Patent Application
20220339894
The present disclosure relates to a method of forming a device of composite material, to a pattern for a composite device, and to a device of composite material during which method inserts and/or functional components are inherently embedded into the pattern and/or the device.
Conventional composite materials are frequently used to form devices, also known as composites, that are light weight and have a high strength, to replace metal devices, such as vehicle panels, device housings etc.
Conventional composites are further used to form lightweight stable parts, e.g. in vehicles, sports equipment, electronic applications, robotics, composite installations, tools etc., where they are used to form panels, frames, interior components, housings etc.
It has been found that during the formation of such devices it is very difficult to embed functional components into the devices during their manufacture, specifically functional components with tight tolerances or components that are aligned relative to one another. This can for example be particularly relevant during the manufacture of vehicle panels, components for robots, tools and electronic applications.
For this reason, it is an object of the present disclosure to disclose a method of manufacturing devices and devices having functional components embedded therein. It is a further object to disclose a device in which the functional components embedded therein are aligned relative to one another. It is yet a further object of the disclosure to disclose a comparatively low-cost method of manufacture of such components.
This object is satisfied by a method of forming a device of composite material having the features disclosed herein.
Such a method comprises the steps of:
The use of patterns to form parts of a mold of a composite is well known, to produce composites with clearly defined internal structures. The general idea underlying embodiments of the present invention is to embed inserts forming either the functional components or supports for the functional component directly in the removable pattern at pre-defined positions, so that these can be embedded in the composite device at the pre-defined positions. In this way also complex housing structures can be formed. The use of patterns thereby makes available a cost-efficient manufacture of composites.
In this connection the support for the functional component can be a negative shape of the functional component and can comprise undercuts recesses or the like used to connect the functional component to the composite.
The step of holding can comprise holding the inserts through the application of vacuum, the use of sliders, functional elements and/or the use of magnets. In this way the inserts can be held in a simple and highly reproducible way.
The inserts can comprise at least one of magnetic material and metal. Such inserts can be held in an expedient way in the mold for the pattern.
The insert can be shaped to form a functional component or can be formed by a functional component of the device, i.e is a functional component. In this way either a functional component or a support for the functional component can be directly embedded in the pattern and can later on be included in the device either directly or at the support formed by the insert.
The pattern of removable material can be produced in an injection molding process or a wax casting process. Such processes enable a swift and cost-effective manufacture of patterns.
The removable material is introduced into the cavity in liquid form. In this way one can ensure that the complete inner surface of the mold is covered with the removable material to produce the desired outer shape of the pattern.
The step of introducing the removable material into the mold can comprise filling between 40 and 99% of the cavity with liquid removable material. In this way shrinkage effects at the outer surface of the pattern can be minimized.
The method can further comprise the step of: introducing gas into the removable material present in the mold and pressurizing the removable material present in the mold with a pressure difference between an outside of the formed pattern and a hollow space within the pattern selected in the range of 0.02 to 20 bar. In this way shrinkage effects at the outer surface of the pattern can be even further minimized.
The method can further comprise the step of: applying a pressure selected in the range of 0.02 to 0.95 bar, in particular 0.05 to 0.5 bar in the cavity prior to the introduction of the removable material into the cavity. In this way a pattern can be expediently formed having an outer surface that is at least substantially free of defects.
The method can further comprise the step of: moving the mold to completely coat the inner surface of the mold with the removable material in liquid form; and solidifying the removable material in the mold. Due to the centrifugal force respectively gravity acting on the removable material one can further prevent shrinkage effects at a surface of the pattern and thereby obtain a pattern in which the inserts have been reliably placed at the pre-defined position at the outer surface of the pattern for forming a functional component at the pre-defined position at the inner surface of a device.
The method can further comprise the step of covering the pattern having the inserts with one or more layers of webs of fiber material, By covering the pattern with the one or more layers of webs of fiber material a composite device having an inner shape corresponding to the outer shape of the pattern can be formed.
