JPS6247695B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a film thickness control method, which allows the thickness to be adjusted with high accuracy when forming a sheet-like polymeric material such as a plastic film, and to reduce the time required for adjustment. This is an improved version.

When a polymeric material is formed into a sheet-like material (hereinafter referred to as a film) by an extrusion film-forming method, the film extruded from an extrusion die of an extrusion molding device has uneven thickness. This thickness unevenness occurs due to the state of the polymer of the polymer material, that is, due to viscosity unevenness, and therefore occurs even if the gap interval of the extrusion die is constant. Therefore, in order to keep the film thickness constant, the film thickness is detected during actual film formation, compared with a pre-given thickness setting value, and the gap between the extrusion die is adjusted to eliminate the difference between the two. The film must be formed while

FIG. 1 shows a conventional example of an extrusion molding apparatus for forming a film by an extrusion film forming method and a control apparatus thereof. As shown in the figure, this example is comprised of a flat die I, which is one of the extrusion molding devices, and a control device. Among these, the flat die I includes a die body 2, 3 equipped with a heater 1, a chain yoke bar 5 to which a plurality of adjustment bolts 4 (only one is shown in the figure) are screwed together and can be moved up and down by rotation of the adjustment bolts 4. The die body 3 and the jaw bar 5 form an extrusion mouth metal, and the gap w therebetween is adjusted by rotating the adjustment bolt 4. In other words, in the polymer material (not shown), the gap interval w is adjusted. The film is extruded through the extrusion nozzle and formed into a film. On the other hand, the control device includes a wrench 7 that is detachably formed on the adjustment bolt 4, a bolt drive device 8 that includes a drive motor (not shown) that rotates the wrench 7, and a rotation amount detector that detects the amount of rotation of the wrench 7. The control panel 10 includes a drive motor control device, a torque detection device, and a computer.

In the conventional technology configured in this way, the thickness of the film (not shown) extruded from the flat die I is detected at multiple locations across its width, and the detected values are input to the computer of the control panel 10. be done. And on this computer,
The input detection value and the preset film thickness setting value are compared, the deviation between the two is calculated, and based on this deviation, the one to be adjusted among the plurality of adjustment bolts 4 is specified, and the adjustment is performed. The direction of rotation of the adjusting bolt 4 and the required amount of rotation thereof are determined. Next, an operation command is issued from the computer to the bolt drive device 8 via the drive motor control device of the control panel 10, and this bolt drive device 8
The adjustment bolt 4 to be adjusted is rotated, and the gap interval w is adjusted. However,
At this time, the rotation amount N of the adjustment bolt 4 and the gap interval w
There is no one-to-one relationship, and as shown in Figure 2a, there is a region (dead zone region) A in which the gap interval w does not change even when the adjusting bolt 4 rotates, and a change in the rotation amount N and the gap interval w. is not linear (nonlinear region)
There are three regions: B, and a region C (linear region) in which the rotation amount N and the gap interval w change linearly.
The dead zone area A and the nonlinear area B occur due to the large backlash provided in the adjustment bolt 4, and this backlash occurs when the rotation is smooth in the flat die I, where the temperature reaches around 250°C. The adjustment bolt 4 is positively provided so as to be carried out in the following manner. Incidentally, the amount of backlash generally reaches around 1/5 to 1 rotation, and this amount of rotation is the amount of rotation N in the dead zone area A. Further, the rotation torque T with respect to the rotation amount of the adjustment bolt 4 has a constant lower limit torque value within the dead zone area A, as shown in FIG. 2b. Therefore, the rotation detection device 9 operates only when the adjustment bolt 4 is located in the linear region C detected by measuring the rotational torque T, and the rotation amount of the adjustment bolt 4 is counted by the rotation detection device 9. The bolt drive device 8 is configured to stop when this amount of rotation reaches a required amount of rotation determined by a computer. In other words, among the rotations of the adjustment bolt 4, only the rotations in the linear region C are counted, and when the amount of rotation reaches the required amount of rotation, the rotation of the adjustment bolt 4 is stopped.
Even if the gap enters the dead zone region A or the nonlinear region B, the gap interval w can be adjusted accurately.

By the way, as shown in FIG. 3, which is a cross section taken along the line - in FIG. adjustment bolt 4
When one of the adjustment bolts is adjusted, the gap w in the part corresponding to this adjustment bolt 4 is adjusted accurately, but the gap interval w in the part corresponding to the other adjustment bolt 4 is adjusted by the adjusted adjustment bolt. 4, the gap interval w may change.

