Lost foam casting

 

In 1958, H.F. Shroyer invented and patented the technology for making metal castings from expandable foam models. The original model was made from polystyrene (EPS) sheets and was molded with a binder-containing molding sand. Germany's Grünzweig and Harrtmann purchased the patent and developed it. The technique of producing castings using binderless dry sand was later patented by T.R. Smith in 1964. The use of a binderless dry sand process prior to 1980 must be approved by the Full Mold Process, Inc., after which the patent is ineffective.

The most common and practical method is to put the refractory coated model into the sand box, the model is filled with dry sand and compacted, and the liquid metal is poured instead of the foam plastic mold. This casting process is called: lost foam casting ( EPC), gasification die casting and solid casting. The Lost Foam Casting Committee of the American Foundry Association adopted "foam casting" as the name of the process. Precision casting

Lost Foam Casting is an innovative casting process that can be used to produce parts for both colored and ferrous metal power systems, including: cylinder blocks, cylinder heads, crankshafts, gearboxes, intake manifolds, exhaust pipes and brake hubs. The process flow of lost foam casting is as follows:

1) Pre-expansion

Model production is the first process of the lost foam casting process. Complex castings, such as cylinder heads, need to be made separately from several foam models, and then glued into a whole model. Each block model requires a set of molds for production. In addition, a set of tires may be needed in the gluing operation to maintain the accurate positioning of each block. The molding process of the model is divided into two steps. The first step is to Polystyrene beads are pre-expanded to a suitable density, typically by rapid steam heating, which is known as pre-expansion.

2) Model molding

The pre-expanded beads are first stabilized, then sent to the hopper of the molding machine, and fed through the feeding hole. After the mold cavity is filled with the pre-formed beads, steam is introduced to soften the beads. Expanding, squeezing all the voids and bonding them together completes the manufacturing process of the foam model, which is called autoclaving.

After molding, the model is cooled by a large flow of water in the water-cooling cavity of the mold, and then the mold is opened to take out the model. At this time, the model temperature is increased and the strength is low, so care must be taken during demolding and storage to prevent deformation and damage.

3) Model cluster combination

Before the model is used, it must be stored for a suitable time to make it mature. The typical model storage period is up to 30 days. For the model formed by the uniquely designed mold, it only needs to be stored for 2 hours. After the model is matured, it can be divided. The block model is glued together.

The block model is glued using a hot melt adhesive on an automatic glue machine. Glued joint seams should be tightly sealed to reduce the possibility of casting defects

4) Model cluster dip coating

In order to produce more castings per box casting, sometimes many models are glued into clusters, the model clusters are immersed in refractory coatings, and then dried in air circulating ovens of about 30-60 C (86-140 F) for 2 to 3 After the hour, after drying, put the model cluster into the sand box, and fill the dry sand to make the vibration tight. The inner cavity of all the model clusters and the dry sand of the periphery must be compacted and supported.

5) Pouring

After the model cluster is filled in the sand box by dry sand vibration, the mold can be poured, and the molten metal is poured into the mold (casting temperature is about 760C/1400F, cast iron is about 1425C/2600F), and the model gasification is The metal is replaced by a casting. Figure 1 is a schematic view of a flask and casting of a lost foam process.

In the lost foam casting process, the casting speed is more critical than conventional hollow casting. If the casting process is interrupted, the sand pattern may collapse and cause waste. Therefore, in order to reduce the difference between each casting, it is best to use an automatic pouring machine.

6) Falling sand cleaning

After casting, the casting solidifies and cools in the flask and then falls. Casting sand is quite simple, and the tilting sandbox castings fall out of the loose dry sand. The castings are then automatically separated, cleaned, inspected and placed in a casting box for transport.

Dry sand can be reused after cooling, and other additional processes are rarely used, and metal scrap can be remelted in production.

Comments (0) Posted to casting 10/10/2018 Edit

Fly Fishing Sunglasses for Nymph Fishing

Fly Fishing Sunglasses for Nymph Fishing Another item of heavy importance is a good pair of polarizedsunglasses. Strike indicatorsare generally bright orange, ungodly looking things that get puton your leader well above the fly or on the fly line itself, atthe junction of the fly line and leader. These strike indicatorsare what you look at when CNC Machine nymph fishing – not the fly itself.Strike Indicators for Nymph FishingFirst, you will need some strike indicators. It’s absolutely imperative that you be able to seethe strike indicator, and polarized sunglasses are very effectivefor this.Exactly where to put the strike indicator is a matter of somedebate, but ultimately boils down to what you are fly fishing forand where you are doing it.Now that we’ve covered what nymph fly fishing is all about, let’snext take a look at what sort of fly fishing gear you're going toneed to do it.

