Hey everyone!
I have been building a vertical mill. Its primarily constructed of 0.375" (9.5mm) steel plate. The steel sections are hollow, consisting of a plate with short sides, and bracing across and along it. The work envelope is 40x18x18 (1016x457x457)

When I started I collected some vibration data on the X base (the largest steel piece) I measured the duration of time that the base vibrated when suspended at one point in the center by dropping an 8 oz weight 12 inches. the average vibration time was ~5 seconds. I have since repeated the test after casting the epoxy mixture and can not detect any vibration, only the initial impact. I also noticed that the deflection we were getting in the table is now gone.

I am going to cast epoxy in the table top now. It is constructed of the same steel. This time I collected some deflection data, getting about 0.005" deflection in 16 inches under 30 pounds of weight. I collected even more vibration data on this piece, which currently has a vibration time of ~3.7 seconds.

Which brings me to my point finally. I have studied some on vibration sensing. Enough to know that there is a lot to know about it.. Once this epoxy is cast in the table, its there forever and I cant repeat any of these tests. Should I be collecting something other than the vibration duration? Is the frequency import, or just the time? Since I cant get it to vibrate by pinging it with a hammer or other weighted object, whats the best way to determine the dampening of the vibration? Would there be a benefit to building a vibrating apparatus to determine a harmonic frequency of the table top after its filled?

Any thoughts on the matter are appreciated.

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