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Comanche Technologies Foundry Product Articles
Comanche Technologies Foundry Product Articles
Comanche Technologies Foundry Product Articles
Comanche Technologies Foundry Product Articles
Comanche Technologies Foundry Product Articles
Comanche Technologies Foundry Product Articles
Comanche Technologies Foundry Product Articles
Comanche Technologies Foundry Product Articles
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Comanche Technologies Foundry Product Articles

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Collection of recent articles highlighting the various foundry products offered by Comanche Technologies.

Collection of recent articles highlighting the various foundry products offered by Comanche Technologies.

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  • 1. A PENTON PUBLICATION Our 118th year NOVEMBER 2010 Visit us on the World Wide Web at www.foundrymag.com Also in this Issue: ■ Simulation predicts shrinkage porosity ■ Energy-saving programs target foundries ■ Five factors for effective management Pouring More Efficiently Increasing productivityCerraFlex TorrentFlow Filter Cups with direct-pouring capabilityon FM&T Cover - November 2010 Issue
  • 2. [POURING ]Next-Generation Investment Casting Filter CupsI nvestment casters have learned to balance the need for high 3,500°F (1,927°C.) This refractory composition significantly enhances levels of molten metal filtration (removing dross, slag and other the rigidity and overall strength of the filter cup, so it handles increased impurities) against a concurrent desire for higher metal through- pouring times and heavier metal flow. The TorrentFlow design alsoput. Given the filtration options of ceramic cellular/foam or silica- incorporates a distinctive interstitial space between the inner wall ofmesh filter cups and their performance characteristics, it’s rarely a the pouring cone and the outer edge of the filter cup that is custom-straightforward exercise. This is because performance factors like calculated per each cup and pouring cone pair, effectively increasingthroughput rate, relative level of filtration efficiency, and others, the filtration area up to 78% over the traditional filter cup design.vary significantly among different types of filters. As a result, it’s Although the notable improvements in throughput and filtrationnot difficult to find investment casters who regularly use all three area achieved with the TorrentFlow filter design successfully met thefilter types depending on the specific application needs. two most favored performance needs, as identified by extensive cus- It had been long while since the last significant technical innovation tomer research, it’s worth noting some of the lesser-known but highlywas made in any of the filter types. This was not because metalcasters valuable additional benefits that are unique to filter cups in general:stopped asking for improvements, but rather that the available filters Enhanced Hot-Top Performance. Filter cups can easily be re-had become cash-cow products for foundry consumables manufactur- moved from the pouring cone prior to the addition of hot topping, so ers, until recently. Being that the filter material does not hamper the feedback of the molten familiar with metal fil- metal. Ceramic filters placed in the base of the pouring cone can im- tration and its technical pede the metal feedback from the hot-topping’s exothermic reaction challenges, the R&D because they cannot be easily removed. team at Comanche Liquid Impurity Capture. As molten metal is poured into the Technologies created filter cup, the heavier, denser impurities of slag and dross typically a “wish-list” on metal sink to the bottom of the cup and are captured in the mesh. At the same filtration from leading time, liquid slags and dross will remain floating on the surface of the U.S. investment casters, molten metal as it drains gently through the filter material. The “swirl- and used the findings to ing” flow driven by the cup’s geometry traps the liquid slag at the bot- define the performance tom of the filter cup, at which point the operator can remove the filter targets of their next gen- cup entirely, ensuring the liquid slag does not enter the casting. eration of investment Formation of Fayalite. Unique to silica mesh filter cups is the casting filter cups. formation of Fayalite (Fe2SiO4) on its surface, when used in ferrous Their clear choice applications. As molten ferrous metal makes contact with the silica The CerraFlex TorrentFlow™ was to have “increased mesh, proprietary surface coatings decompose instantly and form a Filter Cup increases the working throughput,” but with sticky, viscous coating that enhances the ability of the cloth to capture temperature threshold to a new this caveat: “no decrease even micron-sized inclusions. maximum — 3,500°F. in filtration level.” So, No Requirement for Pre-Heat. Unlike ceramic foam and cellularalthough there was initial disappointment among the research team screen filters, TorrentFlow and CerraFlex filter cups require no pre-at not discovering some new and unmet, market-driven performance heating in the investment pouring cone, and thus are easily salvagedneed, it was quickly replaced by their confidence in understanding should any problems occur with the investment prior to pouring.what would define success. It was achieved by a two-pronged strategy Pouring Cone Cost Savings. Because