When Do Original Equipment Manufacturers (OEMs) Outsource the Bending of Pipes?

OEMs often face the decision of whether to make component parts in house or to subcontract them to outside vendors. An analysis of a company’s core competencies often dictates what items to outsource and what to retain. Furthermore, a company’s business plan might specify that the company do as much as possible in house, especially if during slow periods it wants to keep its trained workforce busy, for example. And, of course, a cost/benefit analysis can indicate whether others can produce a part with superior quality, lower cost, more responsive delivery, and/or more overall value to the OEM.

Given the above parameters, are there any special considerations when the part involves the bending of pipes?  What is special about the pipe bending that might affect an OEM’s decision to outsource or insource this process?

Processes commonly used for the bending of pipes include rotary draw bending (sometimes called doing a “mandrel bend”) and 3-roll bending (sometimes called “angle rolling” or “section bending”).  Both types of machines come in various sizes to bend different ranges of parts.

Rotary draw benders can do tube bending from, say, 3/8” diameter to 14” pipe.  They have the virtue of bending pipe to as tight as 1D, that is, they can bend a pipe to a radius that is as small as one time the diameter of the pipe. They can bend a 6” diameter pipe to a 6” radius.  The downside of rotary draw benders is that they can not easily do large sweeps because the dies that the pipe is wrapped around become too large for the machine to handle. And they require a die for each diameter of pipe and radius to which it will be curved.

3-roll benders can easily do large sweeps and can, indeed, bend any size radius except very tight bends.  Some of the larger 3-roll machines can bend up to 24” OD pipe.  3-roll benders require dies that match the OD of the pipe to be bent, but do not require a separate die for each radius that the pipe is to be bent to.

It seems more common for OEMs to purchase and use rotary draw benders especially if they have a high volume of identical parts.  Once the tooling is developed and the operator trained, parts can be produced with good quality relatively quickly.  The payback on the initial investment can be relatively fast.

If, however, the OEM wanted to outsource this work, the bending would most likely go to a contract manufacturer or job shop who might do anything from simply bending the pipe to manufacturing the entire cab of a tractor.  Less likely is it the case that the OEM would send the pipe bending to a specialty subcontractor whose work is primarily pipe bending.  It seems that there are fewer such companies today which to me indicates that rotary draw bending is done either at the OEM level or in the shops of multi-faceted contract manufacturers

It is less common for OEMs to purchase and use 3-roll benders even if they have a high volume of identical parts. Especially if there is a wide variety of pipe sizes to bend to a variety of radiuses, considerable operator training is required. In the OEM factories, unless the operator is well trained and continually operates the 3-roll benders, he will probably have difficulty producing parts with good quality relatively quickly.  3-roll machines are simply more difficult to operate than rotary draw benders.  They often require more space to operate than rotary draw machines.  And the payback on the initial investment is probably slower.  Consequently, OEMs and their subcontract manufacturers often turn to shops that specialize in 3-roll bending for their bending of pipes. Unlike shops that specialized in rotary draw bending, shops that have specialized in 3-roll bending have increased in recent years.

A number of companies have developed the capacity to do both rotary draw and 3-roll bending while striving to meet the needs of OEMs and contract manufacturers.


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