Rexroth Tightening System 350 System Documentation - Rhino ...

42/316 Bosch Rexroth AG | Tightening Technology 5 Construction Guidelines5.2 Tightening system design5.1.3 Tightening case (soft – hard)Soft tightening caseHard tightening caseTightening casedeterminationaccording toISO 5393Tightening casedeterminationaccording to VDI/VDE 2647A soft tightening case exists if a relative large angle of turn 1) is needed to reach the tightening torque. Thisis always the case if elastic (or soft) materials are being tightened, e.g. elastic washers, elastomers, orseals. When creating such bolted connections, the tightening system must stand up to longer-lasting mechanicalloads.A hard tightening case exists if the end torque is reached within a small angle of turn 1) . The demand onthe tightening system here is mainly to quickly end the tightening once the tightening torque has beenreached and to avoid the spindle from slowing down (inertia of masses). Only then can the tightening processbe classified as safe.The definition of a hard or soft tightening case is set out in ISO 5393 as follows:– Hard tightening case: Increase in torque from 10% to 100% of the target torque within an angle ofturn of 27° (or from 0% to 100% within 30°).– Soft tightening case: Increase in torque from 10% to 100% of the target torque within an angle ofturn of 650° (or from 0% to 100% within 720°).The definition is set out in VDI/VDE 2647 as follows:– Hard tightening case: Increase in torque from 50% to 100% of the target torque within an angle ofturn of 30°.– Soft tightening case: Increase in torque from 50% to 100% of the target torque within an angle ofturn of 360°.The tightening case hardness is particularly relevant for selecting the speed in the last tightening step.5.1.4 Tightening processesA bolted connection should be designed so that the minimum clamping force reached guarantees thefunction of the bolted connection, but the maximum clamping force does not destroy the connection orthe bolt.The following tightening processes are available for this:– Angle-controlled tightening process– Torque-controlled tightening process– Yield-point controlled tightening process– Special tightening processes, e.g. loosening or retightening processDetailed information on this can be found in chapter “Tightening Processes” from page 201.5.2 Tightening system design5.2.1 ErgoSpin hand-held nutrunnerThis chapter describes the criteria for designing a tightening system.The ErgoSpin hand-held nutrunner is available in four different versions: SlimLine, GripLine, VarioLine,and pistolgrip nutrunner.5.2.1.1 SlimLineThe “SlimLine” hand-held nutrunner is the model for standard applications. This model consists of astandard machine and an angle head. The angle head is mechanically coded and can only be operatedon the appropriate standard machine. This results in a high level of process reliability. The efficiency ofthe angle head is stored in the nutrunner at the Murrhardt factory before delivery.1) The angle of turn seen here is the angle difference between reaching a threshold torque (10% of thenominal torque) and reaching the tightening torque (end of tightening process).System 350 | 3 608 878 040/05.2008