Screw-joint Analysis

Safety for accurate tightening parameter, sequences and tools

Processing reliability right from the start – due to a comprehensive screw joint analysis during which our experts put your specific screw joint to the test.

Your advantages:

  • Identification of optimal processing parameters
  • Processing reliability right from the start
  • Analysis of seating conditions
  • Recommendations of suitable screwdriving procedures

Frequently asked questions:

  • Which is the ideal torque for my application?
  • What speed should I choose?
  • What tool best fulfils my requirements?

Torque measurement and screw joint analysis, in conjunction with our measurement electronic, satisfy the highest processing specifications and are an essential part of optimal quality assurance.

Analysis of the screw connection is conducted by performing assemblies on an original component. The significant screwdriving process parameters, such as rolling torque, seating point and over-torque are determined using graphic records. In order to ascertain the way in which a component should ideally be assembled, the component must be subjected to assembly using a higher torque than normal until the joint or component itself is destroyed. In this way the over-torque is determined. This experiment is conducted ten to twenty times using original components.

Friction losses:
Friction is generated as the screw is assembled. However, it is dependent on the screw geometry and component material. This friction changes the relationship between torque and obtained preload force and is one of the great unknowns when determining a suitable tightening parameter. The technician loosens the assembled screw and then retightens it. By comparing the torque curve progression of the first and second processes, possible frictional losses can be detected.

Analysis of seating conditions:
Seating conditions can also be detected, for example if a silicone seal is attached to a pump with four screws. Even if the tightening torque is expected to produce 100 percent pre-load force, this can gradually diminish due to the seating characteristics of the silicone. The result: the pump is no longer sealed.

When analysing such a soft joint, the technician first tightens the screw to the established tightening torque and then tightens again after a certain amount of time. The prevail torque reveals the seating conditions and their effect on the pre-load force. In such a case we may recommend carrying out screw assembly in two phases.

Application-specific characteristics:

If, for example, two sheets of metal should be screwed together but their bore holes are not identical, initially a great deal of force is needed to position the holes correctly over one another. If the holes are situated one above the other at the end of the screwdriving process a low torque will be sufficient for final tightening. However, if assembling with constant high torque on such a task the destructive overload torque would be reached and would destroy the screw or component. A screw joint analysis would recognise this issue and reliable parameters and sequences could be determined to prevent the problem.

At the end of a series of comprehensive tests and precise analysis, the manufacturer receives recommendations of suitable screwdriving parameters and tools to fit their specific screwdriving task.

We offer either standard or specialized analysis.

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The screw joint analysis can identify a suitable screwdriving procedure and determine the optimal shut-off torque of the screwdriving tool. Parts for assembly are positioned in an almost identical replication of the assembly conditions. Next a screw is assembled with the screwdriver using a higher torque than reasonably expected so that the assembly is overloaded and fails. The torque, screwdriving time and angle are recorded and saved for this procedure. The torque curve progression can be used to analyse the assembly and to determine optimal processing parameters for the assembly screwdriver.

The standard screw joint analysis includes:

  • Examination of ONE screwdriving application for ONE specific screw on the customer’s component
  • Screw assembly of up to max. 10 screw locations until destruction, each graphically recorded
  • Documentation of assembly torques and destructive torques in the form of a table
  • Creation of a report (including torque recommendation), as a PDF document in German (as standard) or English (please specify when ordering)

Product Details

The specialized screw joint analysis is an expansion of the standard version and includes additional investigations and services relating to the customer-specific application.

The specialized screw joint analysis includes e.g.:

  • Examination of SEVERAL screwdriving applications and/or INDIVIDUAL screwdriving applications with more than 10 screw locations for VARIOUS specific screws on the customer’s component
  • Screw assembly until destruction, each graphically recorded
  • Identification of optimal processing parameters, such as screwdriving time, speed, torque or angle as control or monitoring variables
  • Recommendation for selection of drive type (electric or pneumatic) based on your specific processing requirements (torque accuracy, documentation requirements, etc.)
  • Recommendation for determining tightening strategy (torque assembly, friction-dependent assembly, DEPRAG Clamp Force Control, etc.)
  • Creation of an application-specific screwdriving program
  • Identification of seating conditions: By continuing to tighten a joint which has already been assembled to target torque the true assembly result can be assessed to optimise the screwdriving process
  • Creation of a report as PDF document in German (as standard) or English (please specify when ordering)

Product Details

Additional Information on our screw-joint analysis can be found in our Product Catalog Services D 3330.