Temporary Vibration Damping Material

[THEBurg]

I am machining through slots w/ 10mm endmill in 1/8" wall 2" ID steel tubing of various lengths. Parts are ID chucked on index table on one end & supported w/ tailstock on the other. Parts are as long as 13" so chatter & deflection become a problem.

I inhereted this & company is reluctant to change holding system (I'd like to put it on an expanding mandrel!) Cell takt time does not allow rough & finish passes. I have to finish one side of slot from solid then other side is almost a skim cut.

Have already gone to asymetric flute endmill which helped a great deal, but now I need to attack the part/setup.

Years ago, I machined impeller tips while space between blades was filled with wax. Something like this, or an expanding foam MIGHT help me with my problem, but I don't know what to look for.

Whatever I use must set up quickly (one-piece flow with a takt time of about a minute!), be easily and quickly removable, and prefeerably, either resuable or VERY inexpensive (ah the joys of modern industry!)

Any ideas?

 

[btrueblood]

Agree with the wax approach, as any easily-applied foam likely won't be stiff enough to help hold the parts in place during cutting. But re-use of the wax would require an autoclave or oven to bake/melt the wax back out of the chips and finished parts, and pouring/setting/melting out will all take time. Possibly the melt-out can be done offline from the mill, same with pouring/setting? Pre-cast wax plugs that slip easily into the bore, that you glue in place by pouring only a small amount of additional wax (maybe the plug has precarved grooves to help the wax flow along the length), maybe -- the reduced amount of molten wax poured would reduce the time it takes for the wax to set up...

In space applications we would discuss using "urinal salt" as temporary fixturing for flexible parts during launch (paradichlorobenzene, now a banned chemical; think mothballs) because they would evaporate away... For your part, removal would require you to pull a vacuum on the chips/parts...but dunno if it would work with whatever urinal cakes are made from today. And it still takes time to pour/set/remove the cores.

A laser or waterjet cut would eliminate the chatter/vibration issue, if you can live with the tolerances of the processes...and if you have acce$$ to them.

Hmm. A little more thought: what if you slipped a wax plug into the i.d. that was a bit longer than needed, then compressed the wax by pushing on the ends, causing it to expand to fit the tube. It wouldn't adhere that well, but might offer enough support to be useful.

 

[unclesyd]

Have you tried reducing the rpm of your tool. Also try reducing the number of teeth. These might slow you down a little but you may get more good pieces.

One thing that happened to me on project where we were slotting tubes with a little heaver wall was to us an opposite hand cutter from the one we had been using.

Outside the box:
At one time we use lead putty, since outlawed.
Similar to the wax we used low melting alloys on very critical parts. The could be moulded to take in account your slots.
You try a machinable wax round insert. Not to machine into but act a dampener.
Actually anything inserted in the tube will help like plastic or wood.
Can you build a jig to contact the tube on the opposite side from the milling.

 

[unclesyd]

I should have added that if you reduce the number of cutting teeth/edges you can go up in rpm. I seen where 12 vs 16 cutting edges and rpm almost doubled do good job in decreasing chatter.

 

[ajack1]

Have you considered having a press tool made? Very simple design and inexpensive to pierce on a mandrel, this could even run in a medium size fly press. You should be able to produce them at around one ever five seconds, so a fair savings on the time you quote, also no “skilled labour” is required for production.