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Thread: How to cut 24" circles out of 1/2" thick maple plywood in LARGE quantities?

  1. #31
    I agree with you on this. Since I never run a cnc router, I wonder how much prep/setup I need in order to cut, say, 30 half sheets (4 x 4') of 1/2" maple plywood? Clamping down/ deassembling takes much time?

    Quote Originally Posted by David Buchhauser View Post
    Hi Byron,
    I think that the beauty of using a cnc router like the ones you have mentioned is that your process will be faster and less labor intensive than some of the other band saw suggestions. This could possibly free you up to work on another job while the cnc is running the circles, and I would think that there would be very minimal cleanup and/or sanding of the edges. In my business (metal machining) I often have one or two of the cnc machines running parts while I am working on other parts on the conventional mill or lathe.
    David

  2. #32
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  3. #33
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    Hi Byron,
    Notice that the parts being cut in the video have small tabs to hold the parts in place after the final pass with the router bit. He breaks the parts out with a chisel and probably does some sanding to smooth them out. If he had a vacuum table to hold the plywood down, then these tabs would not be necessary.

    So I suppose that it depends on how much more a vacuum system adds to the cost of a cnc router like the ones you have mentioned (or the one shown in the video). If you really want to know what the edge finish will be like, you might consider paying a visit to one of your local production cabinet shops who have a large cnc and pay them to run a few sample parts for you (circles) with your material. You will find out what bit they use, cutting speed, number of passes, edge finish, etc. to see if the results and time savings are worth the investment cost for a new cnc router.
    David
    Last edited by David Buchhauser; 07-21-2019 at 4:09 AM.

  4. #34
    I just looked at the Axiom Pro+ series, and it has the following speed specs:
    Spindle Configuration ER20
    Included Collets 1/4" & 1/2"
    Electro Spindle 2.2KW
    Spindle speed 0~24000 RPM
    Rapid feed rate 200 IPM (5 MPM)

    Do you think that machine still needs two passes to cut 1/2" plywood? How about their next up machine Elite series with a rapid feed rate of 320ipm?

    Quote Originally Posted by Art Mann View Post
    I own a cnc router and I cut 1/2 inch plywood with it fairly often. First of all, I don't know why one would want to use a single flute bit. A quarter inch 2 flute compression bit like someone else already mentioned would cut faster and produce dramatically better cut quality. I don't have a very powerful spindle but I would cut at 150 inches per minute and I would cut it in 2 passes. A 24 inch circle would take about 20 seconds if my calculations are correct. A fast machine could cut it in a single pass at 300-400 inches per minute. How much do you want to spend on a machine?
    Last edited by Byron Lu; 07-21-2019 at 4:31 AM.

  5. #35
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    Seems to me ANY other cutting tool will have more tearout of face grain than the existing laser that will be more labor to sand out than the existing laser produced "brown"

    Seriously - Spend the $$$ on a computer xy machine to JUST CUT CIRCLES ??

    AND, you will STILL, depending, probably want... have to sand edges anyway even w no face grain tearout.

    Slow down, think this through, and Keep that $$$ in your pocket.


    Solution - Cut as you have been cutting... but setup a faster sanding system... 1.001 ways to DIY do that economically and simply.

    If nothing else mount a belt sander 90 degree to a 2x2' dedicated flat workbench... or make fancier.

    Even though a center hole would make for more possible methods, even without that a simple fence could be made to speed and accurize the sanding and eliminate any hand pressure/ motion error.

    Step by step quasi osscilate w 1/2" ply sub 24" round rotating sled elevator.

    If funds available, buy a osci edge snder and mount a 2x2 table against it... and again, somekinda limiting fence.

    How bout a center SMALL like 1/16 - 1/8" pinhole that is patched at end of fabbing ?


    Marc
    I'm pretty new here, not as as experienced as most. Please don't hesitate to correct me

  6. #36
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    OP said - "I am using a belt sander by holding the circle vertically and rotate as I sand."

    If nothing else... Like I said above - Strap that sander down horizontally, secure a 2x2 table against it to make the most basic edge sander.

    Stop vertically holding and balancing your workpiece... VERY inaccurate in ALL directions, let alone mentally and physically tiring compared to just doing above.

    Marc
    I'm pretty new here, not as as experienced as most. Please don't hesitate to correct me

  7. #37
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    I would like to know where you got that information. I don't mean to be impolite but I have a lot of experience to the contrary. A bit moving through a piece of plywood has no knowledge of whether the motive force is human or electrical. As you can read above, the OP is interested in new equipment, including a CNC router, if it fits his requirements. That is why I brought it up. He was under the false impression that a laser cutter will cut as fast as a CNC router, which is not correct.

