Nomad 3 info, plus something else

I’m hoping the Shapeoko Pro will have dual Y axis homing switches/endstops, to allow for ‘auto squaring’. If this hasn’t been considered for the final production, will you please add it?

On another note, how is the Onefinity cnc able to offer ballscrews on all axes at a pricepoint lower (Canadian company no less, so their parts costs would most likely be higher)? I do wish belts were completely removed.

Would be nice if the HDZ with ballscrew was included instead of the Z plus with leadscrew.

I really like @DanStory HG15 rails more and I don’t think they would look out of place at all on the Shapeoko Pro. MGN rails are typically great for 3D printers.

Onefinity has lower costs in other areas of the machine that mean they can spend some more on ball screws.

No bed…at all.
Off the shelf round rails.
A BOM for the machine that looks like it uses 50 less parts.
An off the shelf controller.
Fewer electronics like homing switches.

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Taking some design cues from the Onefinity would’ve been nice.

However, I’ve yet to see a non paid/freebie review for their CNC online.

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I’m also very interested to see how the machine rigidity works out in the real, unpaid-for review world.

Those round rails only constrain in two dimensions and are separate elements which allow the cutting forces to leverage between them instead of being a single X or Y beam. Whereas, on the Shapeoko Pro the linear rails are on a single large axis beam extrusion with high rigidity and each rail allows only one degree of freedom. That’s a huge difference.

On the subject of ballscrews, not all ballscrews are created equal either, cheap ballscrews with cheap end mount bearings have both substantial backlash and can be quite inconsistent in movement distance over their length.

Belts have some significant advantages on a budget machine, way less motor power is needed as you’re not spinning up the screws, meaning cheaper electronics and cheaper motors. The design backlash in the GT2 belt profile is zero so far as a CNC router is concerned. Belts are much more forgiving than ballscrews too.

I’ve been looking closely at the Shapeoko deflections and how much can be attributed to the belts and it’s not much in terms of absolute accuracy.

To me the OneFinity ticks many of the boxes of the “Beginners’ guide to how not to design a CNC machine”, as said above, their BoM must be heavily skewed to the cost of the ballscrews, motors and electronics which means they’ve saved a lot of money elsewhere, in linear rails, no base frame at all etc.

The jury is very much out…

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New machine looks great. If it was available back when I made my purchase, I certainly would have paid the difference. Belts, including the Z axis, have proven fine for me. The V wheels on the z and x, flexy x/z plates, and terrible bed, have proven inconsistent for my purpose. All told, its a machine I don’t care about crashing, and that is very nice. While hardly efficient, its proven useable and very informative.

I’d hazard a baseless guess that the sub 4’x(x) size is a factor of manufacturing capability, and most likely, common carrier shipping constraints. I enjoy having the little xxl to play with, and as much as I’d like to have the Pro instead, I don’t think its my next machine, even at 1/10th the entry level cost of what I am now actively shopping.

As for Hobby related stuff, The OneFinity does not look appealing to me at all.

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So you disagree with the @AlexN Belt Stretch and Stepper Holding Measured post findings and the wisdom of using less stretchy GT3 or Kevlar belts?

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Nope,

That post was most informative and what set me off doing the measurements.

What I’ve found though is that the V wheels are responsible for considerably more unwanted deflection than the belts are. There is a backlash mechanism in the machine, but it’s not just the belts.

Bigger better belts provide a number of benefits, less deflection on dynamic loads when cutting, less chatter etc. but that won’t necessarily have any effect on final accuracy in almost unloaded finishing passes.

The downside of the bigger belts is that they move the load further away from the stepper motor front bearing and increase the radial load on the stepper shaft which means you need to be even more careful to not gorilla tighten your belts trying to reduce backlash or deflection by winding up the static tension.

I’ve got a bunch of stuff to write up and post, which I need to do whilst I can still take V-Wheel measurements.

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Awesome - looking forward to that! :slightly_smiling_face:

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In the meantime, the Shapeoko Pro upgrade to the slightly wider belts and the MGN rails is, in my opinion, a really good choice based on price, size and utility. It’s close to what I’m doing based on the deflection measurements I’ve taken. The inclusion of a few other things like the flipped motors, wider X beam, Y rails outside the Y beams and the proper T slot bed make a really nice package which I expect will work really well for Shapeoko sort of jobs.

People who want to chase maximum MRR on a Shapeoko with a 2kW spindle will probably still want to mod it more, but even then, it’s probably a better place to start.

