Screeching Sound When Milling

This forum is dedicated to those Hobbyists Interested in CNC machining in their home shops. (Digital Read Outs are also topical, as is CAD/CAM as it relates to CNC)

Moderator: Harold_V

Post Reply
rexcsmith
Posts: 91
Joined: Wed Aug 26, 2015 8:24 pm
Location: Portland, Or.

Screeching Sound When Milling

Post by rexcsmith » Tue Apr 12, 2016 10:59 am

I'm fairly new to CNC milling, although I have successfully made a number of parts now.
I'm having trouble with loud screeching sounds during certain cuts. So loud I have to cover my ears.

Using a 1/2" 4 flute carbide cutter on 1018 steel. Cutting a 100% groove at .1" deep. 2500 rpm, 25 IPM (got values from CNC Zone's calculator). This happens using Kool Mist or Hangsterfers coolant from a fog buster. The cutter is always cool to the touch. You might say to slow down the IPM. I've done that and it still screeches at very low IPMs.

I think I've ruled out the tool slipping in the holder. It's as tight as I can get it, and I see no evidence of scarring on the tool, etc. It seems the noise is coming from the cutter against the metal.

I'm sure someone out there has dealt with this. Any suggestions?

thanks much, rex

User avatar
SteveM
Posts: 6593
Joined: Mon Jun 27, 2005 6:18 pm
Location: Connecticut

Re: Screeching Sound When Milling

Post by SteveM » Tue Apr 12, 2016 11:12 am

If you are cutting a groove in one pass, you need to use a 2-flute cutter, otherwise the extra pair of flutes is going to pull the cutter sideways.

If you need a really accurate width, a better solution is to use a smaller flute, cut down the middle, then do each side.

Not sure if that will stop the mill from screaming at you.

Steve

User avatar
GlennW
Posts: 6654
Joined: Sun Apr 15, 2007 9:23 am
Location: Florida

Re: Screeching Sound When Milling

Post by GlennW » Tue Apr 12, 2016 11:54 am

What's you tool stick out?

Try a shorter end mill.

Always use the shortest flute length cuter possible with the minimum of stick out.
Glenn

Operating machines is perfectly safe......until you forget how dangerous it really is!

rexcsmith
Posts: 91
Joined: Wed Aug 26, 2015 8:24 pm
Location: Portland, Or.

Re: Screeching Sound When Milling

Post by rexcsmith » Tue Apr 12, 2016 12:46 pm

Thanks. I'll try shorter stickout and 2 flutes. The only problem with 2 flutes is that the channel cut is only the first cut in a longer operation where all the rest of the cutting is on one side of the cutter with 50% stepover. As such, the channel cut doesn't need to be accurate either. I can move faster using a 4 flute cutter in the side-cutting part of the operation. May have to consider a tool change after the channel cut; or just stick with the 2 flute and go slower.

Harold_V
Posts: 17143
Joined: Fri Dec 20, 2002 11:02 pm
Location: Onalaska, WA USA

Re: Screeching Sound When Milling

Post by Harold_V » Tue Apr 12, 2016 2:16 pm

The deflection mentioned by Steve occurs whether you use a two or more flute cutter. The difference is, while the tool deflects, there isn't a tooth removing metal from the cut when a two flute is employed. You can achieve the same results with a three flute cutter, although I'm not making that recommendation.

High spindle speed operation tends to create noises that may not be present at lower speeds. If your end mill isn't being harmed (edge failure), choke up on the cutter as Glenn recommended, and wear ear protection. You may have to settle for the noise. Goes with the territory.

In this case, I'd not go to fewer teeth, as that will simply prolong the machining time by the required decrease of feed rate. I might have a different attitude were you not widening the cut.

Harold
Wise people talk because they have something to say. Fools talk because they have to say something.

User avatar
Mid Day Machining
Posts: 417
Joined: Thu Apr 09, 2009 10:58 am
Location: San Clemente, CA

Re: Screeching Sound When Milling

Post by Mid Day Machining » Tue Apr 19, 2016 3:54 pm

rexcsmith wrote:I'm fairly new to CNC milling, although I have successfully made a number of parts now.
I'm having trouble with loud screeching sounds during certain cuts. So loud I have to cover my ears.

Using a 1/2" 4 flute carbide cutter on 1018 steel. Cutting a 100% groove at .1" deep. 2500 rpm, 25 IPM (got values from CNC Zone's calculator). This happens using Kool Mist or Hangsterfers coolant from a fog buster. The cutter is always cool to the touch. You might say to slow down the IPM. I've done that and it still screeches at very low IPMs.

I think I've ruled out the tool slipping in the holder. It's as tight as I can get it, and I see no evidence of scarring on the tool, etc. It seems the noise is coming from the cutter against the metal.

I'm sure someone out there has dealt with this. Any suggestions?

thanks much, rex
What machine are you using? How rigid is your set up? I would say either cut your depth of cut in half or increase your feed rate.
You can buy good parts, or you can buy cheap parts, but you can't buy good cheap parts.

WJH
Posts: 1393
Joined: Sat Jan 16, 2010 9:29 pm
Location: Florida

Re: Screeching Sound When Milling

Post by WJH » Sun Jul 24, 2016 10:11 pm

Such a simple operation, only it isn't. Watched one of NYCCNC videos on high speed cnc slotting. If there was ever a video to convince you that CNC is the way to go, well it did it for me.

User avatar
Rich_Carlstedt
Posts: 1445
Joined: Sat Dec 21, 2002 12:16 am
Location: Green Bay Wisconsin USA

Re: Screeching Sound When Milling

Post by Rich_Carlstedt » Sat Sep 03, 2016 4:01 pm

Think of your baby crying for more food !
The scream is most likely a lack of "feed" in your setup.
Increasing feed will reduce the noise.
Now if the spindle slows dramatically with the increased feed, your spindle speed is too fast ( Most newbies run far too fast RPM's )
as your load is greater than the available Horse Power

Rich

Magicniner
Posts: 453
Joined: Thu May 30, 2013 4:40 am

Re: Screeching Sound When Milling

Post by Magicniner » Tue Sep 06, 2016 3:24 pm

Rich_Carlstedt wrote:Think of your baby crying for more food !
The scream is most likely a lack of "feed" in your setup.
Increasing feed will reduce the noise.
Now if the spindle slows dramatically with the increased feed, your spindle speed is too fast ( Most newbies run far too fast RPM's )
as your load is greater than the available Horse Power

Rich
If you have inadequate rigidity, which is one cause of this, keep an eye out for the cutter deviating from the required path ;-)

User avatar
Bill Shields
Posts: 5142
Joined: Fri Dec 21, 2007 4:57 am
Location: Somewhere in the World
Contact:

Re: Screeching Sound When Milling

Post by Bill Shields » Sun Sep 18, 2016 7:42 pm

the 'screeching' is a more a function of the engaged angle of contact of the tool with the work than the tools, flutes or length.

All of these variables (as described above) can help reduce the problem but will not eliminate it.

I am going to be very blatant here and show you something from the company I work for.

You will notice that any place where the 'arc of contact' gets to 90 degrees or larger, the tool goes in and 'nibbles' at it. The exact algorithms of how this calculate are more than a little proprietary.

https://www.youtube.com/watch?v=gFnvISSLtKg

There are similar methods from other companies.

Fanuc (control manufacturer) calls it Trochoidal machining.

The idea is to keep the engaged arc contact angle of the tool as small as possible and NEVER let it get to 180 degrees and in most cases, keep it below 90 degrees.

Post Reply