One of the most AMAZING solutions we have at Advanced Machine & Engineering Co. is our epoxy mineral-based tombstone-technology. However, most people don't know anything about epoxy-mineral tombstones, so I decided to write an article!
Tombstones? Did Someone Die?
No, not that kind of tombstone - thank goodness. So, what is a non-tombstone tombstone?
Tombstones and Gridplates are foundational structures used in the machine-tool world for clamping raw material or near-net-shaped parts before material removal (e.g. machining or grinding) or shaping (e.g. thread forming or knurling). Sometimes materials are clamped directly to the tombstone or gridplate (e.g. with dowels and toe-clamps) or they are held in clamping devices (e.g. vises, chucks, and pinch-clamps). The most common material used for those foundational structures is cast-iron, though it is not uncommon for aluminum, steel, and stainless-steels to be used.
Putting Tombstones to the Test
Dr. Tony Schmitz, a professor specializing in vibration analysis, came to AME to do a series of tests on the various material types of tombstones. In a video (link at the bottom of this article), he breaks down his findings to determine the best type of tombstone for your shop.
Comparison of Four Materials for Free-Vibration Response
"The maximum acceleration was normalized to one for all tests so a direct comparison was possible for the four tombstones. It is observed that the vibration stops much sooner for the epoxy - this indicates higher dampening," Dr. Tony Schmitz
What does that even mean?
It means that when forces are applied to the system, the energy that is transferred into the tombstone takes longer to dissipate in some materials than in others. This is an important thing to know when we are talking about our "foundational structure."
You can see in the charts above that in the epoxy-mineral material the acceleration due to vibration reaches 0 in hundredths of a second, whereas it could take over a second in aluminum to achieve the same state. The higher and more frequent the forces, the more that matters. With epoxy-mineral tombstones, vibration damping is rated at 10 times that of cast iron and 100 times better than aluminum.
Why does it matter?
In the world of machining and shaping, it is all about making a quality part as quickly as possible for the least cost. Mineral castings do so many things, like reducing chatter, to make that more possible:
- Surface finishes are drastically improved, improving quality
- Tool-life (or insert-life) is improved, lowering cost
- Higher speed cuts can be made, improving lead-time
- Higher dynamic-stiffness is achieved, improving quality
- Lower thermal expansion is achieved, improving part repeatability
Wait, There's More, Brofessor?
There is also the clean-room benefit of not having cast iron or aluminum, which means it is great for the pharmaceutical, medical, and food industries. The low vibration is also great for the grinding industry. And, did I mention it's cool? Not just Elon-Musk cool - I mean literally, it's hard to heat up. Happy machining!
Want to learn more? or get a quote? Go here: https://www.ame.com/tombstones-fixtures
If you want to nerd-out, watch this: https://www.youtube.com/watch?v=3sxOrjgldaE
It's only fair to share...