In this connection it should be noted that the pattern can be used as part of a mold for a so-called resin transfer molding (RTM) process. In this embodiment, the mold can then be covered with roving following which it can be inserted into a further mold for the addition of resin and heat treatment to form the final device of composite mated al in a manner known per se.
In this connection it should be noted that each web of fiber material can be a layer of fabric made from woven fibers that are made by interlacing two or more tows of fibers at right angles to one another. Additionally, or alternatively the web of fiber material can be formed by a tow of fibers. In this connection a tow of fibers is a bunch of fibers like a yarn.
In this connection it should further be noted that tows of fibers can be applied at the positions of the inserts to reinforce the inserts in the completed device, whereas woven fabric can be introduced on areas representing an inner and/or outer surface of the device.
The one or more layers of fiber material can comprise carbon fibers, glass fibers, basalt fibers, natural fibers, such as wood fibers, and hemp fibers, aramid fibers, polyester fibers, in dry condition or as prepreg. Such fibers can be beneficially used in the formation of composite devices. In this connection it should be noted that a prepreg is a layer of fibers which comprise an adhesive.
The method can further comprise the step of placing the pattern having inserts and covered with the one or more layers of fiber material into a further mold. In this way the one or more layers of webs of fiber material can be held in a further mold between the pattern and an inner surface of the further mold to form a pre-defined inner and outer shape of the device by way of the one or more layers of fiber material.
The method can further comprise the step of heating the further mold to first, second and/or third temperatures in first, second and/or third temperature ranges. By selecting the appropriate heating step, the resin can be transported to its desired position within the mold, the resin can be cured within the mold around the one or more layers of fiber material and the removable material can be removed from the mold.
The first, second and third temperatures can be used for at least one of heating the mold to aid the introduction of resin into the mold, heating the mold for curing the material of the device to be formed, and removal of the removable material of the pattern, such as a wax.
It should also be noted that the first temperature range is preferably a temperature range of ±3° centered about the desired first temperature. The first temperature is preferably selected between 30 and 85° C., especially between 50 and 80° C.
It should also be noted that the second temperature range is preferably a temperature range of ±3° centered about the desired second temperature. The second temperature is preferably selected between 60 and 105° C., preferably between 70 and 95° C. In this connection it should be noted that one can also adapt the temperature gradually over the complete temperature range in a step wise manner.
It should also be noted that the third temperature range is preferably a temperature range of ±3° centered about the desired third temperature. The third temperature is preferably selected between 80 and 130° C., preferably between 95 and 120° C.
The method can further comprise the step of introducing a resin into the further mold prior to and/or during the step of heating of the mold to the first temperature, optionally wherein a vacuum is applied during the step of curing the resin. By applying temperature and/or a vacuum the resin can have runnier consistency than at room temperature and thereby flows better into voids between the one or more layers of fiber material arranged between the pattern and the inner surface of the cavity. By introducing a resin into the further mold to coat the one or more layers of webs of fiber material in the space between an inner surface of the further mold and an outer surface of the pattern, one can form the composite device having the desired inner and outer shape with functional components inherently formed in the wall of the device at the position of the inserts present in the pattern.
The method can further comprise the step of curing the resin in the further mold to form the device, wherein the step of curing comprises at least one of the application of heat and UV light. By way of such method steps the removable material can be beneficially cured.
The step of the application of heat can comprise heating the further mold to the second temperature. This is a swift and efficient way of curing the resin at the one or more layers of webs of fiber material.
The resin can be heated to the second temperature, e g. below a curing temperature of the resin on the introduction of the resin into the further mold. In this way the resin can be transported more efficiently around the one or more layers of webs of fiber material present in the further mold in order to avoid the inclusion of air bubbles which might degrade the quality of the housing at the position of the air bubble.
The resin can be one of a one-component resin, a two-component resin comprising a hardener, and a multi-component resin comprising one or several hardeners. The resin can comprise a resin on an epoxy basis, a resin on a polyurethane basis, a resin on a cyanate ester or another basis suitable for injection or infusion. Such resin can be beneficially used in the formation of composite devices.
