One of our more advanced customers brought to us this observation…
It is interesting that this test does not utilize the pack & hold portion of the cycle; just the fill portion. Experience shows, especially with high 2nd stage pressures, that the screw will drift, and some reflection of that would be a good indication of check ring holding. Your thoughts…?
Every check ring will leak and drift. What is most important in maintaining a consistent fill is the repeatability of this leak. The Dynamic Check Ring Repeatability Test is intended to measure this variability in this leak during fill. In most cases, if the drift is variable during 2nd stage, it will also be variable during fill. Although each process is different… if the screw does not bottom out, and cushion varies less than 5% of the overall shot size from shot to shot, usually the amount of drift is not a major factor.
It is always great to hear someone asking such highly technical questions because it means they are focusing on the finer points of processing rather than subjects of general knowledge.
A good friend of mine just asked the following question…
Is there an industry standard for how much torque a set up person will use to clamp a mold? I know there are specs for the bolt used but I think they’re too high. We use multiple clamps and multiple bolts per mold so the load is distributed all around. Our smallest machine is 55 tons and our biggest one is 500 tons. If you know of any standard, please let me know. Thanks in advance.
For your molds, we typically recommend around 50-60 ft-lbs… If the diameter of the platen bolts is larger on your biggest machines, you may be able to go a little higher. The two main factors would be the weight of the mold, and the condition of the platen… many industry people would recommend generic values around 80-120 but they usually assume ideal situations.
Keep in mind, the clamp functions by stretching a bolt to apply a bending force to the clamp which is held back by the platen threads. As a result, the more torque you use, the quicker one of these will fail (this failure is almost always found in the platen threads). This why we recommend a conservative torque value with additional clamps used when necessary.
It is always a good idea to have a specific torque value to be used at your facility. Much time can be lost when a platen bolt hole becomes stripped and needs repair.
A plant manager recently approached me with an issue…
The plant was losing between $20,000 and $50,000 a month in mold damage during mold changes. It turns out, they had changed plant managers a few times in the past two years. As a result, no one really cared since accountability went out the window with each change and new managers came in with a clean slate.
I shared a couple of success stories from the past with him about upper management teaching critical job functions. Your employees are impressed when the plant manager, president, or owner is willing to roll up their sleeves and show someone how to do the job right. In such a role, these managers act as professional mentors to your employees.
In this case, I told the plant manager to learn the proper way to change a mold, and then teach, step-by-step, the most effective way to change a mold at their facility. Also have the employee change a mold side-by-side with the plant manager. Once this has been done, the plant manager can offer to repeat this instruction if any issues occur… but ultimately, the employee is now inherently responsible to the plant manager for doing the job right.
Remember, employees always look up to a mentor… and plant managers often make great mentors.