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  1. #1
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    Need Help! ASAP surface finish issues

    I'm using a 1.4" extra long HSS 4fl cutter to cut a deep pocket. I'm Using recommended speeds and feeds and have played with it all over the board and cant manage a descent surface finish. The walls are rife with chatter marks and nothing seems to be helping. Please Help! Job is already started and deadline is pressing in on me. Any advice would be greatly appreciated

    thanks

  2. #2
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    What material? What machine? At what parameters are you cutting? Climb or conventional? Coolant, oil, or nothing?

  3. #3
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    challenger MM-430 mini mill, 8000rpm max, 6061 AL. climb milling, coolant flood cimcool gl,

  4. #4
    Monkeywrench Technician
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    Extra long cutters are terrible.
    Probably wont get it.
    Carbide helps drastically.
    Larger diameter helps.
    When forced I use a long shank/short flute cutter (carbide) and cut in steps.
    My #1 rule is find a different method to cut it - but you can't always.
    www.integratedmechanical.ca

  5. #5
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    I have the option of using a much smaller (3/16") solid carb cutter to clean up the walls, again, extra long (1 1/2") 3fl stub though. I've been playing with it trying to get a better result, but still getting a **** finish, what would you run a cutter like that at to get a clean finish?

  6. #6
    Monkeywrench Technician
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    Sorry to say, but I would never expect to get a clean finish with that cutter, Without even trying, I would figure this way.

    My best suggestion would be something like this http://www.harveytool.com/products/p...&keyword=34712 at 8500RPM maybe 6 IPM.
    www.integratedmechanical.ca

  7. #7
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    Might want to check runout at the tool.

  8. #8
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    Your doing this thing on a mini mill? Thats 1 problem, how deep of cut are you taking? 6061 is some of the easiest if not easiest to cut material that there is and leaves a beautiful smooth shiny finish whenever I cut it. Your long tool is also a big dangerous problem. I also recommend you use a 2 flute cutter, if your using a puny little mill that isn't rigid your going to get not so good results. Also lower your spindle speed and feed when using large tools, I don't care what your cad/cam output tells you to run it, you need to run it low. There is nothing wrong at all with using HSS cutter your using. But your going to get tool chadder if not run correctly from the length of the tool. Why are you using a long endmill? Any one who tells you to raise your spindle speed while using a larger cutter doesn't know what they are talking about, you always use low spindle speed with large cutters. I guarantee you turn your feeds and speeds up with a big cutter and its in steel your going to destroy your endmill almost immediately in a puff of smoke. What exactly is the size of your mill? I think a good portion of your problem is that, and how is it mounted? Is it just setting on a table or what? Using a longer tool holder like darebee said is also a good one. 2 flutes thats what you need, aluminum doesn't break up like steels, it has longer chips, which is why you need 2 flute because it gets the chips out better. Another thing is your chips, that will also leave you with a pile of garbage for a part if you don't get them gone. Good luck thats plenty of info to get your job done just right there alone.

  9. #9
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    Wow... Not even a thank you, hmm... Seems like to me there's not many machinists on this website. Some programmers who know what there doing but actual machinists who know tools, materials, feeds/speeds, and exc. exc. are quite rare in this community. Not to mention the welders on here who think they know how to weld and repair welds are quite a joke. I've spoke to a few people but the majority don't know their heads from the a$$'s. Not trying to make any enemies, but if you don't know what your doing don't say it. You could get somebody really hurt or worse off dead. Hopefully this guy is'nt in the hospital getting sewn back together after he listened Dare Bee's awful 8500RPM exploding endmill trick. Knowing how to diddle around on your computer and listen to your programs feeds/speeds doesn't make you a machinist.

  10. #10
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    Quote Originally Posted by rough_cut View Post
    I'm using a 1.4" extra long HSS 4fl cutter to cut a deep pocket. I'm Using recommended speeds and feeds and have played with it all over the board and cant manage a descent surface finish. The walls are rife with chatter marks and nothing seems to be helping. Please Help! Job is already started and deadline is pressing in on me. Any advice would be greatly appreciated

    thanks
    You can sometimes oscillate your feed to pull chatter out of a part.

    Rigidity of your fixture is a huge portion of the battle and if you're doing some sort of thin wall with that pocket: that could be the cause of your problem.

    Short of re-enforcing the part with jacks in such a scenerio: another option of last resort would be to take shallower cuts rather than using the full length of the endmill. Then you can sand out the seams.

    How do you make a profit with a mini-mill? CNC Lights off manufacturing?

    I've never been able to hog material fast enough on them to justify not paying someone else to make the parts on a more rigid machine.

