Newbie Bit Keeps Breaking - Need Help!

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    Default Bit Keeps Breaking - Need Help!

    I am attempting to make my first cut on our new CNC and the bit keeps breaking right as in plunges in.

    I am trying to cut a simple shape out of .5" MDF using a 1/8" end mill bit. Setting up the G Code in the ArtCAM software after following a detailed youtube video.

    Is this even the right type of bit to do this?

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    Community Moderator ger21's Avatar
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    Default Re: Bit Keeps Breaking - Need Help!

    What is the exact bit you're using, and what feedrate and rpm? Are you trying to cut in one pass?

    Gerry

    UCCNC 2017 Screenset
    http://www.thecncwoodworker.com/2017.html

    Mach3 2010 Screenset
    http://www.thecncwoodworker.com/2010.html

    JointCAM - CNC Dovetails & Box Joints
    http://www.g-forcecnc.com/jointcam.html

    (Note: The opinions expressed in this post are my own and are not necessarily those of CNCzone and its management)


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    Default Re: Bit Keeps Breaking - Need Help!

    You need to check the speeds and feeds. What speed are you running the spindle? You also need to check your depth of cut, if you go to deep to fast it will break. MDF is soft and easy to cut and 1/8" EM will cut it like butter if you do it correctly.

    If you are trying to do a ArtCam 3D carving you need to process the file correctly. Normally you will do a rough cut with an EM, and then start to do the carving with ball endmills. Do you have a sample of what you would like to get an I can explain what you need to do to get it to cut.

    Russ



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    Default Re: Bit Keeps Breaking - Need Help!

    Feed rate: 100
    Plunge rate: 30
    Spindle speed: 15000
    Bit: 1/8" Carbide Flat Nose End Mill

    It was showing it would do it in 3 passes based on the toolpath simulation.

    I am literally just trying to cut out a circle to see how this machine and these programs work!



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    Default Re: Bit Keeps Breaking - Need Help!

    The spindle speed is fine for MDF. The plug rate is too fast, change that to 8 for a bit that small. The feedrate you can lower that as well for an initial cut until you understand how well you machine handles work. Start off with say 30, then as you see it cutting you can do a feedrate override and increase the feedrate and listen to the noise of the bit cutting the MDF. If the noise starts getting much louder reduce feed, always increase feedrates slow and watch and listen to your machine.

    What was the depth of cut, three passes for 1/2" MDF, means .166 DOC. You have a bit with a diameter of .125, you should never cut more than half the diameter of the BIT for DOC. So in you need to make the passes .0625". Be warned that Artcam has some very aggressive feedrates as defaults, you might want to download a FEED/SPEED calculator. If you follow the rules I just outlined you will no longer break bits. MDF is soft so you can often violate the DOC slightly say 3/4 of the diameter. Try it you will like it. LOL

    Russ



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    Community Moderator ger21's Avatar
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    Default Re: Bit Keeps Breaking - Need Help!

    How many flutes does that have?

    I'd actually plunge faster, and increase the feedrate. But, I'd also cut it in 4 passes.
    But, I'd also never plunge. Always ramp in. plunging is very hard on bits.
    And, if possibly, use a larger bit. 1/8" bits can be fragile if you don't fave the right feeds and speeds.

    Gerry

    UCCNC 2017 Screenset
    http://www.thecncwoodworker.com/2017.html

    Mach3 2010 Screenset
    http://www.thecncwoodworker.com/2010.html

    JointCAM - CNC Dovetails & Box Joints
    http://www.g-forcecnc.com/jointcam.html

    (Note: The opinions expressed in this post are my own and are not necessarily those of CNCzone and its management)


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    Default Re: Bit Keeps Breaking - Need Help!

    On the other hand, for someone just getting started ramping adds another level of complication that shouldn't be needed for a simple "does this even work?" test.

    First step - I'd be using a plunge rate of between 5 and 8ipm to start with, 30 is like trying to smash it in with a hammer until you get a feel for it. Feed rate I'd knock down to about 40ipm and then bring up as you get a taste for how it plays. For full width engagement cuts (ie first pass on a pocket) I'd make depth of cut no greater than about a quarter the tool diameter so 0.75mm per pass to start with and then play with making it deeper.

    Once you've got it going on some slow, basic settings?
    - Get yourself a feed and speed calculator that does the materials you're using.
    - Have a play with your CAM settings and see if you can get it to do a helical ramp entry and then full side engagement shaving passes instead of shallow full tool width engagement.



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Bit Keeps Breaking - Need Help!
Bit Keeps Breaking - Need Help!