Purchase Advice needed


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Thread: Purchase Advice needed

  1. #1

    Default Purchase Advice needed

    So I currently have a 4x8 machine with a 2.2kw Chinese spindle, 1/4 rolled steel Y axis rails (which SUCK and are welded to the machine body), 20 mm round linear rails on X and Z. Chain drive w/ two 1200 oz/in N34 motors on Y, a single 700 oz-in motor on X and a 400 oz-in N24 motor on Z. Its set up with a touch plate and manual tool change macros in Mach3. 99.9% of what I cut is PVC plastic foam (advertising board), normally shallow pockets with a 1" end mill, deeper pockets and profile with a 1/4" end mill, pilot holes with a 1/8" end mill, and sometimes engraving with a 20 degree 0.02 end mill.

    I'm searching for a new machine to solve the following problems with my current machine - or maybe I can adapt my existing machine ?

    Problems -
    1. Vibration on Y axis (dust gets on the rails and the bearing skates from CNC router parts go "off roading" over the dust).
    2. Vibration on X axis - seems to be chain related - cut edges appear scalloped almost the same size as the chain spacing.
    3. Issues squaring the gantry - I think I can solve this with a second home switch and doing some adjustment on that home switch.
    4. Cut/rapid speeds - I'm currently limited to about 300 IPM rapid speed and I'm cutting at 275 (slower it vibrates more).
    5. Tool change - I want ATC so I can produce more - but if I can get set cutting at 600 IPM I might not absolutely need ATC.
    6. Hold down -I've considered making my own vacuum table, if i buy a whole new machine I'm definitely getting one with a vacuum table built in so I can cut things that cant easily be pinned down.

    I'd like to stay under 10k, I'm sure I could adapt my existing machine (It has an 8020 gantry extrusion and z axis, I could probably adapt a lot) for less but who knows.

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  2. #2
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    Default Re: Purchase Advice needed

    Quote Originally Posted by Herptastic View Post
    3. Issues squaring the gantry - I think I can solve this with a second home switch and doing some adjustment on that home switch.
    It depends on the board you have. I'm not the expert on this, but if the two axes are slaved via the board, I don't think you can do this.

    Quote Originally Posted by Herptastic View Post
    4. Cut/rapid speeds - I'm currently limited to about 300 IPM rapid speed and I'm cutting at 275 (slower it vibrates more).
    That could be a result of the gearing on the drive mechanism. Stepper motors produce most torque at slow speed, and large oz-in steppers are no better at faster speeds than smaller oz-in motors, in fact some motors with lower max torque actually do better at the faster speeds. So if your motor is spinning at 1200 RPM when your machine is moving at 300 IPM, that's all you can get unless you change the gearing.

    Or perhaps the drive system is a bit wonky? I don't see why you can't change over to rack and pinion quite easily? Pics?

    Quote Originally Posted by Herptastic View Post
    5. Tool change - I want ATC so I can produce more - but if I can get set cutting at 600 IPM I might not absolutely need ATC.
    I have an ATC spindle I plan to use for my build, I was lucky enough to find a used one at a good price, but it sounds like you only use a few different bit sizes, so perhaps the option of having 2 or 3 spindles with independent Z drives is an option you should consider.

    Quote Originally Posted by Herptastic View Post
    6. Hold down -I've considered making my own vacuum table, if i buy a whole new machine I'm definitely getting one with a vacuum table built in so I can cut things that cant easily be pinned down.
    I really like the way Biesse has designed their machines, especially the way they do work holding. Find some vacuum parts of an old Biesse? At least look at their designs before designing your own.

    Quote Originally Posted by Herptastic View Post
    I'd like to stay under 10k, I'm sure I could adapt my existing machine (It has an 8020 gantry extrusion and z axis, I could probably adapt a lot) for less but who knows.
    Pictures and video of what you have are worth 1000's of words. I can't give you any substantive advice unless I can see what it is exactly you have to work with.



  3. #3

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    Here are a couple pics - I'm considering cutting off the rolled steel rails and adding an 8020 extrusion on both sides to attach linear rail and racks to

    Drive is #25 roller chain with I think 14 tooth gears - it's 914.xxx steps per inch on 1/16. I've changed the steps before to 1/8 to see if that helped it the gantry binds up - I actually upgraded the motors to 1200 oz from 651 in an attempt to get more speed without binding.

