Excessive machining noises during cutting

[blounteng]

I am machining parts on a MAZAK horizontal two pallet, six station table and is experiencing menacing machining noises during the cutting operation. The tool is a ganged cutter of five slot cutters assembled to produce a 0.060"W x 0.380"D.O.C. on five 0.242" thickness bars at a time. Are there any suggestions to reduce this noise. Speeds and feeds are limited options for a resolution.

 

[tomwalz]

Have you found the "sweet spot" for the operation. Boeing term among many others.

Resonance in the tool holder? Cutouts or inserts to change the frequncy?

TiCN cuts up to 15% quieter than WC. Try straight TiCN cermet or coated WC.

 

[blounteng]

Interesting thought though I do not have the technology on hand to find that sweet spot. The cut is an agressive one and TiCN have not been too kind as far as performance, so I use TiALN which serves me best. Anyway do you have any contacts for outside services with the technology to identify the sweet spot? Thanks for the information and I will try to measure the difference using TiCN to see if you're on to something.

 

[jbel]

What material are you cutting? What is the diameter of the slot cutters? Is your setup rigid enough for the operation?
Are you truly getting a benefit from running five parts simultaneously or are you experiencing too many problems with chatter to make it worthwhile?
More info please!!!

 

[mrainey]

What about the overall rigidity of the setup? How far are the tools extended? Are the workpieces well-supported? Give some more details - feeds, speeds, specific cutter type, number of teeth, workpiece material, size of toolholder, arbor length and diameter, etc.

There are a dozen different things that could be causing your problem.

 

[blounteng]

The set-up is rather rigid. The machining cycle for the whole operation is 55 minutes for the six position. Stacking them five high is a cost per piece benefit. Material is 4140-Rc25 cutting with 600RPM and 28IPM. Five ganged cutters eah with 20 teeth and cuts 0.080" and 0.063" width grooves. Tool holder is a CAT50 with stickout length of 4.750". Stack height of bars clamped 1.300" high.

 

[mrainey]

The feedrate sounds reasonable (.0023 IPT). What diameter cutter are you running at 600 RPM, and what material is the cutter made from? At that speed, for example, a 2" cutter would be running at 314 SFM, which would seem to be much too fast for a HSS cutter. For that matter, a 1" cutter at 157 SFM sounds too fast in 4140 Rc 25 material.

Even if the cutter is made from a material that will take that speed without burning up, understand that the most common cause of noisy cuts in rigid setups, assuming the cutter is ground correctly, is excessive speed.

 

[blounteng]

Point noted mrainy and I am aware of the principles. This particular project has become a science in my organization with me as the Doctor. But I am at an end for knowledge and at this point tricks. I designed the tool after my predecessors many attempts of type of cutter and grade of cutter material.

Saying that the cutter is a 3" solid carbide. The carbides characteristics is one of a tough, wear resistance without the super hardness (avoid chipping) type grade. I have played with relief angles, rake, fullradius nose or half radius you name it. I have settled out at 275 minutes per set of cutters which is up from 115 minutes since I started with the age old project almost a year now. I will welcome any unorthodox recommended treatment, provided of course tested before.

 

[mrainey]

Well, I truly wish I could be more help. A few other thoughts.

To me, 275 minutes of actual cutting time is pretty darn good. Noisy cuts usually result in shortened tool life.

Normally, I would expect excessive noise in a cut to be reflected in the machined surface finish (chatter, etc.). Is the finish acceptable? Are machined surfaces consistently in tolerance dimensionally?

Is the noise such that it's an environmental hazard, or just something that doesn't "sound right".

If an environmental hazard, you have a problem that needs to be fixed.

If just a strange noise, but the tool is not breaking, the finish is okay, and dimensional tolerances are being held, maybe the problem isn't so bad.

As a last (I promise) suggestion - have you considered putting the operation onto a conventional horizontal milling machine, where the arbor could be supported at both ends? It would be much more rigid that way. With some thought, I'll bet you could match the productivity of the HMC without wearing earmuffs.

Good luck.

