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Skateboard shaping machine

Discussion in 'CNC Mills/Routers' started by Jestah, Aug 15, 2015.

  1. Jestah

    Jestah Veteran
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    Our little OX has seen a lot of cutting but now its time to go bigger!


    Mega thanks to Mark and Trish for the original OX build and amazing service we get from the Openbuilds Part Store, keep up the amazing work!!!

    Also a MASSIVE HUGE thanks to every builder out there as your help, tips and tricks that are posted up on the forum is priceless! Without your help and inspiration we would still be struggling to get the most from our routers! Hopefully we can give a little back with this next build that takes a lot from the basic OX platform.

    big ox.PNG

    This OX variant will be 1200x600 working envelope with 85-90mm of Z clearance for cutting 3d molds. The Z will also be setup to allow a long tool to be retracted completely over a full 85mm tall stock so that the full Z is usable for cutting.

    Z up front.PNG z down front.PNG

    A bigger and slightly different configuration of the gantry will use two sticks of 80x20 as the main beam and a third stick in the front as a support brace (we are going to mount a universal carriage plate onto the front support for mounting a dust hood holder to take the pressure of the Z axis). For the first prototype, we are going to stick with the standard d0uble belt for the Y axis (I sway away from Openbuilds axis naming convention as the way I was taught is that X is always the longest axis not by naming in relationship to how the machine is orientated to the operator).

    Box v1.PNG
    There is an option in the future for the gantry main beams to be swapped out for a single C-beam and a lead screw if required, but I have been very impressed with the performance of the double belt system and think it also keeps gantry weight nice and balanced. I have added in extra wheels as well into the carriage assembly to both support the extra weight of a 800w watercooled spindle as well as providing better engagement of the belt and a "lockdown" section between the first and second wheel when double belts are used.

    double leggs.PNG
    The inner support plates are as tall as possible to protect the wheels from dust and chip. I hope the extra corner brackets will add a lot of extra stiffness by creating a bigger full "box" enclosure around each of the X main linear rails. The X axis slaved steppers have both been moved a little higher and cut outs added to the inner support plates to give clearance for an allen key to the stepper bolts without collision into the main linear rails.

    side on.PNG

    A lot of time was spent making the bigger spindle and mount fit between the gantry rails. Fingers crossed I have measured everything spot on as there is only 4 or so mm of clearance! The Z stepper is kicked back and driven by a closed loop belt to help pull some weight to the rear of the build and help offset the 6kg of spindle! I think I have found some suitable closed loop belts but won't know for sure until they arrive!
    While most of the design is based around this configuration of the Z axis I have hopefully put enough extra mounting holes into the design that will allow for the Z assembly to be removed, flipped around and then bolted back to the carriage to allow the green plate to stay stationary and the Z stepper mounted inline like a traditional OX if my new method fails.
    Z up front.PNG z down.PNG Y prox.PNG Z prox.PNG

    I like the simplicity of mechanical switches for homing but have added mounting points on the gantry sizes, Z C-beam and base end caps to mount prox homing sensors so that both options are easy enough to implement.

    Any advice or opinions would be well appreciated as I hope to lock this design down asap and get the plate out for laser cutting. I have tried to work in as many of the common upgrades we see most OX builders adding. The main ones I can think of at the moment we have incorporated are:
    • double belts
    • higher belt engagement on all pulleys
    • belt clamps that don't twist or cut the belt (compared to using a tee nut and screw to pinch it down)
    • tapped gantry side plate holes for the corner brackets
    • higher mounting of the steppers above the main X rails for tool clearance
    • 8 wheels for the Z with a much wider overall spread
    • mounting holes for prox homing sensors and
    • ability to tram the spindle in two axis (critical for such tall 3d milling)
    Once its up and tested we will be posting a full BOM, plate kits and the DXF for those wishing to cut them locally. Of course once tested, we will release our design under an opensource license. Could anyone recommend the right license to give the most access?

    Once again thanks to all the openbuilders out there who have given me many of the ideas you will see incorporated into this design. Please let me know what I have missed as I am keen to add it in!

    Cheers
    Krishna KC
    www.CNCkits.co.nz
     

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  2. Jonny Norris

    Jonny Norris Veteran
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    Looks good, your y plate setup is similar to how I originally had mine, the only issue you have, having plates both sides of the y profiles is you are not able to fix the y and has to be left floating.

    This is where over 1500mm I found the flex was an issue.

    My plates were originally as such:

    [​IMG]

    I now have cut the inside plate half way horizontally through where the center of the y profiles run and removed the lower half.

    This allowed me to fit L brackets between the center of y profile and bed.

    I would say the rigidity was instantly improved by 150%.

