2.5 Special Attachments
These made-to-order products require careful consideration. Should a manufacturer supply them, or should you make them in house? Here are some points to weigh:
The most common requirement is the height from the guide rail to the upper edge of the A or K attachment. The "ground upper surface" type of Plus α Alpha attachments has high accuracy. The tolerance is approximately 0.2 mm, depending on the chain size and manufacturer. For standard attachments, the tolerance range is wider: about two to three times that of the Plus α Alpha attachments. During normal service, the chain will wear, and the height will change.
If you require greater accuracy than is available from Plus α Alpha attachments, make a shuttle that supports the conveyed objects, and use chains only for tracking.
When you need high accuracy in other dimensions besides height, contact the chain manufacturer.
The reason chain manufacturers can produce attachments at low cost is that they use a punch-press process, which is efficient but takes time to set up.
To absorb the cost of set-up, parts need to be produced in large quantity: hundreds of pieces. (The smaller the part, the more parts needed to offset the set-up costs.)
If you need a special attachment in low quantities, the chain manufacturer can help work out a design that can be produced at lower cost.
Chain manufacturers can supply almost all the standard attachments from stock. Special order attachments require lead times. The lead time for specialty attachments runs from several weeks to several months. To prevent a crisis situation, in the event of normal wear or catastrophic failure, you should stock replacement chain and re-order well in advance. Figure 2.32 shows several examples of specialty attachment chains that can be made.
Figure 2.32 Specialty Attachments