    Quote Originally Posted by Mel Fulks View Post
    A single flute bit cuts faster for the same reason a 5 point hand saw cuts faster than a 10 point. OP doesn't have a CNC

  8. #38
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    Quote Originally Posted by Bill Space View Post
    I could be wrong, but my gut is telling me a 4x8 sheet should be good for six pieces 24” in diameter.
    Only if the router bit is 0.0" in diameter.
    Sharp solves all manner of problems.

  9. #39
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    The o.p. said "I can usually cut a 4x8 into 8 pieces of 24" rounds (well 23.5" each instead)."

    Any cutting method is going to require some sanding depending on the finish requirements. If the circles are cut with a compression bit in a cnc router at a reasonable speed the cleanup will be faster than sanding out burn marks from a laser or the corrugations from a bandsaw, and the faces will be free of tearout due to the bit design. A circle jig on an oscillating edge sander would probably be the way to go for quantity production.

    I expect the Axiom router mentioned with a 2.2 kw spindle will cut 1/2" ply with a 3/8" bit in one pass but overall machine rigidity and the hold-down method have to be stout enough to counter the cutting forces to get a good result. A vacuum table is the best option for this sort of work. There are a lot of options out there so do your research and try to "buy the cnc you need the first time".

    As suggested previously, it would pay to sub out a batch to a cnc shop to see the process and assess whether a router would be a good investment- it definitely can add a great deal of capability to a small shop.

    Last edited by Kevin Jenness; 07-21-2019 at 9:59 AM.

  10. #40
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    We don't know what you're making, or what else you make, so it's hard to tell if a CNC would be the right choice for you financially. It does seem like it has the potential to speed things up quite a bit, but if you've got nothing else to do while it's working or if your profit margins are thin, it might not make sense.

    IMO, the next best option is to improve the sanding process. Definitely don't do it vertically - get some kind of oscillating belt sander and make a table, as others have suggested. The easiest way is with a hole in the center of the circle and a pin to index off of. If you don't want the hole, here's a possibility:

    circlesander.png
    Cut out a very slightly bigger circle from a sheet of ply and mount it on top of a solid sheet. Sand or cut the jig along the top until it just kisses the top of the circle, leaving a small opening. Mount the jig to your sander. To sand, drop your rough/brown circles into the hole and rotate by hand.

    Frankly, circles will always be easier with a hole in the center. Can you use a dowel or some putty to fill the hole?



    Edit: Sorry, decided to edit my diagram after posting, but couldn't figure out how to delete the previous versions.
    Attached Images Attached Images
    Last edited by Brian W Evans; 07-21-2019 at 11:05 AM.


  11. #41
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    Not sure if it was mentioned, but sanding the edges could be done using a pivot point on a sturdy disc/ belt sander setup. Such as the cutting setup on the bandsaw. Mount the pivot point so that it slides to the desired point of contact complete with a stop. Dare say you can sand very quickly with a 120 grit disc.

  12. #42
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    Quote Originally Posted by Rob Luter View Post
    Only if the router bit is 0.0" in diameter.
    Since the OP really only needs 23.5” the point is moot, as he likely can get 8 pieces from a 4x8 sheet.

    But it if he really needed 24” or slightly larger circles, couldn’t he get six of them out of a 4x8 sheet by offsetting the center points of the circles somewhat? Wouldn’t work for rectangles or squares, but with circles it would probably even be possible to get six circles larger than 24” diameter. This is what my minds eye was telling me...

    Apologies to the OP as this really is a tangent to his question.
    Too much to do...Not enough time...life is too short!

  13. #43
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    Seems like the perfect job for an Aigner Cirquick mounted to a shaper after the part is cut oversized via laser.
    Bumbling forward into the unknown.

  14. #44
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    Quote Originally Posted by Byron Lu View Post
    So I still need sanding the edges of the circles cut via a cnc router or a bandsaw?
    Right now the circles I laser cut has very smooth but brown edge. I am using a belt sander by holding the circle vertically and rotate as I sand. Since all the circles are stained afterward, some stains (lighter stains such as antique white) require cleaner sanding.

    My current complaints about laser cut circles: 1. slow speed, at about 30 inches per minute, so each circle takes almost 3 mins to cut; 2. brown edges requires sanding.

    So if other methods also require sanding, then I could still benefits from having a higher productivity with shorter time spent on cutting all the circles?
    If you use the correct bit there is no sanding and speed is more then doubled what you are cutting now. Big advantage is less likely to catch fire.

  15. #45
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    A CNC Router with a 1/4" bit and two passes less than 40 seconds for each disk.
    If you use tabs instead of a vac hold down system that is pretty expensive you cut the tabs with a multi tool, 20 bucks at Harbor Freight and it takes less than 5 seconds to cut each tab. A couple hold down screws into the spoil board and your total time per disk is easily under 90 seconds each.

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