    Hope this helps
     
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  3. Jestah

    Jestah Veteran
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    Cheers @Jonny Norris for the photo but can I trouble you for an image of what you ended up with as I am not sure I am picturing it correctly in my head.
     
  4. Jestah

    Jestah Veteran
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    Actually I think I am with you, with the full plate fixing the longer main Linear rails to the spoil board is a mega killer to overall rigidity.

    I hope with my narrower gantry (600ishmm) I can getaway from it as adding the outside supports to the wheels I think adds to much goodness into the mix to bail out on.

    What about running a under spoilboard support to connect the bottom of the gantry side plates together therefore helping stop flex along the main table linear rails?
     
  5. Jonny Norris

    Jonny Norris Veteran
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    Yes sure, it will have to wait though I'm afraid until I'm back in the shop tomorrow.

    But til then, the altering factor being that my y was now fixed instead of floating that made the difference.

    Now I haven't published this yet and I'd like to, it's an idea I've had floating around since c beam came out that I'll let you in on if your interested, is taking 6 lengths of c beam and bolting them together to make 3 H shape profiles, run two in the y fixed with spacers an inch off the bed to allow room for a vwheel underneath, all profile sitting the same orientation as the letter H, sit the last H shape beam across the two, your x. The mover on the x is simply a box with v wheels that surrounds the entire h profile, motor running in the top cavity of the H. And the x h beam sat on what is a similar movers at either end, to the x except the bottom is open for clearance for those spacers, and the motor instead of sitting on the top upside down it is horizontal like the original ox but pinion runs inside the lower cavity of the open ended x axis h beam.

    Simple and strong, feel free to publish it, unfortunately I'm a bit busy to do so at the moment.
     
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  6. Jonny Norris

    Jonny Norris Veteran
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    Yes that would work to a similar effect, except do you mean your now floating the bed though? Id say yes if you can weld a steel frame to float your bed on.

    I had with mine considered running a profile that is fixed to the bed horizontally alongside the y gantry outside plates with added wheels on the outside of the plates to run in the fixed profile.

    This would combat the horizontal flex whilst leaving the design intackt.
     
    #6 Jonny Norris, Aug 16, 2015
    Last edited: Aug 16, 2015
  7. Renoir

    Renoir Well-Known
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    I toyed around with a design with a few similarities to what you are creating here some time ago. It might have something worth using.

    I've attached the extremely rough Sketchup model of my design based on the Charging Ox by Motions and his original Sketchup model. (http://www.openbuilds.com/threads/charging-ox-cnc-machine.1067/). And have a look at that too. It may fit your needs better.

    I didn't like the spindle hanging so far from the Y-axis seen in the typical CNC router, so I made it supported on both sides driven with one stepper through belts and pulleys. It's not exactly space efficient and I have no idea whether it would be practical at all in the real world. It may be slighty overkill with just a 600mm gantry span, but that of course depends on spindle weight among other things.
    Charging Ox - Modified and Adapted.png
     

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  8. Jonny Norris

    Jonny Norris Veteran
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    In fact The way you have used a half plate on the inside is exactly as I was describing.

    Certainly going to be a lot stronger than leaving the y's floating.

    Applying this method to the first floating version along with a H beam (two c beams) on the x is something I'd personally pursue.

    The twin x profile either side of the z would give you some added strength though I find these things twist more than bend over the x so if you wanted to do a twin configuration, you may find it more beneficial to stack them vertically.

    I'll put together a model of the H beam and gantry idea later this evening.
     
  9. Jestah

    Jestah Veteran
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    Wow, a lot of good ideas @Jonny Norris and @Renoir but sadly I was a little past the point of no return with my design so going to give it a hoon any way. Having a look at it tho, I think I may be able to sneak the H Cbeam idea in at the sacrifice to some machining space, if the double 80x20 is not stiff enough for my needs.

    I have attached a few photos showing the final prototype that is out at the laser cutters that they assure me will be ready any day now! I hope that on pickup, I can have a chat to them about how accurate parts are after some folding, as this could also open the door for what you could build. I have been sneaky and added a second motor mounting area under the gantry as well as some extra supports.

    Renoir, I really like the double supported Z axis but sadly due to the space I have I may not be able to squeeze it in. I hope to work up some more prototypes once my plate maker is finished and get something like that working if my Z is not stiff enough.
     

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  10. Jestah

    Jestah Veteran
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    a few photos of what I hope is the last prototype!

    Worked out all the kinks and getting methods setup to process the laser cut parts efficiently

    Fingers crossed this Z will cope with 3kgs of water cooled spindle!!!!! I Guess I could also try a double stack of Z wheels on the C beam..... I was also wondering if having the longer section of bolt inside a thicker mounting plate gives an open ended bolt more rigidity....
     

