JPS6247694B2 - - 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. It was planned.

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 apparatus 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, and this is compared with a pre-given thickness setting value, and the gap between the extrusion tips 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. Of these, the flat die I includes die bodies 2 and 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 these, and a retainer. The die main body 3 and the die yoke bar 5 form an extrusion mouth metal, and the gap w therebetween is adjusted by rotating the adjustment bolt 4. In other words, the polymeric material (not shown) is extruded and formed into a film through the extrusion die whose gap interval w is adjusted. On the other hand, the control device includes a wrench 7 that is detachably formed on the adjustment bolt 4 and a bolt drive device 8 that has a drive motor (not shown) that rotates the wrench 7.
and a rotation amount detector 9 that detects the amount of rotation of the wrench 7.
and a control panel 10 in which a drive motor control device, a torque detection device, and a computer are built-in.

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, which one of the plurality of adjustment bolts 4 should be adjusted is detected, and which one should be adjusted. The direction of rotation of the adjustment bolt 4 and the required amount of rotation thereof are determined. Next, from the computer to the control panel 1
An operating command is issued to the bolt drive device 8 through the drive motor control device 0, and the adjustment bolt 4 to be adjusted is rotated by the bolt drive device 8, thereby adjusting the gap interval w. At this time, the relationship between the rotation amount N of the adjusting bolt 4 and the gap interval w is not one-to-one, and as shown in FIG. )A, a region (nonlinear region) B in which changes in the amount of rotation N and gap distance w are not linear (nonlinear region), and a region (linear region) C in which changes in amount N in rotation and gap distance w are linear (linear region). The dead band area A and the nonlinear area B are caused by a large backlash provided in the adjustment bolt 4, and this backlash occurs as the temperature increases.
The adjusting bolt 4 is positively provided to ensure smooth rotation in the flat die I, which reaches temperatures of around 250°C. 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, the linear region C of the rotation of the adjustment bolt 4
Only the rotation at is counted, and the rotation of the adjustment bolt 4 is stopped when the amount of rotation reaches the required amount of rotation.As a result, even if the adjustment bolt 4 enters the dead zone region A or the nonlinear region B, the gap interval w cannot be adjusted. is done accurately.

By the way, FIG. 3 is a cross-section taken along the line - in FIG. 1, and the corresponding adjustment bolt 4 and jaw bar 5
As shown in FIGS. 4a to 4e, which show the relationship between the shape of Although w is adjusted accurately, the gap interval w in a portion corresponding to another adjusting bolt 4 may change due to the influence of the adjusted adjusting bolt 4. These phenomena will be explained in 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. Further, 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 tie yoke bar 5, and the two-dot chain line indicates the backlash of each adjustment bolt 4.
This shows the position of the jaw bar 5 when it is not pressed. Here, the jaw bar 5 is adjusted upward (indicated by the arrow in the figure) by an amount of adjustment X=X ₁ as shown in FIG. 4a.
Considering the case of moving +X ₂ , (i) In the state shown in Figure 4a, the No. 1 and No. 6 adjustment bolts 4 are upward, and the No. 2, No. 3, No. 4, and No. The adjustment bolts 4 of 5 press down on the jaw bars 5, respectively.

(ii) Then, when adjusting bolt 4 No. 3 is rotated by rotation amount X ₁ corresponding to adjustment amount X ₁ , (iii) as shown in FIG.
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.

(iv) 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, during this time, the position of the tie bar 5 does not change.

(v) After passing through the dead zone area A, the No. 3 adjusting bolt 4 comes into contact with the choke bar 5 as shown in FIG. 4d.

(vi) From this point, 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 No. in Figure 2b.
This shows that the adjusting bolt 4 of No. 3 has rotated from point c to point d.

By the way, in the state shown in FIG. 4e, due to the fact that the yoke bar 5 is pressed upward by the No. 3 adjustment bolt 4, in the state shown in FIGS. 4a to 4d, no. 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 portion of the gap w corresponding to the No. 3 adjusting bolt 4 is accurately adjusted, the interval of the portion corresponding to the No. 5 adjusting bolt 4 changes.