TorrentFlow and CerraFlexof 1) redesigning the geometric shape of the filter cup, and 2) modify- filter cups are held in place at the top of the pouring cone, investmenting the mesh material itself. casters can reduce costs by eliminating the need for pouring cones Extensive testing proved conclusively that the product developers custom-made to fit a specific size ceramic foam or cellular filter, andhad delivered a revolutionary new filter cup. Extensive test results tal- instead use the less expensive, standard pouring cones.lied an average 20% boost in full-production throughput, a higher tem- “Our hope is that this new generation of filter cups provide investmentperature threshold, and a dramatic increase in active filtration area. casters another tool to reduce scrap rates and push down production costs The CerraFlex TorrentFlow™ Filter Cup, a proprietary, “next gen- in order to be more competitive globally,” said Jason Hitchings, generaleration” of high-performance filter technology incorporates a tailored manager of Comanche Technologies. “We chose AMETEK Foundryzirconia refractory coating that effectively increases the working tem- Products (www.ametek.com) as the exclusive manufacturer for the Tor-perature threshold several hundred degrees to a new maximum of rentFlow line, as they’ve already done an incredible job ramping up the production of our CerraFlex products. Comanche’s technology strategy Jason Hitchings is general manager with Comanche Technologies. of incremental improvement over complete process redesign seems to Contact him at JHitchings@comanchetechnologies.com, or visit resonate with our customers, and provides a smoother new product www.ComancheTechnologies.com adoption path.”WWW.FOUNDRYMAG.COM FOUNDRY MANAGEMENT & TECHNOLOGY 17
  • 3. 2011 ➤ Databook ➤ Pouring Improved De-Gating Techniques Yield High Cost Reductions for Metalcasting Finishing Operations W hile the drive to reduce operating costs may seem like a never-ending road for metalcasting operations, an organi- zation’s ability to convert those cost-efficiencies into pow- erful and immediate market leverage is undeniably a deciding fac- tor in their long-term survival. What makes this formidable task even more challenging is the acceptable “cost” of cost reductions. Significant capital investment in new production equipment yields true savings only after the “payback” period is complete. At the same time, should a more attractive solution arise later it may be difficult for a customer to change again. Technical flexibility is an advantage few organizations actively manage well, but those who do expose Above: Custom-cut CerraBreakers pre-placed in themselves to the least risk. a pattern for an aluminum casting, using No-Bake molding. Below: the resulting flat cleavage plane from Cleaning room or casting “finishing” operations have long been a CerraBreaker used in a ductile iron application. The target areas for increased efficiency and cost-reduction efforts, and runner was “knocked away” using only a shop hammer. can represent a significant portion of total production cost. Removing runner systems and risers from a finished casting typically requires foundry personnel to use cutting saws, abrasive wheels, or cutting torches. Although effective, these techniques also expose workers to risk of injury from repetitive vibration, high noise levels, heavy lift- ing, and respiratory dust. While some of the largest foundries (mostly captive OEM) have the financial ability to purchase one or more automated robotic systems to handle finishing operations, most medium-sized and smaller met- alcasters continue to search for less costly options simply to remain competitive. Not surprisingly, innovative foundries that find ways to squeeze costs or make their cleaning operations more efficient tend Standard CerraBreaker/ to protect their discoveries, particularly when those methods do not silica-mesh cloth RiserBreaker require large capital expenditures and can be adopted easily. Molten alloy Molten alloy pour temp max: 2,800°F pour temp max: 3,500°F Internal Best-Practices One of the most surprising, yet effective techniques that has been Incompatible with Compatible with copper, a “back-room best practice” for many foundries is using standard copper and aluminum aluminum, and more silica-mesh fabric in runner systems and in the base of riser sleeves to create “cleavage planes” that typically come apart during vibratory Deflection into body No deflection — shakeout, or with the minor impact of a shop hammer. For anyone of casting or riser sleeve flat cleavage plane watching cleaning room personnel spend hours cutting small cast- ings from runner trees, or witnessing a hydraulic ram violently bash risers from large castings, the value of “low-impact” de-gating is no not exceed the recommended level as the mesh material can quickly mystery. An additional benefit of using standard silica-mesh material “break-through”. Therefore, casting stainless steel or other high- as a de-gating aid is that it acts as a molten metal filter wherever it’s temperature alloy applications must be monitored carefully to avoid placed. While it’s not uncommon for foundries to use ceramic foam temperature variations. filters placed directly in runner systems or in the bottom of riser • Incompatibility with aluminum and pure copper – Typically, sleeves for additional filtration, ceramic foam filters do nothing to standard silica-mesh cloth is treated with