The method can further comprise the step of removing the removable material from the device. In this way one can remove the pattern without destroying the composite device. The method can further comprise the step of heating the further mold to the third temperature. By heating the removable material to a temperature above the melting point of the removable material allows a swift removal of the removable material.
In this connection it should be noted that the third temperature step can be conducted in a further device such as an oven or furnace.
According to a further aspect, the present invention relates to pattern of removable material, optionally obtainable by a method described herein, the pattern comprising one or more inserts placed at one or more predefined positions along an outer surface of the pattern. Such patterns can be beneficially used during the manufacture of composite devices.
The pattern of removable material can have a melting point selected in the temperature range of 80 to 130° C., preferably in the range of 95 to 120° C. The pattern of removable material can remain stable in shape to temperatures selected in the range of 60 to 100° C., preferably in the range of 70 to 95° C. The pattern of removable material can remain stable in shape at temperatures below a melting point of the removable material. Such properties of the pattern make it particularly suitable for 4)w-cost but high accuracy production of composite devices.
According to a further aspect the present invention relates to a device of composite material, optionally obtainable by a method described herein, comprising one or more functional components placed at one or more predefined positions along an inner surface of the pattern, with the functional components either being integrally formed in one piece with the device, or embedded within a structure integrally formed in one piece with the device.
The functional component can be selected from the group of members consisting of a tappet with an undercut, a pocket with an undercut, an internal seat (cylindrical), a bearing seat optionally with points of insertion for a circlip, a t-shaped groove (outwardly shaped and inwardly shaped), outer threads, such as bolts or studs with outer threads, inner threads such as sleeves with an inner thread or a nut, bayonet connections, open wedge sockets, eyelets, ball studs, dowels and dowel pins both optionally with points of insertion for a circlip, hooks, spring elements, bearing blocks, bearing blocks with clamping, saw tooth pins/couplings with or without bores, sleeves, apertures, supports for one or more of the foregoing and combinations of the foregoing
The device can have a pre-definable wall thickness with a tolerance of the wall thickness lying in the range of ±0.5 mm, in particular of ±0.1 mm, especially of ±0.05 mm, for a wall thickness selected in the range of 1 to 4 mm, in particular for a length of material of the device cut from the device in the range of 1 to 5 cm and at a width selected in the range of 0.5 to 2.5 cm. Using prior art molds such tolerances are not possible for hollow devices.
The device can have a tolerance of the wall thickness lying in the range of ±0.3 mm, especially of ±0.2 mm, very preferably of less than 0.05 mm, for a wall thickness selected in the range of 1 to 4 mm.
The device can have a tolerance of the surface profile of ±0.1 mm. In this way devices having particularly smooth surfaces can be achieved by the present disclosure.
In this connection it should be noted that the tolerance of the surface profile is a standard measurement technique used to define the surface quality of objects. The more uniform the surface is, the lower its tolerance is. The surface profile is defined by a uniform boundary around a surface within which the elements of the surface must lie. The surface profile is a complex tolerance that simultaneously controls a feature's form, size, orientation, and sometimes location. The surface profile is a three-dimensional tolerance that applies in all directions regardless of the drawing view where the tolerance is specified. It is usually used on parts with complex outer shape and a constant cross-section like extrusions.
To measure the tolerance of a surface profile two planes are placed around the surface whose tolerance profile is to be measured and the tolerance is defined by the spacing between the planes that are placed around the surface.
The device can have a tolerance of the surface profile of ±0.05 mm, in particular of ±0.03 mm, especially of ±0.01 mm at the position of the functional component forming a second insert. Such a device has a particularly smooth surface.
