Calculation of The Motion of Electrode of Resistance Spot Welder Operated Through Compressed Air
1964 Volume 33 Issue 4 Pages 393-398
Details
1964 Volume 33 Issue 4 Pages 393-398
The variation of air pressures P1, P2 of the parts (1), (2) of the cylinder of a spot welder operated through compressed air, as well as the velocity ν and displacement z1 of the piston are calculated under the assumption that the pressure of the air source is maintained constant at the value PH at the inlet (1), Fig. 1.
The results are shown in Figs. 2-5 and in Table 1, in which Fig. 2 is the case when the effect of moving mass M is assumed to be zero and Fig. 6 is the case when the gravity effect is taken into consideration.
With the time constant Ta2 as defined in equ. (1), variations of P1, P2, v and z1 are related to time t in dimensionless forms as shown in the figures, the parameters being the dimensionless acceleration (equ. (9)), and the ratio of the effective sectional areas S1. S2 of air circuits (1), (2). The boundary conditions are shown in the figures, V10 being the initial volume of (1) and V0 the sum of volume of (1) and (2) : V0=V1+V2=V10+ V20.
When the piston moves at the velocity ν0 as defined in equ. 5, the pressure P2 does not vary, and the air in (2) is discharged through S2 at sound velocity (See equ. (7)). This velocity is taken as the denominator of the dimensionless velocity.
It is interesting to note that the accelerating force, which is proportional to (P1-P2) or (γ1-γ2) in dimensionless expression, decreases when J (or M) is decreased, and the time tm required for the piston to reach the bottom (i.e. V1=V0, z1=z0) varies only in small range even when j (or M) is changed in wider range.
Calculation was made by the step-by-step method, i.e. dγ1, dγ2, dν/ν0, dz1/z0 corresponding to dt/ Ta2 were calculated from equ. (11), (12) and (18).
It is assumed that equation (6) holds true for the whole range of P2.
