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Thread: Building an accurate positioner.

  1. #1
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    Building an accurate positioner.

    I知 planning a new system for my chop saw setup and wondering if it wouldn稚 be possible to incorporate a programmable stop.

    I can make a linear rail and ball screw setup but I知 wondering if there is a single axis controller out there made for this sort of function?
    Bumbling forward into the unknown.

  2. #2
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    Look for "linear Actuator" You should be able to control it with an Arduino
    Gary Campbell
    CNC Replacement & Upgrade Controllers
    Custom 9012 Centroid ATC

  3. #3
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    Quote Originally Posted by Brian Holcombe View Post
    I’m planning a new system for my chop saw setup and wondering if it wouldn’t be possible to incorporate a programmable stop.

    I can make a linear rail and ball screw setup but I’m wondering if there is a single axis controller out there made for this sort of function?
    It is possible to do without an Arduino but the only person I know with the knowledge is in Oz. I am building a router table and the fence control is done by putting the dimension in you want and press go, the fence moves to the entered dimension. I happened upon a guy who coded all this himself including the lift which does the same thing and it will store jobs as well for production. The whole thing is managed by a single screen and I am thinking of putting it on my table saw rip fence as well. PM me if you are interested.
    Chris

    Everything I like is either illegal, immoral or fattening

  4. #4
    Quote Originally Posted by Brian Holcombe View Post
    I知 planning a new system for my chop saw setup and wondering if it wouldn稚 be possible to incorporate a programmable stop.

    I can make a linear rail and ball screw setup but I知 wondering if there is a single axis controller out there made for this sort of function?
    Watching with interest. I want to automate the outboard fence on one of my shapers. I planned on a couple of Z drives and a controller. I spoke with Tigerstop, they were interested until they weren't. They went communication dark on me.

    I'm going to try Razorgage next, I just haven't contacted them yet.

  5. #5
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    Thanks gents! Chris, that sounds exactly like what I'm looking for.

    Martin, that's interesting I'm surprised they weren't up for it. The RazorGage site is interesting since they show a cut-away view of their system and of their 'competitor' system which is presumed to be TigerStop. I had been wondering how they provide 16' lengths (and probably longer) and so it was illuminating to see a belt drive system, which makes sense. I was expecting a long ball screw. The longest I can find is 8' and the is plenty for me for furniture parts.

    The way most people layout cuts is to take a stick and just cut length then length, so the stop is moving after each cut. I don't do that since I'm cutting around defects, so a stop for me is to ensure to cut multiple parts to exact matching lengths. So I'm thinking that something that can be programmed at 'zero' then drive out to the length I type in would be the way to go.
    Bumbling forward into the unknown.

  6. #6
    Pushers aren't that common in cabinet shops. We and every shop I've worked at, use it exactly as you describe.

    8' is fine. Make it cut between 9" and 105". Most cuts are greater than 9". Cuts less than 9" can be handled with a 10" block between the stop and the work. Need 8"? Set the fence to 18" and drop the block in there. Zero is still zero, it just can't get there.

  7. #7
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    Quote Originally Posted by Martin Wasner View Post
    Pushers aren't that common in cabinet shops. We and every shop I've worked at, use it exactly as you describe.

    8' is fine. Make it cut between 9" and 105". Most cuts are greater than 9". Cuts less than 9" can be handled with a 10" block between the stop and the work. Need 8"? Set the fence to 18" and drop the block in there. Zero is still zero, it just can't get there.

    Ah, sorry I didn't realize. I always see TigerStop showing them as a pusher and so I assumed.

    That makes sense, the saw fence is in the way and if you add a sliding stop then you're moving that every time you want to cut something short and you have to find zero again which adds time to the process.

    I was cutting kumiko (latticework) for a shoji (Japanese screens) project this past week and decided it was time for a better setup to position stops and a digital setup would have turned that job which took quite a long while on the router into something that would take not much time at all gang cutting them on a radial arm with a digital stop.
    Bumbling forward into the unknown.

