GB2108894A

GB2108894A - Compression moulding reinforced plastics sheet

Info

Publication number: GB2108894A
Application number: GB08227290A
Authority: GB
Inventors: Shigeru Masuda; Masatami Fukuda
Original assignee: Kawasaki Yucoh Co Ltd; Kawasaki Hydromechanics Corp
Current assignee: Kawasaki Yucoh Co Ltd; Kawasaki Hydromechanics Corp
Priority date: 1981-09-26
Filing date: 1982-09-24
Publication date: 1983-05-25
Also published as: JPS6330845B2; DE3234592C2; AU540133B2; JPS5871124A; FR2513563B1; AU8800482A; DE3234592A1; GB2108894B; FR2513563A1

Abstract

Reinforced plastics sheet is compression moulded by transferring mould parts (42, 48) between a main press (10) and auxiliary presses (12, 14). The main press (10) is of large press power and short stroke. The auxiliary presses (12, 14) are of small power and long stroke. In operation, first in the auxiliary press the sheet is charged to the open mould (18) and the mould (18) closed. Then, the mould (18) is transferred to the main press (10) and the sheet compressed and cured. Next, the mould is moved from the main press to the auxiliary press to remove the moulded sheet. This method can be applied to mass production of automobile parts. <IMAGE>

Description

SPECIFICATION Method for producing sheet moulding compound parts by compressing This invention relates to a method for producing sheet moulding compound hereinafter referred to as (SMC) parts such as parts of automobiles or the like by compressing.

SMC sheets, which are thermosetting plastics reinforced with composite materials, such as unsaturated polyester resins reinforced with glass fibre, have been recently applied to parts of automobiles or the like instead of metal sheets.

Heretofore, the SMC parts have been produced by conventional hydraulic press systems, and their typical operational stroke and time diagram is as shown in Figure 1 of the accompanying drawings.

The process consists of the successive steps of charging a SMC sheet A, closing a mould B, gelling or softening the SMC sheet, flowing and filling the SMC sheet into the mould cavity C, compressing and curing the SMC sheet D, opening the mould E, and removing the formed SMC part F. The cycle is then repeated. When the SMC parts are used as parts of automobiles or the like, they serve to reduce the assembling processes and lighten weights, and the like, but they necessitate long cycle times for producing parts. Various researches have been tried to shorten the cycle time, but the special property of the SMC materials such as curing of the chemical reactions made it impossible to shorten the cycle time by any significant amount.

The present inventors have analyzed the above cycle time diagram for overcoming these shortcomings. It was found that the compressing and curing times occupy somewhat more than one half of the cycle time and the rest is occupied for the pressless operations such as charging the SMC sheet, closing and opening the mould, and the like. Consequently, the effection forming efficiency is not high. In addition, in the compressing and curing of the SMC sheets a predetermined large press power is needed, but in the pressless processes the operations can be sufficiently performed by a much smaller power than the compressing power without requiring such a large force. Furthermore, as shown in Figure 1, in the compressing and curing the operation can be performed within an extremely short stroke, but in the pressless operation a long stroke is required.It follows that the conventional SMC compression systems were uneconomically constructed and of low production rate.

The SMC material is heated to be gelled or softened, compressed to be flowable and filled into the mould cavity, and is then further compressed and heated to be cured and formed into a desired shape within the mould cavity. In the forming process, the curing process is much longer than the others. This is the most serious shortcoming for lengthening the cycle time of the conventional SMC compression moulding method.

Accordingly, if the compressing and curing operation and the other, pressless, operations such as opening the mould, charging the SMC sheet into the mould, closing the mould, gelling the SMC sheet and flowing and filling the SMC sheet into the mould cavity and the like, are separated, and the pressless operations are performed during compressing and curing the SMC sheet, the product rate can be duplicated.

An object of the present invention is to provide a novel and useful method for producing SMC parts economically by compressing.

Another object of the invention is to provide a method for producing SMC parts by compressing, which can be produced SMC parts at high production rate such as double productivity of conventional methods, without raising the cost of the system in proportion to the productivity.

According to the invention, there is provided a method for producing SMC parts by compressing, which comprises: separating the operations of forming SMC parts into a compressing and curing operation for forming a SMC sheet into a desired shape in a mould device and pressless operations including charging the SMC sheet in the mould, during closing and opening the mould, performing said compressing and curing operation in a main press equipment which is compactly constructed of predetermined large press power and short stroke, performing said pressless operations in the auxiliary press equipment which is simply constructed of predetermined small power and long stroke, and connecting said operations by transferring the moulds from the main press equipment to the auxiliary press equipment, vice versa.

