9/15/2011 - Tips for Buying picnic cooler bags in the Internet

Do you want to have your own bag at very cheap price? Visit here to experience the most up-to-date selection and enjoy shopping there.As in my last article, I share with you three handy methods for buying picnic cooler bags. But I have to say, I love the first way (buying through the internet) and enjoy the benefits of it. After many times of satisfying online picnic cooler bags shopping, now I could to write about my experience and provide some tips for you to shop online. One of the most important elements in my happy online shopping experience is that I know what I need.

There are seas of picnic cooler bags online and it would take you a large amount of time if you do not make clear what you are looking for. You could make clear your target by sorting the brands, the price, the material and the style. Start from your favorite brand. And then settle down your budget. Make sure the material and style you are looking for and go directly to your target when you are browsing on the internet. If you are not sure about what style to buy, you could pause and take a look to your clothes and shoes as they matter a lot whether the bag goes with you or not.

After knowing your target, you could begin the tour. I usually shop from the websites I trust, which could be the one with well reputation or the one that I have shopped with satisfying quality. For those who have never shopped online buying a replica or never get the satisfying online shopping service, websites with good reputation are recommended.

To find out those well reputed online stores, you could visit some bags forum often and see their comments. Or you could also buy through the recommendation of the one that you trust. After you are clear about your target and find out a trust website, the rest thing is much less to worry about and all you have to do is find the one you like and take order as the website��s instruction. Hope all of you have happy online shopping experience.

8/11/2011 - Aluminum alloy die casting Components

Aluminum alloy die casting is a process in which hot, liquid metal is injected into steel molds. These molds are known as dies. Aluminum is a desirable alloy to use for die casting because it creates lightweight, corrosion-resistant materials that can operate in very high temperatures. These die castings are used to produce parts for cars, airplanes, pumps, light fixtures and power tools.

Die Casting Tooling

Dies are made of two sections: The fixed die half, also known as the cover half, and the ejector die half which is movable in order for the castings to be taken out. The sides of the die fold together and close like a book and are securely kept together by locking pins. Ejector pins are used to help remove the casted part. Located on the inner side of the two folding sections are negative reliefs of the metal part that is going to be made. On the cover half there are open holes called sprue holes and this is where the molted metal is poured into the die until it fills all of the nooks and crannies of the cavity on the inside of the mold. The ejector half contains passageways called runners and inlets called gates. These depressions in the die route the molten metal and force it to move into the hollow cavity of the mold. There are also openings in the dies for coolant and lubricants to be added. Lubricants are necessary as they allow the cooled product to be easily removed.

Die Casting Machinery

These machines hold the two die halves together under intense hydraulic pressure. The place where the two fixed halves meet the ejector is called the die parting line. The projected surface area of the part that is being cast is measured at this line, and that number is used to determine how much hydraulic pressure is needed to inject the metal into the die cavity. There are two kinds of die casting machines: hot chamber and cold chamber. Hot chamber machines are used when the dies are made out of lead, magnesium, copper or zinc. These metals and other low melting-point alloys are used to made metal pots and other things that can chemically interact with other metals and be corroded easily. Cold chamber machines are used for aluminum dies and have a metal sleeve into which molten metal is poured. This can be done manually or by a computer-automated system. A hydraulic plunger pushes into the sleeve and forces the metal into the aluminum die at a very high pressure to ensure that the cavity is filled.

How Dies Are Made

Dies for aluminum casting are made by creating a model of the part to be manufactured and then enveloping it with aluminum and allowing it to cool. When the aluminum is removed, it contains the cavity where the product will be formed. Dies can be made via squeeze casting, where a molten metal alloy is created at a very high pressure to make dense, high-quality, heat-treatable components. Semi-solid molding uses semi-solid billets to make a die that is heat treatable and has a low porosity. The surface of the pieces made will it have a smooth, clean-looking appearance.

Types of Dies

Single-cavity dies produce a single aluminum alloy die casting component. Multiple-cavity dies produce a number of identical parts and may look like branches of a tree, with the trunk forming the separation point. A unit die is used when several different parts need to be made for a particular assembly; a master lock for the front door of a house, for example.

