect measurement B, and so on.

The operator is then faced with the challenge of determining how to adjust tools C1, C2und C3 to bring measurement A back into specification.

Even though this example may seem simple, in reality, parts are much more complex, and the adjustment process can take a significant amount of time.

To address this difficulty, a Closed-Loop Manufacturing software such as CLOOMA automatically calculates the optimal adjustment for each tool.

The automation of the adjustment process is based on a configuration file that can be built either:

• a) From the individual impact of each tool, or
• b) From a 3D measurement file of the part

In this case, configuring CLOOMA Software involves determining how each control parameter affects the measured characteristics.
The question to ask is simple: If I modify this parameter, which characteristics will be affected?

Once the individual impacts are determined—something that only needs to be done once during product industrialization—Ellistat’s algorithms automatically calculate the required adjustments for each tool.
For example, the result might be:

C1: -0.3  C2: -0.3  C3: -0.2

In this case, configuring CLOOMA software is even simpler. You just import a 3D measurement file and specify the types of correction parameters used by the machine. CLOOMA’s algorithms handle the rest and automatically compute the optimal settings.

Whatever the chosen configuration, the operator no longer needs to perform manual calculations—the correct adjustments are provided automatically.

Compared to traditional process control methods, Closed-Loop Manufacturing offers numerous advantages:

• Monitors dozens or even hundreds of characteristics simultaneously

• Automatically determines relationships between multiple correction parameters

• Eliminates calculation and sign errors

• Proposes the most probable and consistent adjustment method across teams

In SPC-based process control, control charts are used to monitor variation. The process is deemed stable as long as measurements remain within control limits. When a measurement falls outside these limits, it indicates that the process has drifted and must be adjusted.

The problem with SPC is that it only reacts once the process has already drifted significantly.

In the following example, the process has started to drift, but only about half of the measurements fall outside the limits, meaning corrective action comes too late.

Using digital tools to compute adjustments allows for much more precision than the binary “inside/outside” logic of SPC.
With CLOOMA, the process is corrected continuously—at each measurement—to minimize drift.

Implementing closed-loop manufacturing software delivers far superior results compared to traditional SPC.

The examples below illustrate process monitoring with SPC versus with CLOOMA’s software:

By automating production process control, Closed-Loop Manufacturing enables quality levels that were previously unattainable and significantly increases machine utilization by minimizing downtime due to adjustments.

CLOOMA software is the first software solution to fully implement the principles of Closed-Loop Manufacturing. Its deployment is simple and has a transformative impact on both productivity and quality.

Whether for monitoring a drifting process or controlling a complex one, CLOOMA’s algorithms simplify the operator’s task and introduce an entirely new way of thinking about process control.

• Setup parts reduced to one: Closed-Loop Manufacturing minimizes the number of setup parts required. Scrap due to setup (typically 1–3%) is reduced by a factor of three.

• Setup time minimized: With automated adjustment, only one part is needed to calibrate a machine. Setup time is drastically reduced, increasing machine uptime. For example, a gearbox housing that used to take half a day to set up before CLOOMA implementation can now be adjusted in just 30 minutes (one production cycle).

• Maximized quality indicators: Closed-Loop Manufacturing dramatically reduces the number of out-of-tolerance parts compared to traditional control. Experience shows that scrap due to nonconforming parts is significantly reduced, with Ppk values exceeding 1.33 across all characteristics.

• Operator training in a single day: Implementing CLOOMA is remarkably straightforward—operators can be fully trained in just one day.