| HotFlo! | Machine Nozzle Bore | |
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An important difference required in the Die Casting machine set-up for a die with a hot sprue compared to a die with a cold sprue is the internal bore diameter of the machine nozzle. For a hot sprue, the nozzle bore diameter at the tip must be the same size or larger than the internal bore of the hot sprue. |
Correct Nozzle Bore |
The reasons for this are :
This last reason is very important to the proper functioning of the system.
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If you use a machine nozzle bore which is smaller than the hot sprue diameter, then a pool of molten metal will be trapped at the bottom of the hot sprue. Depending on its depth, and the platen incline angle of the Die Casting machine, this trapped metal can run forward and spill out onto the die face when the casting is extracted. This can prevent the die from closing. |
Incorrect Nozzle Bore |
For the same reason above, it is important that the die setter carefully aligns the nozzle bore with the recess in the hot sprue seat.
On some Die Casting machines this can be a very difficult task, due to space restrictions around the back of the platen, and the radiated heat. In this situation, it may help to make the machine nozzle bore slightly larger than the hot sprue diameter. For example, the machine nozzle bore on a Series 16 hot sprue could be made 16.5mm diameter.
It is recommended that the nozzle bore alignment, and diameter, is checked before taking the first shot on a hot sprue system. Use a small mirror mounted on a support rod and a small flashlight.
With the dies open, position the mirror so that the flashlight shines down the hole in the hot sprue bush and reaches the junction with the machine nozzle. Check that there is no step in the lower half.
Another test can be made by placing some small diameter brass rod down into the hot sprue bush and checking that there is no step at the junction - especially on the lower half.
It is important that the information and instructions as to the correct machine nozzle bore to be used with each die are added to the machine set-up sheets in your plant.
Finally, it is important that all die setters and machine operators in your plant are properly informed and trained on the need for special care in the selection and fitting of the machine nozzle with a hot sprue system.
Remember to include all shifts in the training program.
If only some of your dies have a hot sprue system, there is always a real chance that an operator will neglect to read the set-up sheets and fit a machine nozzle as used on a cold sprue system. The consequences could be defect castings, increased porosity or production delays due to metal dribble.
Proper training, and occasional review, are vital to an understanding of these issues.
| Document Control | Issue 1 | 1st July 2000 | www.hotflo.com |
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