Two or more inserts can be provided and an angular tolerance of positioning between the two inserts in the device can be less than 0.3°, preferably less than 0.2°, if the two or more inserts are fixed relative to one another in the pattern then the angular tolerance between the two inserts can be less than 0.1°, preferably less than 0.05°. Two or more inserts can be provided and an axial tolerance of positioning between the inserts in the device can be less than 0.2 mm, preferably less than 0.1 mm, if two or more inserts are provided and are fixed relative to one another in the pattern then the axial tolerance between the two inserts can be less than 0.1 mm, preferably less than 0.05 mm. Two or more inserts can be provided and a tolerance of positioning between the inserts at a spacing between the inserts in the device can be less than 0.1 mm+1 mm/m, preferably less than 0.05 mm+0.5 mm/m, if the two or more inserts are fixed relative to one another in the pattern then the positioning tolerance between the two inserts can be less than 0.05 mm+0.5 mm/m, preferably less than 0.05 mm+0.2 mm/m
The device can be a head of a golf club and the one or more functional components can be selected as at least one of a weight integrated into the golf club, a shaft connector insert forming a connector to a shaft of the golf club, and a surface acting as a face of the golf club. Using the above described method a golf club with a very favorable weight distribution can be made.
One or more functional components can be provided that act as one or more weights of the head, one functional component can be provided that acts as the shaft connector insert and one functional component can be provided that acts as the face of the head of the golf club. In this way one or more weights can be formed separate from the face and one thereby yields a particularly favorable weight distribution within the head of a golf club. In this connection it should be noted that heads for both irons and woods can be formed in this way, especially using the method described herein. By embedding a shaft connector insert an angular precision of the face relative to the shaft position can be increased in comparison to prior art golf clubs.
The invention will be explained in more detail hereinafter with reference to the drawings.
In the following the same reference numerals will be used for parts having the same or equivalent function. Any statements made having regard to the direction of a component are made relative to the position shown in the drawing and can naturally vary in the actual position of application.
The functional components 12′ shown in
The functional component or support for a functional component can be one of the following types of functional components 12, 12′ which are selected from the group of members consisting of a tappet with an undercut, a bearing seat with points of insertion for a circlip, an outwardly t-shaped groove, outer threads, such as bolts or studs with outer threads, inner threads such as sleeves with an inner thread or a nut, bayonet connections, open wedge sockets, eyelets, ball studs, dowels and dowel pins both optionally with points of insertion for a circlip, spring elements, bearing blocks, bearing blocks with clamping, saw tooth pins/couplings with or without bores, apertures, supports for one or more of the foregoing and combinations of the foregoing.
In order to form the device 10, a pattern 54 of removable material M (see
A seal 19 is present between the top and bottom halves 18′, 18″ in order to seal off the cavity from the outside. Such seals 19 can for example be formed by an O-ring.
First and second kinds of inserts 24, 24′ are arranged and held at the inner surface 22. The first kind of insert 24 is formed by structures that can be inserted into the cavity 20 via e.g. a slider 26, and thus project into the cavity prior to and during the manufacture of the pattern 54 for the device 10 to form a structure at an outer surface 56 (see
The second kind of insert 24′ is an insert that is intended to remain within the pattern 54 after this has been formed. This second kind of insert 24′ can likewise form structures at the outer surface 56 of the pattern 54. These structures can either form supports for the functional components 12, i.e. have a shape complementary to the functional component 12′. Alternatively the second kind of insert 24′ is the functional component 12 (see
The second kind of insert 24′ can be held within the cavity 20 of the mold via one or more magnets 28 or through the application of a vacuum V. For this purpose, the second kind of insert 24′ is connected via a vacuum passage 30 to a vacuum pump 32 that is connected to the mold 18 via a vacuum port 36.
In order to form the pattern removable material M (see e.g.
In order to pressurize the pattern 54 a gas G can be introduced into the removable material M via a gas supply 44 which is connected to the mold 18 via a gas port 46 and a gas line 48. Additionally or alternatively, the cavity 20 is sealed off in such a way or can be sealed off, such that gas present in the cavity is compressed on the introduction of the removable material M to form pressurized gas G within the cavity.