    I'm using a 5 axis parallel break out board with relay for the spindle.

    I'm honestly thinking about getting the cnc router parts pro kit but the Chinese machine with 3 spindles is about the same price so that's a tough choice

    Attached Thumbnails Attached Thumbnails Purchase Advice needed-img_1509-jpg   Purchase Advice needed-c1767c8b-3be4-46d2-8ace-973e9d557e33-jpg  


  4. #4

    Default Re: Purchase Advice needed

    I also un-slave the Slave motor to square up the gantry - I've figured out if I hit the end stops toward y- square for the gantry is y0.18 a-0.18

    I'd just like it to be easier to accomplish



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    Default Re: Purchase Advice needed

    Quote Originally Posted by Herptastic View Post
    Here are a couple pics - I'm considering cutting off the rolled steel rails and adding an 8020 extrusion on both sides to attach linear rail and racks to
    Are those rolled steel rails structural? Is there anything on the other side of them? I can't tell from the pictures.

    I'd borrow or rent or find some way to get one of those drill presses that can clamp onto things, or perhaps one with a magnetic base, and I'd drill and tapp those rolled steel rails before considering replacing them with aluminum extrusion. You could mount your rails and rack right on that surface. I assume it's pretty flat?

    If there's nothing behind them, that's an issue. There should be a steel tube there.

    Is this machine sitting on wheels? I wouldn't do that. It should be sitting on blocks or adjustable pucks. You could weld a few pieces onto the legs that you can either mount pucks with or put blocks under.

    I think if you were careful you could grind off those rails and mount a new set of rails in the same spot, then mount the gear rack on top. If you want the gantry stiffer you can bolt some square steel tube to the bottom and back faces where nothing is mounted.

    How valuable is your time, and how much money do you have? You could fix this one up to your liking for a fraction of the cost to buy a new one. It would still be pricey. You could replace the entire gantry with one that is longer and mount more than one spindle.

    You have a few options. I honestly don't know which is better. Perhaps you should start by pricing the rails and gear rack, and finding out what that will cost you. Then figure out what you could sell this one for. Then decide what your time is worth.

    It's definitely "fixable" though.

    Are you in Canada or the US?



  6. #6

    Default Re: Purchase Advice needed

    Well having no machine while fixing this one is part of the issue - we did end up cutting the legs about 4" above the wheels it was creating more vibration than you could imagine, it's sitting on 2x4 blocks now , there is thin wall tubing behind the rolled steel rail. I do think part of the issue with my speeds is the weight of the gantry - we sealed the ends and used the gantry extrusion as a water vessel and heat sink, which worked well, but I think all told with the steppers and spindle and water the gantry is 50-60 lb. stiffness of the gantry hasn't been too much of an issue, it's just a whole lot of mass to be moving. I've considered emptying it and getting a radiator and fan or going to an air cooled spindle as well.



  7. #7
    Community Moderator Jim Dawson's Avatar
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    Default Re: Purchase Advice needed

    I think you have a good base to work with and I think you can make a decent machine out of it if you want to rebuild it.

    I'm wondering why the X axis leaves a scalloped edge and the Y axis doesn't given that they are both chain drive. Motor or controller problem? Drive system needs some love? The whole gantry system is twisting? Z axis mounting/guideways are loose?

    Here is how I would approach it....

    Replace the Y rails with Hiwin 25mm Linear Guideway Rails

    Replace the X drive system with a ball screw, about 1 inch dia with a 1 inch lead or 25mm x 25mm. Or a rack & pinion system, both work well.

    Regear the Y axis to get your 600 IPM. If the chain drive is working on the Y axis then no problem there, just needs to be geared correctly

    Replace the control system.

    If step & direction is accurate enough for you then, concider ClearPath SD servos. These might be cheaper than high quality steppers and drives.

    For the vacuum table, use a piece of reclaim UHMW about 1 inch thick. Reclaim is about 1/2 the cost of virgin UHMW and not as slick. Cut a waffle pattern in it about 1/4 inch deep, maybe 1.5 inch centers, and maybe 3/8 wide grooves whatever closed cell urethane weather stripping will fit in. Set up about 4 zones that are valve controlled.