8/4/2011 - Reducing residual stresses during sand casting molds

Residual stress is reduced in light metal alloy articles, e.g. aluminum alloy articles, formed as castings against a sand casting molds body by incorporating a wax composition of suitable softening or melting temperature with the sand particles of the mold or core body. The hot cast metal heats adjoining surfaces of the mold body. As the cooling metal forms a solid shell, the surrounding sand particle and wax mixture are heated sufficiently to melt or soften the wax incorporated on or between sand particles. This softens portions of the rigid mold body that could otherwise restrain shrinking surfaces of the casting and produce unwanted stressed regions that are retained in the casting and must be removed by subsequent processing.

The art of casting molten metal into sand molds to make useful articles has long been practiced. The casting art also includes casting molten metal into permanent molds in which sand cores are used to define internal surfaces of the casting. Today many ferrous and non-ferrous metal alloys are cast in green sand molds, resin bonded sand molds, or in other more permanent mold material structures using sand cores to define a portion of the surfaces of the cast articles.

Aluminum alloys are used in producing many cast articles, particularly in the automobile industry. Many engine components and other drive-train components are cast of various aluminum alloys in sand molds, and aluminum parts are produced by diecasting or permanent mold casting in which sand cores are used. For example, there is a family of aluminum-based alloys variously containing, by weight, about five to twelve percent silicon, and smaller amounts of other alloying constituents such ascopper, magnesium, and/or zinc. These alloys have good fluidity at pouring temperatures of, for example, about 700กใ C. for flowing into intricately shaped mold cavities in such casting practices.

Molding sand materials containing fine silica sand particles and small amounts of clay and water may serve as the mold or core material for casting aluminum alloys and other light metal alloys such as magnesium alloys. The pouring temperaturesof these casting alloys are relatively low (as compared, e.g., to ferrous alloys or other higher melting point metal alloys) and special, high temperature resistant mold compositions are not normally required. Complex parts such as aluminum alloy enginecylinder blocks, engine head blocks and the like may be cast in sand molds with sand cores to good dimensional accuracy. But aluminum alloys have a high volumetric shrinkage upon solidification, and there is additional shrinkage as solidified cast metalexperiences further cooling. The sand mold body is initially at ambient temperature and it has relatively low thermal conductivity. Those portions of the mold close to the mold cavity are heated by the sudden charge of hot metal. So mold surfaces andcores may expand in directions that press against surfaces of the solidifying cast metal. There are shapes in aluminum castings, such as those formed by surfaces in the cast body having intersecting faces at angles of about ninety degrees and lower,which may shrink extensively against acute angles (for example), adjacent sand mold surfaces and experience unwanted compressive or tensile stresses. This mold surface induced stress may cause cracks in affected surface regions of the cast light metalarticle. But more commonly, the cooled casting has regions of residual compressive or tensile stresses that may have to be relieved by a costly heat treatment.

There is a need for a method of making sand casting molds and sand cores that reduce such thermal shrinkage damage to cast light metal alloy parts.

8/1/2011 - Sand casting mold riser and sprue sleeve

The sand casting molds sprue/riser sleeve has a tubular, preferably cylindrical wall extending between an inlet end and an outlet end. The sleeve has a woven mesh filter extending across a central passageway with a periphery of the filter embedded into the wall. The periphery has three or more, evenly spaced tabs formed thereon that project further into or through the wall to secure the filter to the wall without materially weakening the wall. Preferably, the filter has a square-shaped periphery with corners that define the tabs. The main portion of the periphery extends into the wall less that one-half the thickness of the wall, whereas the tabs extend into the wall a distance greater than one-half the thickness.

It illustrates a sand casting mold for casting metal parts. The sand casting mold is generally identified with the numeral. The illustrated mold is formed in two complementary parts forming a mold cavity. The cavity is surrounded by mold sand. Molten metal is poured into the cavity through a mold sprue. One or more risers are provided to permit air to escape from the cavity while the cavity is being filled and to provide a reservoir for molten metal while the metal in the cavity is cooling and contracting.

Refractory insular sleeves are provided at the sprue and riser to protect the sand and to prevent sand from being carried into the cavity as the molten metal is being poured.

Considerable effort has been expended to develop insular riser/sprue sleeves that not only perform the traditional function of facilitating the pouring and uniform filling of a sand cast mold cavity with molten metal, but also filters the molten metal to remove foreign particles as the molten metal is being poured without materially hindering the flow of the molten metal into the mold cavity.