a thermal setting phenolic make runner segmentation or riser-removal any easier. resin and pre-shrunk to create the rigidity necessary to hold the spe- cific shapes for foundry applications. This treatment, although nec- No “one-size fits all” essary, also precludes it from being used with pure copper because Of course, there are certain drawbacks and limitations to using the resin chemicals are attacked by the oxides and slag generated standard silica-mesh cloth that foundrymen should consider for their by melted copper and lead to a rapid structural failure, and the mesh specific application. These considerations include: breaks through. A different problem can occur with aluminum alloys • Molten metal temperature maximum of approximately as standard silica-mesh material will “off-gas” as the molten alumi- 2,800°F/1,534°C – The application alloy pouring temperature should num passes through it, often causing porosity-related defects. 2 FOUNDRY MANAGEMENT & TECHNOLOGY JANUARY 2011
  • 4. 2011 ➤ Databook ➤ Pouring• Deflection or “flexing” of material into casting body – Withregard to keeping the molten alloy pouring temperature below maxi- For more in-depth technicalmum, standard silica-mesh fabric typically deflects or “flexes” (butdoes not break) in the direction of alloy flow. This deflection is usu- information on the wide varietyally an acceptable drawback, as the material remains intact as a filter of unique foundry products offeredand provides the cleavage plane necessary for easier runner segmen-tation later. However, when placed in the bottom of a riser sleeve, by Comanche Technologies, visitthe silica mesh can deflect downward into the body of the casting orupward into the riser sleeve, and when “knocked off” will create a us on the web:surface problem that must be machined away later. The best result is aflat cleavage plane that requires no additional re-work. www.ComancheTechnologies.comClosing the gaps Considering the wide-ranging benefits that could be realized infinishing/cleaning room operation by addressing the problems ofstandard silica-mesh fabric, Comanche Technologies has developedtwo new products — the CerraBreaker® and the RiserBreaker®— that leverage the technical strengths of CerraFlex®, a ceramic-coated, high-strength silica mesh filter material. Each CerraBreakeris a custom-cut piece of CerraFlex that’s placed directly in the runnersystem where the mold designer wants break-points. Because eachCerraBreaker is also a molten metal filter, designers often place ad-ditional units earlier in the flow stream to capture slag and inclusionsdirectly in the runner network, as well as directly at the contact areafor each casting. A RiserBreaker is a CerraBreaker that has been “framed” withina core-sand breaker core, attached to the base of any variety of riser-sleeve. This frame design is critical to ensure there is no deflectionof the CerraFlex material in either direction of molten metal flow,while the breaker-core itself creates a smaller contact area that makes“knock-off” even easier. Each RiserBreaker-Sleeve unit is custom-calculated according to customer provided, application-specific datato ensure optimal performance.Operational cost savings So the larger (and easily the most important) question for everyfoundry should be “how much will we save by using CerraBreakersor RiserBreakers in our finishing operations?” The honest answer is“it will depend …,” because the scale of cleaning or finishing roomoperations varies significantly from one foundry to another basedon average size of castings produced, alloys cast, etc. Moreover, asthese techniques are used across the metalcasting process spectrum(green sand, no-bake, permanent mold, investment casting, etc.),average cost-savings will vary as well. Ultimately, this question canbe answered by your operations team, as they should be driving thecost-saving, efficiency-finding initiatives. But, the workers doing thegrinding and sawing will thank you.Jason Hitchings is the general manager of Comanche Technologies.The author gratefully acknowledges the previous research publishedas “Use Fabric, Breaker Cores to Cut Ductile Iron Finishing Cost,”(Modern Casting, 1999) as a reference for this article.Contact him at JHitchings@comanchetechnologies.com, or visitwww.comanchetechnologies.com .WWW.FOUNDRYMAG.COM FOUNDRY MANAGEMENT & TECHNOLOGY 3
  • 5. Meeting Customer Quality Specs – B Choosing the Right Molten Metal Filter by Jason Hitchings, plication factors that drive the choice of of the filter, while smaller particle inclu- Comanche Technologies filter are: sions may pass through and on into the • Alloy or base molten metal pouring end casting. While most investment casters today temperature The first situational-dependent ex-employ one type of molten metal filter or • Amount and type of slag or inclusions ception to this rule is the oft mentionedanother as part of their standard produc- • Additional performance factors – “filter-cake” principle, by which a largetion process, those who do not are find- throughput rate & hot-top use particle inclusion becomes trapped on theing a growing number of end-casting • Filter price surface face of a given filter and thereaf-customers that now include a specific re- It’s a good practice to define these ter begins to attract and capture addition-quirement for the cast alloy to be filtered factors relative to your targeted casting al chemically-similar inclusion particlesin the request for quote. application