Investment casting foundries who produce mission-critical components such as single crystal turbine blades for aircraft jet engines have a defect tolerance rate of zero, knowing full well that a shortcut in quality can easily cut short someone’s life later on as a direct result. In similar fashion, investment casting produced medical implants such as hip or other joint replacements that will ultimately end up in a human body demand quality levels beyond the reach of all but a few …and those same few are the majority of Comanche Technologies customer base. As a preferred solutions provider for many of the world’s most recognizable and successful investment casting foundries, we are fully committed to your success as our first and foremost priority.
Meeting YOUR Specific Application Requirements
By far, the most important factor in choosing a molten metal filter is how well it meets the technical performance requirements of your casting applications. What type of inclusion(s) are you seeing? Are they new, or is this a longtime issue? Have you tried using a filter? If yes, what type and what were the results? These are just a few of the many questions we discuss with a customer to get a solid understanding of their technical application details before moving on to an initial recommendation. If you’d like to get a head start on learning what we can do for you, please fill out our casting application data sheet and email it to us today.
Filter Cup vs. Ceramic Foam/Honeycomb-Cellular Filter
In terms of general filtration (inclusion capturing) ability, there’s no significant measurable performance difference between filter cups, ceramic foam or honeycomb-cellular type filters. Whereas one may provide a slight advantage factor over another such as a fine PPI ceramic foam filter’s edge in capturing smaller-particle inclusions versus other filters, there is almost always a reciprocal disadvantage or “price” to be paid for it. For example, while a fine pore (high PPI) ceramic foam filter may excel in capturing smaller particle inclusions, the smaller pore size of the filter slows the throughput rate of the molten alloy.
While this might cause some to conclude that “all filters are basically the same”, our CerraFlex and Flexsil filter cups prove otherwise in that they can provide additional value and performance as follows:
• Increase filtration efficiency without the drastic reduction in throughput rate – Our proprietary filter cup design provides a 20% faster throughput rate and an active-surface filtration area that is 85% larger (versus competitor filter cups). Compared to ceramic foam and or honeycomb-cellular filters, moving to a smaller mesh size (finer PPI) filter cup to better capture smaller sized inclusions does not cause the usual drastic reduction in throughput rate associated with the former. This is because with a filter cup, the molten alloy flow path is not limited to the very bottom of the investment casting pour cone (as is the case when using a standard ceramic foam or cellular filter). Instead, the molten alloy can flow through both the lower sides and the bottom of the filter cup, offering larger active filtration areas for capturing slag, dross and other inclusions while maintaining a stable throughput rate. Regular ceramic foam or cellular honeycomb type filters simply cannot do this.
• Investment De-gating Tool – Small, flat-cut shapes of CerraFlex or Flexsil placed at the ingate of an end casting (aka “inline”) can not only capture secondary-turbulence created inclusions but also create a convenient “cleavage plane” whereby the end casting can often be safely detached from the investment tree with the slight blow of a shop hammer, eliminating the need for manual cutting. This can have a significant impact on reducing finishing/cleaning room cycle time and costs for any investment caster!
• Maximize Exothermic “Hot Top” Performance – A CerraFlex filter cup can be safely removed from an investment casting pour cone after being poured (removing the captured slag, dross and other inclusions along with it) so that there is nothing blocking the “feeding” action of any exothermic agent (aka “hot topping”) added to the pour cone later. Ceramic foam or cellular type filters are not easily removed in this manner, and thus remain in-place to hinder and or slow the exothermic agent’s performance.
• Eliminate Custom Pour Cone Requirement – Ceramic foam and cellular filters are often glued in-place at the very bottom of an investment casting tree pour cone so that the filter is held securely during the actual pour, as otherwise the filter can often “float” up and out of the bottom of the cup and stay on the molten alloy surface (which in turn may allow subsurface slag and inclusions to drain around and below the surface bobbing filter and down into the investment). Using a pour cone that has a customized ledge or lip on the bottom inner perimeter that matches the dimensions of the ceramic foam or cellular filter ensures there is a sufficient bonding area for the high-temperature core-glue to hold the components together. While this technique does a great job in holding the ceramic foam/cellular filter in place during the pour, the first downside is that it requires the investment caster to utilize custom-made pour cones, which makes for additional costs. The second drawback is that gluing the filter in place eliminates the option of removing it after being poured to enhance the efficiency of any exothermic agent that might be used later.
• Filter Pre-Heat Not Required - Standard practice when using ceramic foam or cellular filters is to pre-heat them along with the investment tree in order to prevent thermal shock fracture or possible cold-shut incidents with the filter. Should something happen during the pre-heat to the investment tree such as refractory cracking or other accidental damage, the ceramic foam or cellular filter is typically non-recoverable and forfeit along with the investment tree. A CerraFlex or Flexsil filter cup, on the other hand, does not require pre-heating and are both designed to be placed in the pour cone of the pre-heated investment casting tree just minutes before being poured. This makes the filter cups easily saved for future use should something happen to prevent the investment from being poured.
Global Leader in Investment Casting Filter Cup Design & Technology
How do we compare with the imported silica mesh filter cups of low cost competitors? In all honesty, there is no comparison. But don't take our word for it, test one of our filter cups for yourself. For specific details on how Flexsil and CerraFlex filter cup performance outclasses the competition, please see the chart below.
FLEXSIL® Filter Cup
CERRAFLEX® Filter Cup
CerraFlex filter cup being removed from the pour cone (along with captured slag) just before exothermic "hot top" is added. This ensures optimal exothermic performance in feeding the castings.
Ceramic foam and honeycomb/cellular filters cannot be removed from the pour cone post pouring, which drastically reduces the effectiveness of exothermic hot top by creating a physical barrier between the heating action occurring in the pour cone and the sprue metal beneath.
Flexsil filters placed at the ingates of an investment casting tree will act as a filter in capturing inclusions AND perform as a de-gating aid to eliminate the need for manual cut-off. Ceramic foam and honeycomb/cellular filters do NOT provide this benefit.
CerraFlex filters placed at ingates of an Aluminum-Beryllium investment casting to minimize the generation of hazardous airborne dust during fettling.
* On a scale of 1 - 10, with 10 being "Best"