Did that injection mold making salesman really just say precision surface grinding basics are obsolete? Yes, sir, he did; in fact I’ve heard this a few times. I think he was trying to impress the customer by focusing on our flashier CNC’s with more bells and whistles.
It is true that CNC milling and WEDM have both taken a great deal of work that used to be done manually on a surface grinder. Nevertheless, the fact that several highly skilled injection mold makers work every single day in the grinding room demonstrates that it is not obsolete. The mold making process begins and ends with precision grinding.
How would you feel if the salesman said you were obsolete while you were producing the injection mold components that he was selling?
How is precision surface grinding used in injection mold making?
First, there should be a distinction between manual surface grinding and hydraulic surface grinding. For the purpose of this article, manual precision surface grinding means the grinding of mold components, such as core pins, slides, lifters, core and cavity details, etc. Hydraulic surface grinding refers primarily to squaring up blocks and plates for subsequent machining, such as CNC milling.
Some common applications of manual precision surface grinding
- Finishing shut-offs on core and cavity blocks
- Making lifters
- Finishing core pins and inserts
- Electrode manufacture
- Ejector pin grinding
- Finishing slides and cam blocks
- Squaring up small inserts and blocks after heat-treat
- Removing tabs and finishing heels on WEDM’d inserts
Invest in a precision surface grinding machine
Sure, a good toolmaker can produce quality components on an old, worn out surface grinder, but why waste the time and money? Global competition means that other companies are buying ultra precision surface grinding machines and training people to run them.
A high precision surface grinding machine such as Mitsui, Elb, Okomoto or Parker Majestic will pay for itself many times over and make everyone’s life easier. They are reliable, accurate, durable and not that expensive when compared to a CNC milling machine or sinker EDM.
Less expensive high precision surface grinding machines
If the budget just won’t allow the best you can still buy a good surface grinder, such as a Kent, Chevalier or Harig. Just bear in mind that these are what they are: good, but not excellent.
Train new people to replace the aging workforce before it is too late. Soon all those old-timers will be retired.
Why apprentices need to learn precision surface grinding basics
Precision surface grinding gives the mold maker an appreciation for the finesse required to finish a quality injection mold. The leap from good to excellent is huge.
The apprentice learns proper set-up procedure, cleanliness, how to handle precision tooling correctly, the direct application of trigonometry, and how to focus on the machining of mating parts.
Another good effect of precision surface grinding is the humility gained through trial and error. Many cocky apprentices have been brought down to earth in the grinding department! An apprentice named Mike once declared to the guys in the grinding room: “You guys make this sound so hard, it isn’t hard at all”.
I warned him about boasting and Murphy’s law, but he just shrugged it off. A few days later he decided to be the first one to run the brand new Mitsui hydraulic grinder. With the owner and 3 senior toolmakers standing by the machine at the end of lunch Mike fires up the grinder.
When I saw that he had a little System 3R Mini-cube on a big wet grinder I knew he was in trouble. Then BAM! On the first pass the chuck flew off the grinder and crashed into the guard like a small bomb. We all hit the deck, Mike sheepishly turned off the grinder and slunk off in shame. He was really quiet for a long time and became quite teachable.
Find a reliable outsourcing company
If all else fails, you can find reliable companies that offer precision surface grinding services. Once you find a good partner take pains to maintain a good working relationship because they will probably save your project from disaster someday.
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