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  1. #1
    Current machine:

    Shapeoko 3 XXL to which various things have been done. I've used this machine for a couple of years now, got to know what it can and can't do, learned how to use Fusion to do CAM, machined a reasonable amount of wood and a bit of aluminium and think I know what I'd like it to do better.

    Click image for larger version. 

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    I have the HDZ upgraded Z axis and a 2.2kW Chinese spindle with HuanYang VFD which I plan to transplant to the new machine, also a large torsion box bench it lives on which the new machine will initially live on until I get time to build a new steel frame base.

    The Shapeoko got Hiwin rails (from Fred at BST) and dual 15mm belts on the X axis which improved it substantially. The Shapeoko machined all it's own upgrade parts using single flute cutters in 6061 with just dust extraction, it will also be making parts for the new machine.

    What I want to do with the machine:


    I will be machining hardwoods, plywood, epoxy, plastics, non-ferrous metals. I don't expect to be able to cut steel. I would like to get an acceptable surface finish and machining speed in Aluminium, not talking VMC mirror smooth, just something acceptable. I expect to put a compressor and fogbuster type lubricant spray on for metals.

    I am not a commercial shop, I don't need huge throughput but I would like to spend fewer hours watching low depth of cut toolpaths in baltic birch and aluminium.

    Why I think I should upgrade:

    • The XXL Shapeoko is quite different to the smaller machines, there is much (10x) more deflection in the extrusions and double the belt deflections, I would like decent rigidity and the XXL size.
    • The max DoC without bad noises in baltic birch is about 6-8mm and I can't feed this faster than about 1,000mm / min before vibrations build up in the machine.
    • Cutting more complex shapes in Aluminium I am hitting the minimum step size on that controller / stepper / belt combination which leaves staircase lines in the finish on Aluminium. The wall finish once I go more than about 10mm deep or use 4mm cutters is problematic, I can see resonance lines due to the belts unless I turn the accelerations way down.
    • Squeezing a vice onto the spoilboard under the stock X gantry is hard, there's < 100mm of clearance, when you do it's then hard to use an indicator on the part, I'd love to have the room to put a proper touch probe or Haimer type tool in there instead.
    • I have some frustrations with GRBL and the supplied software which I don't think it's reasonable to ask a consumer oriented company to change, I think it's time I went to MachX, LinuxCNC, UCCNC or similar and made my own compromises.


    Current design:

    First, thanks to those who've posted their experiences and knowledge here to read, I've read lots and learnt some. There are certainly a few dumb design decisions that have been corrected after that reading.

    I plan a moving gantry machine using aluminium extrusions which re-uses the Shapeoko HDZ Z axis, my spindle & VFD and, erm, that's about it. I've modelled several versions in Fusion 360 and have attached some renders of the various bits for comment, critique and suggestions please. Below is the main assembly, I've not yet added details like the homing switches or drag chains, I'll add those once the base design stops changing too much.

    Click image for larger version. 

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    I plan to use ballscrews on the X and Y axes, 1610 is my current thought to get decent rapids speeds without having to spin the screws fast enough to start whipping. It seems that double-nut ballscrews are only for 1605, which causes me to wonder what backlash I'm going to get just for having the 1610 ballscrews and whether that is a smart trade off?

    I have modelled in room for either Nema24 closed loop steppers or similar sized servos. I plan to use belt & pulleys to couple the motors to the ballscrews to give me the option to adjust gearing, I can gear the servos down to shaft speeds this way.

    I've looked at quite a few of the servos, JMC and Delta on Ali, the 220V AC powered units seem to make sense for lower part count in the electronics box. What I am not sure about is whether the servo tuning is a pain on these types of servos and whether I should import Clearpath and put up with the import duty and 70VDC supply requirements to get the smarter tuning software and better support? I'm looking at the 400W AC servos, not sure about stepper torque.