Mike

 

[EdDanzer]

Kennametal has a system that listens to the sounds generated in a cut and uses that information to match the resonate frequency of the cutter to a speed.
The problem with this is it will not take into account some stiffness problems in the machine or part being machined.
Are you seeing fretting on the 50 taper? Are the parts generating some of the noise? The material you are cutting tends to vibrate more than others so much of the noise could be from the cutters strumming the parts after cutting. To reduce this you may need to add additional side clearance to the cutters, or change clamping to control part vibration.

 

[funnelguy]

Perhaps a finer tooth spacing?

Make the cutter OD larger with larger hardened spacers and a custom arbor with an eye to improving the stiffness of the cutter stack. A means of controlling tension in the stack may be of help also.

.0023 IPT for what is essentially a slitting saw sounds like a lot of feed, IMO.

Make sure the teeth are staggered from one cutter to the next. Don't have a tooth entering the cut at the same time on all cutters. Vary the number of teeth from one cutter to the next to try to avoid resonance.

 

[blounteng]

Thank you funnelguy for the input. I already have in place all of what you have suggested except for the larger OD cutter and the eye on the special tool holder. The spacing is process specific and cannot be changed (spacing is relative to the required placing of the slot and the number of bars stacked). The OD on the other hand would mean major layout changes on my palletizer as my tool paths are moving between parts stacked close enough only to accomodate a 3" diameter cutter. I am not however, familiar with your term the EYE please explain?

 

[tomwalz]

"Sweet Spot" is that point where a combination of feeds, speeds, etc. gives the best results. I apologize but I am materials and very, very little (almost none) machining. I have seen master machinists familiar with their work and equipment "dial" a machine into a sweet spot. A fair part of the process involves listening. It seems to be a lot like tuning an instrument or a race car. Obviously a big part of it is control of resonance.

Sorry I can’t be more help.

You might try Dave Vale at Kennametal. Dave Vale - 724 539 6807 He is an expert on cermets.

 

[ornerynorsk]

800 rpm on a 3" cutter is suitable for aluminum, but certainly not for hrc25 4140! A feedrate of .0023" per tooth is also a tad much for that size of cutter, but if you are not experiencing broken tooling, it may not be too bad.

 

[funnelguy]

blounteng,
Sorry. I wrote, "custom arbor with an eye to improving the stiffness of the cutter stack". Perhaps a better way of stating the same thing would have been, "custom arbor with the intent of inproving the stiffness of the cutter stack". Forget the "eye" thing. It was just a sort of figure of speech.

Your description makes it obvious that you need to stay with your basic tooling sizes. Perhaps a custom arbor with the arbor made out of carbide or a heavy metal and brazed into the appropriate taper shank. You would need to make a tie bolt or stud that would extend through a clearance hole in the carbide arbor and would anchor its threaded end in the alloy steel taper shank. Hardened and ground spacers of the largest possible OD used with this type of arbor would make this setup as stiff as I know how.

Have you considered reworking the toolholder/arbor so that it contacts the flange face as well as the taper? I have seen this system advertised, but have no personal experience with it. Maybe other forum members could comment?

Good luck.

 

[blounteng]

I want to thank everyone for their input and while some of the suggestions have been tried, there are some I am looking forward to experiment with. Should it take me a while to follow up on these posts it means I am off trying some of your suggestions. Please continue to submit your input and I will post what works best.

I realise the machine will make machining noises but the inherent sounds, as I will note it since I cannot pin point its origin at this time, is a sqeeling sound fine and high enough to summon all dogs across the nation. Keep em' comming please, these input are much appreciated. Sacrificing tool wear for speeds to minimize these annoying noises seem to be the best effort at this time and will be monitoring its effect on tool wear (tooling costs)

 

[funnelguy]

That type of high pitched squeal is probably due to the factors described by EdDanzer. More side clearance might quiet down the operation, but it may also create problems with cutter wear and breakage. Test, test, test.

Is the squeal consistant for as long as the cutter is making chips? Does the sound change depending on what part of your fixturing you are working?

 

[JBurgess]

I run mazak fh4800 40 taper machines. The cabinets on these are like giant speaker. Place a 12" square piece of dynamat (available at stereo shops) in the middle of cabinet panel that you can.

I have found that cutters with asymmetrical teeth produce much less pronounced vibration.

After your outermost cutter place a steel ring mounted on rubber. I use one about 1" thick and 2" in diameter mounted to an upper control bushing off an import truck. Helped a lot.

Good luck