As indicated in
Typically the wax can be selected to be a wax molten at a higher temperature in range from 60 to 140° C., in particular 70 to 120° C. and to be solid at a lower temperature in a range from 30 to 100° C., in particular 60 to 90° C. The temperature difference between the higher temperature and the lower temperature is preferably selected to be less than 40° C., preferably less than 30° C., in particular less than 20° C. and especially less than 10° C.
The wax can have a viscosity of greater than 2000 mPas for a temperature of less than 85° C. and a viscosity of less than 800 mPas for a temperature greater than 105° C. Such waxes have found to be particularly stable in shape up to their melting point and the transition between the liquid state and the solid state takes place over comparatively small temperature ranges making the waxes more cost effective in their use.
On forming the wax pattern 54 the mold 18 can be heated to a temperature below a solidification temperature of the wax, in particular to a temperature selected in the range of 1 to 40° C., in particular 5 to 25° C., below the solidification temperature of the wax. In this way the wax can be solidified in a more controlled manner and the shrinkage effects at the surface of the wax pattern can be reduced as the wax does not automatically solidify on contact with the surface of the mold cavity.
The mold cavity can be evacuated to a pressure selected in the range of 0.02 to 0.95 bar, in particular to a pressure selected in the range of 0.05 to 0.5 bar.
Following this the mold can be rotated about one or more axes of rotation. The first possible axis is indicated about the vertical axis 36 in which case the mold 18 can be rotated in or against the direction of the arrow indicated about the vertical axis 36. The second possible axis of rotation is about a horizontal axis H, in which case the mold 18 can be rotated in or against the direction of the arrow indicated about the horizontal axis H. By moving the mold 18 in this way the centrifugal force or gravity urges the pressurized removable material towards the inner surface 22 of the mold 18, so that this is completely coated with the removable material and the resultant pattern has an outer surface 56 (see
To form the pattern 54 having functional components 12, 12′ placed at one or more predefined positions a vacuum can be applied at the mold 18 using a vacuum pump. Once the desired vacuum of e.g. 0.3 bar is achieved in the mold 18, a valve can be closed to maintain the pressure within the cavity. Thereafter a liquid form of the removable material M can be introduced into the mold 18. For example 80% of the volume of the mold 18 can be filled with liquid material M, e.g. wax W. Thereby the residual air in the mold is compressed through the addition of the wax W in such a way that the pressure in the mold can now be in the range of 1.02 to 4 bar depending on the initial vacuum pressure and the amount of wax added.
The mold 18 can then be rotated about an axis of rotation while the mold is cooled, due to the pressurized gas in the mold and the rotation of the mold, the initially liquid wax covers the complete surface of the mold such that a wax pattern can be formed having the outer shape resembling that of the inner shape of the mold, with the wax pattern having a hollow interior.
If a pattern having a particularly complex outer shape is to be formed, additional gas can be added to the mold prior to, during and/or after the addition of the liquid removable material M. Additionally or alternatively more than 80% of the volume of the cavity 20 can be filled with the removable material M. This additional pressure in the mold can guide the liquid removable material into the complex negative geometries of the mold to ensure that a pattern having an outer surface substantially free of defects can be formed.
The pattern 54 comprises two inserts 24, 24′ placed at one or more predefined positions along the outer surface 56. The pattern 54 of removable material M can have a melting point selected in the temperature range of 80 to 130° C., preferably in the range of 95 to 120° C. The pattern 54 can remain stable in shape to temperatures selected in the range of 60 to 100° C., preferably in the range of 70 to 95° C. Generally speaking the pattern 54 of removable material M can remain stable in shape at temperatures below a melting point of the removable material M.
The one or more layers of fiber material 60, 62 can comprise carbon fibers, glass fibers, basalt fibers, wood fibers, hemp fibers, aramid fibers, polyester fibers, in dry condition or as prepreg.
Thus, the pattern 54 of removable material M can be used as a mold in resin transfer molding (RTM) processes to form composite devices in a manner known per se.
