NordicCNC's build log

[NordicCnc]

Hello, I like the way you're showing how your design is evolving, it's great for other people to learn from.

I notice your servo mounts for the x axis (long axis) are separate pieces. Could they be combined into the aluminium end plate you're using to hold the profiles into a 90degree corner?

Regards
Bob

Hello,

Thanks for your feedback! I am glad that you appreciate it.

About the servo motor mounts (the long axis is the Y-axis in my case). The servo motor mounts and the BK15/BF15 bearing spacers are exactly the same as the ones used in the X-axis (gantry). The goal here is to have as few different parts as possible (commonality and re-usability).

Yes, it would surely be possible to have the motor mounts integrated into the end plates. The design of the BK15 bearing plate would perhaps need to look a bit different and. The servo motor axis length and the end plate thickness are the constraints. Machining is needed in the servo motor mounts in order for the motor axis to align with the ball screw (the F-length can be machined longer but the motor axis length can't be changed) and also allow for timing pulley mounting. Too thick end plates or too shallow motor mount machining, will make the motor axis length to short for mounting any kind of pulley. I also like to have the motor mount bracket separated from the machine. This way I can design new brackets later if I want to change the servo motors for some reason, without tearing down the machine itself and then having to realign the axis/ball screw.

Good point anyway and I like your idea. I will have to check the feasibility of this!

[JAZZCNC]

If you are bolting into the 80x80 ends through the 160 sides then I wouldn't waste the aluminum on those endplates because they offer very little to the stiffness, There are no forces involved in those areas so they are more cosmetic than structural.!

[NordicCnc]

Quick update based last feedback collection. Many thanks to everyone contributing with their opinions!

- Raised gantry design with 200x80 item profiles. This allows for significantly lower gantry sides and will increase stiffness. It will also protect the Y-axis rails when they are further away from debris.
- 120x80 item profiles as table bracing, bolted through the 200x80 using counter bored holes. Alternatively I will use some item equivalent connectors, but I think bolting through is better in terms of rigidity.
- Motors on the outside, to allow for shorter belts and also lowering the table bracing to the bottom plane.
- End plates replaced with end caps from Item. These are only for aesthetics.



Next up will be figuring out cable routing and placement of proximity sensors. Is there any significant difference in terms of tolerances when comparing mechanical and optical sensors?

[Sterob]

Its coming along very nicely Nordic.
What software are you using?

[NordicCnc]

Its coming along very nicely Nordic.
What software are you using?

Thanks Sterob! I am using Siemens NX for CAD. I would probably use Fusion but I am lucky to have a work computer with a NX license. In the future I plan to move to Fusion, to ensure that whatever happens with work, I will still have CAD access, lol.

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[NordicCnc]

Home & limit switches

Z-axis home switch at the top end of the travel. Soft limit will be used for the lower end of the travel.


X-axis home switch & limit switch on the moving part. Adjustable bolts in the t-slot in the lower right and upper left of the picture. The lower right will be used for home & limit switch and the upper left will be used for limit switch.


Y-axis home and limit switch on the moving part. Adjustable bolts in the t-slot on the left side of the base frame. Upper left one is used for limit switch and lower right one is used for home & limit switch. On the opposite side (right side) is the second home switch. The purpose with 2 home switches is to be auto to auto square the gantry when homing the axis.


Alternatively I could have all the proximity sensors fixed and not on the moving parts. Then I could use soft limits for all axis's in the opposite end of the homing position, same way as with the Z-axis. Would that be a bad idea? It would be less cable routing of the sensors in the cable drag chains,

[AndyUK]

I'd recommend having the homing positions on the dual screw axis finely adjustable - like how your Z position can be adjusted by turning that bolt. At the moment you'll have to loosen that bolt and t-nut and just hope you can push it accurately back and forth. It'll help when trying to square the gantry, where you need (ideally) sub-mm changes to switch triggering position and I wish I'd thought of that earlier. I've had to do quite a bit of back and forth trying to get the gantry squared.

You can work around it in software (I can't remember what controller software combo you're planning to use - but generally speaking its possible), but easier done once in hardware.

[NordicCnc]

I'd recommend having the homing positions on the dual screw axis finely adjustable - like how your Z position can be adjusted by turning that bolt. At the moment you'll have to loosen that bolt and t-nut and just hope you can push it accurately back and forth. It'll help when trying to square the gantry, where you need (ideally) sub-mm changes to switch triggering position and I wish I'd thought of that earlier. I've had to do quite a bit of back and forth trying to get the gantry squared.

You can work around it in software (I can't remember what controller software combo you're planning to use - but generally speaking its possible), but easier done once in hardware.

Extremely good point, thanks for letting me know. I will make some changes to the design to allow for fine adjustment.

[Clive S]

Z-axis home switch at the top end of the travel. Soft limit will be used for the lower end of the travel.

I personally would have the switch fixed and have the target moving

[NordicCnc]

I personally would have the switch fixed and have the target moving

Yes, that is how the Z-axis switch is planned in the picture.