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32075Re: Bit life in steel

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  • brianpimm@rocketmail.com
    Nov 26, 2012
      Yes it's on parallels on the ends so the middle is unsupported. I'll add a backer and see what happens.

      --- In mill_drill@yahoogroups.com, "mattdbartlett" <mattdbartlett@...> wrote:
      >
      > Yeah, that could do it, the thing would be flexing pretty bad in the middle. Are you supporting it on parallels? I would contemplate a backer, or adding more parallels/clamps around the perimeter.
      >
      > If you are worried about wood chips, you might try a piece of acrylic (plexiglass). It's dimensionally accurate, and and chips should not cause rusting or contamination issues with the coolant.
      >
      > --- In mill_drill@yahoogroups.com, "brianpimm@" <brianpimm@> wrote:
      > >
      > > What about vertical deflection of the workpiece, it was a piece of 1/4" plate 5" wide and was clamped at each end probably a 10" span. I'm thinking that could be a cause of the chipping cutting edge. I'm thinking of using a piece of plywood as a sacrificial support, I just don't like the idea of wood shavings and flood coolant. Any thoughts?
      > >
      > > Brian
      > >
      > > --- In mill_drill@yahoogroups.com, "brianpimm@" <brianpimm@> wrote:
      > > >
      > > > I couldn't hear the touchdown over the machine noise, the gibs are tight, using a large screwdriver almost as tight as I can get them, I wanted to make sure they weren't adding to the backlash measurements then never backed them off, the steppers don't seem to mind. I think strait plunge is my only option with meshcam, I'll look again. I trammed it to less than .001 in 12" but then moved the head and now it's around .007 in 12", if my math is correct that's .000109" in a 3/16 tool, is that enough to cause problems?
      > > >
      > > > Could the spindle bearings be causing this problem? I haven't checked them other than by hand feeling for play which I don't feel any by hand. What is the proper procedure for checking the spindle bearings?
      > > >
      > > > I was running at 1220 RPM, would a higher RPM help or hurt? Just thinking maybe 1220 hits a resonance in the machine and upping it by a bit might move it out of resonance?
      > > >
      > > > Thanks
      > > > Brian
      > > >
      > > > --- In mill_drill@yahoogroups.com, "mattdbartlett" <mattdbartlett@> wrote:
      > > > >
      > > > > The feed rate seems ok. How does it sound when it touches down? 2-3 thou backlash is not that much.. I've got about 12 on my knee mill, though it has more mass in the bed. How loose are your gibs? If they are really loose, your backlash is going to have more effect, though they would have to be pretty loose for a 3/16" endmill to start throwing things around. I'm guessing it's having some issues with the entry method, can you set it to a 2d or 3d entry rather than a straight plunge (not sure, never used meshcam). Another thing you might double check is the tram of your head, if it is off, then one side of the cutter is going to touch down first, and that can set up some nasty vibrations when plunging.
      > > > >
      > > > > --- In mill_drill@yahoogroups.com, "brianpimm@" <brianpimm@> wrote:
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      > > > > > Entry is a plunge at .7 IPM.
      > > > > >
      > > > > > What should I be looking for as a cause for the breakage if it's not the plunge rate. I still have .003 backlash in the X axis and .002 in the Z axis, would those contribute to the problem?
      > > > > >
      > > > > > I'm assuming that unwanted motion of the part vs the end mill is the source of the problem. Am I correct in my assumption?
      > > > > >
      > > > > > Brian
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      > > > > >
      > > > > > --- In mill_drill@yahoogroups.com, "mattdbartlett" <mattdbartlett@> wrote:
      > > > > > >
      > > > > > > The tips of those flutes are broken off. I know the look well. What kind of entry move are you using? If you are plunging straight in, make sure the feed rate is appropriate, as it's hard on the bits. That kind of damage I usually see from running into something hard, or introducing the cutter to the work too quickly. The tips are very delicate. I would say, try 40 thou depth, its about 2x what you are doing now, and it may spread the load on the flutes out better.
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      > > > > > > --- In mill_drill@yahoogroups.com, "brianpimm@" <brianpimm@> wrote:
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      > > > > > > > --- In mill_drill@yahoogroups.com, "mattdbartlett" <mattdbartlett@> wrote:
      > > > > > > > >
      > > > > > > > > I don't have any experience with SGS. It's probably better than the unmarked import mills in any case.
      > > > > > > > >
      > > > > > > > > You're using flood coolant, is it a good stream? IE, can you tell if chips are being flushed effectively? I also find it a little strange that you are using a waterline with a square end mill. Waterline is usually used on profiled surfaces, the kind of thing you would use a ball mill for. I don't have much experience with different cam software though, so that could just be the way that Meshcam does things. In AlibreCAM for example, I would use a profile pass with a square end mill.
      > > > > > > >
      > > > > > > > Yes it's a good stream, I have trouble containing the spray, ;) I'm using the waterline finish pass to minimize the amount of material removed, if I use the roughing pass it cuts the path twice as wide for clearance, but half of that is full width cutting anyway and I'm just cutting out a part from flat stock. A CNC Plasma table would be a better fit but I have the mill. There is 1 place where the thickness is milled down but it's a small area compared to the whole part. Plus Meshcam is a 3D program and I'm fudging it use it as a 2D.
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      > > > > > > > >
      > > > > > > > > I ran your situation through GWizard, and I get slightly different numbers that you reported, but nothing significant. You say you are running 4 parts. How much cutting are we talking about here? Maybe you are just pushing the cutter past its limits.
      > > > > > > >
      > > > > > > > 1 part was 270" of full width cut so 4 would be 1080" @ .020 deep. If I bump up the depth of cut it would shorten the length of cut. Gwizzard seemed to want .062 deoth of cut but I was afraid to try it, to many broken end mills in the pile. :(
      > > > > > > >
      > > > > > > > >
      > > > > > > > > I can't give you a number for how long these things should last, as I have never worn an end-mill out, I always break them before that happens ;)
      > > > > > > > >
      > > > > > > > > One thing you might try, especially if you are removing lots of material, is a roughing end mill. They should let you take a deeper pass, with less chatter.
      > > > > > > > >
      > > > > > > > > Another thing you can do is to take a look at the end mills with a magnifier and see if they are really dull, or if you are chipping the cutting edge. This is more common with carbide than HSS, but I have done it to my fair share of HSS tools too.
      > > > > > > >
      > > > > > > > It looks dull to me, here are some comparison pics of new and worn, and the part in question.
      > > > > > > >
      > > > > > > > Dull End mill Pic
      > > > > > > > http://i101.photobucket.com/albums/m57/bdpimm/Mill/IMG_6101.jpg
      > > > > > > >
      > > > > > > > New End mill Pic
      > > > > > > > http://i101.photobucket.com/albums/m57/bdpimm/Mill/IMG_6100.jpg
      > > > > > > >
      > > > > > > > Tool Pics
      > > > > > > > http://i101.photobucket.com/albums/m57/bdpimm/Mill/IMG_6093.jpg
      > > > > > > > http://i101.photobucket.com/albums/m57/bdpimm/Mill/IMG_6096.jpg
      > > > > > > > http://i101.photobucket.com/albums/m57/bdpimm/Mill/IMG_6095.jpg
      > > > > > > > http://i101.photobucket.com/albums/m57/bdpimm/Mill/IMG_6094.jpg
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