How will I know when my tube and pipe tooling needs to be sent in for rework? The answer can be summed up in one word: performance. Obviously, the goal is to send in the tube and pipe tooling for rework before it can no longer perform as needed. Performance factors include the ability to hold tube size, straightness and product quality.
Each producer needs to establish a threshold for when their tube and pipe tooling needs to be sent in for rework. Some may earmark footage as a threshold. The only way this method is useful is if the same gauge and the same type of material are run day after day. However, most companies run a wide variety of gauges and material types. The heavier gauges and more abrasive materials will wear the tooling more quickly than their lighter gauge counterparts.
There are several roll dimensions that can be checked for wear that will give you this threshold. When tooling needs to be reworked, this threshold needs to be incorporated with the production mill reports which in turn can be used to monitor the tooling’s performance.
Which of these dimensions will indicate when a roll set needs to be reworked? One dimension alone will not answer this question. The throat diameter, condition of the contour, and bore and face wear are all areas to look at collectively.
One primary dimension to check is the throat diameter (along with tracking rim clearances), which can be used for the next setup. This dimension is normally measured by using a blade or ball micrometer.
Another wear indicator is the contour (radius) of the roll. Why the contour? The throat diameter could have a minimal wear of only .001” yet you could have a contour problem where the sides of the radius are “blown” open or flared out. This condition would necessitate a rework because of the inability to hold ovality on a round tube size. There may also be some pits or nicks in the contour that are causing unacceptable marking.
Contour inspection is a good way to see if the tooling has been set up and used properly. For example, if the contour is worn on one side more than the other, this indicates that something might have been wrong in the setup of the tooling or there may be a mill alignment problem. Disc gauges and templates are the most common devices used to check roll contours for wear.
The bores and faces of the tooling are also important attributes to monitor. An excessively worn bore may cause issues on the mill that could lead to damage to the O.D. of the driven shaft. If you have this movement going on between the O.D. of the shaft and the I.D. of the roll, the faces of the roll will become worn along with the spacers. This will start to affect the alignment of the tooling on the driven shafts. These problems can be remedied by chrome plating then grinding the bore and side grinding the affected faces back to the original dimensions and manufacturing new spacers to make up the difference in width. The general rule for bore wear is for every inch of bore you are allowed .001” wear. For example, wear on a 2.000” bore should not exceed .002”. Any bore exceeding this general rule should be chrome plated or the roll should be replaced (depending on what is more cost effective).
Once you start a maintenance program for inspecting the tooling between runs, it is simple to establish a threshold that will fit your operation. As you document these inspection measurements as we have outlined in this article (and your quality standards for finished tube or pipe get to within 90% of your maximum allowable tolerance mandated by the quality standards set by your customers) you can then establish a threshold for sending us your tooling for rework.
Once established, you can then predict how much life is left in any roll set at any point in time, eliminating the guesswork of when to send your tooling to us for rework.
A proper tooling maintenance program will ensure maximum tooling life, minimize costly downtime, and produce a top quality end product.
Author: Steve Zienka
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