Several attempts have been made to construct such sleeves having filter systems mounted within the sleeves themselves. One such sleeve is commercially available under the brand name "Dypur" from Foseco, International Ltd. of Birmingham, England. The "Dupur" sleeve utilizes a rigid porous ceramic foam disc separately mounted to the interior wall of the insular sleeve to filter the molten metal as the metal flows through the sleeve into the sand cast cavity. Shoulder or wedge structures are utilized to rigidly secure the disc filter to the interior wall to minimize the possibility of the disc filter being dislodged and passing with the molten metal into the mold cavity, thereby ruining the casting.

Although the "Dupur" sleeve has met with some commercial success, it is rather expensive and has other disadvantages. Attempts have been made to place a less expensive circular flexible refractory mesh filter within an insular sleeve to perform the filtering function as well as providing a weakened fracture plane to facilitate the removal of the resulting metal sprue or riser after the molten metal has solidified.

One of the principal objects and advantages of the present invention is to provide an inexpensive sprue/riser sleeve having a woven mesh filter that does not materially weaken the sleeve wall while at the same time is unlikely to become partially or wholly dislodged from the wall from the combined head and flow pressure exerted by the molten metal as it passes though the sleeve into the mold cavity.

8/1/2011 - Computerized numerical control automatic sewing device

A CNC (Computerized Numerical Control) automatic sewing device comprises a sewing head and a workpiece holder movable in two co-ordinate directions perpendicular to one another for holding a workpiece to be sewn. A thread trimming device is provided adjacent to the stitch forming place and stationary relative to the latter and directly below the workpiece holder.

The invention relates to a CNC (Computerized Numeric Control) automatic sewing device comprising a sewing head having a stitch forming place with a thread cut-off device and a workpiece holder for holding a workpiece to be sewn, the sewing head and the workpiece holder being movable relative to one another in two co-ordinate directions by means of two carriages displaceable perpendicularly to one another each along a sliding path to produce a seam within an operating range of the workpiece holder, and a maxium sliding path in both co-ordinate directions being at least the same as the stretch of an operating range in the corresponding co-ordinate direction.

When sewing having sewing machines with a thread cut-off device, wherein the needle thread or upper thread, respectively, and the hook thread or lower thread, respectively, are automatically cut off at the end of the sewing action, there is the basic problem that the thread ends hanging down from the workpiece must be severed, i.e. the workpiece must be trimmed. The same applies to the thread ends at the starting point of the seam.

In order to solve this problem it is known for household sewing machines to secure clamping and cutting plates pivotably to the fabric presser foot and to provide a pivotably supported knife below the stitch plate, i.e. directly below the stitch hole. These two knifes are actuated by means of two electro-magnets to be actuated simultaneously. Thus the needle thread is cut off on the upper side of the workpiece and the lower thread is cut off directly below the stitch hole. With this thread cut-off device the cutting off of threads takes place in such a way that only infinitely short thread ends remain which need no more trimming.

It is the object of the invention to provide a CNC (Computerized Numerical Control) automatic sewing device, in which trimming of the thread ends hanging down from the lower side of a sewn workpiece is incorporated into the sewing cycle.

According to the invention this is achieved by providing a thread trimming device adjacent to the stitch forming place and stationary relative to the latter and directly below the workpiece holder. The maximum sliding path into each co-ordinate direction is in each case at least equal to the stretch of the operating range in the corresponding co-ordinate direction plus the distance of the trimming device from the stitch forming place in the corresponding co-ordinate direction. The features according to the invention make it possible to feed the workpiece held in the workpiece holder to the thread trimming device which is situated directly below the workpiece holder and in which these thread ends are severed, i.e. cut off, almost flush with the workpiece. As a result of the stationary placing of the thread trimming device in relation to the stitch forming place on the one hand, and of the constructive featuring of the sliding paths of the workpiece holder in relation to the sewing head in both co-ordinate directions on the other hand, it is possible to carry out this trimming immediately after sewing and with a final thread cut-off action. The trimming device is particularly simple. In a very advantageous embodiment of the invention the thread trimming device ensures a fusion or welding together, respectively, of the thread ends, so that a seam is achieved which is efficiently locked at its starting and end point.

Numerous further advantages and features of the invention will become apparent from the following description of an embodiment with reference to the drawing.

8/1/2011 - Computerized numerical control automatic complex lathe

Computerized numerical control automatic complex lathe has a main spindle for gripping and rotating a work to be machined. A first machining tool performs a main machining of the work. A turret tool rest has an outer peripheral surface for holding a set of secondary tools along the outer peripheral surface thereof. The turret tool rest is selectively indexable to bring a selected secondary machining tool into a position to effect a secondary machining of the work and is selectively movable relative to the work to enable the selected secondary machining tool to perform the secondary machining of the work. The turret tool rest further includes a plurality of tool holders for holding a plurality of secondary tools. A back spindle is disposable on a side of the work opposite the main spindle for holding a selected secondary machining tool selected from the plurality of secondary tools. The back spindle is selectively movable to enable the selected secondary machining tool to perform the secondary machining of the work.

