Squealing noise when cutting tabs?

[hipstomp]

Hi everyone,

I'm cutting 3/4" plywood and 3/4" poplar and am getting a horrific squealing noise when cutting tabs and at corners. To be clear, the bit noise is normal until it gets to the tab, but as soon as it "bumps" up and down for the tab, or changes directions to cut a corner, the noise comes; it sounds like metal-on-metal to me, although I'm cutting wood.

I thought perhaps the collet was no good, but switched to a new collet and the problem persists.

Details of set-up:

- ShopBot Desktop
- Bit is 1/4" double-flute upcut spiral, Onsrud 52-910
- Have tried 7500 rpm @ 2 i.p.s. (chipload .008)
- Have tried 3750 rpm @ 1 i.p.s. (chipload .008)
- Have tried 5000 rpm @ 1 i.p.s. (chipload .006)
- Have tried 7000 rpm @ 1 i.p.s. (chipload .004)
- Have tried both 0.25 and 0.125 pass depth

Any advice greatly appreciated. Or if there are more details of my set-up I can provide, please let me know!

thanks,

- Nick

[bleeth]

When you are going around a corner or doing a tab the speed slows down and the sound changes.
You may want to adjust your ramp values. There is a very good article by Brady Watson on maximizing ramp values in his column on the main SB site.
Different values work better for different types of cutting. He goes into the various parameters for cutting out parts, doing 3-d, etc.

[scottp55]

Nick,
"ONSRUD 52-910 1/4" Solid Carbide Two Flute Upcut Extra Heavy Duty for Woods and Composite Woods"
Not quite sure what the "Extra Heavy Duty" implies for geometry and don't cut much Ply or any Poplar, but my 2 similar 2F .25" center cutting ups in hardwoods like higher rpm than yours. For a simple/long rectangular cut out with .5"R corners 20X5" for instance with 1/2D passes in Hard Maple one gives best finish at 1.6IPS,10K, and the other at 2.2,14K. Go figure.
Are you using 3D tabs and can you put a very small radius on corners? Helps quite a bit, as machine never has to come to a complete stop.
Agree with Dave that changing VR settings after reading Brady's article will probably help (need to start playing with that myself for small complex shapes and just getting into 3D), but still using default VR settings myself.
Don't like that"sounds like metal on metal". Can you post a vid?
Is bit dull or are there complex shapes involved? Are you getting good edge quality at those rpm's?

[garyb]

As the guys have noted above check your ramping but more so, rpm is your problem. The bit is overheating and is screaming feed me.
The 52-910 has an aggressive grind and needs to be fed, chiploads are recommended start points for a tool and need to be dialed in to suit your machine/spindle and especially the material being cut. I would expect your min to be 120ipm and 11500-12000 to be closer for you.
second point if your cutting plywood that would not be the recommend tool, the 60-100 series would be the recommendation.

I'm cutting 3/4" 9-ply birch, with a 60-123MC at 530ipm and 16500 in one pass. If I went by the recommended chipload I would be around 620ipm but due to the material density I've adjusted for the sweet spot that suits me.
Gary

[scottp55]

Gary,
What does Onsrud mean by "Heavy Duty" exactly?
Why would a person buy that for...fairly clean Hogging?
Not finding anything.
Thanks

[Ger21]

If you look in their catalog, they show a cross section of each tool. The heavy duty bits appear to be thicker in the center, with shallower flutes.

[garyb]

Gerry is correct, there is less material removed during grinding leaving a more rigid tool, hence the term heavy duty. You will also find the grind angle on that tool a little higher
Normally selected for profiling and pocketing, example; cutting a profile with an LP, in say hard hickory, the standard tool 52-200 series may have a tendency to flex and bounce off the material, while trying to maintain feedrates, (especially if your LP pass is taking less than .02), the heavy duty is designed to counter those issues and let you be more aggressive with your cutting.
Gary

[dlcw]

Like Dave and Gary said, this is pretty normal when using tabs. Your machine feed speed has to slow down to cut the tabs (and corners also), but the RPM's do not get lowered. Therefore you cutting at a much slower feedrate then the RPM's call for. This results in the screaming bit.

My machine is heavily tuned for cutting LOTs of plywood. I cut a single pass at 5ips at 12000RPM and my machine is pretty quite. When it gets to corners and tabs it screams "feed me" because the RPMs remain at 12K but the feed rate slows way down.

If the machine is not screaming on straightline cuts you are Ok on feeds and speeds. Go through the ramping document Brady did and see if you can tune your machine even more.

Each machine is different and will have a sweet spot when all the planets align. You just have to find yours.

[Davo]

Seem to experience that on 3d work, when it slows to make a lot of Z adjustments is squeals sometimes

[scottp55]

Thanks Gerry....and Gary for elucidating with the examples.
Davo, Brady also gives some examples for 3D work for VR settings.
http://www.shopbotblog.com/2008/03/a...m-performance/