Cast Iron and steel casting applications require filters capable of withstanding some of the highest pouring temperatures, longest exposure times, and heaviest throughput quantities of any metalcasting process. Early on, CerraFlex set a new industry standard and remains the strongest molten alloy filter material commercially available. Together with Flexsil, our products offer foundry professionals a unique blend of highly efficient filters that are cost-competitive when choice is an option, and technically capable where others are not.
Inclusion removal and scrap rate reduction are critical tasks for any foundry in both consistently meeting high quality standards for end castings and aggressively managing production costs. However, the performance of any given filter is absolutely dependent upon its “fit” amongst a determinant set of measurable casting application factors which include:
• Alloy pouring temperature
• Pouring weight or volume
• Target throughput rate
• Known inclusion or slag specie data (if present)
• Mold characteristics (type, runner configuration, likely turbulence points, etc.)
A single factor may alone dictate the filter options available to the casting engineer, as every filter type has an optimal range of capability for each criterion that should not be exceeded. And thus, it becomes quite clear that a “filter’s performance” ends up far more a reflection of the success or failure of matching the appropriate filter to the target casting application parameters.
Riser removal is one of the more difficult tasks in the overall fettling process, and if done poorly, can easily damage an end casting to the extent where costly re-work is required. While there are many tools and techniques available, to include cutting saws, torches, hydraulic wedges and powerful air-hammers, the process remains time consuming and expensive.
In recent years, a steadily growing number of foundries are adopting the use of pre-fabricated breaker cores that enhance the performance of traditional riser removal methods by reducing the diameter of the riser contact area. This reduction in size of the contact area equates to a faster cut-off rate, or a thinner cross section to break off. While the use of breaker cores does improve the performance of traditional riser removal techniques, it does not eliminate the problem of occasional damage to the end casting from any of these same removal methods.
Fortunately, there IS a way to maximize the speed and efficiency of riser removal while simultaneously minimizing the risk of end casting damage, and it is currently being used by many of the largest production foundries in the US.
A RiserBreaker is a riser sleeve custom fit with a Flexsil or CerraFlex filter screen firmly secured between the bottom of the riser and the contact area of the end casting. The filter screen acts as a filter in preventing slag or inclusions from entering the end casting but more importantly creates a ready-made cleavage plane that will also be the line along which the riser breaks off during shakeout or in the fettling room. The cleavage plane permits the riser to be removed with the slight impact of a shop hammer, and leaves a uniformly flat surface. The benefits of using RiserBreakers quickly pay for themselves:
• Drastically reduce fettling cycle time
• Eliminate end casting damage from riser removal mishaps
• Less grinding and cutting saves time and direct labor cost
• Significantly safer method of riser removal for fettling personnel
RUNNER SEGMENTATION & DE-GATING
For the vast majority of foundries, the removal of casting mold runners and gating systems share the same methods, challenges and direct/indirect costs associated with riser removal. Fortunately, the same savings in time and cost can quickly be realized by placing CerraFlex or Flexsil filters directly in a wide variety of locations in the runner and gating network of a casting mold.
The filters are typically placed in gating sections where a break-point is desired, such as directly at the ingate of an end casting or at the mid-point of a lengthy runner. Filters placed within gating sections are also often utilized to reduce turbulence, with the break-point being an additional benefit.
On average, a typical foundry that utilizes RiserBreakers and or CerraFlex/Flexsil filters for runner segmentation and de-gating can realize an immediate and measurable direct cost-savings of 50% in fettling operations expenses when compared to traditional methods of riser and gating removal. Overall cycle time savings, on the other hand, may be even more dramatic with regard to the average cutting time required for risers and ingates.
Contact our technical support team to learn what filter best suits your casting application requirements and we’ll work with you to plan and test a cost effective solution today.
FLEXSIL® and CERRAFLEX® Filter cups can be placed in a mold downsprue or used as an upstream pre-filter.
CERRAFLEX® Filter cup set in green sand mold pouring basin.
CERRAFLEX® Filter cup set in a Direct-Pour Riser Sleeve (DPI). This technique minimizes gating requirements as the riser contact area sits on the casting ingate.
CERRAFLEX® and FLEXSIL fitted RiserBreakers are easily "knocked off" during fettling with the minor impact of a shop hammer, leaving a uniformly flat cleavage plane on the riser contact area.
CERRAFLEX® and FLEXSIL filters can be placed directly in the gating of a casting to both capture slag and inclusions and provide convenient "break points" for gating removal during the fettling process.