Need Help! ASAP surface finish issues

[rough_cut]

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

[beege]

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

[rough_cut]

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

[DareBee]

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.

[rough_cut]

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?

[DareBee]

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.

[ee_t]

Might want to check runout at the tool.

[universalfab]

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.

[universalfab]

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.

[tusavision]

Originally Posted by rough_cut 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.

[universalfab]

Originally Posted by tusavision 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.

[Pro-dea]

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