Monthly Archives: January 2021

Its Snowing

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“Snow” doesn’t beautify a interior

Snow for Christmas day like we had this year is wonderful. It makes the world seem clean and bright. “Snow” inside a die cast plant just makes a mess. Yes we all know that die cast dies require venting to work properly. The trick is to vent out the gas without venting out the aluminum. It is the vented aluminum that we in the die cast community call “snow”

For those practitioners who have not invented a strategy for controlling snow, it is discovered after the die is put into service. At that point in time the production demand for parts prevents implementing proper fixes. Been there. Just because it is not possible to completely fix the die at that time, doesn’t mean that it is not possible to do something to get better results. In all cases vent features on the die increase the frontal area of the molten metal. The applied pressure multiplied by the frontal area determines the tonnage required. It really starts to “snow” when the applied pressure exceeded the tonnage of the machine because the die blows open. Die vents need to be attached at the last place to fill. Do a short shot to determine where that is. Vents attached to earlier places in the fill only bleed off metal that should have been available to fill porosity at the far end. In many cases a line of weld can block these off or undercuts can stick the overflow into the die filling the unneeded vent.

Every cavity replacement for dies prone to “snowing” includes a redesign of the vent system. Waffle style vents achieve vent path shut off using less frontal area. Zig zag vent shut off works for other dies that are not as close to consuming the available machine tonnage. The knowledge gained from this Kaizen activity makes it possible to launch “snow” free new jobs out of the box.

More is Better?

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When you are choosing materials to create a chiller block- more heat conductivity is better. Beryllium copper has 5 times the heat conductivity of H13. Fast freezing of the aluminum creates the crumbly shut off that makes chill vents work. Somewhat messy as the leading crumbs fill the casting machine pit. When choosing the main insert material, more heat conductivity may not be better. Most customers do not wish to buy crumbly parts. Otherwise we would make all of the inserts out of beryllium copper. Fortunately H13 has poor conductivity. It makes it possible to get the molten metal to the far side of the mold before it freezes. Interestingly a thermocouple drilled into a H13 insert to 6mm from molten metal does not rise in temperature until almost one full cycle time has elapsed.

A few proponents of conformal cooling have chosen to over simplify. A die does not run faster simply because more is better. Quickly making good quality parts occurs when proper choices are made. In a 390 alloy (740C cast temp) valve body heat is a problem. An Anviloy ( 3 times the conductivity of H13) roto pocket sub insert proved to be more effective than a conformal cooling sub insert. ( Having tried both) The scale in the water passages of the Anviloy sub insert could be drilled out each run such that the casting quality did not deteriorate with die age.

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However I believe more is better when it comes to the Nanaimo bars that my Canadian wife makes for me. I can even put up with the fact that they crumble.

FORMer CONTACT

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Contact forms eliminated incoming email spam

We all quickly discovered that posting e-mail addresses on our websites made them the target for spam. This ushered in the contact form. Contact forms historically were filled out by sales people who built a relationship to the point where the potential customer would give them the information. Web designers hoped that they could force users to fill out the forms by blocking access to the website until that was accomplished. This worked the first time. Users quit filling out forms when they discovered that giving out their e-mail only made them a target for spam. The impersonal nature of the contact form and the lack of actual response by the company was to blame. This brings us to where we are today. Clicking on “CONTACT US” brings up the “HTTP/1.1 New Session Failed” error. Companies do not bother to even fix the website functionality. What went wrong with the contact form? The answer is embedded in the name. Potential customers make inquiries. Salesmen fill out contact forms. An inquiry is actually a question. Questions are one of the best indications of buying interest. In this COVID 19 era is is better to replace “CONTACT US” button with an “MAKE AN INQUIRY” button. Educate your sales people to build a relationship by trading timely response to questions asked for contact information. This is the best time to train your sale staff in remote selling. (they cannot visit in person) Yes web developers, cookies can be used to send answers to the questioner the next time they log in without pressuring them to give out their e-mail upfront. Trust takes some time and effort to rebuild. A “BUY NOW” button to replace the “CONTACT US” button only applies if you want to to do the massive investment needed to take on web players like Mc Master.

100C

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100 degress centigrade is the boiling point of water. Usually die casters wish to keep the water in the die thermal passages below the boiling temperature. This is because the cooling tower water we use contains minerals. The evaporation process that the cooling tower uses concentrates these minerals to the saturation point. If boiling occurs within the die thermal passages the minerals deposit as scale. Scale blocks the thermal heat transfer we require to make good castings. Usually the set temperature of the hot oil units that we use is greater than 100C. During operation the water within the die does not boil because it is flowing. When we shut down for the holidays, setting the hot oil units back to 100C avoids boil out of the water in the die. In many cases the die remains warm enough to avoid start up scrap even whan shut down for a few days. As the picture shows only a small fraction of the power is required to keep the die hot.