Ball screw assembly (high-load ball screw and nut assembly for electric injection moulding machines and presses, with nut cooling)

01

High-load series, shaft size and the DN limit on speed

NSK lists its HTF series of high-speed, high-load ball screws for injection moulding in four types: HTF-SRC for high speed and high loads, HTF-SRD with large leads for higher speed, HTF-SRE for large screws with shaft diameters of 140 mm or more, and HTF-SRM for heavy duty and high temperatures, with options of an S-HTF series in tougher steel, an A1 series with better sealing and long-life technology; it states the aims as maximum allowable dynamic load and maximum life through load distribution. [1]

Linear Motion Tips reports that THK's SBKH combines the high load capacity of its HBN caged ball screw with the speed of its SBK type, reaching "up to 92 m/min while carrying heavy loads", with end-cap recirculation suitable for a DN value of 130,000, shaft diameters of 83 to 120 mm, and a resin cage that separates the balls and retains grease, aimed at injection moulding machines and presses. [4]

Editorial calculation: DN is shaft diameter (strictly ball-centre diameter) in mm × speed in min⁻¹, so at DN 130,000 a 100 mm screw is limited to about 1,300 min⁻¹; reaching 92 m/min at that speed needs a lead of about 92,000 ÷ 1,300 ≈ 71 mm. The diameter is an assumed example; use the maker's ball-centre diameter and rated speed for your size. [4]

Give the ball screw maker the axis (injection, clamp, ejector, press ram), peak and mean axial load and duty cycle, stroke, speed and acceleration, required life, shaft diameter limits, lead, mounting and support bearings, lubrication method, cooling available, ambient temperature and quantity.

02

Cooling the nut instead of drilling the shaft

THK's nut-cooling ball screw has "a coolant channel inside of the nut", which keeps the screw at an optimal temperature during high-speed operation and stabilises positioning accuracy and preload torque; it notes that "even for long screw shafts, which are difficult to hollow out", the screw can be cooled through the nut, and that cooling can be built into a wide range of models irrespective of shaft diameter, recirculation system or preload method. [3]

NSK states that its nut cooling gives cooling capacity "greater or equal to existing hollow-shaft ball screws" without sliding seals or rotary joints, because piping attaches to the outer periphery of the nut flange; the preload torque does not increase when the nut is cooled, heat transfer to the table is blocked, and for its HMD nuts the mounting dimensions are unchanged so machine designs need not change. It lists injection moulding among the industries. [2]

03

Published high-load ball screw data

04

High-load ball screw order details

Paste it into your enquiry below or into an email to a maker, then replace every bracket.

Axis: [injection; clamp; ejector; press]
Load: [peak; mean; duty cycle]
Motion: [stroke; speed; acceleration]
Screw: [shaft diameter; lead; life]
Cooling: [nut; hollow shaft; none]
Mounting: [supports; lubrication]
Quantity: [assemblies]

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