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C‑parts made of rub­ber or

plas­tic also deserve attention

22.06.2022   | Thomas Wutke


Rub­ber and plas­tics in mod­ern agri­cul­tur­al technology 

Learn how agri­cul­tur­al engi­neer­ing can meet most of the cur­rent challenges

Although C‑parts account for up to 80 per­cent of a prod­uct, they lead a shad­owy exis­tence in design. Design­ers tend to focus their atten­tion on high-priced A parts. C‑parts, on the oth­er hand, are often only dealt with by the pur­chas­ing depart­ment. This approach is under­stand­able. But neglect­ing C‑parts can lead to prob­lems in the long term, espe­cial­ly in the rub­ber and plas­tics sector.

C‑parts are neglect­ed due to their low mon­e­tary value

C‑parts are among the hygiene fac­tors in most com­pa­nies. As long as they ful­fill their func­tions and do not cause any prob­lems, their han­dling is reduced to pro­cure­ment. They are rarely the tar­get of opti­miza­tion mea­sures. Instead, C‑parts made of rub­ber or plas­tic often only receive atten­tion in design when the equip­ment designs have been com­plet­ed. As a rule, design­ers sim­ply select a stan­dard part whose prod­uct descrip­tion super­fi­cial­ly meets the require­ments. Addi­tion­al mea­sures, for exam­ple com­plex analy­ses or val­i­da­tions, which are stan­dard for A‑parts, only take place rudi­men­ta­r­i­ly, if at all. The rea­son for this is sim­ple: Com­pared to A and B parts, the opti­miza­tion of C parts has a low cost-ben­e­fit ratio. C‑parts are cheap and hard­ly con­tribute to the core prop­er­ties of a prod­uct. Opti­miz­ing them costs time, but this is hard­ly reflect­ed in the end result. What advan­tages would it have for a com­pa­ny to jeop­ar­dize the Start of Pro­duc­tion (SOP) for such mar­gin­al effects?


C‑parts are com­po­nents that account for a dis­pro­por­tion­ate share of a pro­duc­t’s total vol­ume but only mar­gin­al­ly affect its val­ue. Accord­ing to Pare­to, C‑parts account for 80 per­cent of the vol­ume but only 20 per­cent of the val­ue. Exam­ples of C‑parts are seals, O‑rings or plas­tic caps. 

How­ev­er, the niche exis­tence that C‑parts made of rub­ber or plas­tic lead does not only affect the design. They also enjoy only low pri­or­i­ty in the ongo­ing pro­duc­tion process. If it becomes nec­es­sary to replace a C‑part (for exam­ple, due to deliv­ery prob­lems on the part of the sup­pli­er), the new part is usu­al­ly not test­ed again for suit­abil­i­ty. Those respon­si­ble sim­ply select an alter­na­tive com­po­nent that, accord­ing to the man­u­fac­tur­er’s spec­i­fi­ca­tions, has com­pa­ra­ble prop­er­ties. The fact that a new com­po­nent may, in the worst case, not be ful­ly com­pat­i­ble with the spec­i­fi­ca­tions is often accept­ed in view of the threat of delay.

In addi­tion, C‑parts in indus­try are often select­ed based on price. Giv­en the small con­tri­bu­tion to the core prop­er­ties of the fin­ished prod­ucts, the design depart­ment likes to choose inex­pen­sive mate­ri­als to reduce over­all costs.  In places, com­pa­nies also lack the exper­tise to give rub­ber or plas­tic C‑parts the atten­tion they deserve. They under­es­ti­mate the com­plex­i­ty behind such com­po­nents and instead focus on cost. The result is that high-priced A and B parts are sup­ple­ment­ed in pro­duc­tion by cheap goods that pose a risk of dam­age to the over­all system.

This is not a crit­i­cism of pur­chas­ing or con­struc­tion. The col­leagues mere­ly act accord­ing to the spec­i­fi­ca­tions and incen­tives they receive. C‑parts are sim­ply not giv­en enough impor­tance in typ­i­cal pro­duc­tion com­pa­nies. How­ev­er, this can lead to prob­lems occur­ring or poten­tials remain­ing unused.