The present invention relates to a computerized numerical control automatic complex lathe having a main spindle and a back spindle. More particularly, the present invention relates to an improvement adapted to increase the number of work processes performed on the back spindle thereby enhancing the utility of back spindle.

A conventional computerized numerical control automatic complex lathe, having a main spindle and a back spindle is known. The main spindle is constructed to grip a rod-shaped work in a work chuck so that the work can be rotated and machined for machining it and rotating it. The back spindle is positioned on the side facing the main spindle via the work and in parallel to the main spindle. On the work side of back spindle is integrally fixed a machining chuck as a back spindle tool.

The above-described computerized numerical control automatic complex lathe is so constructed that a rod-shaped work gripped in the machining chuck on the main spindle is machined with a cutting tool for main machining or a machining tool on a turret tool rest, and after the work is regripped in the work chuck on the back spindle, the work is machined with a machining tool as described above while being gripped in this chuck.

With the above-described conventional computerized numerical control automatic complex lathe, it is impossible to change the chuck on the work back spindle without stopping the machine. Also during cutting, only one kind of work that matches the chuck can be gripped. Also, a tool other than a chuck, for example a drill, cannot be mounted on the back spindle. Therefore, the work process which can be performed by the back spindle is limited to gripping only one kind of work.

It is an object of the present invention to provide a computerized numerical control automatic complex lathe with improved back spindle to perform a complex machining processes.

In the numerical control automatic complex lathe of the present invention, the number of machining process which can be performed on the back spindle is increased by constructing the machine in such a manner that the back spindle tool can be changed. To attain the above object, the present invention provides a chuck mounted for clamping and unclamping a back spindle tool. The chuck is mounted on the work side of the back spindle on a computerized numerical control automatic complex lathe. The lathe has a main spindle for holding and rotating a work and a back spindle positioned at the side facing the main spindle via the work and in parallel to the main spindle. The work may be machined with a cutting tool for main machining and also by a machining tool on a turret tool rest.

With the computerized numerical control automatic complex lathe according to the present invention, a plurality of kinds of chucks for gripping a work and a drill or other tools can be mounted on the back spindle since the chuck for tool for clamping and unclamping the back spindle tool is mounted on the work side of the back spindle as described above. Therefore, the number of work processes which can be performed on the back spindle, for example, the holding of a work with the chuck or the front machining of a work with a drill can be realized.

7/25/2011 - Aluminum alloy die casting method

Aluminum alloy die casting method comprising the steps of providing a die casting machine having a gate for allowing passage of molten aluminum alloy, setting a flow rate of the molten aluminum alloy at the gate to be in a range of 5 m/sec to 15 m/sec, and press-injecting the molten aluminum alloy into a cavity of a die. With this arrangement, it becomes possible to obtain a weldable casting with no entrapment of air.

An aluminum alloy for a vehicular part, which is formed of a die cast product manufactured by the die casting method of the present invention, is weldable and also dense in structure. As a result, these vehicular parts formed of the die-cast products are manufactured on a large scale at a low cost.

Casting a molten aluminum alloy in a die in atmospheric air using only gravity as a force is called a "gravity die casting method" or simply a "die casting method". Such a casting method has been effectively used to manufacture aluminum alloy castings for use as parts of a two-wheeled or lightweight vehicle body, or for engine parts.

However, the gravity die casting has problems, as in a sand mold casting method, such that its long cycle of casting limits productivity, the produced castings have poor dimensional accuracy, and a post heat-treatment is required to improve the strength of the castings.

In an attempt to solve these problems, it became necessary to consider adopting a die casting method which provides improved dimensional accuracy and has an extremely short cycle of casting. The principle of this die casting method resides in press-injecting molten metal into a cavity of a die at a high speed and pressure. In this die casting method, since molten metal is injected at a high speed, air is entrapped in the molten metal and remains as bubbles in a casting, with the result that the bubbles produce blisters on the surface of the casting upon heating of the latter. On the other hand, this die casting method is advantageous in that since molten metal is injected at a high pressure, a die-cast product obtained by the method has a dense structure and a flat cast surface, which lead to increased strength of the product and thus eliminate the necessity for giving a post heat-treatment to the product.