    I'm not trying to be a snob, (I don't have better than a minimill myself.) But if I was going to go in to business I'd get a loan for ~$3K and get a used horizontal mill or bridgeport depending on what my business plan looked like.

    You would loose $3K worth of productivity in a single month of babying your roughing passes on a minimill.

  11. #11
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    Quote Originally Posted by tusavision View Post
    You can sometimes oscillate your feed to pull chatter out of a part.

    Rigidity of your fixture is a huge portion of the battle and if you're doing some sort of thin wall with that pocket: that could be the cause of your problem.

    Short of re-enforcing the part with jacks in such a scenerio: another option of last resort would be to take shallower cuts rather than using the full length of the endmill. Then you can sand out the seams.

    How do you make a profit with a mini-mill? CNC Lights off manufacturing?

    I've never been able to hog material fast enough on them to justify not paying someone else to make the parts on a more rigid machine.

    I'm not trying to be a snob, (I don't have better than a minimill myself.) But if I was going to go in to business I'd get a loan for ~$3K and get a used horizontal mill or bridgeport depending on what my business plan looked like.

    You would loose $3K worth of productivity in a single month of babying your roughing passes on a minimill.
    Completely agree with the mini mill theory, I have never understood why people buy those peices of garbage "no offense". Even mini mills are in my opinion very expensive for what they are and what you can do with them. Sure if they are U.S.A. made they take time to manufacture, but they really are for very small projects and that is at best.

  12. #12
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    Just observing the post,, and comments,,, "mini mill" ,,,, Well, mini means different things to different people,,,, But I am assuming this thread assumsion leads to a bench top,,,whereas the mill in question is mini reative to a Mazak FJV35. Believe this machine weighs about 7000 lbs ,,, 15hp BT-40 spindle ,,,16 tool ATC,,etc
    Just a thought

  13. #13
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    Well I guess I will add in my 2 cents for what it may be worth. I never did see where you actually stated the actual depth, width, profile or fillet radius required within this deep pocket or what the actual finish requirement is. 125, 63 32?

    With the limitations you did state, I would at least try drilling out as much material as possible first then take a plunge capable end mill and plunge out again as much material as possible. The rpm you mentioned is way too high for a high speed cutter with an extended length. Ideally a solid carbide ski-carb end mill would do the job very nicely. Reduce the rpm to say around 700 -1100 rpm with a 10 - 20 ipm and make your milling moves to shape the pocket leaving it undersize about .050 on the side walls. Then go back and make a finish pass at half the feed. This should give you better results but will also need tweaking to see waht works best. With the conditions you are faced with, too much rpm & too much feed along with a machine setup or work holding device that is not ideally rigid is going to give you a poor finish. If you get the finish closer to what is acceptable you can also use a deburring disc like a 3m scotch brite unitized wheel to buff out some of those tool lines. Again it really does depend on what your actual finish requirement is.

    **Just a note for the future. Anyone asking for help will always get better results for what they need if they provide all working parameters up front.

    The machine being used, complete tool description & the way the tool is being held, rpm, feed, depth of cuts, coolant, fixturing. Everything you can think of so you get more good feedback and less questions.

  14. #14
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    Quote Originally Posted by tusavision View Post
    How do you make a profit with a mini-mill? CNC Lights off manufacturing?

    I've never been able to hog material fast enough on them to justify not paying someone else to make the parts on a more rigid machine.

    I'm not trying to be a snob, (I don't have better than a minimill myself.) But if I was going to go in to business I'd get a loan for ~$3K and get a used horizontal mill or bridgeport depending on what my business plan looked like.

    You would loose $3K worth of productivity in a single month of babying your roughing passes on a minimill.
    Did you guys look up the mill he has? It doesn't look all that mini. They call it a micro mill, but it's not a benchtop or anything like that.


    edit: pro-dea beat me to it by 17 days, lol.. missed that post

  15. #15
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    Thanks for all the feed back gentlemen, in the end I did work out some strategies and got the job done to spec. and on time using some of the tips i read here.

    As regards to the "mini mill", thank you pro-dea and plv0dr, it is a mini machine center akin to the Haas super mini, starting at about $40,000 its not a light machine. Good rigidity and minimal following error though I produce cells and tooling for custom optics manufacturing so circularity and concentricity are a major concern for me so I rarely interpolate holes with it. At any rate thanks again.

  16. #16
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    I produce cells and tooling for custom optics
    *perk* that's handy to know... I make custom optics! ah, you're in Canada... I'm in the UK
    I love deadlines- I like the whooshing sound they make as they fly by.

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