The further mold 64 can be heated to first, second and/or third temperatures in first, second and/or third temperature ranges via a heating and/or cooling device 96.
In this connection it should be noted that when the further mold 64 is heated to one of the first, second and third temperatures, the heating steps can be carried out gradually in a stepwise manner or continuously.
Particularly during RTM processes, it should be noted that the composite of fiber and resin is typically heated in steps to below the glass transition temperature of the resin in order to prevent the device to be formed from becoming soft and thereby obtaining a device with a deformed outer and/or inner surface.
In this connection it should be noted that the top half 18′ of the mold 18, the bottom half 18″ of the mold 18 and the further mold 64 are each preferably formed from a thermally conductive and non-magnetic material, such as aluminum or an aluminum alloy.
The resin R is introduced into the further mold 64 during the step of heating of the further mold 64 to the first temperature. The resin R is heated to below a curing temperature of the resin R on the introduction of the resin R into the further mold 64. In order to enhance a flow of the resin R of runny consistency a vacuum V can be applied simultaneously via a vacuum pump 74 connected to a vacuum line 78 via a port 76.
The resin R is cured in the further mold 64 to form the device 10. The step of curing comprises heating the further mold 64 to the second temperature. The second temperature is higher than the first temperature.
The resin R can be one of a one-component resin R, a two-component resin R comprising a hardener, and a multi-component resin R comprising one or several hardeners. The resin R comprises a resin on an epoxy basis, a resin on a polyurethane basis, a resin on a cyanate ester or another basis suitable for injection or infusion.
Thus in the RTM process described in the foregoing at least one layer of roving is provided as a first layer of fiber material 60 optionally also a second layer or several layers of fiber material 62 is provided. The pattern 54 covered with the first layer of fiber material 60 and optionally also the second layer of fiber material 62 is then placed into the further mold 64. The further mold 64 is then evacuated to create a vacuum in the further mold 64. The resin R is then injected into the further mold 64 at a temperature above room temperature but below the ideal hardening temperature of the resin R possibly under pressure. The resin R at elevated temperature and which is possible pressurized is more flowable than unpressurized resin R at room temperature and hence can flow more easily through the roving and the further mold 64 in order to ensure, if possible, that no air pockets are formed in the composite material of the final device.
The resin R is then permitted to solidify, i.e. harden, at a temperature selected below the melting temperature of the wax pattern 54, preferably while gradually increasing the temperature of the mold between the boundaries of the second temperature range from the lower temperature to the higher temperature, e.g. from 90° C. to 100° C. If required, openings and/or apertures can be applied at the hardened composite device. Following which the temperature of the further mold 64 is gradually increased from e.g. 100° C. to 120° C. in order to melt out the wax pattern 54. The melting out of the wax pattern 54 can optionally also be carried out outside the mold 64, for example in an oven.
As is known to the person skilled in the art of RTM processes, the glass transition temperature of the resin can be increased temporarily in the mold during the stepwise gradual increase in temperature to above the melting point of the wax to form the device. The liquid wax can then be removed via the openings and/or apertures applied at the device 10.
Also the inserts 24′ can be removed following the removal of the liquid wax in order to enable the placement of functional components at the position where a support therefore has been formed. For example, in
The device 10 of composite material, thus comprises two functional components 12 placed at two predefined positions along the inner surface 14 of the device 10. The functional components 12 are integrally formed in one piece with the device 10.
The device 10 can have a pre-definable wail thickness with a tolerance of the wall thickness lying in the range of ±0.5 mm for a wall thickness selected in the range of 1 to 4 mm, in particular for a length of material of the device 10 cut from the device 10 in the range of 1 to 5 cm and at a width selected in the range of 0.5 to 2.5 cm.
In
Not shown in
As also indicated in
This application is a U.S. National Stage application of International Application No. PCT/EP2019/075253, filed Sep. 19, 2019, the content of which is hereby incorporated by reference.
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/EP2019/075253 | 9/19/2019 | WO |