well before digging into the via their relative affinity. Fortunately, this trend towards filtra- technical specifications of one filter tech- This is a situational-dependent ex-tion comes at a time when there is a larger nology or another. ception to the general sieving rule be-choice of proven and effective molten cause the creation of a “filter cake” onmetal filter technologies than ever before.That said, it is well worth the time and The Mechanisms of Investment the surface face of a filter relies on the capture of that first large particle inclu-effort of investment casting professionals Casting Molten Metal Filtration sion which ideally includes some type ofto refresh their familiarity with the major Although a great deal of promisingcategories of filter types with an empha- research on improving molten metal fil-sis on their respective pros and cons. tration technology and efficiency con- It is also worth noting that there re- tinues in both industry and academia,ally is no “perfect” or one-size-fits-all the vast majority of currently availablemolten metal filter. Each has its own molten metal filters rely on their rela-strengths and weaknesses that need to be tive “sieving” or “screening” ability toconsidered carefully. Ideally, an invest- remove slag and other inclusions fromment caster’s choice of filter solution the base metal as it passes through theshould be driven by a list of key perfor- body of the filter. In short, each filtermance requirements, each weighed in type (ceramic foam/pressed cellular ororder of importance and specific to their honeycomb/filter mesh, etc.) will capturecasting application. Typically, the ap- those inclusion particles that are too large Figure 1– to pass through the pores, cells or holes Zirconia foam filter, post pour24 May 2012
  • 6. metallic inclusion compound. The chemi-cal nature of that metallic inclusion willdrive its ability to attract and hold like-inclusion compounds and thus grow thefilter cake to where it works most effec-tively. Non-metallic inclusions such as in-dividual sand grains by themselves typi-cally do not produce the most effectivefilter cakes. Moreover, if the base alloyor molten metal does not have some mod-erate level of inclusions or slag to beginwith (which is not typically a bad thingto have), then the probability of a filter-cake developing on the surface face ofthe filter will drop considerably and ulti-mately may permit the smaller inclusionparticles through the filter. The second situational-dependentexception to the sieving rule is the “tor-turous path” principle best epitomizedby the internal structure of a reticulated Figure 2– Stereo microscope image of a cross-sectioned silicon carbide foam filter, deep-ceramic foam filter. As the molten metal etched to reveal the interior of the filter post exposure. While two sand grain clusters are shownpasses through the interior of a ceramic entrapped within the “tortuous path” of the filter, it is the metallic slag surrounding the sandfoam filter, the pulled-along inclusion grain cluster that ”sticks” to the filter body. Individual sand grains sans metallic slag will notparticles must negotiate a random maze “wet” the filter body on their own.of internal passages and channels thatalso cleverly include some “dead-end” cloth. When a ferrous alloy or base metal Similar material improvements havecavities. It is through these tight spaces is poured through this filter material, a been made in both Silica and Fiberglassand irregular cavities that the foam filter chemical reaction takes place between mesh filter cups over the same periodcan sometimes capture a slightly higher iron present in the alloy and the resin of time, as seen with the developmentpercentage of inclusions than their appli- that results in the creation of a “sticky” of Zirconia-treated filter cups that dras-cation-specific equivalent filters. by-product called Fayalite. This ferrous- tically increased both the filter mate- However, this is also a situational- specific compound creates an adhesive rial strength and its upper temperaturedependent exception to the sieving rule surface to which even small particulate threshold of reportedly 3400°F / 1871°C.as it is still possible that some percentage inclusions may become trapped. While In aggregate, these and similar improve-of the smaller particulate inclusions will this dual-filtration capability is indeed ments in virtually every category of fil-nevertheless make it through the tortur- unique to silica mesh, it also only occurs ter present the investment caster with aous path structure. in ferrous alloy applications. much wider selection than in years past. One filter type that provides a Until recently, each of the standard So where to begin?supplemental filtration mechanism is filter morphologies tended to be domi- nated by a small group of primary basephenolic-resin treated Silica mesh filter materials. For example, ceramic foam Alloy or Base Metal Being Cast In most cases, the primary consider- filters tended to be made of zirconia or ation towards choice of filter relative to silicon carbide, with little or no alterna- the alloy or base metal being cast is the tive material choice. pouring temperature. Due to innovative research efforts on Investment casters working with the part of some of the larger filter suppli- super-alloys will typically pour at or near ers in recent years, it’s not difficult to find 3100°F/1704°C, which in turn drastical- foam filters made of more exotic materials ly limits their choice of filters as only a such as graphite-refractory compounds handful of filter base materials can with- that in addition to filtering out inclusions, stand that high temperature. can reduce the occurrence of cold-shuts. At the opposite end of the tempera- Advances have been made with pressed ture spectrum, aluminum applications cellular filters as well, including reduced pouring at or near 1450°F/788°C haveFigure 3– Zirconia treated filter cup showing filter base material density and increased more options to consider.captured slag resistance to thermal shock. May 2012 25