The invention will be further described with reference to the accompanying drawings, in which: Figure 1 illustrates a typical conventional cycle time diagram for forming SMC parts; Figure 2 is a schematic fragmentary sectional side view of an embodiment of an apparatus for carrying out the invention; and Figures 3 to 5 a respectively schematic fragmentary sectional side views illustrates each successive step of forming SMC parts in the embodiment of Figure 2.

The invention is now described in the following with referring to an embodiment of the invention.

Figure 2 shows an exemplary embodiment of a preferred system of the invention, which comprises a main press equipment 10 and two auxiliary press equipments 12, 14, two transfer devices (not shown), and associated parts. The main equipment 10 is compactly constructed of predetermined large press power and short stroke, and used for compressing and curing a SMC sheet 16 in a mould device 18. It has a predetermined large press and short stroke hydraulic cylinder 20 on an upper frame 22, and is provided with a moving platen 24 between uprights 26. The platen 24 is arranged to be moved slidably in the vertical direction against the lower frame 28 by the cylinder 20 according to a servo control system (not shown) or the like.Between the platen 24 and the lower frame 28 is placed the mould device 18 which has been closed by lowering to a predetermined height in the auxiliary equipment 12 or 14. In the mould device 18 the SMC sheet 16 is compressed into the mould cavity 30 to be formed to a desired shape. The auxiliary equipments 12, 14 are symmetrically constructed to the main equipment 10 and arranged transversely of the main equipment 10.

They are simply constructed of predetermined small power and long stroke, and used for pressless operations such as charging the SMC sheet 16 in the mould device 18, closing and opening the mould device 18, flowing and filling the SMC sheet 16 into the mould cavity 30 and removing the formed SMC part 32 of the like. On the lower frame member 40, they are respectively provided with a plurality of predetermined small power and long stroke lift cylinders 34, 36 for moving a beamed upper frame member 38.The upper mould half 42 is demountably secured to said beamed upper frame member 38 by clamping devices 44, 46 and is suitably moved in the vertical direction by the lift cylinders 34, 36. The lower mould half 48 is securely mounted on a bolster 50 and arranged so as to be placed to a predetermined position on the lower frame member 40 or lower frame 28. The bolster 50 is respectively arranged reciprocably to traverse between the main equipment 10 and auxiliary equipments 12, 14 by each of transfer devices such as hydraulic cylinders or the like, and the mould device 18, coupled by closing the removed upper mould 42 onto the lower mould 48, is suitably carried between them according to the schedules.The mould 18 is suitable constructed, not shown, so as to maintain the SMC sheet 16 at a suitable temperature depending upon conditions by circulating heating medium, such as steam or oil or the like. Reference numeral 52 shows traverse rails for the transfer devices. Description with respect to structures such as temperature control members for the moving platen, guiding members and reinforcement members against eccentric load, and the like are omitted, in accordance with normal practice in the art.

The forming operation is described below with reference to Figure 3 to Figure 5.

At first, as shown in Figure 3 a suitable size SMC sheet 16 is charged onto the lower mould 48 in the auxiliary press equipment 12, in which the upper mould 42 has been raised to the predetermined height by the lift cylinders 34, 36.

When the upper mould 42 is rapidly lowered against the lower mould 48 by simultaneously actuating the lift cylinders 34, 36, and the upper mould 42 is smoothly put onto the SMC sheet 16 so as to lightly press it as shown in Figure 4, the SMC sheet 16 is caused to flow into and fill the mould cavity 30. If necessary, levelling devices (not shown) may be used. As the upper mould 42 and the lower mould 48 are heated as above mentioned, the SMC sheet 16 is softened and fluidized, it can be flowed and filled to the mould cavity 30 by the loads as small as the weights of the upper mould 42 and upper frame member 38.