  8. #8
    Quote Originally Posted by Martin Wasner View Post
    .... Zero is still zero, ....
    The challenge with motion control is not typically the range or even repeat-ability, but 'zero' can be a problem. You have to have some means of moving to a known point and 'telling' the controller "this IS zero" (...or 123.456789 inches, or whatever other reference you want).

    Automation systems (CNC, as example) have various methods to accomplish finding a known point automatically (kinda goes w/o saying, I guess). Some use a micro switch 'trigger', moving at hi speed to hit it initially, then backing off slightly, followed by a lo speed 'search' of the last few mils. Some use rising torque when the axis hits a stop. And probably many others I've never worked with, I'm sure. (Once upon a time, I built a control system to run a roll program on a rotary axis spec'd at +/- 0.01 degrees. We think it was accurate to much better tolerances :: +/- 0.002 degrees, including backlash in the special gearbox, but we didn't have the means to measure it accurately enough to prove it ...and customer didn't care.)

    Motion is not my specialty, and it sounds like Chris has beat me to the punch....

  9. #9
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    I treat zero on a mitre saw the same as Martin and use a known dimension packer to set the shorter lengths. I used an Incra fence for my miter saw for repeatability, this was before I met the guy who did the router table but for my use it is fast enough and only slightly painful.

    On the router table which I can't link to here but do a Google search for "yet another router table build" we use a hard stop to set "height" zero at the bit ignoring where the bit is set in the spindle and the fence is set by limit switches. The fence travel relies on Igauging digital readers for measuring information and the whole lot is controlled by a 7" touch screen which uses no OS just the code developed by the designer. Now the hard part of what I now call target dimension control has been cracked without a computer of any sort it has got a lot of scope for being used many different ways. The router table build should be required reading for anyone thinking about building one.
    Chris

    Everything I like is either illegal, immoral or fattening

  10. #10
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    Ah, I was thinking a large glass slide might be necessary to keep track of the position.
    Bumbling forward into the unknown.

  11. #11
    I have built the same idea with an Arduino. I was building a linear clock, but much the same function - a single axis CNC basically. I don't think it would be very hard to do what you are thinking. You would, as mentioned, need a way to calibrate and set a zero stop (just like my CNC router). I used a stepper setup that was a surplus item for printers I think. A screw with two blocks and a stepper. The Arduino controls the stepper via a standard Arduino library. You do have to use a board to control the stepper - more power than the Arduino can handle. You could use a pot and a display connected to the Arduino to make adjustments. I used tiny lever switches for stops at either end (like my 3D printer). Moving the stepper very slowly helps with accuracy. As mentioned above, rapid hi the switch, back off until disengage, then move very slow until engaged again.

    Sounds like a fun project. If had more time.... It would be interesting to see just how accurate and repeatable a system like this could be. Might look into 3D printer self builds. All of the hardware is available and is pretty affordable.

  12. #12
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    Brian was just here (for another matter) and we took a few minutes to look at how my CNC is setup for initialization limits, etc., so he could brainstorm this even more.
    --

    The most expensive tool is the one you buy "cheaply" and often...

  13. #13
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    I suppose the big thing that we have managed to do is not to use an OS or computer of any sort thus simplifying the whole thing and operating it using a single touch screen. The router table incorporated this for all its control.
    Chris

    Everything I like is either illegal, immoral or fattening

  14. #14
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    I think Chris's idea seems neater than typical CNC for this application. I found the link, and it seems to have a magnetic tape with an encoder. The CNC startup routine seems tiresome and you never need to be concerned about squaring for a single axis application like this. Here is another readout I noticed in my searching: https://www.elgo.de/en/products/controls/p40/

    Is there something wrong with the Razor gage or Tigerstop? I am not sure how much cheaper it will be building your own. A long linear guide with a low spec backlash belt drive is not cost friendly unless you import from China.

  15. #15
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    Setting a zero stop using a flip stop will be dead simple using the same method as used in the router table, on CNC we used to have a pop up stop that set the zero point then it retracted, the same method could be used on a flip stop.
    Chris

    Everything I like is either illegal, immoral or fattening

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