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  11. Hamdi Hirzallah

    Hamdi Hirzallah Well-Known
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    neat 3D work man!
    which software are you using? can you do simulation on it?
     
  12. Ronald van Arkel

    Staff Member Resident Builder Builder

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    Hello Hamdi,

    It looks like SketchUp, just with the components colored so it's easy to see what size a bolt, screw or nut is (for example). SketchUp does have a simulation program but doesn't seem to work on 64bit (last time I checked) and called sketchyphysics.

    I hope that helps ;),

    -Ronald
     
  13. Jestah

    Jestah Veteran
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    Solidworks but as I have to work around a mates schedule (we can go into his work afterhours) until I can afford my own licence it has made things tricky. SW has a good FEA setup but its only as good as the info you put into it. In saying this I did use it to strip about 40% of the weight off a set of downhill skating trucks I designed usi
     

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  14. Ronald van Arkel

    Staff Member Resident Builder Builder

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    Darn, I really thought it was SketchUp.

    Ow yes, SW is absolutely great for production and manufacturing, but indeed, only worth the price if you can make money with it. Those skating trucks look awesome! One day we might be able to make our own 5-axis CNC :D.

    -Ronald
     
  15. Jestah

    Jestah Veteran
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    I have been dreaming of a 5 axis for well over 6 years @puntoMX but this will have to do until I finally finish it!

    I have test fit the spindle and really happy with how my clam worked out as the nylon printed part is 1/4 the weight of the ally mount I had purchased with the 800w spindle. Just got to find a way to mill 3 sticks 80x20 and 2 sticks of 40x20 all the exact same length.... Its a bit to big of a job for my mill drill so may have to out source this part of the project...
     

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  16. Florian Bauereisen

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    HI,
    why on earth you want to save weight on your spindle mount?
    CNC is all about rigidity, especially if you want to cut 3d jobs. Rigidity usually doesn`t come with using softer and lighter materials.
    If you are worried about your stepper - just use a stronger one (eventhough i doubt there will be problems).
    Or change your design...
    On my last mill i used a 0,9NM Stepper along with a 1205 Ballscrew to haul my 800W HF Spindle around. It would easily squeeze your arm off - if not carefull.

    Just a rough estimate:
    you will need a 0,8 NM Stepper to haul a 25kg weight at 3000mm/min and 0,1cec accel- still putting out aditionally 500N of force net.
    Asuming aprox 150mm travel, Spindle of 10 mm dia and 4mm pitch.
    Just to get that further into perspective you would have to lean with all your might onto your handheld drill to get that kind of force. Likely you break a 3-4mm drill while pushing that hard....
    With cnc we rather try to cut into materials....

    Just food for thought.

    greets

    flo
     
  17. Ronald van Arkel

    Staff Member Resident Builder Builder

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    I would like to add to Florian´s post that weight is most of the time a good thing with CNC when you put it on the right spot. More weight on your X/Z body translates in vibration reduction (as long as the V-Slot/C-Beam doesn't flex/torque). Now, the V-Slot/C-Beam also reduces vibration by itself as it's made of aluminium and tubular. Honeycomb structure will reduce vibration more and is also sturdier.

    To add to the food ;).

    -Ronald
     
  18. Jestah

    Jestah Veteran
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    While I agree that weight is often better, (have spent months working on learning how I will cast my epoxy granite mill - don't hold your breath for this project as it's still awhile off ;) ) in the case of this machine my worry is not the power of the steppers being able to move everything around, but having too much weight in the Z that would then require each linear motion stage to be beefed up to account for the extra moving mass. While this extra strong build may be a good thing, I can't help but feel it will be overkill and not needed for the machine's intended purpose so going to try going as light as possible, while still maintaining as much stiffness needed to get good quality cuts. Reducing any unrequired weight will help maximize acceleration and motion smoothness over the ability to take massive cuts or material removal rates.

    The 800w was the smallest I could find but is still 3kg (that is almost a whole kg more than the wood routers most are using on their OX) and as this load is cantilevered off the gantry beams I think adding a extra kg of ally spindle mount will be more issues than it's worth. The nylon insert that has a fiberglass backing plate is a fraction of the weight and as far as I can tell clamps down just as well. The plate has oversized clearance holes to pick up on threaded holes in the Z plate so that they can be slackened and the spindle rotated around a center dowel pin to tram the spindle left to right and then using shims to get front to back tilt. This system is independent to the Z stage and similar to what is used in the commercial CNC routers I use to install, as with long tooling and tall vertical cuts good tram is critical. I am still a bit worried about getting the Z stage vertically moving with eccentrics but may end up drilling a few holes in my gantry so I can get a tool to the 4 bolts that hold the Z stage to the carriage so I can make adjustments if required.