  • 7. of the major cast metals, with each of the main filter base materials graphed according to its respective working-temperature to illustrate overall suitability between alloy and filter. Alloy-Filter Temperature MatrixNote: The cast metals listed are only intended as general categories as there are far too many subsets and alloy combinations to put in a singlegraph. In similar fashion, the filter base materials discussed are intended as broad categories and are not all inclusive. As a general rule, the higher the pour- as conservative operating limits. While For example, ceramic foam filtersing temperature of the alloy, the more ex- it may be possible to use a specific filter specify “pores per linear inch” (PPI)pensivepouring temperatures given for the identified cast metals are onlyand areas “averages” or examples The the filter. This is illustrated by in an application that has an alloy pour- used typically bracketed as followsthe comparatively high price of a zirconia ing temperature slightly above its recom- – 10PPI/15PPI/20PPI, etc. So “10PPI” so as to benchmark them against the filter base material capabilities. Similarly, the filter base materialfilter, which has the highest temperature mended maximum, the chances that the decodes to ten pores per inch across thethreshold of commercially available fil- as conservative operating limits.fail surface face of possibleA 10PPI a working-temperatures are given filter material may break or otherwise While it may be the filter. to use ceram-terspecific filterpresent-day skyrocket- duringan alloycan increase dramatically. slightly above designed to capture large types. The in an application that has pouring pouring temperature ic foam filter is its recommendeding price of zirconia is a separate issue particle inclusions, as the more pores peras maximum, the chances thatbeen filter material may break or otherwiseinch, during pouring can increase zirconia filters have historically the fail the smaller each one is.expensive, but it certainly doesn’t help Magnitude of Inclusions Thus, a 20PPI foam filter is intended dramatically. Without a doubt, the primary reasoninvestment casters either. to remove much smaller inclusion par- for using a molten metal filter is to pre- On the other hand, aluminum invest- ticles as the pores are equally minute. vent slag and other harmful inclusions Magnitude of Inclusionsment casting applications can enjoy the from entering the tree and ending up in Cellular or honeycomb filters are mea-option of using the least expensive filter Without a doubt, the primary reason end using a molten metal filter is to prevent slag andof cells per square the for casting. However, to guarantee sured in by the number other harmfulmaterial; fiberglass mesh. The alloy filter inch, again with larger number indicating inclusions from entering the tree the best performance from any filter, it is smaller holes or pores. Both besttemperature matrix (next page) highlights and ending up in the end casting. However, to guarantee thesilica mesh critical to have an understanding of thethe typical pouring from any filter, it’s critical to have an understanding of the physical characteristics of the performance temperatures of major physical characteristics of the slag or in- cloth and zirconia-treated silica meshcast metals, with each of the main filter material use “mesh size” to indicate the slag or inclusions particular to your application. First to application.is thesize of the holes,(or state) from 1.5mmbase materials graphed according to its re- clusions particular to your consider physical size and range of the First to consider is the physical sizespective working temperature to illustrate the filter to remove. Each filter type (the physical structure or (largest). problem inclusions targeted for (or state) of the problem inclusions tar- mesh (smallest holes) to 2.5mmoverall suitability between alloy and filter. While it may be tempting to choose geted for the filter to remove. Each filter The pouring temperatures given for a filter specification that captures the type (the physical structure or morphol- 3the identified cast metals are only used as smallest inclusions possible without re- ogy of the filter) offers a range of hole“averages” or examples so as to bench- gard to the inclusion specifics of the ac- sizes that correspond roughly to the sizemark them against the filter base mate- tual application, best practice is to deter- of the inclusions in the subject cast alloy.rial capabilities. Similarly, the filter base mine the pore size that is small enoughmaterial working-temperatures are given to capture the inclusion particles without26 May 2012