These phenomena will be explained in more detail based on FIGS. 4a to 4e. In FIG. 4, the adjustment bolts 4 are numbered from No. 1 to No. 6 in order from the left. In addition, in the same figure, L indicates the backlash of each adjustment bolt 4, the solid line with the symbol 5 conceptually indicates the position across the width direction (horizontal direction in the figure) of the jaw bar 5, and the two-dot chain line indicates the adjustment bolt 4. 4 shows the position of the jaw bar 5 when it is not pressed. Now, if we consider the case where the tire cover 5 is moved upward (indicated by the arrow in the figure) by an adjustment amount of X=X ₁ +X ₂ as shown in FIG. 4a, (a) In the state shown in FIG. .1 and No.6 adjustment bolts 4 are placed upward, No.2, No.3, No.4, No.5
The adjustment bolts 4 of
is being pressed.

(b) Then, when the No. 3 adjusting bolt 4 is rotated by _{the rotation amount x 1 corresponding} to the adjustment amount
As the No. 3 adjustment bolt 4 moves upward by _X1 , it becomes in a state where it is simply screwed into the chain yoke bar 5 without pressing the yoke bar 5. This shows that the No. 3 adjusting bolt 4 in FIG. 2 has rotated from point a to point b.

(d) When the No. 3 adjusting bolt 4 is further rotated, the jaw bar 5 is positioned in the backlash L as shown in FIG. 4c. In other words, it enters the dead zone area A. Therefore, the position of the cheeseburger 5 does not change during this time.

(e) After passing through the dead zone area A, the No. 3 adjustment bolt 4 is again screwed into the choke bar 5 as shown in FIG. 4d.

(f) From this point on, adjust No. 3 adjustment bolt 4 by the amount
When it is rotated by an amount of rotation x ₂ corresponding to X ₂ , the No. 3 adjusting bolt 4 presses the yoke bar 5 upward, as shown in FIG. 4e, and the yoke bar 5 moves upward by x ₂ . This is shown in Figure 2b.
This shows that the No. 3 adjustment bolt 4 has rotated from point c to point d.

By the way, in the state shown in FIG. 4e, the No. 3 adjustment bolt 4 presses the jaw bar 5 upward, and in the state shown in FIGS. The part that was pressed downward by the adjustment bolt 4 of .5 is now
It is located within the backlash L of No. 5 adjustment bolt 4. Therefore, although the interval of the part of the gap w corresponding to the No. 3 adjusting bolt 4 is adjusted accurately, the interval of the part corresponding to the No. 5 adjusting bolt 4 changes. Become.

SUMMARY OF THE INVENTION In view of the above-mentioned prior art, it is an object of the present invention to provide a film thickness control method that can accurately adjust the thickness of a film when forming the film and shorten the time required for this adjustment. To achieve this object, the present invention is designed to reduce the variation in film thickness when adjusting the gap interval as the adjustment bolt rotates, so that when the adjustment bolt reaches the dead zone region, the adjustment is performed within the dead zone region. The basis of the technical idea is that when starting from a region, the rotation is stopped at the end of that region to avoid unexpected deformation of the chain yoke bar.

Embodiments of the present invention will be described in detail below based on the drawings.

FIG. 5a is a graph showing the relationship between the amount of rotation of the adjustment bolt 4 and the rotational torque. As in the past, the rotational torque indicates the rotational torque of the adjustment bolt 4 itself, and in this example, the adjustment is terminated regardless of the required rotation amount when the lower limit torque value is detected on the way to providing the required rotation amount. show. FIG. 5b is a graph showing the relationship between the amount of rotation of the adjustment bolt 4 and the rotational torque. As in the past, the rotational torque indicates the rotational torque of the adjustment bolt 4 itself, and in this example, the detected torque value starts from the lower limit torque value, and when the lower limit torque value ends, it is independent of the required rotation amount. Indicates when to end adjustment. The film extruded with flat die I is
The thickness is measured at several points along the width direction, and the measured values are input into the computer of the control panel 10. The computer compares this measured value with a predetermined thickness setting value, calculates the deviation, determines the adjustment bolt 4, its rotation direction, and the required amount of rotation, and adjusts the gap between the jaw bars 5. For example, with No. 3 adjustment bolt 4 in Figure 4, x = x ₁ +
A case in which the jaw bar 5 is displaced in the direction of the arrow by a movement amount X=X ₁ +X ₂ corresponding to the required rotation amount of x ₂ will be explained based on FIG. 5a. When the adjustment bolt 4 of No. 3 is rotated by x ₁ while detecting the rotational torque, the states shown in Fig. 4a to Fig. 4b will be obtained. This corresponds to the change from point a to point b in FIG. 5a. At this time, the torque detector (not shown) detects that the dead band area A has been reached, so the above-mentioned No.
The adjustment is completed by stopping the rotation of the adjustment bolt 4 of No. 3. At this point, the coupling relationship between the adjustment bolt 4 and the jaw bar 5 is in a stable state, as shown in FIG. 4b, so that no adverse effects on the neighborhood will occur.

