Simple Solutions That Work! Issue 8

7 This is especially true with crucible furnaces. Although it may have less of an effect on efficiencies it will definitely shorten your bowl life. Crucible furnaces have very hot surfaces as heat rises up against the steel plate on top when you remove 5-6” of metal from the bowl it is replaced with air which is an insulator. So you have this buildup of heat at the top and nothing to transfer it into. Now you get a temperature gradient from the middle of the bowl to the top and this cracks the top of the bowl. Simply evenly charging this crucible furnace so as to never let it get lower than a couple of inches, may increase your bowl life substantially! So establishing a molten metal and scrap and ingot delivery system to the furnaces will help manage furnace tenders time and hopefully show where you need more or less people in the department. In larger casting operations that deliver scrap to the metlers by fork lift as well as ingots or sows it is critical to get this schedule right. This should make it clear as to when you have time to clean your metal and your furnace linings. One of the most expensive budget items in a foundry or die cast operation is the constant relining of furnaces. Some companies are spending hundreds of thousands of dollars on refractory relines but won’t hire one more person to clean their furnace every day. Aluminum melting furnaces regardless of the manufacturer need to be cleaned every day. The aluminum may need to be cleaned more often than that depending upon your alloy and ratio of scrap to new metal. The holding furnace should be cleaned every other day unless they are the electric immersion type and those can generally go about 5 days between cleanings. Molten metal launder systems should be skimmed every day and the bottom lining scraped every week. Pay the melt shop people on an incentive program. I hope you have tracked your refractory costs and dross metal losses (if not you sure should be) give them an incentive that for every dollar they save you off that monthly average you will give them a quarter of it. Run energy audits on all your furnace so you know your casing temperature baselines and can tell when the refractory has been compromised. Cold clean all furnaces once a year. This means draining them and having a qualified refractory contractor come in and get whatever oxide is present out of the furnace and patch it. Gunning over bad refractory is the worst type of repair and hot gunning is even more of a risk. Gunning any refractory produces a final product that does not have the same properties as a cast lining. It is sometimes much lower properties than is desired. I am always amazed at how much aluminum is sent out with the dross. Why on earth would you want to have someone else to melt metal that you have already melted and then sells it back to you? I actually had one person tell me they make money off the aluminum then sell in their dross. Even if you don’t buy it back from the dross recovery guy you have to replace that metal with new somewhere. That costs you much more money than the scrap guy gives you for your dross and it never saves you money. Finally the last thing you should consider is a SCADA control system for your production facility. This allows you to collect data from every casting cell and can even control that cell so that it cannot make a part out of specifications. You can measure various parts of the casting process and record them and if one of them gets out of your designed parameters it will actually stop the cell from producing the casting till the issue is resolved. The whole thing can be placed on a computer screen at the production manager’s desk like below: CONCLUSION: 1. Get a molten metal management program started with your melt shop foreman. Try it for one month and I guarantee you will see measurable results. 2. Train your employees on the best practices for your specific operation. 3. Clean melters every day and holders as discussed above. Clean your metal as needed. 4. Pay melt shop people on an incentive program! 5. Work towards delivering clean metal on time and at temperature every day. 6. Control refractory costs through energy audits and yearly cold cleans and if you do this buy premium refractories. If they give you one year longer life they have more than paid for themselves! 7. Reduce the amount of aluminum in your dross. Don’t pay twice to melt metal ever. 8. “You cannot control what you cannot measure” (from the famous quotes of Peter Drucker) implement a SCADA Control System. He also said “Management is doing things right; leadership is doing the right things”. These few basic simple things will positively affect your bottom line. Contact: DAVID WHITE [email protected]