I have an idea (caution—-pure speculation) that the pressurized runner/gate strategy was developed for production environments where molds necessarily had to be placed level on the casting floor. In many of these circumstances tilting molds would have been cumbersome and repeating castings in very large numbers would be the norm. So, tweaking a somewhat complex system of gates and runners would pay off once the right combo was reached where all the mold cavities filled simultaneously. But, that happy state is not easy to achieve nor necessarily calculate to work first time out of the box. On the other hand, simply tilting the mold guarantee’s an orderly bottom to top fill. I put my runners in either the cope or drag (preferred) and tilt the box. Cold shuts just do not happen that way. And I like the simplicity. Just another take… Denis
Thank you Denis and Kelly. Sound suggestions. I am still learning about the feeding of castings and every working practice suggested by experts is greatly appreciated, Cheers Charlie PS looked in a casting book I have "The Complete Book of Sand Casting" by CW Ammen, and he says to have the runner in the cope, which is probably where I picked the habit from. I will try to get it in the drag in future.
From the book, Pg 148; "The most effective system is to place the runner in the cope and gates in the drag..." And, Pg 149; a diagram confirming the previous statement. Cheers
Ok for long(er) flat patterns in a single cavity mold but in multicavity molds that alone still means the down stream higher cavities get colder metal at different feedrates, thus the intent of the variable area runner wiht gates at the same mold/runner height. No idea why he would say that. Most effective for what and why? Though not optimal, an approximation with the the runner in the cope would have a constant height runner that tapered in width (instead of height) from the sprue/well to the successive cavity in gates. Best, Kelly
That is wrong, bring the metal in low and raise into the casting, Best practice is drag runner, cope ingate, run casting in the cope. Not always practical, has to be weighed against several factors. Many times a world class casting can be achieved with simpler gating. Question my experience, fine. I have been doing this for 50 years, and am currently pouring 250,000 lbs aluminum a year. I do this for a living
It is true that downstream cavities get colder metal in a tilted multi-cavity mold. I have used this system for 4-cavity molds max and you can see the difference in finish further away from the sprue. I am sure people probably have 20 cavity molds. For my purposes tilting the mold has been much more likely to work the first time. Using the tilt, I do not have to try to calculate runner and gate sizes in hopes of getting proper balance. I suspect calculated runner/gates would be more optimal. It is simply a practical solution for me. Whatever method is used, stagnation of flow seems to be the sure cause of cold shuts. And a sure recipe for cold shuts is to use level molds without proper gate,runner systems that allow unbalanced and inconsitent flow into cavities. One of the classic problematic designs is to use a central sprue with many equal branch points to cavites radiating from the center. If that type of mold can be poured fast enough, there will be no stroublesome stagnation. But if it is poured just a bit slowly, sludging can occur in one or more of the cavities and that will be trouble. Even level two-cavity molds poured at a reasaonable rate can stagnate---I've done it more than once. Good discussion and good to hear different ways to skin the cat. Denis
It appears that I may have offended you FR? If so I apologise. I do not question you at all, it has been quite clear to me after reading your posts, that you are an expert at this trade, Cheers Charlie
Not been in a good mood, girls will do this to a man... And frustration about terminology being used, there is a clear misunderstanding about metal flow. Kelly pointed out quiet accurately about an imbalance in metal temps with this runner, downgate. We shown several pics with the downgate right in the middle, and it goes to the side.. It is such a simple part, It should'a shipped by now. God Bless everyone. Terminology, names for parts, etcetera, in the foundry, especially on the working floor, is not standardized across the country, and to someone not very familiar with can become confused with what is going on, I have tried creating a new thread for something but have not figured out how. No big deal, eventually I will get it... I am glad its Monday, I have a great crew, going to be good to see them.