Therefore, the auxiliary equipments, 12, 14 are enough of a small power and simple structure. The flowing and filling of the SMC sheet 16 is performed by strict rules, but abbreviated. During the time, in the main press equipment 10 the SMC sheet 16 in the mould 18, which has been closed in the another auxiliary equipment 14 as above mentioned, is compressed and cured by the large power cylinder 20 to be formed into a desired shape, as shown in Figure 3. As the main equipment 10 is used merely for compressing and curing the SMC sheet 16 in the closed mould 18, it can be sufficiently performed by the large press power and short stroke hydraulic cylinder 20 without the long stroke and large power cylinder such as conventional systems. Consequently, it is not required a sufficient stiff and large size structure as before, and it can be compactly and economically constructed.When the SMC sheet 16 is completely compressed and cured, the platen 24 is raised. And, as shown in Figure 5, the mould 18 is carried out to the auxiliary equipment 14 by the transfer device, and simultaneously the another mould 18, which has been closed in the auxiliary equipment 12 as above described, is carried into the main equipment 10 by the another transfer device. In the main equipment 10, the SMC sheet 16 is compressed and cured likewise as above mentioned. On the other hand, in the auxiliary equipment 14 the lift cylinders 34, 36 are lowered and the clamping device 44, 46 clamp the upper mould 42 to fix beneath the upper frame member 38, and the upper mould 42 is raised to the predetermined height. Then, the formed SMC part 32 is knocked out by a discharge device (not shown) and removed from the mould 18, and next SMC sheet is charged onto the opened mould 18.

In this manner, by being interchangeably transferred between the main equipment 10 and auxiliary equipments 12, 1 4, the SMC sheets are formed into the desired configuration and dimensions, in turn.

Accordingly, as the compressing and curing operation is performed in the main equipment and the other pressless operations are performed in the auxiliary equipments at the same time, the SMC forming cycle time can be reduced to approximately one half of the previous cycle time, depending on the materials or forming dimensions or the like. And, since the flowing and filling of the SMC sheet into the mould cavity may be performed within the time in the main equipment, flowable materials can be used easily to flow and fill into all the corners of the mould cavity.

Furthermore, although the cycle time can be reduced to approximately a half of the former to double the productivity, the system can be decreased in cost, without raising the cost in proportion to the productivity, because of the simplification as described. In addition. the small volume of the main press cylinder causes the compressibility of the hydraulic oil to be less and to improve the response, positioning accuracy, pressure controlling accuracy, and the product quality. These advances accrue from the avoidance of a system requiring both large press power and long stroke.

In the embodiment, as the moulds may be respectively designed to form the SMC sheet into different shapes, they can be easily managed in the uses for such as automobiles parts in which symmetrical parts are plentifully used.

In the above embodiments, the moulds are carried simultaneously between the main equipment and auxiliary equipments, but the moulds may be carried respectively according to the schedules. And, they may be designed to be transferred by using well known quick die changers or the like. Furthermore, in the plant where a plurality of the main press equipments and auxiliary press equipments are arranged, the moulds handling system may be provided to deliver the moulds to them according to the computer control system. Furthermore, the above system may be easily designed to be produced a plurality of the SMC parts at once.

The press equipment is described as an hydraulically operated press, but the invention may be suitably applied to the mechanically operated or other presses.

While the invention has been illustrated and described as embodied in the press equipments, it is not intended to be limited to the details shown since various modifications and structural changes may be made without departing in any way from the scope of the present invention.

Claims

1. A method for producing SMC parts by compressing which comprises: separating the operations of forming SMC parts into a compressing and curing operation for forming a SMC sheet into a desired shape in a mould device and pressless operations including charging the SMC sheet in the mould device, closing and opening the mould; performing said compressing and curing operation in a main press equipment which is compactly constructed of predetermined large press power and short stroke; performing said pressless operations in the auxiliary press equipment which is simply constructed of predetermined small power and long stroke; and connecting said operations by transferring the moulds from the main press equipment to the auxiliary press equipment, and vice versa.

2. A method as claimed in claim 1, wherein at first said SMC sheet is charged into the mould and the mould is closed in the auxiliary press equipment, then the moulds charged with the SMC sheet is transferred to the main press equipment to form the SMC sheet into a desired shape, and next the mould and the formed SMC part is transferred again to the auxiliary press equipment to open the mould and remove the SMC part from the mould.

3. A method as claimed in claim 1 or 2, wherein a plurality of the auxiliary press equipments are arranged across the main press equipment, transfer devices are arranged between them, the mould in which the SMC part compressed and cured in the main press equipment is charged is transferred to the auxiliary press equipment by the transfer device, and simultaneously another mould which is closed after charging the SMC sheet in the another auxiliary press equipment is transferred to the main press equipment by another transfer device.

4. A method for producing SMC parts by compressing substantially as hereinbefore described with reference to figures 2 to 5 of the accompanying drawings.