Minutes of the meeting on the holding point in industry,
01/04 2005
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Present:
Marta Bajko, Paolo Fessia, Jean-Pierre Koutchouk, John Miles, Frederic Savary, Elena Wildner
Excused: Gijs de Rijk (discussion with Gijs before the meeting)
Pen: ElenaWildner
Background and discussion:
Geometry data in industry have tolerances (to be compared with the holding point for magnetic measurements, where statistics and patterns in the measurements are used to trigger a hold). If data are out of tolerance, a non conformity is opened; it may be critical or not critical. A critical non conformity must be repaired by the firm whilst a non critical non conformity may be accepted after circulation of information about the non conformity to a list of “experts”. This list of people to which the non conformity was sent for comments has been reconsidered.
The sagitta is an important parameter for the geometry acceptance. There is no tolerance on the sagitta, however all points measured along the magnet by the Leica (cold bore tube centers) have to be within a certain range (±1.5mm from the theoretical value). To keep all points within this range has been difficult on this object and a certain number of magnets have been accepted with points lying outside the allowed bounds. These magnets can be allocated to mid-cell positions in the machine. Now, the adjustment procedures and the allocation/installation scheme are such that we can only accept a very small number of mid-cell magnets (<10%). We also need a large enough number of golden magnets (13%-19%).
The statistical adjustment procedure at WP08 demands a stable mean value of the sagitta. It is also important to reduce the spread of the sagitta increase between industry and CERN but for this we have no control handle yet. The mean value of the sagitta can, to some limited extent, be controlled by welding press adjustments.
The first indication of the shape of the magnet we have from the geometry measurement immediately after the magnet comes out of the welding press (“itp15”). If the shape is out of tolerance, the shrinking cylinder can be cut and replaced. This does not always, according to experience, remedy the problem. Apart from expenses, the fact is that there are not enough half-shells produced to allow extended use of such actions, limits our possibility to control by cutting the shells. To control the shape, “measurements under press” to adjust the welding press should be made regularly.
After the meeting, discussions have shown the interest to monitor also itp15 data immediately before the assembly of spool pieces and flanges (last itp15 measurements during the assembly). We will put those in the data base in the same way as we do for the “after welding press” data from now on. To recuperate this data from the EDMS system or CDs will be a major effort (project engineers, data base experts and programmer) and we have to consider the man power, the time schedule and the necessity do this work for all magnets.
The holding point in industry:
Preventive:
Adjustments of the welding press should be done regularly (once every 3-4 months).
Mesurements “under press” should be done regularly (once every 3-4 months).
The mailing list for the non conformities on the shape should be:
Project engineers, Jerome, Elena, Jean-Pierre, Jos and Lucio. The subject field in the mail should always be the same, example:
To: Project engineers, Jerome, Elena
Cc: Jean-Pierre, Jos and Lucio
Subject: Geo-Holding point industry: Magnet 1203