For manufacturing a three-dimensional structure such as a two-wheeled vehicle body, it becomes necessary to weld castings together. A casting obtained by the above-described gravity die casting is weldable but not a casting obtained by the latter die casting method.

Various improved die casting methods have been proposed for the manufacture of weldable die-cast products. An example is Japanese Patent Laid-Open Publication No. HEI-4-172166 entitled "METHOD OF MANUFACTURING ALUMINUM CAST PARTS FOR BRAZING".

According to this method, as shown in the drawing figures of the publication, a flow rate of molten metal at a gate (gate velocity) is switched stepwise between a low flow rate ranging from 0.3 m/sec to 0.6 m/sec for a first half of processing and a high flow rate ranging from 10 m/sec to 30 m/sec for a latter half of the processing.

However, in an associated die casting machine, an expensive control mechanism and a highly advanced control technique are required to switch the moving speed of a piston in the course of forward movement thereof. Further, the die casting machine is required to have increased rigidity so that it can withstand a large accelerating or decelerating force generated due to the change in moving speed of the piston. There has also been known a die casting machine having two cylinders that can be selectively used for effecting the change in moving speed of a piston. Although such a die casting machine facilitates the control of the movement speed of the piston to some extent, it becomes large in size.

It is therefore an object of the present invention to provide an aluminum alloy die casting method which enables the manufacture of a weldable die-cast product without requiring expensive modifications to an existing die casting machine and a highly advanced control technique.

To achieve the above object, according to the present invention, there is provided an aluminum alloy die casting method comprising the steps of providing a die casting machine having a gate for allowing passage of molten aluminum alloy, setting a flow rate of the molten aluminum alloy at the gate to be in a range of 5 m/sec to 15 m/sec, and press-injecting the molten aluminum alloy into a cavity of a die.

7/22/2011 - Continuous casting mold

Continuous casting mold for casting a billet with a polygonal cross section has side walls delimiting a mold space with a polygonal cross section and the side walls have a center region extending from an open top end to an open bottom or exit end of the mold with a first degree of taper and, at the sides of the center regions, abutting side regions with a lesser degree of taper than the first degree. In order to obtain even growth of the casting shell with low frictional forces, the center region has a degree of taper which is greater than the amount from the billet contraction and the width of the side regions increases as the distance from the exit end of the continuous casting mold decreases.

A continuous casting mold of this type is known from EP-A - 0 179 364. According to this document, the interfacial angle between adjacent side walls of the continuous casting mold diminishes in the moving direction of the strand, i.e. in the casting direction, provided that the tensile stresses in the edge region which are caused by the shrinkage of the strand shell continuously diminish and/or compensate each other. Hereby, detaching of the strand shell from the cooled mold wall in the region of the comers is to be avoided with a view to achieving uniform shell growth, particularly a shell having a uniform thickness.

This is, however, disadvantageous, namely for the following reason:

In conventional continuous casting molds, a particularly pronounced shell growth results in the edge or corner region of the strand already in the initial solidification phase of the strand, and thus directly below the meniscus, due to the two-dimensional heat transport taking place in the edge region. Hereby, the rigidity of the strand shell in the edge region increases to such an extent that the ferrostatic pressure inside the strand is no longer sufficient for pressing the strand shell against the mold side walls in the edge region. Hence contact loss in the edge region will ensue. Due to this contact loss, further cooling of the strand in the edge region can only be effected by heat radiation, but no longer by heat conduction.

As a consequence, the shell growth will immediately fall short of that of adjacent strand zones which rest against the side walls of the continuous casting mold. Directly at the edge of the strand the cessation of heat transmission is, however, compensated for by heat conduction through two-dimensionally acting heat radiation. Thus, there form zones of weak spots having slighter shell thickness, each closely adjacent to the edges of the strand, said zones of weak spots extending in the longitudinal direction of the strand. These local shortfalls in shell growth lead to the strand shell being inhomogeneous and thus richer in tension and more susceptible to cracking and results in a risk of breakout. As the strand passes through the mold, these weak spots move slightly away from the comer regions of the mold toward the center of the side walls.