Plas­tic cov­er caps in var­i­ous designs and O‑rings

A fail­ure of C‑parts can cause seri­ous damage

From a finan­cial point of view, C‑parts may have lit­tle rel­e­vance. Nev­er­the­less, they are an essen­tial part of any machine or sys­tem. Dam­age to a C‑part can have seri­ous con­se­quences for the entire sys­tem, even lead­ing to its failure.

Con­sid­er, for exam­ple, a feed pump in a chem­i­cal indus­tri­al plant, a case that con­cerned Jäger a few years ago. The cus­tomer had cho­sen a shaft seal to seal the pump — a low-cost option, but one that had insuf­fi­cient chem­i­cal resis­tance. After some time, the seal became porous and chem­i­cal solu­tions leaked out. The plant had to be tem­porar­i­ly shut down, and replac­ing the pump and restart­ing it result­ed in lost pro­duc­tion and high costs. A suit­able shaft seal would have been more expen­sive than the cheap ver­sion, but would have avoid­ed the sub­se­quent costs of sys­tem damage.

Unfor­tu­nate­ly, those respon­si­ble had not paid the nec­es­sary atten­tion to the seal, a C‑part. They opt­ed for the cheap­er part and accept­ed the short­er ser­vice life of the component.

Anoth­er exam­ple: dampers are rub­ber-met­al ele­ments whose mate­ri­als are joined by a chem­i­cal bond­ing agent. If the bond­ing agent is incor­rect­ly cho­sen (for finan­cial rea­sons, for exam­ple), the damp­ing can fail after a rel­a­tive­ly short time, expos­ing the machine to harm­ful vibra­tions. The finan­cial advan­tages are thus negat­ed by a short­er ser­vice life of the products.

Poten­tial is not exploited

When deal­ing with C‑parts, most man­u­fac­tur­ing com­pa­nies focus on pro­cure­ment costs and process­es, not on opti­miza­tion. Many pro­duc­ers install C‑parts as stan­dard that have not been mod­ern­ized for years.

But mate­ri­als sci­ence is con­stant­ly evolv­ing. New elas­tomers and plas­tics are con­stant­ly com­ing onto the mar­ket that are lighter, more resis­tant, more envi­ron­men­tal­ly friend­ly or cheap­er than pre­vi­ous mate­ri­als. Replac­ing an obso­lete C‑part can have a pos­i­tive impact on the char­ac­ter­is­tics of the fin­ished prod­ucts, out­weigh­ing the cost of upgrad­ing despite the low val­ue of the material.

In some cas­es, it turns out that a C‑part is obso­lete and no longer meets the require­ments of its intend­ed use. This prob­lem can occur when a machine or sys­tem is fur­ther devel­oped with­out adapt­ing the installed C‑parts. These are then designed for con­di­tions that no longer cor­re­spond to the cur­rent status.

As a result, the prod­uct prop­er­ties are neg­a­tive­ly affect­ed, for exam­ple by a seal that becomes brit­tle more quick­ly because it comes into con­tact with media for which it was not designed. In the worst case, there is even a high­er risk of prod­uct failure.


In the rub­ber and plas­tics sec­tor, it is tempt­ing to save on the com­po­nents that make the small­est con­tri­bu­tion to the mon­e­tary val­ue of a prod­uct. How­ev­er, neglect­ing C‑parts can have neg­a­tive con­se­quences. Not only does the risk of fail­ure of the over­all sys­tem increase due to a short­er ser­vice life of some com­po­nents. The orga­ni­za­tion also leaves opti­miza­tion poten­tial lying fal­low that could sig­nif­i­cant­ly improve the prop­er­ties (and thus the per­for­mance) of the end product.

Com­pa­nies should there­fore not save at the wrong end. It is worth­while not only reduc­ing C‑parts made of rub­ber or plas­tic to their pro­cure­ment cost, but also mak­ing them a stronger focus of the design.

Rub­ber and plas­tics in mod­ern agri­cul­tur­al technology 

Learn how agri­cul­tur­al engi­neer­ing can meet most of the cur­rent challenges


Autor: Thomas Wutke

Thomas Wutke has been man­ag­ing the Jäger site in Frank­furt am Main since 2020 and was pre­vi­ous­ly respon­si­ble for anoth­er site. He has more than 35 years of expe­ri­ence in sales (KAM/B2B) of rub­ber and plas­tics as well as in project man­age­ment and appli­ca­tion development.

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