As a result, if the rotation amount is the required rotation amount X = X ₁ + X ₂ excluding the rotation amount in the dead zone area A, the fourth
As shown in Figure e, the coupling relationship between the No. 5 adjustment bolt 4 and the jaw bar 5 changes from a state in which it is pressed downward to a state in which the jaw bar 5 is free.

Therefore, adjusting the No. 3 adjustment bolt 4 causes an undesired change in the coupling relationship between the neighboring No. 5 adjustment bolt 4 and the chain yoke bar 5, resulting in a large change in the film thickness pattern and hunting. However, there is a risk that it will take a lot of time to converge, or the product film may exceed the allowable amount and become unusable as a product.

SUMMARY OF THE INVENTION In view of the above-mentioned prior art, an object of the present invention is to provide a film thickness control method that can accurately adjust the thickness of a film when forming the film and shortens the time required for adjustment. The configuration of the present invention that achieves this object detects the thickness of a sheet-like polymer material extruded from an extrusion die of an extrusion molding device in which the gap interval between the extrusion die is adjusted by a plurality of adjustment bolts. In the film thickness control method, the thickness of the sheet-like polymeric material is adjusted by comparing this detected value with a pre-given thickness setting value and rotating the adjusting bolt by a required amount of rotation based on this deviation. The rotational torque of the adjustment bolt is measured so that the rotational torque becomes a constant lower limit torque value over a rotation range in which the gap interval does not change even when the adjustment bolt is rotated. In normal times when there is no influence of backlash, the adjustment bolt is rotated by the required amount based on the deviation to adjust the gap interval, and when the rotational torque reaches the lower limit torque value during the rotation of the adjustment bolt, this After rotating the adjustment bolt by a certain amount of rotation less than the amount of rotation from the point in time, this rotation is stopped, and if the rotational torque has been at the lower limit torque value from the beginning of rotation, the rotational torque exceeds the lower limit torque value. It is characterized by controlling the adjustment bolt to stop rotating at a certain point.

Embodiments of the present invention will be described in detail below based on the drawings. Note that parts that are the same as those in the prior art are given the same numbers and redundant explanations will be omitted.

An embodiment of the present invention will be described with reference to FIG. 4 and FIGS. 5a and 5b. Based on the deviation calculated by comparing the film thickness detected at multiple locations across the width of the film and a preset film thickness setting amount, the No. 3 adjustment bolt 4 of the adjustment bolts 4 is moved upward. To explain the case where it is detected to move the amount of adjustment X=X ₁ +X ₂ , the following adjustment is performed depending on the state of the No. 3 adjustment bolt 4.

(i) First, when the No. 3 adjusting bolt 4 is in the state shown in Fig. 4a, first turn the No. 3 adjusting bolt 4 by a rotation amount X ₁ corresponding to _the adjustment amount Adjust the adjustment bolt 4 to the state shown in Fig. 4b. This indicates that the No. 3 adjusting bolt 4 in FIG. 5a has rotated from point a to point b.
Next, by rotating the No. 3 adjusting bolt 4 located in the backlash L by a certain rotation amount less than the backlash amount and then stopping the rotation, the No.3 adjusting bolt 4 is turned as shown in Fig. 4c. The stop adjustment is completed by moving the lever into the backlash L by a moving amount l corresponding to a constant rotation amount. This shows that the No. 3 adjusting bolt 4 in FIG. 5a has moved from point b to point e. In other words, if the No. 3 adjusting bolt 4 enters the backlash L during rotation, the No. 3 adjusting bolt 4 will be moved into the backlash L by the moving amount l, regardless of the adjustment amount X = X ₁ + X ₂ . Let it slide in and complete the adjustment. At this time, the direction in which each of the other adjustment bolts 4 presses the jaw bar 5 is the same as the state before adjustment, and each of the other adjustment bolts 4 within the gap interval w
The portion corresponding to is not changed by adjusting the No. 3 adjustment bolt 4.

