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Thread: Cut Parameter Recommendations

  1. #1
    Join Date
    Jan 2018
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    4

    Question Cut Parameter Recommendations

    I normally cut plastic with my PRS standard (2.2hp spindle) but I'm looking to cut some parts for a vanity out of 3/4" hardwood plywood. I'm hoping some folks with more plywood experience can provide recommendations for good spindle speed, feed rate, and cut depth. I'm planning to use an Onsrud 1/4" compression bit (PN 60-111). The quality of the cut is more important to me than speed. I'll be using a somewhat weak vacuum hold down but the parts will have a good amount of surface area. I may include a few tabs just to be safe. Any recommendations would be appreciated - thanks!

  2. #2
    Join Date
    Sep 2008
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    San Jose del Cabo based since 1997
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    Default

    There is a lot of info on this forum about this...
    Don't be lazy! do some research about cutting ply with your compression bit...
    Vector Studio 22

  3. #3
    Join Date
    May 2014
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    MA
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    On a PRS Standard I'd do this:

    First find out how deep you need to cut to get past the upspiral portion of your compression bit so you don't tear up the top veneer. My guess would be .35".

    Do .35" per pass make your part about .005 larger than it needs to be (you can use offsets in VCarve/Aspire).

    Cut almost all of the way through (about .04 shy of being all the way through)

    On the final pass reverse the direction of the cut and eliminate the offset.

    Your parts should come out barely needing any sanding.

    Don't go much faster than 2.5 to 3 IPS at 12-14k RPM.

    https://forum.vectric.com/viewtopic.php?t=25333

  4. #4
    Join Date
    Jan 2018
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    Default Thanks

    Very helpful info. I appreciate it!

    Quote Originally Posted by EricSchimel View Post
    On a PRS Standard I'd do this:

    First find out how deep you need to cut to get past the upspiral portion of your compression bit so you don't tear up the top veneer. My guess would be .35".

    Do .35" per pass make your part about .005 larger than it needs to be (you can use offsets in VCarve/Aspire).

    Cut almost all of the way through (about .04 shy of being all the way through)

    On the final pass reverse the direction of the cut and eliminate the offset.

    Your parts should come out barely needing any sanding.

    Don't go much faster than 2.5 to 3 IPS at 12-14k RPM.

    https://forum.vectric.com/viewtopic.php?t=25333

  5. #5
    Join Date
    Jan 2018
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    4

    Default

    I'm not lazy. I run my own business and I'm fixing up a house almost entirely on my own. This is a small project and so yes, I was hoping someone would lend their expertise to help save me some time. You could have just passed up the post rather than stopping by to make assumptions.

  6. #6
    Join Date
    Jan 2008
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    Hobby-Tronics, Chiloquin Oregon
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    The quality of the plywood will make a big difference in the final result. I cut ply all the time and multi ply cabinet grade from a wood store is best not cabinet grade from HD. If you have some scrap to test with make a few test cuts and LISTEN to your machine, it will give you instructions on feed and speed! Russ
    AKA: Da Train Guy

  7. #7
    Join Date
    Jan 2018
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    4

    Default Thanks

    Thanks for the advice - I'll keep it in mind!

    Quote Originally Posted by chiloquinruss View Post
    The quality of the plywood will make a big difference in the final result. I cut ply all the time and multi ply cabinet grade from a wood store is best not cabinet grade from HD. If you have some scrap to test with make a few test cuts and LISTEN to your machine, it will give you instructions on feed and speed! Russ

  8. #8
    Join Date
    May 2014
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    MA
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    Default

    Totally agree, I would also add that if you dial in your toolpaths/bits well you can get great edge quality even on bad plywood!

  9. #9
    Join Date
    Dec 2008
    Location
    Diamond Lake, WA
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    I cut over a thousand sheets of plywood a year for cabinet jobs. What I found works for me with MY machine is:

    FIRST pass is a climb cut
    With a compression bit, plunge down the depth of the upspiral portion of the bit
    Ramp down to half the thickness of the plywood (plywood over 1/2" thick). Run two climb passes leaving 1/32" skin
    The climb pass is going to push the bit AWAY from your cut line
    Now do a last pass in conventional direction, cutting 1/32" thru your material in ONE pass
    This last conventional pass cut will pull the bit to the line and create a super clean cut exactly on the line

    Been using this method for 11 years on my 2009 PRSAlpha with 2.2hp spindle and it's worked perfect. I recently upgraded to an ATC with 5hp spindle and still use the same cutting method.

    I cut with a 1/4" compression bit running 13,500RPM at 7ips cutting speed. My limit is NOT HP, it's the fact that I'm at an altitude of 2500' and my vacuum system doesn't have the hold-down capability that a lot of folks at lower altitude have. If I had the hold down capability, I'd probably use a 3/8" compression bit cutting around 9-10IPS in one climb pass and one conventional pass. ShopBots have to much flex to cut in one conventional pass and have a good clean cut exactly on the line. Just a fact after 11 years of tuning and tuning the machine.
    Don
    Diamond Lake Custom Woodworks, LLC
    www.dlwoodworks.com
    ***********************************
    Life is not a journey to the grave with the intention of arriving safely in one pretty and well preserved piece; But to skid in broadside, thoroughly used up, worn out, bank accounts empty, credit cards maxed out, defiantly shouting "Geronimo"!

    If you make something idiot proof, all they do is create a better idiot.

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