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It will also not surprise you that I’m in favor of the double drag chains :wink:

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I pray they mount the electronic enclosure on the side rail of the smaller machines as well and have drag chains. I really dislike the x gantry mounting spot on the standard so3 as I dont want my power and usb cables dragging along the machine edge. Plus it’s a pain to spin the machine around to access the control board in my enclosure.

wishful thinking.

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It wouldn’t be a large modification project to buy a £10 drag chain on eBay or AliExpress and fit it to your machine with some 3D printed or sheet Aluminium brackets to carry the USB and DC power cable up to the controller.

Just a thought.

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Except that the wiring isn’t long enough to reach a different position — in order to modify the placement of the electronics you usually need:

  • Molex KK pins and connectors
  • crimping too
  • 4 conductor 18–20 gauge shielded wiring — ideally a sort suited to bending
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Is that the DC power cable that’s short then?

I wasn’t thinking of moving the controller, just managing the incoming USB and power leads.

OIC.

For the USB and power leads a pair of drag chains at either side of the machine makes a lot of sense if one is having issues with their runs.

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Actually it does, since spindle motor E/M coupling could be virtually eliminated by routing its wiring perpendicular to the other wiring and keeping it as far as possible from the electronics. I.E. by routing it alongside the dust collector hose. :wink:

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Well…

Firstly, I’m already guilty of the double drag chain to keep the spindle wiring and plumbing separate;

Secondly, in the double chain, facing in opposite directions install, a large chunk of the chain length is not running close and parallel, even where it is we have the inverse square law in our favour so even just a couple of inches gives us a huge drop-off in EMI.

If we were really concerned to the extent of fully diverse routing then the real fix would be to use properly screened cables instead, as already done for most VFD spindle power cables, a simple vertical plate between the two drag chains on the X rail would cure any cross-contamination concerns.

If I were fighting VFD noise pickup in my signal and motor cabling, I’d just use screened cables for those or wrap the whole bundle in the drag chain in a copper braid and ground it.

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Screened cables suppress the radiated electric field component but not the magnetic field component. But, twisting the power conductors would as would enclosing them in a magnetic shield. It seems to me that since its basically a low impedance system, the magnetic field component would far exceed the electric field component - right?

This is a reasonable summary of the noise source behaviours;

(Although it’s a bit of a cable advert)

There is a shed-load (new colloquialism for Julien) of electrical noise coming off the VFD or nasty commutated universal motor wire thanks to the high frequency interruptions of either the VFD chopping or the commutator brushes. Whilst there is some magnetic field from the power cable, there’s just not that much current being delivered so it’s comparatively small.

As I understand it we’re much more concerned with the low voltage, low current cabling as this is most susceptible. There can be issues with EM pickup on things like stepper power cables but this needs to be several orders of magnitude worse to show up, basically injecting noise back into the drive electronics. In most cases suppression at source is preferred (e.g. easier to stop a tool using Twitter than stop all the followers reading).

For the Shapeoko wiring;

  • The wires to the old homing switches are twisted, which is good as these are signal level. I’m not sure about the new proximity switches (still not in the shop, grumble, grumble), hopefully lessons were learned and those are TP and shielded. For the old microswitches I considered going screened by swapping the wiring for some CAT6 Ethernet STP as it’s dirt cheap but I don’t have an interference problem to fix so left them alone
  • The wiring to the steppers is power delivery and a source of EMI itself, the current flows should be sufficient to outweigh any pickup, if not then you should turn the plasma cutter head off and think carefully about your upgrade urges
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I guess the lack of output filter inductors on the VFDs would cause an increase in high frequency impedance at the motor because of the motor inductance. But, IMO it would be better to add filters to the output (and input) of the VFDs to prevent the E-field radiation rather than try to suppress it with stiff and expensive shielded cables.

Good point about the universal motor routers. Their untwisted and unshielded power cables would carry more current than higher voltage HF spindles for the same power draw. Also both their PWM drivers and brushes would generate E-Fields. So, it seems prudent to run their cables perpendicular to and away from others and to keep sensitive things away from the router and/or properly shielded.

BLDC routers run at even lower voltage and proportionally higher currents for the same power output. So, they’re likely to generate higher M-fields and lower E-fields on the cable between the motor and its driver.

An effective KISS (I think @Julien already knows that one) solution for all types is to keep things well separated with perpendicular spindle cable routing.

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