    For the base frame I have 60x60 Misumi extrusions bolted through to produce the box, I can machine the counterbores myself

    Click image for larger version. 

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    I've included some corner plates below for the levelling feet to screw into

    Click image for larger version. 

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    I am not sure about the work area, at present I have two 8mm steel plates drilled on 50mm centers and tapped to provide workholding anchor points. These are topped with MDF spoilboard. I am not sure whether these steel plates on top of the Aluminium base will just keep warping the machine with differential expansion or some other problem I've not thought of. The other options are to cover it in EFS-30300 type extrusions or spend lots of money on aluminium tooling plate.

    Click image for larger version. 

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    The Y rails are Misumi 60 120 braced down to the base in the center and bolted in both ends with the Y end plates. The Hiwin linear rails sit in the top center of these, currently on a 6mm slice of tooling plate to add some meat to the top of the extrusion and let me extract the stiffness the extrusion shows in bulk.

    Click image for larger version. 

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    The ballscrew sits to the side of the linear rails and there is a Y transit carriage which allows the X assembly to be bolted on afterwards (a change after reading Jazzcnc comments).

    Click image for larger version. 

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    The X gantry is Misumi 80 160 which has moments of inertia sufficiently above the Shapeoko extrusions that I think it should be sufficient for my needs. Again the Hiwin rails are mounted on a 6mm aluminium tooling plate, bolted through to sliding nuts in the extrusion. I hope the use of the tooling plate will help spread the load into the extrusion and give me the chance to scrape, file, shim or otherwise fix any deviations from straight I find. I plan to purchase a decent straight edge and use that during assembly to get the rails reasonably flat and straight. I've installed linear rails on the X extrusion of the current machine so I have made one set of mistakes to learn from.

    Click image for larger version. 

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    I have a simple adapter plate mounting the Hiwin rail blocks and ballnut mount which the HDZ is then bolted to the front of, this is how the Z axis is mounted to my current X rails.

    Click image for larger version. 

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    I have used the FK ballscrew ends in the end plates on both X and Y, I don't know if there is any substantial difference between these and the BK type? I plan to order the ones with decent angular contact bearings however.

    The end plates on the X axis are mostly supported by the end of the extrusion with a small extension down to the flat mounting plate (with rebate) which bolts to the Y transit carriages.

    Click image for larger version. 

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    Click image for larger version. 

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    These then, hopefully, attach to the Y rails and give me a moving gantry.

    Click image for larger version. 

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    I have not yet chosen a controller or software, as above, I'm thinking Mach 3, LinuxCNC or UCCNC. I may add a 4th axis later on, I definitely want to be able to auto-square the Y axes on independent home switches. I'd like to control the spindle, air jets, dust extraction etc. as accessories. I don't think I want to spend the money to go ATC, if I did, maybe the controller would have to change too.

    I'm planning Misumi for the extrusions and figured I should pay for the 'precision machining' on the X and Y gantry beams to get really clean square ends. I've not bought from them before though so I don't know if I should expect the ends to be clean and square on the others or whether I need to pay the extra £10 on all of them?

    Any comments and suggestions would be appreciated, I'd prefer to learn about my mistakes in CAD not metal.

  2. #2
    I haven't really got the time to read all of the post so just quickly flicked through the images but I can see straight away that you are going to run into trouble with alignment and setup because you haven't got any adjustment so even with a machine to help you make parts you won't make them so accurate that you won't need some way to make adjustments.

    The golden rule of DIY building is to allow for Adjustment, then a little more adjustment for good measure.
    -use common sense, if you lack it, there is no software to help that.

    Email: dean@jazzcnc.co.uk

    Web site: www.jazzcnc.co.uk

  3. #3
    Thanks,

    Where would you suggest adding the room for adjustments?

    I've got some adjustment laterally on the linear rails on the extrusions, how much wiggle room should I be looking for?

    Is that a reason for using the BK style ballscrew mounts bolted to the axis instead of the FK in the endplates?

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