It is thus rendered feasible to selectively release the edge regions of the strand within the continuous casting mold, whereby frictional forces are reduced and jamming of the strand is reliably avoided. It has emerged that by the membranous bending behavior of the strand shell in the central regions where the strand shell is in contact in the center regions of the side walls of the continuous casting mold, elastic recession of the strand shell is enabled, without, however, entailing a heavy increase in the frictional forces acting between the strand shell and the side walls of the continuous casting mold. The construction according to the invention of the side regions in combination with the center region of the side walls of the continuous casting mold not only makes possible the selective release of the edge region of the strand but also permits to achieve contact of the strand shell in those regions where the above-mentioned local weak spots are incurred in conventional continuous casting molds.

Preferably, the center region extends from the end of the continuous casting mold at least into the meniscus region, wherein suitably the center region is formed by a flat surface and has a constant taper throughout its length.

A heavy increase in the frictional forces acting between the strand shell and the mold side walls is reliably avoided if the center region has a taper in the region of 1.5 to 2.5%/m mold length, preferably in the region of 2 to 2.5%/m mold length.

Preferably, the side regions from the end of the continuous casting mold extend to a point below the meniscus region but into the upper half of the mold, i.e. it is sufficient if the side regions extend only until the approximate point where lifting-off of the strand shell in the edge region occurs for the first time.

7/22/2011 - Aluminium alloys casting Problems

Aluminium alloys casting has played significant role in development of aluminium industry since its inception in late 19th century. The first aluminium products were castings such as utensils and decorative parts which exploited the novelty and utilization of new discovery. Those early parts quickly expanded to meet the requirements of a wide range of engineering specifications.

Alloys development and analyzation of physical and mechanical features gave basis for product development through the decades which followed. Casting systems were processed to increase capabilities of foundries in new commercial and technical uses.

The system of melted metal processing, solidification, and property development has been advanced to assist foundry man with means of cost effective and trustable production of components which regularly meet specific needs.

Nowadays aluminium alloy castings are manufactured in hundreds of ways by all commercial casting systems including green sand, dry sand, composite mould, plaster mould, investment casting permanent mould, gravity casting, low-pressure casting and pressure die casting.

Material constraints which previously limited the design engineers alloy choice once a casting process was selected are continuously being blurred by advancement in foundry techniques. Similarly process selection is also less restricted these days. Like the many alloys previously thought to be unusable in permanent moulds because of their casting features are in production by that very process.

Melting and metal treatment:

Aluminium alloys may be melted in various ways. Coreless and channel induction furnaces, crucible and open-hearth reverberatory furnaces fired by natural gas or fuel oil and electric resistance and electric radiation furnaces are all in routine use. The nature of furnace charge is as different and important as the choice of metal casting operations. The furnace charge may differ from pre-alloyed ingot of high quality to charge made up of low quality scrap. Even under best melting and melt holding situation melted aluminium is at risk to these types of degradation.

a) With time at temperature, adsorption of hydrogen results in increased hydrogen content.

b) With time at temperature, oxidation of melt occurs.

c) Transient elements featured by low vapor pressure and high reactivity are reduced.

Turbulence or agitation of melt and increased holding temperature, significantly increase the rate of hydrogen solution oxidation and transient element loss. The mechanical properties of aluminium alloys depend on casting soundness which is highly influenced by hydrogen porosity and entrapped non metallic inclusions. Aluminium alloys casting and products manufactured by them are things of the future due to their cost effectiveness and lightweight.

7/22/2011 - Computerized numerical control method

The present invention relates to a computerized numerical control (CNC) method of controlling a plurality of paths with a single computerized numerical control apparatus, and more particularly to a CNC method of sequentially executing part programs for respective paths.

There has recently been used a multipath control method which controls a plurality of paths with a single computerized numerical control (CNC) apparatus in order that the CNC apparatus can operate with more functions and a workpiece can be machined in a shorter period of time.

In computerized numerical control apparatus controlled by the multipath control method, part programs for respective paths are generally executed simultaneously, i.e., parallel to each other.

It is however difficult or even practically impossible to check the part programs which are executed parallel to each other.

In view of the aforesaid problems of the conventional CNC method, it is an object of the present invention to provide a CNC method which can sequentially execute part programs for respective paths.

To achieve the above object, there is provided in accordance with the present invention a CNC method of controlling a plurality of paths with a single computerized numerical control apparatus, the method comprising the steps of designating an order in which to execute part programs for the respective paths, and sequentially executing the part programs for the respective paths in the designated order.

The part programs for the respective paths are designated in a certain order in which they are to be executed. The part programs are then executed in the designated order, and contents thereof are checked for each of the part programs.

