The present invention generally relates to a part mounting process in the manufacture of electrical or electronic equipment, and more particularly, to a part mounting method for mounting electronic parts, etc. on a printed circuit board or the like.
Recently, as the automation of factory facilities proceeds, with a simultaneous requirement for higher productivity, the part mounting method as referred to above is required to be provided with higher performance and function for improved efficiency.
Referring to FIGS. 3 to 5, one example of conventional electronic part mounting methods will be described hereinafter.
In FIG. 3, there is shown an electronic part mounting machine provided with a part supplying mechanism of a circulation moving type, which generally includes a part holding member mounting ring 1, a plurality of part holding members 2 mounted on said mounting ring 1, a plurality of part supply cassettes 3 disposed around the mounting ring 1, and part inserting heads 4a and 4b (referred to merely as a head means hereinafter) for inserting the electronic parts on a circuit board (not shown). The part mounting machine further includes a main control panel 5 (referred to as a control panel hereinafter) having a keyboard, a control unit 6 for controlling the entire processing of the part mounting method, and an X-Y table 7 as shown.
In FIG. 4 showing a flow-chart for a conventional electronic part mounting method, step N1 is a supplying step in which the electronic part is supplied from the part supply cassette 3 to the part holding member 2 for displacement up to the position of the head means 4, while step N2 is a mounting step in which the electronic part is discharged from the part holding member 2 to the head means for mounting the part on a printed circuit board.
FIGS. 5(a) to 5(d) are schematic diagrams of the circulation moving type part supplying mechanism for explaining the conventional part mounting method, in which FIG. 5(a) represents the state before supplying the electronic part from the part supply cassette 3 to the part holding member 2, FIG. 5(b) denotes the state in which the electronic part A is supplied from the part supply cassette 3a to the part holding member 2a, FIG. 5(c) shows the state where the electronic part B is supplied from the part supply cassette 3b to the part holding member 2b, while simultaneously, the electronic part C is fed from the part supply cassette 3c to the part holding member 2c, and FIG. 5(d) indicates the state in which the part holding member 2a is displaced to the position of the head means 4.
With respect to the conventional part mounting method based on the arrangement as described above, the functioning thereof will be described hereinafter.
If attention is directed to one of the part holding members, after starting, the electronic part is fed to the part holding member 2 at the supplying process of step N1 in FIG. 4 and the part holding member 2 is then displaced up to the position of the head means 4, while at the mounting process of step N2, the electronic part is discharged onto the head means 4 from the part holding member 2 so as to be mounted on a printed circuit board. The empty part holding member 2 not holding any electronic part is subsequently moved up to the position of the part supply cassette 3 so as to be again supplied with another electronic part. In the steps of steps N1 and N2 in FIG. 4 as described above, the state of the part holding member is not particularly checked, and the electronic part is supplied or discharged unconditionally.
The conventional electronic part mounting method as referred to above will be explained hereinbelow for a more specific example with reference to a part supplying mechanism of a circulation moving type.
It is to be noted here that, for mounting the electronic parts on a printed circuit board in the order of the parts A, B and C, such parts must be arranged in the order of A, B and C at the position of the head means, and what effects such arrangement is the circulation moving type part supplying mechanism.
In the case where the part holding members 2a, 2b and 2c are set to receive the electronic parts A, B and C as in FIG. 5(a), the electronic part A is supplied when the part holding member 2a has arrived at the position of the part supply cassette 3a. Upon further rotation of the part holding member mounting ring 1 in a direction indicated by an arrow, when the part holding member 2b has reached the position of the part supply cassette 3b as shown in FIG. 5(c), the electronic part B is supplied. When the part holding member 2c has arrived at the position of the part supply cassette 3c simultaneously as in FIG. 5(c), the electronic part C is also supplied at this time. Then, the electronic parts are arranged in the order of A, B and C as shown in FIG. 5(d) so as to be fed to the head means 4 in that order, and the head means 4 mounts said parts onto a printed circuit board (not particularly shown).
In the conventional part mounting method as described so far, however, there have been such disadvantages that, if even one of the part holding members should become out of order, such a faulty part holding member drops the holding part, or even if it holds the part somehow, the part can not be correctly mounted at the mounting process, and thus, the mounting rate is undesirably lowered, with a simultaneous reduction in the working efficiency, since a processing machine had to be stopped until completion of replacement of the faulty part holding member.