# Multistep Tightening Introduction

A multistep tightening is a tightening done in several steps. The number of steps and the type of the steps vary depending on the tightening to be done.

Often a multistep tightening is run with many tools in parallel, for example, to tighten the five bolts holding a wheel on a car. To make sure the tightening is done properly all the tools must run synchronized so they reach the same torque at roughly the same time.

To make sure this synchronization happens, the multistep program uses synchronization points. At a synchronization points each tool stop. When all of the tools have reached the synchronization point the tools continue with the next step until they reach the next synchronization point.

The number of steps between the synchronization points is flexible and could vary from 1 to 10. It is not necessary for the multistep programs running on different tools to have the same number of steps between the synchronization points. A multistep tightening program is highly configurable and the actual layout of different multistep programs can vary wildly.

Example: Multistep tightening program

Pos |
A | Step 1 and 2 engage the tool on the bolt.
B | A fast rundown is made with step 3.
C | Step 4 and 5 run the actual tightening
D | Step 6 is used to release the socket from the bolt.

Restrictions
Restrictions are used to make sure the tightening stops if something unexpected occurs. These restrictions could, for example, test that a maximum set torque is not reached or that a part of the multistep tightening does not take too long to run. Every step can have up to four restrictions each.

Monitors
Monitors are used to verify that the tightening was made according to the specification. This can be, for example, angle limits or torque limits. Every step can have up to four monitors each.

Sync mode
With sync mode it is possible to run different tightening programs on different tools at the same time. The main function of the sync mode is to define the tools that shall be included in a synchronized tightening and specify the tightening program each tool shall run.

Reject management
If something goes wrong in a tightening program the program can either do a repair or the program is terminated.

The reject management works like this, when all tools have reached a synchronization point the status of each tool and the total status is evaluated. If all channels at the synchronization point are OK the program continues with the next step. If something is NOK the program will repair or terminate according the set action.

In this Section

- Tightening Program History