Cylindrical Die Rolling Process
Cylindrical Die Rolling
Cylindrical die rolling is a metal forming process used to form screw threads and other helical, axial, and annular geometries on products such as fasteners, power transmission shafts, and precision lead screws. The rolled profile geometry is formed into the surface of a round blank by two or three round forming dies which have the inverse of the rolled profile on their surface. The dies rotate in phased relationship while they simultaneously penetrate the surface of the blank and force it to rotate by friction. The blank material is displaced radially into the precise shape of the dies by plastic deformation.
Material is not added or removed during the rolling process which can take just a few seconds to complete. Compared to traditional cutting processes, rolling can result in 20% material savings and can be more than 10X faster. The speed of roll-forming is generally governed by the ability to transfer energy through the dies and into the blank to deform the material.
Cylindrical die rolling is commonly applied to parts having pre-roll hardness up to the mid-30’s Rockwell C but can also be applied to parts with pre-roll hardness up to and exceeding Rockwell C 48. However, die life becomes very poor in this high hardness range. Rolling is typically carried out as a cold forming process with blanks at room temperature, but high hardness blanks can be rolled at elevated temperatures as a warm-forming process to help improve the metal flow.
Cylindrical die rolling is used to produce a variety of precision forms such as threads, worms, gears, splines, knurls, fins, and modified thread forms like ball screws and lead screws. It is well suited for processing precision parts with tight dimensional tolerances and statistical process control requirements.
Benefits of Cylindrical Die Rolling
Infeed Rolling, also known as plunge rolling, is used to produce discrete lengths of rolled geometry by plunging the dies into the blank at controlled speed and then retracting them when the form is fully rolled. The dies and part are aligned on parallel axes to each other which results in little to no axial feed of the workpiece during rolling. When the dies have reached full penetration depth, they are held in fixed dwell position long enough to calibrate the roundness and fullness of the rolled form before being retracted.
The working face of the dies must be as long or slightly longer than the length of thread or form being rolled. The face width will also depend on the shape and configuration of the blank. Infeed rolling minimizes incomplete or under filled rolled geometry which typically occurs at the extreme ends of the rolled form. The area of under fill will be governed by the die edge chamfers or the blank chamfers. Infeed rolling allows threads and forms to be rolled very close to protruding features such as shoulders or heads with minimal cycle time.
Two-Die Infeed Rolling
Three-Die Infeed Rolling
Two-Die Throughfeed Rolling
Three-Die Througheed Rolling
Single Revolution Rolling
Superior Cylindrical Die Rolling for Demanding Applications
Power Tool Shafts
Electric Motor Shafts
Precision Ball Screws
Nuclear Studs & Tie Rods
Turbine Disc Bolts
Oil Field Components
Mine Roof Bolts
Turbine Case Studs
Tower Constraint Rods