Closed-loop manufacturing

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Closed-loop manufacturing (abbreviated CLM) is a closed-loop process of manufacturing and measuring (checking) in the manufacturing machine. The pre-stage to this is inspection in manufacturing. The idea is to reduce costs and improve the quality and accuracy of the produced parts.

Closed-loop manufacturing can be done in different ways dependent on the manufacturing technique and on the accuracy requirements.

1. Planning the sequence (iterations)
2. Producing nearly the target value on the part
3. Measuring the real value
4. Calculating the residual (stop if residual is smaller than needed accuracy)
5. Manufacturing the residual
6. Repeat from Step 3

CLM is very suitable for electrical discharge machining. Milling or turning is also suitable for CLM.

In machining measurement techniques have to fulfill special needs. In particular optical techniques have the advantage that they do not touch the part. The following parts are practically used:

• Focus variation
• Tactile probes

The advantages are:

• Reduce tool costs
• Improving accuracy
• Quality control is done in the machine directly
• Measuring can be more accurate because the part does not need to be unloaded
• Better deployment of personnel
• Integrated sensor eliminates clamping errors

The disadvantages are:

• Planning is needed
• If planning is not done, machine time is increased

• EU EMRP project on traceable in-process dimensional measurement