Part-Off big noise/vibration Cincinnati Hawk 150

[stcharles]

My CNC Cincinnati Hawk 150 started to make a big noise/vibration while Part-off. Then it stops turning.
I make the machine turn counterclockwise with the tool upside down to be able to speed production. Somebody told me the problem could be (this is only a possibility) the ways are worn because it's not a normal/good practice to use the CNC that way to Part-off.

What do you think about, is that true ?
Has somebody had this problem?
What do you suggest? , changing the ways is a VERY expensive test to do and it's not sure that's the problem. I have a small machine shop and I need this machine for my more important customer.

Thanks very much for your help

[txcncman]

Check tool center line. What RPM? What tool size? What feed?

[stcharles]

Hi txcncman

Thanks for your answer.

The tool is centered to the center of the piece; the piece is parallel to the axis.

Tool is 1/8'' thickness

Tool used: Kenametal : A4SMR120314
Tip : A4G0305M03U04GMN KC5010
Feed : 0.006 start end 0.003

This is the program, PART-OFF section
(MSG, PIECE ;[#PIECE]:0.0; over ;[#TOTAL]:0.0; CUTTER)
N0690 G92 S3000
N0695 T6 M6.1
N0700 S1000 M4
N0705 X2.2 Z-1.882 M8
N0710 G95 G96 S1100 M4 F0.006
N0715 G1 X1.367 F0.006
N0720 G0 X1.467
N0725 G1 X0.534 F0.003
N0730 G0 X2.2
M1
M5
M9
:0080 G0 G61 G62 G90 G94 G70
(MSG, PIECE ;[#CONT]:0.0; )
(IF [#CONT]=0 GOTO [LOOPX])
M1

[txcncman]

Usually, noise, vibration, chatter, etc. is due to harmonics in the physical parts of the machine, the work holding, the tool, and the material. It is always there, speed and feed just bring it out to a level it is noticed.

You made a comment in your first post that has me curious, "Then it stops turning." Does this mean the spindle stops revolving? Is the spindle and chuck or collet revolving and the part stopped revolving? Does the machine alarm out at this point and stop execution of the program?

Is your machine spindle direct drive, or belt drive?

I forgot to ask before, what material are you cutting? (At S1100 I assume aluminum.)

[stcharles]

Yes, the spindle (and jaws / and the part) stops revolving. The machine alarm out at this point and Yes it stops execution of the program with the following message : ''Turret Unclamped ''

The machine is belt drive.

I'm cutting mild steel 1045.

Do you think it's not usual to make turn the machine counterclockwise with the tool upside down? The technician who came to check the machine told it was an unusual technique and it was possible that had worn the ways, but he was not able to swear on that.

[txcncman]

Ok. Here is my best guess. Your drive belts are worn. With this type of cutting you are causing the belts to slip making the spindle lose RPM, effectively increasing your feed rate, which causes more belt slippage and even less RPM and even higher feed rate until the spindle stops completely.

I am really surprised the technician did not figure this out. But then again, it does not surprise me at all.

For a work around, try decreasing your feed rate to 0.001 for the entire cut and see what happens.

[stcharles]

Thanks A LOT txcncman

I'll try your suggestion and I let you know what happened.

[stcharles]

I checked the straps, all is OK.

I spoke with the tools salesman, he confirm he sells a lot of CCW cutting tools; so I think cutting CCW is not a problem for this kind of machine.

Some ideas?

I repeat: I have intermittent vibration problem at Part-Off. It has arrived with different rod diameter's and RPMs. The vibration becomes so intense that the machine send an error message.

Thanks for your ideas.

[neilw20]

Use constant surface speed, and get the feed rate correct.
Lots of coolant, and a lower speed than you would expect often works. Speed, 50% to 70% I found OK.

Chatter? Lower the speed and or increase the feed.

But once the tool/job deflects more than the chip thickness it will be unstable regardless,
unless the speed is above the resonant frequency which you will never achieve, once the diameter gets too small.

Tough stringy material is often a problem.
I often take little cuts with either side of the tool, making the cut slightly wider than the tool. Push a bit, deflect. Other side now, push a bit deflect.
Helps to break the chips on the stringy stuff, which I suspect the 1045 will do.

Try a few different chip geometries. Chip breaking will make all the difference.

[greg b]

Hi I own one of these machines,and apart from some electrical probs I absoultly love it,very easy to use,extreamly flexable,will machine super small parts up to quite large parts.The problem you are having is reasonably common in parting off with this machine and a lot of the issue is the profile of the insert,on many occasions I have purchased new inserts of differant brands and they chatter like mad and if let run im sure the machine would error out but I shut it down before it goes that far.I know this sounds incorrect but if you have a diamond wheel handy you can touch the insert up and it will cut all day with out a prob which I have done many times especially when machining gummy alluminium.The best insert I have used is a sanvik 2.6mm with side rake that leaves the pip on the clamped side of the bar,I also use a 3mm insert flat face,guess you need to experiment a bit,I also find when the machine warms up a bit it also is less touchy.I also dont use surface speed which will make some guys cringe but it works well for me.My program on 50mm mild bar goes something like this oops you guys work in inches anyways here goes.
G90 G62 G94 G71 G0 M6 T9 X52 Z-20
M13 S1000
G1 X0 F60
G0 X52
G28P4
M2
Play with f untill you get what you want.Regards Greg.