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Thread: Reference material for machine tightening

  1. #1
    Join Date
    Dec 2011
    Piedmont, SD

    Default Reference material for machine tightening

    Anyone able to direct me towards info regarding optimizing table tightness for higher speed performance?
    I'm certain I'm just missing a thread here somewhere.

    Shifting into higher gear, meaning swapping .25 for .375 compression bits with higher speeds and feed rates associated with doing so.
    I already "over tighten" pinions, as I use a grip clamp to pull motors snug as I torque motor fasteners. Current set only a few months old. Cursory check shows nothing loose, decent hold down vac, but I do have some slight irregularity in straight edges, especially short distances, like 8>".


  2. #2
    Join Date
    Dec 2008
    Diamond Lake, WA



    If you follow the ShopBot tune-up routine that should work well. That's what I use. I also check every nut and bolt every 6 months. I do a tune-up, gear and rail cleaning after each project. Most of my projects involve cutting 20 to 50 sheets of plywood over a space of a couple of days. Heavy use for many hours. One thing I did was to take several hours making sure the spindle was perfectly 90 degrees to the table by using brass shims. Very time consuming, but worth it.

    I use a 1/4" compression and cut 3/4" plywood at 6IPS at 14K rpm. The first pass leaves a 1/32" skin and that pass is done in one shot. I then do a climb cut to remove the skin and trim up the part to exact size. REALLY smooth and accurate cuts this way. I cut 5/8" Appleply (baltic birch) conventional in one pass leaving a 1/32" skin at 5.5IPS at 14K rpm. I have a 2.2hp spindle that has been working great. I ALWAYS perform a warm-up routine before doing any cutting. My jog speed is set at 15IPS.

    The problem with the PRSAlpha is that gantry is pretty top heavy. If you get going to fast, it can tip over. Not sure if this was a design decisions or just happened that way based on Shopbots design. The other problem with the Shopbot machines is the USB communications link is weak, at best, and it's very easy for the controller and the control software to lose communication (brain fart) when running. The speed you can move the machine is limited by this archaic communications channel and there's not a lot that can be done about.

    So, if you can cut plywood at 6IPS and jog at 15IPS your machine is closing in on top end. I don't think changing to a 3/8" bit is going to make any difference. It will increase your kerf's though. I used to use a 3/8" at 6IPS at 14K rpm. By going to a 1/4" I can fit more cabinet parts on a sheet. For cutting thick wood I use a 1/4" Super O single flute upcut bit. I slow down for hardwoods of course and change my depth of cut. Yes, I have broken a few of these bits over the years getting zeroed in on speeds and feeds for different woods.
    Diamond Lake Custom Woodworks, LLC
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