    I think you can have a high quality machine, starting with what you have, and come in under your $10K budget with a little re-engineering and some sweat.

    The 1200 in/oz steppers have plenty of power and speed to achieve your speed targets if you have the gearing correct and a decent control system. Just to put this in perspective, my machine is the same work area as yours, but weighs over 5000 lbs. It is a moving table machine with a fixed gantry. All ball screw driven. There is one NEMA 34 1280 oz/in stepper on each axis. My table weighs about 700 lbs. I can cut at 400 IPM at normal cutting accelerations, and it rapids at 600 IPM with slightly reduced acceleration. The X axis will do 600 without reducing the acceleration, but it only weighs about 250-300 lbs



  8. #8
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    Default Re: Purchase Advice needed

    Is it the same tubing that was used for the legs?

    I would get rid of that water. Not because of the weight per se, but because of the water sloshing around in there every time you change direction.



  9. #9

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    X-axis leaves scalloping due to vibration (I have a coolant nozzle on my spindle mount that I'll probably never use so I have it pulled straight up and you can watch the tip bounce and yaw) I've found that lubricting the chain and all linear motion mechanicals with teflon spray is helpful on this front.

    The tubing is similar to the legs but instead of square it's flat rectangular (like 3x1"). I can get some pics at the shop today.

    My drivers are 2x cw8060 for the Y and Slave axis, 2x cw230 for x and z. I am running a parallel port breakout board and have a 36v 600 watt power supply. Any recommendations for electronics upgrade would be good.

    My drive gears are 14 tooth - what should I look for more teeth ?




    Quote Originally Posted by Jim Dawson View Post
    I think you have a good base to work with and I think you can make a decent machine out of it if you want to rebuild it.

    I'm wondering why the X axis leaves a scalloped edge and the Y axis doesn't given that they are both chain drive. Motor or controller problem? Drive system needs some love? The whole gantry system is twisting? Z axis mounting/guideways are loose?

    Here is how I would approach it....

    Replace the Y rails with Hiwin 25mm Linear Guideway Rails

    Replace the X drive system with a ball screw, about 1 inch dia with a 1 inch lead or 25mm x 25mm. Or a rack & pinion system, both work well.

    Regear the Y axis to get your 600 IPM. If the chain drive is working on the Y axis then no problem there, just needs to be geared correctly

    Replace the control system.

    If step & direction is accurate enough for you then, concider ClearPath SD servos. These might be cheaper than high quality steppers and drives.

    For the vacuum table, use a piece of reclaim UHMW about 1 inch thick. Reclaim is about 1/2 the cost of virgin UHMW and not as slick. Cut a waffle pattern in it about 1/4 inch deep, maybe 1.5 inch centers, and maybe 3/8 wide grooves whatever closed cell urethane weather stripping will fit in. Set up about 4 zones that are valve controlled.

    I think you can have a high quality machine, starting with what you have, and come in under your $10K budget with a little re-engineering and some sweat.

    The 1200 in/oz steppers have plenty of power and speed to achieve your speed targets if you have the gearing correct and a decent control system. Just to put this in perspective, my machine is the same work area as yours, but weighs over 5000 lbs. It is a moving table machine with a fixed gantry. All ball screw driven. There is one NEMA 34 1280 oz/in stepper on each axis. My table weighs about 700 lbs. I can cut at 400 IPM at normal cutting accelerations, and it rapids at 600 IPM with slightly reduced acceleration. The X axis will do 600 without reducing the acceleration, but it only weighs about 250-300 lbs




  10. #10
    Community Moderator Jim Dawson's Avatar
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    Default Re: Purchase Advice needed

    The gearing may not be an issue. I didn't even concider that you would have a 36V power supply on a machine that size. You need around 75 volts to get the performance out of the motors, and of course compatible drives.

    I would install these drives, these are the ones I am using on my router https://www.automationdirect.com/adc.../STP-DRV-80100
    The drives are fully programmable, no DIP switches. They can be programmed to work with your existing motors. The goal is to keep the stepper motors at <800 RPM at max speeds, so changing gearing might be needed.

    and this power supply

    https://www.automationtechnologiesin...vac-or-230vac/

    The other option is to go with ClearPath SKSD servos, and the above power supply. I retrofitted a customer machine with that system and had very good success.
    https://www.teknic.com/products/clea...sShowPopUp_100
    The motors have built in drives, so no external drives needed. Just connect the motors to the power supply and your breakout board.

