Challenge/Solution Case Study: Reducing Maintenance Costs and Downtime by the Redesign of an Extruder Drive Stand for Ceramics Manufacturer

Nestor Rentas Challenge/Solution Case Studies


The design for a new drive stand arrangement reduced downtime on the primary clay extruder, ultimately decreasing maintenance costs and improving overall efficiency.


The client’s primary clay extruder was plagued by routine maintenance problems associated with the drive system, shafts, and bearing arrangement, resulting in significant maintenance costs and downtime. The equipment was custom designed and manufactured in Japan, so working through a re-design with the OEM was not practical or cost effective.


The extruder has two independently driven shafts. The top, or pug mill shaft, feeds clay into a vacuum box and into the bottom shaft which actually extrudes the clay into dies that produce various size cylinders. The bottom shaft is driven from a reducer by a large spur gear. The shaft is restrained radially in plain bearings and axially by a ball-type thrust bearing.

The radial loads imparted by the spur gear produce significant wear on the plain bearings causing run-out of the shaft at the thrust bearing. This results in premature failure of the thrust bearing.

EFI Group developed the basic design of a new drive stand arrangement in order to eliminate the spur gear and drive the bottom shaft directly. This re-design incorporated a new bottom shaft reducer and reconfiguration of the top shaft drive arrangement to implement a jack shaft and couplings which allow for proper maintenance access to both motors and both reducers.

EFI Group also analyzed the bearing loads and worked with bearing manufacturers to determine a new arrangement for the bottom shaft that uses tapered roller bearings instead of the existing combination of brass plain bearings and thrust bearings.

Additionally, EFI Group evaluated stresses on the extruder shafts and determined changes needed for the new shafts.


  • General arrangement drawings of the new drive system.
  • Selection of a new reducer and the required shaft couplings.
  • Analysis and recommendations for a new bearing configuration to improve maintenance reliability.
  • Detailed design of the new drive stand, new shafts and bearing mounts.

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