    The Z stage is also designed to have the spindle retract a 100mm long tool 105mm over the stock so that even with my 105mm travel I can machine a full 100mm rather than most of the OX builds, which can only cut a max of half of its Z travel. For work where I need short tooling, I can either loosen the band clamps and drop the spindle down or I think I my preferred method will be to have a drop on MDF torsion box table that brings any thin stock work up closer to the gantry.

    Generally my CNC build method starts by looking at the cutting tools I will use and designing the entire drive train back from these loads and speeds. This machine will cut with small, less than 7mm, tools in relatively soft materials (timbers, foams, thin composite layups and tooling board for mould making) so I was leaning towards an outrunner solution. After cutting a bit of ally on my small OX with a outrunner spindle, I found it seems to bog down when it enters a cuts. That could be due to my inability to setup the ESC but for this machine as it may end up in a light duty production service I wanted something a little stronger. I also wanted a little less runout as I may run extra long tools which I just don't think will be as usable between two skateboard bearings. I did look for a 10mm shaft outrunner so I could use some AC bearings to gain a stiffer spindle but no luck in the KV I want so gave up and went back to buying a watercooled spindle and VFD off the shelf.

    There are many different theories going into this build but at the end of the day the proof will be in the pudding so time to get cracking into the build so I can show you guys some results and also see if my balance of design choices will be a good fit for a shaping machine!
     
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  19. Florian Bauereisen

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    Hi,
    each to his own.
    It is apparent that you have put quite an effort into designing to your needs from the base up.

    Still the z-colum (and whole mill) will restrict max accellerations by its general layout (like any design) - running on wheels that is.
    It would have been a much more sensible mod to invest into (short) linear rails and wagons (square type) on z and make use of their tight tolerance and tremendous load capabilities than to save 1 kg. I doubt that your machine will accel. noticeable faster than a standard c-beam/ox-type cnc.
    Aditionally you spend a lot of weight on yor third beam - whoose reason i still do not quite understand. (If it woud directly support your spindle - well then..)

    Hopefully you prove me wrong. :)

    Even the small(est) 15mm sice rail and wagons are cappable to take loads your 800W spindle will never ever generate...
    One single 20mm rail on y would easylie suffice, while keeping cost down using wheels on x.

    My diy- machine in the pic below has same design criteria, retracting spindle above y-beam, 800 W Hf spindle, cutting 3d moulds and so on.
    Its sturdy design will make accellerations of 12.000 mm/secsec possible on all axes. The whole gantry alone weights aprox 50 kg, complete machine more than 145 kg.... Still 12.000 will likely break your router-bit while cutting - so i turned it down to 4000 accel. each axis. All that is on 1 and 2 NM Servos.

    Btw. your decision to raise your cutting bed if cutting flat material is very sensitive. Not only the accuracy will be better (leverage) but saving the hazzle of getting your spindle 90Degree to all axes again will make you think twice about it anyway.

    As i mentioned above - just food for thought.

    Good luck with your project i will be following with intrest.

    Greetings from Germany

    Flo
     

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    #19 Florian Bauereisen, Nov 7, 2015
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  20. Jestah

    Jestah Veteran
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    Thanks @Florian Bauereisen for the comments. I agree that a set of 15mm blocks would be much stiffer but giving Vslot parts a go first as so far I have been really impressed with the performance. Your machine looks amazing and extremely strong!

    Got all the sticks back from the machine shop this week and spent a bit of time drilling and tapping the ends. Getting the critical length milled dead square has really helped make squaring the gantry very easy without much fuss. as I might do some light testing and then teardown for anodizing so I am not going to any huge lengths to get it perfect this time round. I also added 30mm bolts to lock all of my double stacked Vslot together and quite impressed at the difference it made. I think this should be suggested as a standard upgrade to any one using double rails on a build.

    Got the gantry and spindle mounted up and very happy with the balance of the assembled rig. The whole thing is well weighted around the center line of the gantry and the Z axis feels a bit stiffer than my desktop OX. I feel the gamble of adding the extra rails in each corner of the gantry side plates acts to make a much bigger box structure that has ended up very square and stiff.

    I have just glue the lower belts in finishing the frame and wiring over the weekend. Happy with the build so far and only a few small details I would like to change to make installing double belts less of a nightmare.

    Also a bit annoyed to find that the spindle connector 4th pin that I was assured was grounded is very much not..... I am considering adding an internal earth connection by drilling and tapping into the cap of the spindle or do most consider a separate earth wire connected from star ground to the spindle mount/external jacket acceptable? Part of me wants to run the earth as well via a thick bra
     

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