Removing swarf automatically from long bore

[markkirby]

Hi,
We are finish boring stainless parts up to 80" long, with through hole already machined, internal dia is approx 4", straight bore. We finish bore from both ends, ie 40" of bore depth. Boring process needs to be stopped and stringy nest of swarf removed every 15" of boring depth. The operator goes in with a hooked stick and fishes out the swarf. Has anyone tried this as a machining process, using the hooked stick as a programmed tool? I know the root cause solution would be "don't generate stringy swarf", but for now I'd like to automate process more. Another idea would be to try and flush through part from back end, but not sure that wouldn't take some more engineering development (we seal the back end with an expandable bung at present). Any ideas, especially if you've actually made it work!
Thanks
Mark

[WOLOG]

Is it possible to bore from inside out? I assume you are using a sandvik Devibe? What type of machine are you using. As far as programming a shaving hook, I see no big deal. What about blowing air? How much material do you have to remove?

[markkirby]

Hi,
Yes we are using Sandvik antivibe bars. Not sure if you can bore from deep inside to outside - do they work fine this way in terms of loading, this would be reversed from "usual" direction - have you done it successfully? Do you see this bringing swarf to the entry end of the part better? Machines are Mazak CyberTurn 4500's. We don't have air blast option on turret (at this stage).
Mark

[Geof]

Have you tried using a G74 pecking cycle? I have done this on aluminum to break the chips into small sections.

[WOLOG]

Mark,

What type of insert are you using? Going from the inside out just gives the operator a heart attack the first couple of times. I have done this quite a few times. I try my hardest to get it to make tiny chips and blow them away with coolant or air.

How does that Mazak handle the devibe bar. Using the boring bar stocker thingy? Is it a well built machine? I thought about one of those but chose Mori's instead

[markkirby]

Hi WOLOG (?),
The inserts are all Sandvik, typically with fairly small nose radii (process developed/frozen before my time!). The Mazak seems good (I ran/owned an aerospace machine shop in UK, so my perspective is hands on owner, but I'm not a machinist.) and yes we use the bore bar stocker, which is remarkably repeatable whenyou look at what it does. Some discussion as to whether it holds the bore bar as well/rigidly as it might do. Have you bored from inside to out with a Sandvik 80mm or 90mm antivibe bar?
Thanks
Mark

[WOLOG]

Mark,

I haven't used a devibe bar that big. I use 1 1/2" & 2" on a regular basis. Regarding the insert, what style? VBMT, TNMG, CNMG? I will look at my Sandvik catalog to see if I can come up with a little more help.

I have a few ideas. Let me fix a drink and think a little.

James

[WOLOG]

Mark,
Take a look at this. The middle one looks like a "DCMT". You can rapid to the end of the cut, ramp in slowly and cut toward Z0.

http://www.teeness.no/Products/Pages...tingHeads.aspx


The 580 bar should have an adapter to fit the 570 head. There may even be a 580 head that I don't see. I would use a "DP" rather than a "DC" insert I think they are a little sharper. That was idea #1. I'll be back in a few.

[markkirby]

James (that's better!)
The inserts are DCMT. I think we are "breaking all the rules" according to our Sandvik rep in terms of insert geometry and nose radius. If we were sharing a Scotch (you said you were fixing a drink, I assume coffee if at work, something longer if at home!) I could tell you more, but suffice it to say changes to the process are hard to implement for many reasons. This machine shop is not mine, so it's no longer my bat and my ball. I am looking to get better utilisation from the machines/process hence the idea of using the swarf fishing stick as a tool - may sound dumb, but if you take out a programme stop M00, I've usually found quite big improvements in floor to floor times. Right now the operator has to fish the swarf out about 3 times per boring pass, and he makes 3 boring passes.....
Mark

[WOLOG]

Mark, I don't have a whole lot of faith in "reps" anymore. My Sandvik rep sucks! I continue to buy Sandvik products and last month they canceled my contract because "I did not spend enough money" but the rep only comes around when I start complaining to everyone that he doesn't show up but once a year.

Is there any chatter? Next step would be to take a deeper cut and a little faster feed. I still think that cutting toward Z0 would work. If you use a VBMT332 with a negative lead of around 7-15 degrees, that should give a 45ish degree rear angle. Then the whole chip thinning thing comes in to play by being able to increase the feedrate which should mean you can get it to chip. What grade of stainless is the material?

Was the rep ever a machinist/programmer? Probably not. See my point?

[markkirby]

James,
Rep was a machinist, mainly milling. He's a good guy, and not the problem. The stainless is 403 and 410. I'll keep you posted, thanks for your suggestions (I won't get to try new grades/feeds/speeds for a while, if ever)!
Mark

[WOLOG]

Mark,

Is 410 stainless also called 9chrome? I did a lot of parts with 13chrome 110K yield (420stainless). The stainless grades did not hold up at all. I ended up using GC4425 with a PM chip braker. That is the steel grade inserts. I had 100's of parts with those inserts. Some had 20" deep bores.