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Sample Case: Setting Up for 5 Stack Ups Using Single Trigger


This document describes and records an experiment for a case study of welding 5 different stacks using one single gun trigger. The user can develop a different strategy given different circumstances and given different current regulation schedule tables. There is really no single correct methodology for setting up a RAFT Weld Gun Station. The RAFT DCIT Weld Gun Station is very versatile and there are many tools to accommodate different strategies.

 

01

Document the table of the normal constant current schedules that would exist under normal circumstances where a specific weld schedule can be selected

02

Use mean force based on lowest and highest settings for gun tip pressure = (2.6 + 3.6) / 2 = 3.1 kN = 697 lbs. Calculate the % increase over the lowest ((3.1-2.6)/2.6 = 0.192) or 19.2%. This increase of force on the smallest stackup will reduce resistance.

Since weld energy is represented by the formula for Energy, a decrease of resistance may require an equivalent increase in time to maintain the target energy. In this experiment, the base schedule used for the lowest energy demanding spot weld used agressive weld schedules with limited weld time. Other users may have for the same stackup, much longer weld times. In such cases, extending weld time for the reference stackup may not be necessary.

03

Set the weld time to the least demanding energy setting multiplied by the force increase; in this case Stack #1 ; weld time is set for 179 mS (150 x 1.192). This rule was effective in this experiment since the 150mS of time in the lowest energy demanding spot weld is agressive as compared to other users' base schedules.

04

Install new weld caps on the weld gun and measure the gun resistance (Rmeasure) . If a tip dresser is used, dress the weld caps prior to taking an Rmeasure

05

Make sure that all stepper boosts are programmed to zero - but do put counts for tip dressing frequencies (request submitted at step 3)

06

Verify that the "Portable Gun Mode" function is inserted above the weld function in the weld schedule

07

From the Status Screen, turn ON Rmeasure by clicking the "R Measure is OFF" radio button

08

Verify that the weld graph resistance (in yellow) looks similar to the graph

09

Season the weld caps by making 10 - 15 welds in current regulation mode on the thinnest metal stack up and least coatings (Stack # 1)

10

Make a Reference on the target stackup (Stack #1). Adjust weld current to produce an expulsion free weld with R drop of over 30% for stackup that are bare; 15% - 25% for stackup that are coated

11

A good reference weld will produce a nugget size that meets the minimum requirement in size. Producing reference weld that has oversize nuggets will most likely produce more expulsion in all ranges of stack ups.

12

Turn on Adaptive using the function "ADAPTQ MODE = 1 RATE = 100% WSLIDE = 100%


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