    I think Mach3 has the ability to un-slave the motors for homing if they are wired to separate outputs. Not sure about that. I hope that one of the Mach3 gurus will comment here.

    Before changing out the control system, it might be best to get the rest of the system up to spec first. Then if you are still not getting the performance you want then is the time to look at a different controller. Mach3 is a popular system and there is a lot of support for it, and more importantly you are already used to using it. You might be pleasantly surprised once the mechanics and electronics are working as they should. There are some better options for Mach3 breakouts than the parallel port, but you don't want to make too many changes all at once, one step at a time.



  11. #11

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    I'm attaching pics of the scalloped cut and the way my gantry connects -- I think I can drill a few holes in the rolled steel rails and attach an 8020 extrusion to attach linear rails and racks easily. I'm still unsure if it would just be easier to get a cnc router parts kit though

    I didn't really think power supply voltage could create problems. I tried speeding up the rapids again today and similar result - somewhere along the way the gantry twists and binds - so clearly at higher speeds the two steppers aren't keeping in sync. Could be communications, inductance, or just not getting rated torque

    Based on my current gearing it's 200 rpm to achieve 700 ipm so that's not really all that fast. I have the stepping set to 1/16, perhaps lowing the micro steps to 1/8 or 1/4 might make some difference?

    Wish I could hire someone to come look at and upgrade this machine - that would make my life so much easier albeit more expensive

    Quote Originally Posted by Jim Dawson View Post
    The gearing may not be an issue. I didn't even concider that you would have a 36V power supply on a machine that size. You need around 75 volts to get the performance out of the motors, and of course compatible drives.

    I would install these drives, these are the ones I am using on my router https://www.automationdirect.com/adc.../STP-DRV-80100
    The drives are fully programmable, no DIP switches. They can be programmed to work with your existing motors. The goal is to keep the stepper motors at <800 RPM at max speeds, so changing gearing might be needed.

    and this power supply

    https://www.automationtechnologiesin...vac-or-230vac/

    The other option is to go with ClearPath SKSD servos, and the above power supply. I retrofitted a customer machine with that system and had very good success.
    https://www.teknic.com/products/clea...sShowPopUp_100
    The motors have built in drives, so no external drives needed. Just connect the motors to the power supply and your breakout board.

    I think Mach3 has the ability to un-slave the motors for homing if they are wired to separate outputs. Not sure about that. I hope that one of the Mach3 gurus will comment here.

    Before changing out the control system, it might be best to get the rest of the system up to spec first. Then if you are still not getting the performance you want then is the time to look at a different controller. Mach3 is a popular system and there is a lot of support for it, and more importantly you are already used to using it. You might be pleasantly surprised once the mechanics and electronics are working as they should. There are some better options for Mach3 breakouts than the parallel port, but you don't want to make too many changes all at once, one step at a time.




  12. #12

    Default

    Here are the pics
    Quote Originally Posted by Herptastic View Post
    I'm attaching pics of the scalloped cut and the way my gantry connects -- I think I can drill a few holes in the rolled steel rails and attach an 8020 extrusion to attach linear rails and racks easily. I'm still unsure if it would just be easier to get a cnc router parts kit though

    I didn't really think power supply voltage could create problems. I tried speeding up the rapids again today and similar result - somewhere along the way the gantry twists and binds - so clearly at higher speeds the two steppers aren't keeping in sync. Could be communications, inductance, or just not getting rated torque

    Based on my current gearing it's 200 rpm to achieve 700 ipm so that's not really all that fast. I have the stepping set to 1/16, perhaps lowing the micro steps to 1/8 or 1/4 might make some difference?

    Wish I could hire someone to come look at and upgrade this machine - that would make my life so much easier albeit more expensive


    Attached Thumbnails Attached Thumbnails Purchase Advice needed-img_0512-jpg   Purchase Advice needed-img_0513-jpg   Purchase Advice needed-img_0514-jpg   Purchase Advice needed-img_0515-jpg  

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