If necessary an actual order may be modified.In the selection display area 3, a sequential execution mode is selected, and an order in which to execute the part programs is preset in the sequence number section 6. According to the preset order, a computerized numerical control apparatus does not execute the part programs parallel to each other, but executes the part programs in the order set in the sequence execution section 6. As a result, the programmer can confirm the contents of the part programs while they are being executed one by one. Furthermore, the programmer can correct errors in the part programs, if necessary, and can also vary the parallel execution order or the like.

Therefore, one channel can read, decode, and execute numerical control commands, and can also control devices such as the CRT/MDI unit. Consequently, each of the channels can execute commands for a certain number of axes, which have heretofore been executed by a conventional computerized numerical control apparatus.

7/20/2011 - Computerized numerical control for a servomechanism

Computerized numerical control system is provided for controlling a servomechanism under the direction of a general-purpose computer system. The system implements in software a PID controller for determining appropriate inputs to the servomechanism. The system further includes a Field Programmable Gate Array which is loadable with custom logic for remotely interfacing to the servomechanism.

The present invention advantageously provides for a computerized numerical control (CNC) system for controlling a servomechanism. With a unique software implementation of the control algorithm that is assisted by a hardware I/O control, real time computations needed for direct motion control can now be performed by a low cost PC. The present invention addresses the need to substitute a software implementation of certain servo functionality including commutation and current loop control that is conventionally implemented by dedicated hardware. The same PC used in a conventional PC-based system now takes on the new role of direct motion control, the principal function of a costly servo amplifier.

As a consequence, the cost of the system is substantially reduced since the requirement for customized hardware is reduced. The substitution of hardware by software also allows a high degree of flexibility, added system reliability, and new functionality that would otherwise be unattainable by a strictly hardware implementation.

In response to feedback derived from the operation of the servomechanism, a general-purpose computer system generates through software in real time, an input to the servomechanism to maintain the desired operation of the servomechanism. The general purpose computer system utilizes an operating system to control the execution of application tasks on the computer system, and the software controlling the operation of the servomechanism is intended to execute concurrently with these application tasks.

In one aspect of the invention, a PID control algorithm is implemented in software to generate an input to the servomechanism in response to feedback from the servomechanism. The PID algorithm includes gain coefficients associated with the respective proportional, integrating and differentiation factors of the algorithm. The gain coefficients are dynamically alterable on the computer system.

In a further aspect of the invention, a local controller is provided that interfaces to a communications bus for communicating with the software executing in the computer system.

In a yet further aspect of the invention, the local controller includes a Field programmable Gate Array (FPGA) for executing custom logic circuits to facilitate communication by generating an interrupt to invoke software for controlling the servomechanism.

In a still further aspect of the invention, the software for controlling the servomechanism includes a device driver for servicing interrupts generated by the local controller. The device drives a PID controller to provide a response to feedback obtained from the servomechanism.

The local controller advantageously includes a communication port for receiving feedback from the servomechanism and transmitting a response to the feedback. The communication port preferably interfaces to one or more fiber optic cables.

The computerized numerical control system of the present invention includes a remote controller that communicates with the local controller for interfacing to a Digital Power Stage to drive the operation of the servomechanism. The remote controller receives feedback from the operation of the servomechanism through the Digital Power Stage and communicates that feedback to the local controller. The remote controller includes a communication port to interface to a fiber optic cable for effecting the communication with the local controller.

In one aspect of the invention, the remote controller includes a Field Programmable Gate Array (FPGA) for executing customized logic to adapt the remote controller to the particular servomechanism that is controlled. The remote controller is loaded with the customized logic from the general-purpose computer system via the local controller and the fiber optic cable. The remote controller includes a generator to generate a Pulse Width Modulated (PWM) signal to provide an input to the Digital Power

In one aspect of the invention, the servomechanism controlled by the computerized numerical control system is embodied as a synchronous AC motor.

7/20/2011 - Types of Casting Molds

Casting is a process in which a liquid is poured into a mold in order to produce a product. There are several types of molds that are used in the casting process. Some are temporary and are destroyed during the casting process. Others are permanent and are reused again and again. The type of mold chosen is usually based on the requirements of the final product.

Sand casting mold

Sand casting mold are one of the oldest and most basic types of molds. Dry sand is pressed into a box (called a flask). A pattern made of wood or metal is pressed into the sand, creating a mold. Liquid metal or another material can then be poured into the mold, and the excess sand is brushed away when the part has cooled.

