PITA job

Got a bad one. Cast Inconel 625, shitty pickling/annealing? from the customer. Has 5 ribs 40mm by 6mm, 45 mm tall, at odd angles and
distances, on a 125mm square surface. Need to remove 5mm from each, and all have to be flat to each other within .05mm and 1.6 surface finish. Got the easy part working. <G> parallel and smooth. Roughing sucks. Of course, cycle time is the most important thing, you know the beancounters. Got 10,000 of the buggers. Leaving .01 for finish, to remove the majority of the burr left by the rougher, and keep the finisher living for a while. Using 7 flute coated carbide endmills made by Helical. 80 sfm, .0015"/flute chip load, .19" d.o.c.. Climb milling, with .100" overhang through the rib. Any better ideas, suggestions? Can't let the tool get too dull, as deburring becomes problematic,as they require <.25mm chamfers, hand done, as it's a casting you know.
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Steve Walker
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Maybe cast a low melt alloy over the part and recover it from the chips ?
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On 2/26/2013 23:46, PrecisionmachinisT wrote:

Thought of that, but 10,000 would take forever to preprocess, and cost would kill.
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Leave zero for finish, process by stepping down about .050 at a time milling one side then the opp side of the rib using an extension end mill that's been necked so that it won't make contact with any material thats already been cut.
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http://imageshack.us/f/560/dsc0013m.jpg/
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The rougher is worn in tight corners. Attack corners first with trochoidal cuts - no sharp corners.
If you can send me the details I can send you a picture of what the roughing toolpath should look like.
DanP
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On 2/27/2013 02:37, DanP wrote:

I'll post a print to the metalworking dropbox tomorrow, if there's no NDA. Otherwise, I'll e-mail you one, boss has no problem with consultants looking at prints. <G>
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Steve Walker wrote:
Climb milling,

Geez, climb milling poorly supported ribs can be a real bear. If they start to deflect, the cut gets deeper and then the whole rib gets bent. Have you done a test part, yet?
Jon
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On 2/27/2013 16:56, Jon Elson wrote:

Done over 400 so far. Tool life sucks. Burrs get really bad, that's when we change it out. Actually, the centerline of the cutter is about .05" to the left of the rib edge, so that the radial doc is 6mm, with about .100" going through the right edge of the rib.
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when

That you were taking material only off rib tops was not previously clear to me.
Carry on...
--if finish and parallism become a huge problem maybe you can leave .010 or so and then send out to someone with a big ass blanchard or a double disc grinder.
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For those interested, file is inconel_casting.jpg. Thanks for the help so far.
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On Friday, 1 March 2013 01:27:17 UTC, Steve Walker wrote:

I found the drawing at
http://www.mwdropbox.com/dropbox/inconel_casting.jpg . It looks like you have to machine the coloured surfaces plus the steps around the bosses to the sizes mentioned, 22mm and 44.45mm. That means there the walls and the bottom face do not need to be cut.
There is not much metal to be cut. However, cutting conditions are not great as it means the part will vibrate a lot. A way to dampen the vibrations is with a filler like PrecisionmachinisT said. Try http://en.wikipedia.org/wiki/Pot_metal
Make sure the rougher has a big enough chamfer on it (or a rad).
DanP
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wrote:

the bosses to the sizes mentioned, 22mm and 44.45mm. That means there the walls and the bottom face do not need to be cut.

it means the part will vibrate a lot. A way to dampen the vibrations is with a filler like PrecisionmachinisT said. Try http://en.wikipedia.org/wiki/Pot_metal

I wonder how well simple #8 birdshot would work in the cavity? Put in a bottom plug, fill and cap the top.
Or put the critter on a pallet with high sides, fill with birdshot and then mill. It will pack down as you start cutting. It will be a decent enough dampening media once it gets packed in. Pull the pallet, dump the shot into a screen on a bucket, put in the new work, dump pellets back in and repeat.
The only other way I can see is a very high durometer elastemer "plug" that fits the inside of the box with the ribs and whatnot sticking through. Would have to spray a bit of WD on it before wedging in the "plug". How many of these have to be done?
Gunner
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Steve, Have you considered making a smaller bit of geometry in the center of each island, and then climb milling around that geo so that the e/m is always cl imbing through the cut, thus pulling the burr "into" each island, eliminati ng the "push out" burr, and also, loading the tool the same for each cut ma y yeild better tool life. A tad more cycle time, but better tool life and a more reliable cut, and le ss deburring, even with tool wear. if I am not explaining myself correctly, the shop # is 951-245-8850, will b e there in the morning after 8:00am
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On 3/3/2013 19:04, "D" wrote:

island, and then climb milling around that geo so that the e/m is always climbing through the cut, thus pulling the burr "into" each island, eliminating the "push out" burr, and also, loading the tool the same for each cut may yeild better tool life.

I've done this,at your suggestion, deburring is much better, but need approval for tool life test and cycle times, before long term implementation. (I'm using deburr time as part of overall cycle time, so it may be a wash, to the good of the operator, anyway. Frees him up for less stress.)
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