  • 8. dramatically impacting the overall or a turbine blade, and even minutethroughput (feed) of the pour. imperfections are unacceptable, the Using a small-pore filter in cost of the filter becomes far lessan application with a significant important than its ability to removeamount of large particle inclusions inclusions. On the other hand, high-can quickly clog the filter to the volume Aluminum casting produc-extent that the feed is drastically ers using Fiberglass mesh screen fil-slowed or worse, the molten alloy ters may change suppliers based onoverflows the pour cone. Best prac- a mere fractional difference in price.tice in determining the pore/cell/ If your core-application require-mesh size that is most appropriate ments can be met by multiple filterfor your application is to test several types, it’s worth the effort to deter-different filter sizes and analyze the mine “what else” each candidate canresults. Foundry suppliers typically do for your application in additionprovide free test filters to potential Figure 4– Zirconia-treated filter cup being removed prior to to simply filtering out inclusions.customers for just this purpose, so hot top application, ensuring optimal hot top performance Increased throughput, optimal hot-take advantage of it. for alloy feed. top performance, turbulence reduc- tion capability, and others if rel-Performance Trade-Offs This interstitial space design opens evant should be weighed in your decision Once you’ve narrowed the choice the sides of a filter cup for the molten al- process. The last consideration in filterof filters based on pouring temperature loy to pass through, in addition to the bot- choice, and one often overlooked, is le-compatibility and have some idea on the tom of the cup. This increased “active fil- veraging the technical expertise of yourpore/cell/mesh sizes that may be appro- ter area” will increase the throughput rate filter supplier. Your filter solutions pro-priate for the slag or inclusion charac- with no loss of filtration efficiency as the vider should be sufficiently well-versedteristics specific to your application, it’s pore size of the filter remains the same. in metallurgical defect analysis to ensuretime to consider additional performance Another performance factor to con- you’re getting the most out of their filterfactors such as throughput speed or the sider is whether or not you use exother- technology. In fact, leading suppliers areuse of exothermic hot-top. mic “hot-top” to aid the molten alloy feed typically more than happy to help solve If increasing the throughput (flow into your end castings. Ideally, it’s best a potential defect problem even if it doesrate) of your application is a perfor- to have nothing impeding the alloy feed- not involve your purchasing more prod-mance objective, then realizing that goal ing into the tree after the hot-top has been ucts from them, so don’t hesitate to lever-may come at the cost of reduced filter applied. But in using a ceramic foam or age that valuable resource when needed.efficiency. In most cases, the only way cellular filter placed securely in the bot- Over time, an investment castingto raise the throughput rate of a filtered tom of the pour cone, the filter remains facility may end up using multiple filterapplication is to increase the pore size of in place and can impede the alloy flow types as their application requirementsthe filter. that the hot-top is promoting. If the use change with new casting customers, Unfortunately, depending on the of hot-top is critical in your application, which should drive home the importanceinclusion characteristics of your ap- using a filter cup may be an option as a of maintaining a working knowledge ofplication, this can also result in a larger filter cup can easily be removed from the molten metal filter types and capabilities.percentage of inclusion particles success- pour cone after the initial pour is made, Casting designers who maintain an activefully passing through that larger pore fil- but prior to the addition of hot-top. Using filter testing program can reap significantter. Similarly, applications with smaller this technique, the base metal has already benefits as they learn how to manage fil-particle inclusions that require small- been filtered and in removing the used ter variables such as pore/cell/mesh size,pore filters will generally have slower filter cup, there is nothing impeding the pouring temperature, and flow rate basedfeed rates. Therein lies the tradeoff when flow rate. on constantly changing application re-considering the ceramic foam or pressed quirements.cellular filters as the active filter area is Price ***focused on the bottom of the pour cone. Without a doubt, the best filter is One notable exception to the filter ef- Jason Hitchings is the General Man- the one that meets or exceeds your ap-ficiency vs. higher throughput tradeoff is ager of Comanche Technologies, and plication requirements and is reasonablyillustrated by investment casters using a can be reached at 866-925-6750, or via priced. As mentioned earlier, the generalspecially designed filter cup that employs email: JHitchings@comanchetechnolo- rule is that the higher the pouring tem-an interstitial space between the inner gies.com. More information on molten perature of your application, the higherwall of the pour cone and the outer wall metal filtration can be found at www.co- the price of the filter. In instances whereof the filter cup itself. manchetechnologies.com. the end-casting will be a critical high-per- formance item such as a medical implant27 May 2012

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