At first sight, this ingate system looks complicated. Where there are at least two filters in an ingate system, one of the critical parameters that has to be considered is the symmetry of the system. In this example, 72 filters were installed and it was necessary to maintain the symmetry to avoid some filters or filter chambers receiving more liquid metal than others. With this thought in mind, having the same lengths of ingate tubes from the bottom of the pouring basin down to the ingates is important so the friction is the same in each direction and the system is symmetrical.
For that casting, a flask size of 3.6x3.6x4 m and around 24 m of ceramic ingate tubes were used to get enough space for the installation, and it worked well.
With the new generation of filters, the design could be changed to use just 20 filters. To put four ingates in each sec- tion of the casting, four filter chamber cores with five filters in each corner could be installed. Foundry engineers would feel comfortable with these changes because it would be similar to the former system and provide them with a cost savings. But this idea could be expanded more. Moulds often have many more parting lines, some of which can be used for filters, such as the parting lines between core prints and the mould.
Of course even in this casting, the core print for the in- ner hollow is not large enough to contain 20 filters sized 150x150x35 mm and support the core weight at the same
time. But with a bigger filter size of Ø 200x35 mm, we found it was possible to reduce the number of filters to 10 and use the core print with its parting line for the installation. The result is shown in principle in the sketch in Figure 8.
Two downsprue tubes under the pouring basin were used, which were simply connected with the filter chamber. In this filter chamber, 10 filters were evenly distributed around the circumference. The filters were connected with ceramic in- gate tubes with the mould cavity. This design needed only 17.5 m of ingate tubes and a round flask with a diameter of 3 m. The benefits and savings of this system are:
• 6.5 m ceramic ingate tubes. • Approximately 23 m³ moulding sand due to the round flask.
• Less work, less returns. • Simple design, absolutely symmetrical. • Less risk of filter breakages.
This example shows that the purchase cost of the ceramic filters is not the only consideration; the savings of the whole system are also very important in order to realize the addi- tional benefits.
The results of this impressive initial example gave the green light for the redesign of all ingates systems. Figure 9 shows an example of a 24 ton hub for a wind turbine, where just eight Ø 200x35 mm filters were used in the parting line be- tween the core print and the mould.
Some important conditions should be checked in advance for an installation of filters in a core print:
• Is the core print large enough to contain all neces- sary filters?
• If so, is there enough material left to support the core weight?
• Is the level of the core print underneath the ingate level?
Figure 7. Ingate system for 30 ton casting.
If the answer to the first and second question is no, other al- ternatives for placing the filters must be checked. If the level of the core print is a little above the ingate level, that is a pos-
Figure 8. New ingate system for 30 ton casting. International Journal of Metalcasting/Volume 8, Issue 2, 2014
Figure 9. 24 ton wind turbine casting. 21
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