On the other hand, as shown in Fig. 4b or c, if the detected rotational torque value is the lower limit torque value corresponding to the dead zone area A from the beginning, as shown in Fig. 5b, the dead band area A has ended. The adjustment ends at point c. At this time, the coupling relationship between the adjustment bolt 4 and the jaw bar 5 is in a stable state as shown in FIG. 4d, and there is no adverse effect on the surrounding area.

After completing the adjustment of each adjustment bolt 4 through this process, measure the thickness in the width direction again, calculate the new deviation, determine the rotation direction and required amount of rotation in the same way as above, and perform the same adjustment. implement.

In addition, the rotational torque of the adjustment bolt 4 itself is used as the rotational torque value in the above embodiment, but the value obtained by adding the mechanical loss of the bolt drive device 8, etc. to the rotational torque of the adjustment bolt 4 itself is used as the lower limit torque value. It is also possible to do this.

As specifically explained above with the examples,
According to the present invention, when adjusting the adjustment bolt, when the adjustment bolt reaches the dead zone region, the adjustment is made at that point, and when the adjustment starts from the dead zone region, the adjustment is made at the end of that region, regardless of the required adjustment amount. Since the rotation of the bolt is stopped, the connection between the adjustment bolt and the yoke bar can be maintained in a stable state, which reduces the adjustment time required for thickness control, and at the same time ensures that the product is within the allowable value of the product film. can do.
Incidentally, Figures 6a to 6c show examples of product thickness data measured with a thickness measuring device, and show the measurement results when the data shown in Figure 6a is obtained and adjusted using the conventional method. FIG. 6b shows the measurement results when adjusted by the method of the present invention, and FIG. 6c shows the measurement results, respectively. Referring to these figures 6a to 6c, in the case where the film thickness is thin at the part indicated by the arrow shown in figure 6b, it becomes too thick and other parts become thinner, resulting in the hunting phenomenon. On the other hand, it can be seen that in the case shown in FIG. 6c, the amplitude, that is, the variation in thickness is certainly reduced.

[Brief explanation of the drawing]

Fig. 1 is a sectional view showing an extrusion molding device and its control device, Fig. 2a is a characteristic diagram showing the relationship between the gap interval w and the amount of rotation N, and Fig. 2b is a diagram showing the relationship between the rotational torque T and the amount of rotation N. FIG. 3 is a sectional view taken along the line - in FIG. 1, FIGS. 4 a to e are explanatory diagrams conceptually showing the relationship between the adjustment bolt and the shape of the jaw bar, and FIG. 6a, b are characteristic diagrams showing the relationship between rotational torque T and rotation amount N, and FIGS. 6a, b, and c are characteristic diagrams showing actual measurement data of film thickness. In the drawing, 4 is an adjustment bolt, I is an extrusion molding device,
L is the backlash, and w is the gap interval.

Claims (1)

[Claims] 1. Detecting the thickness of the sheet-like polymeric material extruded from the extrusion nozzle of an extrusion molding device in which the distance between the extrusion nozzles is adjusted by a plurality of adjustment bolts,
In a film thickness control method that compares this detected value with a pre-given thickness setting value and adjusts the thickness of the sheet-like polymeric material by rotating the adjusting bolt one revolution based on this deviation, the thickness of the adjusting bolt is adjusted. The rotational torque of the adjustment bolt is measured so that the rotational torque becomes a constant lower limit torque value within a rotational range in which the interval does not change even if the bolt is rotated. If the rotation torque reaches the lower limit torque value during the rotation of the adjustment bolt, the rotation is stopped at that point regardless of the required rotation amount, and furthermore, the rotation torque reaches the lower limit torque value from the beginning of rotation. If the rotation torque exceeds the lower limit torque value, the adjustment bolt is controlled to stop rotating regardless of the required rotation amount.