(ii) Next, when the No. 3 adjusting bolt 4 is in the state shown in FIG. 4b or 4c, that is, when the No. 3 adjusting bolt 4 is located in the backlash L, the No. The adjustment bolt 4 is rotated until it reaches the state shown in FIG. 4d, and then the rotation is stopped to complete the adjustment. This indicates that the No. 3 adjusting bolt 4 has rotated from point b or e to point c in FIG. 5b. In other words, from the beginning of rotation
If the No. 3 adjustment bolt 4 is inserted into the backlash L, move it to the point just before the No. 3 adjustment bolt 4 comes out of the backlash L, regardless of the adjustment amount X = X ₁ + X ₂ . This is the end of the process. At this time, as in the case of (i) above, No.
Adjustment of the third adjustment bolt 4 does not change the portion of the gap w that corresponds to each of the other adjustment bolts 4.

After all, in this embodiment, if the adjustment bolt 4 to be adjusted enters the backlash L during rotation or is located in the backlash L from the beginning of rotation, the adjustment will be performed in each case regardless of the adjustment amount X. Accordingly, the adjustment ends midway through. When the adjustment of the predetermined adjustment bolt 4 to be adjusted is completed, the thickness of the film is detected at multiple locations across the width direction, the adjustment bolt 4 to be adjusted is determined based on this, and the adjustment bolt 4 to be adjusted again is determined. Make adjustments. Note that, in order to determine whether or not the adjustment bolt 4 has entered the backlash L, it is detected by measuring the rotational torque T of the adjustment bolt 4, as in the conventional case.

FIGS. 6a, 6b, and 6c show actual measurement data for film thickness control controlled by the conventional technique and this embodiment. 6A shows the state of the film before the control, FIG. 6B shows the state of the film controlled by the conventional technique, and FIG. 6C shows the state of the film controlled by the present embodiment. From these figures, it can be seen that in the prior art, a hunting phenomenon occurs in which thinner portions of the film become too thick after control, and thicker portions conversely become too thin. On the other hand, in this example, it can be seen that the film thickness approaches a predetermined value.

As specifically explained above in conjunction with the embodiments, according to the present invention, when the adjusting bolt enters the backlash during rotation, the adjusting bolt is rotated by a certain amount of rotation from this point and then stopped, and the rotation is stopped. When the adjustment bolt is located in the backlash from the beginning, the adjustment bolt is rotated until just before it leaves the backlash, so even if the adjustment bolt is adjusted, other adjustment bolts will not be affected The corresponding gap spacing remains unchanged. As a result, hunting does not occur, the adjustment time required for thickness control can be reduced, and the film thickness falls within the allowable value, making it possible to produce a high-quality film with uniform thickness.

[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 conceptual diagrams showing the relationship between the adjustment bolt and the shape of the jaw bar, and FIGS. 5 a, b 6 is a characteristic diagram 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, l is the constant rotation amount, 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 polymer material by rotating the adjusting bolt a required amount of rotation based on this deviation, the thickness of the adjusting bolt is The rotational torque of the adjustment bolt is measured so that the rotational torque becomes a constant lower limit torque value over a rotation range in which the above-mentioned interval does not change even if the bolt is rotated. In normal times when there is no influence of backlash, the adjustment bolt is rotated by the required amount based on the deviation to adjust the interval, and if the rotational torque reaches the lower limit torque value during the rotation of the adjustment bolt, From this point on, the adjustment bolt is rotated by a certain amount of rotation, which is less than the amount of rotation, and then this rotation is stopped. Furthermore, if the rotational torque has been at the lower limit torque value from the beginning of rotation, the rotational torque exceeds the lower limit torque value. A film thickness control method characterized by controlling the rotation of an adjustment bolt to be stopped when the adjustment bolt is reached.