Vacuum Form

Vacuum forming can create many thin, weak molds in a short period of time. A sheet of plastic is suspended over a form, or "buck." The plastic is heated until it is soft, then pressed down on the buck. A vacuum is then turned on beneath the plastic to form it to the shape of the buck. These molds are strong enough to be reused, but thin enough to be cut from the final casting if needed.

Ceramic Molds

Ceramic molds are typically employed with the "lost wax" process of casting. A wax model is created of the desired item. It is then encased in ceramic, leaving a small channel open. When the ceramic is fired the wax melts away, leaving a ceramic mold. The casting material can now be poured in, creating an exact replica of the wax model. When the casting material has hardened, the mold is shattered, freeing the cast.

Permanent Mold

Permanent molds are often made of steel, iron, silicone or urethane. The casting material is either poured in or injected. Once the cast has hardened, it is removed from the mold. Permanent molds can only be made of hard materials if there are no undercuts in the cast (areas where the cast and the mold lock together). Soft mold materials do not have this issue.

Multi-Piece Mold

For especially complex castings, multi-piece molds must be used. Often these are two halves that are locked together while the casting is taking place, but molds comprised of many more pieces are used as the casting gets more intricate.

Die Casting Mould

Die casting mould is the preferred method for creating many small castings. Liquid metal is forced under pressure into a steel mold, or "die." Often many identical castings are built into the same die, allowing rapid manufacture of parts.

7/20/2011 - Copper Alloys Casting Problems

Pure copper is extremely difficult to cast as well as being prone to surface cracking, porosity problems, and to the formation of internal cavities. The casting characteristics of copper can be improved by the addition of small amounts of elements including beryllium, silicon, nickel, tin, zinc, chromium and silver.

Copper alloys casting is used for applications such as bearings, bushings, gears, fittings, valve bodies, and miscellaneous components for the chemical processing industry. These alloys are poured into many types of castings such as sand, shell, investment, permanent mold, chemical sand, centrifugal, and die casting.

Pure copper is extremely difficult to cast as well as being prone to surface cracking, porosity problems, and to the formation of internal cavities. The casting characteristics of copper can be improved by the addition of small amounts of elements including beryllium, silicon, nickel, tin, zinc, chromium and silver.

Copper alloys in cast form (designated in UNS numbering system as C80000 to C99999) are specified when factors such as tensile and compressive strength, wear qualities when subjected to metal-to-metal contact, machinability, thermal and electrical conductivity, appearance, and corrosion resistance are considerations for maximizing product performance. Cast copper alloys are used for applications such as bearings, bushings, gears, fittings, valve bodies, and miscellaneous components for the chemical processing industry. These alloys are poured into many types of castings such as sand, shell, investment, permanent mold, chemical sand, centrifugal, and die casting.

The copper-base casting alloy family can be subdivided into three groups according to solidification (freezing range). Unlike pure metals, alloys solidify over a range of temperatures. Solidification begins when the temperature drops below the liquidus; it is completed when the temperature reaches the solidus. The liquidus is the temperature at which the metal begins to freeze, and the solidus is the temperature at which the metal is completely frozen.

7/20/2011 - Aluminum Alloys Casting Techniques

Few people likely realize how present aluminum alloys casting is in daily life. In fact, aluminum makes up 32 percent of all metal castings and is integral to the automotive industry. In this process, foundries melt aluminum or aluminum alloys and form them into complex shapes once cooled. aluminum alloys casting can be performed via a number of unique processes, all of which require some level of skill and, because they involve working with molten metal, involve some degree of danger, so caution and care is in order.

Construct the mold that will be used for the casting. One easy way is to take ordinary home insulation foam, slice it into sheets, cut out the shapes that will form the mold -- depending on the object you wish to cast -- and use hot glue to hold them together.

Coat the foam with sheetrock mud but take care to leave a hole where you will have to pour acetone in the next step. Let it dry, then repeat several times. Then pour acetone in the opening to dissolve the foam.

Take the remaining mud shell and fire it in a kiln, where it will harden into a porcelain coat.

Heat the base aluminum (or aluminum alloy) in the foundry until it has melted into its liquid state. Use 4000 or 6000 series aluminum; its higher silica content makes it better suited for casting.

Remove the crucible, which contains the molten aluminum, from the foundry.Pour slowly and carefully into the mold. Let it cool and the separate it from the mold.

7/20/2011 - How to Make Sand Casting Molds