Small Weights for Nymph FishingThe second thing you’ll need for many rivers will be some smallweights to add to your fly line or leader. Using these types of weights, an anglercan put on as much or as little weight as needed to bring the flydown to depth, while at the same time preventing the fish frominhaling toxic lead (which can kill them). Theseitems are strike indicators, some small weights, and a good pairof fly fishing sunglasses. While nymph fly fishing uses pretty much the samegear you use when dry fly fishing, there is a few small itemsthat any successfully nymph fisherman will want to have. Wary Brown Trout in heavily fishedwaters, like the Missouri River, are not likely to be real wildabout seeing a bright orange object just a few feet above thefly.

Sink-tip fly lines have the tip of the flyline weighted to sink, thus allowing it to sink the nymph flymore quickly.With practice and patience, you’ll eventually be able to tellwhen “unnatural” movements occur in the strike indicator – whichmost likely indicates that a fish just took your nymph flyimitation.This is best done with the newer “twist on” non-toxic weightsthat are now available. . Inshort, use your judgment, erring on the side of caution (placingthe strike indicator as far away from the fly as possible, foryour abilities). On the other hand, more gullible trout or trout that receiveless fly fishing pressure could probably care less about it.Should you plan on fishing in really deep or fast rivers whereeven a weighted leader will not get the fly down to depth fastenough, then you will also want to look at investing in asink-tip fly line. In many, if not mostnymph fly fishing situations, a floating line is still used.However, to get the fly down to the depth you want it to go willrequire weighting it (at least in faster water)

Comments (0) Posted to Generalna 09/18/2018 Edit

Rig a castingfurnace it is not always advisable

When searching for an appropriate casting torch the hobbyist will need to takeseveral things into consideration. If the hobbyist plans to use natural gas like the kind that is providein households they may find that the pressure is just not enough and thedesired temperatures will not be reached.All the metal caster needs is an idea and red hot liquid metal. One of the furnaces functions isto help the flame reach optimum temperature and in the case of ReverberatoryFurnaces, a furnace torch is an absolute requirement.Several online shops also sell torches for the hobby metal caster. The size of the furnace, and what metals youplan to use are chief among the considerations. Don't worry, this is completelynatural.Price is brass Bushings suppliers yet another consideration. The same is true for Butane. Always usecaution when dealing with a furnace torch. Most hobbyists begin theircasting careers with a modest sized furnace to fit their most basic needs. Many think that just because you need afurnace torch you are going to need a large furnace.

Many jewelers are able to use small independent casting torches but whendealing with metal casting in furnaces you will need to use a torch that can bemounted and used in such a fashion.To say that metal casting is addictive is an understatement.The furnace is the pride and joy for the metal caster. .Within a few months, the hobbyist might find that the furnace has grown andthat they are casting at every chance that comes along. This is simply nottrue.Casting torches can be found in some hobby shops and in hardware stores. When buyinga torch hobbyist should shop around in order to find the best deal.Oxyacetylene torches are a favorite with many casters especially for castingiron. Many casters will use a torchthat uses propane gas as it provides enough pressure and heat to melt mostmetals.MetalCasting provides the hobbyist with a great way to create personalized parts andpieces that may otherwise be unattainable or far too expensive.

Except as a paper weight; a very ugly paperweight. This skill is a valuable one that promises toprovide the hobbyist with a rewarding past time. Most will constructtheir own furnace tweaking the design here and there to better suit theirneeds. This is perhapsone of the greatest parts of the entire metal casting process like seeing whatwas once just sketches solidify from liquid iron, or whatever metal is used. Casting is anancient art that is still is use to this day by major industries to artists tothose with backyard foundries. Torches can range in price from $40 toseveral hundreds of dollars depending upon the size, the use, and accessories. Whilenatural gas and Butane can be used, propane seems to yield the best results. While it may be possible to rig a castingfurnace it is not always advisable. Many home foundries are based on home made furnaces and if constructedcorrectly can prove to be highly effective. A small furnace and furnace torch can produce enough heat to meltaluminum, iron, and a number of other metals. Metal castingprovides a way for an idea to materialize through molten metal. The crucial part of thefurnace is the furnace torch. The torch brings the heat, incredibly high heat,and without it that chunk of metal would just sit in the crucible and never seelife as something new and exciting

Comments (0) Posted to casting 09/05/2018 Edit

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Comments (0) Posted to Generalna 08/21/2018 Edit


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