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  • Endmill "squealing" in corners.

    Machinists,
    I'm running a .5" carbide endmill in C1018 at 1500rpm and 4.8ipm, .050 DOC. Cut is nice and smooth until I get to the inside corners (climb milling). As the travel slows down and the direction is changed, the endmill squeals. What's causing this? Is there reason for concern? Not running any coolant but do have mist available if it would help.

    I'm assuming it's because the feed is so slow, but I need to run backlash correction to keep dims accurate.

    Thanks in advance,
    Jimno

  • #2
    It sounds like the feed is slow as a slug to me. Crank it up.

    Comment


    • #3
      Just my guess; when the endmill is in the corner, it suddenly has a contact arc of 90 degrees, and this causes chatter. Do you see any fine chatter marks on the corner radius? If not, I probably wouldn't worry...

      Ian
      All of the gear, no idea...

      Comment


      • #4
        Hmmm

        Didn't notice any chatter marks, but will look when I get home.

        I'm thinking I'm spinning the EM too fast.. most calculators are telling me between 480-490 at .002 chipload (4.8ipm)

        I'm gonna slow down the speed, increase the feed. If anyone wants to advise a speed and feed, I'm all ears.

        Regards,
        Jim

        Comment


        • #5
          You don't say, so I assume it's a manual mill.

          At 1500 rpm you are climb milling .050" doc and not experiencing trouble with table jump? That's interesting!!!!

          When the mill is in the corner at 1500 rpm running dry it is in high friction mode. What the heck do you think it's going to do?

          I suggest you use a coolant mister directed on the cutter and get out of the corner as fast as posible.

          If you slow the cutter down you will have to slow the feed down or the cutter load will be high and the finish will be rough.

          You can maintain the speed you are using if you use a flood or spray coolant as a CNC would do.

          I can't believe you are cutting at 1500 rpm dry. Are you a CNC operator???
          Last edited by Carld; 10-10-2007, 04:57 PM.
          It's only ink and paper

          Comment


          • #6
            Originally posted by Carld
            You don't say, so I assume it's a manual mill.

            At 1500 rpm you are climb milling .050" doc and not experiencing trouble with table jump? That's interesting!!!!

            When the mill is in the corner at 1500 rpm running dry it is in high friction mode. What the heck do you think it's going to do?

            I suggest you use a coolant mister directed on the cutter and get out of the corner as fast as posible.

            If you slow the cutter down you will have to slow the feed down or the cutter load will be high and the finish will be rough.

            You can maintain the speed you are using if you use a flood or spray coolant as a CNC would do.

            I can't believe you are cutting at 1500 rpm dry. Are you a CNC operator???
            Its a carbide endmill 1500 in 1018 should be no problem, regardless it is having a problem and I would bet he is trying to leave a .250 radius on the inside corner. If it is a CNC use a smaller endmill, a 3/8" or 7/16 will do you a lot better, if it is a manual machine then you are going to just have to slow it down rpm wise.

            Also are you leaving material for a finish pass?

            Comment


            • #7
              Carld, it sounds like it is a cnc mill as he mentioned backlash correction and a feed of 4.8 IPM.
              Steve

              Comment


              • #8
                Hi,

                Yeah, if you're doing this manually, you will get that squeal when you change directions on a corner. The feed rate drops to zero as you "turn the corner". Sometimes even a cnc will squeal bit.

                Climb-milling can be done on a manual machine with a lead screw. All you need to do is apply a bit of drag with a table lock. A little tough on the gibs and ways, but it works.

                Speeds and feeds for carbides are not really a straight forward calculation. The tables and charts one sees for carbide tooling should be considered as a starting point. Much depends on not only material condition, but how ridged the setup is and how much power to run the cutter is available and whether you are running coolant or not. This is where the experience of breaking an end mill or two teaches you what you can get by with . Education costs.

                Assuming a 2hp turret type mill and cutting without flood coolant, I'd run that carbide like it was HS steel. So, cut your RPMs in half, and consider doing a full DOC with that endmill or at least as much your set up will allow. Take advantage of the rigidity of the tool if possible and put some load on it. A .050" is a light finish cut in my book. Carbide tools like to eat, so feed them.

                And I'd not use a mist coolant on carbide tooling. Flood or nothing. Carbide can take the heat. But doesn't tolerate thermal shock well. At best, misting will induce micro cracks and spalling, leading to early wear. At worst, it can cause a catastrophic failure of the tool.

                dalee
                If you think you understand what is going on, you haven't been paying attention.

                Comment


                • #9
                  Deltic

                  Deleted by author.
                  Last edited by oldtiffie; 10-12-2007, 04:34 AM. Reason: Irrelevent post

                  Comment


                  • #10
                    Umm, forgot about the thermal shock with the mist. At that speed flood would be best anyway.

                    I have never tried full doc with anything but a roughing end mill doing side milling. However, I don't do any CNC work.
                    It's only ink and paper

                    Comment


                    • #11
                      Cutting metal is like feeding a baby...
                      When you hear squeeling, it means its hungry
                      Doesn't matter if it's a lathe or a mill..all the same !
                      More food....errr feed

                      Rich

                      Comment


                      • #12
                        I would guess @ 2,000 rpm at 14+ ipm with a 4 flute carbide .500 endmill would eat it up just fine taking ".050. add some coolent and scare the metal off. it should be eating it up.

                        LOL just for laughs I have a smithy 1220 that fusses over a .050" with a .500" end mill cut in steel.

                        Comment


                        • #13
                          Deleted

                          Deleted by author
                          Last edited by oldtiffie; 10-12-2007, 12:38 AM. Reason: Deleted

                          Comment


                          • #14
                            Yes, it's cnc, no I'm not a CNC machinist.

                            Guys,
                            I appreciate everyone's time to answer the question at hand. I'm going to try cutting in the conventional direction and up the backlash velocity to achieve more constant feedrate.

                            Gonna leave it dry for now. I've got a lot of material to remove and may drill the corners with a holesaw first, then just hog it out the remaining material.

                            I don't know much about hogging or roughing endmills so if someone has a suggestion on a good one, I'd love to hear it.

                            The straight cuts and outside corners are cutting like butter at this speed.

                            Regards, and thanks again,

                            Jim

                            Comment


                            • #15
                              How thick is the material?

                              You may want to go into your program and see if you can put less pause in the corner when it changes direction. I know nothing about programing but I have seen them change direction pretty fast.

                              If you undercut you can use a roughing end mill to cut close to the size and finish up with your carbide end mill. You can make a very heavy cut with roughing end mills but you will have to use oil or flood coolant.

                              Any time you are end milling you should use a coolant or oil or just buy a box full of end mills and start cutting dry.
                              Last edited by Carld; 10-11-2007, 11:46 AM.
                              It's only ink and paper

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