Comments sought on new build: A CNC Router for RC Gliders and Planes

[njhussey]

Cut up some of the 100x50x4 rectangular section steel to make a temporary gantry and just placed it on the x axis rails to check I cut it to the correct length!

Apologies for the blurred photo, took it on my phone...



Close up of the steel...fresh off the bandsaw so still got swarf and cutting coolant.



I'll hopefully weld up the two pieces tomorrow and drill the mounting holes for the 20mm carriages in the 200mm long bits. I'm thinking of bolting the L shaped gantry to the 200mm pieces and then once it's square I'll stitch weld them to keep them square. Going to epoxy the face of the gantry for the rails and also the bottom of the 200mm pieces so the carriages sit flush unless by some miracle the steel is perfectly flat...

Had a delivery of some cap head bolts last week, I know I'll need more and different sizes but this should get me going!

[EddyCurrent]

Any recommendations on 'best' place to get bolts ?

[njhussey]

I was going to use our local supplier Hereford Fasteners but they were over twice the price of fasteners :: set screws socket allen key :: cap head metric bzp ::

I was happy with the price so went with them. Delivery bumps it up a bit but I needed some F clamps and a few other bits so wasn't that bad!

[EddyCurrent]

I must be blind today, you already provided that link a few posts earlier , I have also found a local supplier that seems quite reasonable so will compare prices later.

[njhussey]

Well spent the 1/2 hr in lunch marking and drilling the holes for the X axis carriages in the 100x50 box section. Used the 6mm transfer punch and the 60x60 angle that I've already drilled as a template to mark the holes and then the pillar drill to drill them (obviously.)

I'll probably dummy mount the rails to get an idea of how it will fit together and then mark the L section gantry for drilling the holes and bolt them together for a play....a bit like this...

[njhussey]

Today's small advancement....wish I could have a few hours uninterrupted in the workshop to crack on! Anyway I only managed to mark out (wrongly ...what is it, measure twice, cut/drill once??!!) the holes for the bottom section of the gantry and drill them and put the carriage mount pieces on the carriages. Marked out one carriage mount but ran out of time to centre punch and drill.


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[routercnc]

Looking good Neil. You just have to keep chipping away at it.

In post #224 and #221 the Y ballscrew looks like it is some way off the Y axis, dropped down on some spacers. Would it instead fit under the Z stepper motor and attach directly to the trapezoidal shaped plate on the side of the Y axis (i.e. ballscrew on top of the gantry)?

[njhussey]

Looking good Neil. You just have to keep chipping away at it.

Thank you, that's what I am doing, it's just frustrating!

In post #224 and #221 the Y ballscrew looks like it is some way off the Y axis, dropped down on some spacers. Would it instead fit under the Z stepper motor and attach directly to the trapezoidal shaped plate on the side of the Y axis (i.e. ballscrew on top of the gantry)?

Re-drawn the gantry as I realised that if sent vertical there was a nice shelf for the chips/dust to collect on. How about this way?



This shows the Y axis ball nut holder attaching to the Z axis plate.

[EddyCurrent]

Neil,
You've turned the gantry round !, I thought the idea was to have the ball screw at the back out of harms way ? I know this reversed way puts the ball nut nearer to the Z axis but it's been stated that in practice it makes little or no difference to have it at the back.
I like the box section idea between the bearing blocks and gantry, it allows easy access for bolts and does not require counter boring.
Seeing as you have spacers between the frame and ball screw bearings on the long axis, why not extend them up so that the ball screw is more in the same horizontal plane as the rails ? I had them like your drawing at first but decided to raise them as far as possible. I'm thinking a limit switch could also be mounted on the extended spacer, above the ball screw bearing.

[njhussey]

Don't forget my machine will be mounted at 75° from horizontal (eventually!) so before the gantry would have collected all the crap being thrown up by the cutter. This is only going to be a temporary gantry (famous last words!) as I'll use it to cut the aluminium parts for the "proper" gantry from the 800x1000x20 sheet of Ali I have lying around gathering dust, which will then be enclosed to protect the ball screw.

I've put the ball screws there to protect them from flying crap as much as possible from the cutter as they are hidden behind the rails where they are. They are only 45mm below the X axis carriages so I'm not sure that it would make any real noticeable difference in terms of performance?