My first go at making a CNC router

[Norgmonster]

Hi All,

Thanks for the feedback on my last design. I had a feeling that it would not hold up but it was an opportunity to use Fusion 360 for the first time.:-)

I have taken on your comments and hope that this next one is a step closer.

For what ever reason, a lot of the components in the design could not be rendered to look like they should be so i hope you can tell what it is you are looking at.

The size is approximately 2' x 4' with the idea to extend it to 8' x 4' in the future. The z axis trail will be around 20cm.

I have not done a Z axis yet or properly defined how i plan to mount the stepper motors for the R&P system so beyond that let me know your thoughts.

[Norgmonster]

I shore this Rack and Pinion mounting setup and was wondering what any of you guys thought of it?

https://www.youtube.com/watch?v=-m_aoWduEXI

Is it worth replicating for my router design?

Any feedback on my design would be great as well (see photos one posting above).

[JAZZCNC]

Yes the principle of spring loading into rack is ok and how it should be done. But wouldn't copy is weak design for router (he's using Plasma so not so much an issue on the cut). Watch how the mounting flexs @ 0.22s when he puts is hand on it.
This flex will show in the machine. Maybe not in accuracy but will in resonance and this resonance transfers thru the machine and into the final cut. Is too bad it will cause excess wear in the pinion/rack.

[Norgmonster]

The flex is down to the plate being quite thin (looks to be around 5-10mm). I have also see other spring mounted systems that use a belt between the stepper motor pinion and another pinion that makes contact to the rack. I assume this reduces kickback?

Could you also have a look at my new designs and let me know what you think (smaller bed, lower gantry and less rails)?

[JAZZCNC]

Ok we are cross purposes here. The Mechanism of being spring loaded is what I thought you was wanting advise on.
The fact it's direct drive off the stepper shaft is because it's being used for plasma machine which doesn't require the same resolution and torque that router requires.

This is why you have seen other systems that use belts n pulleys. It's got nothing to do with Kickback. The belts/pulleys are applying ratio to increase resolution and torque.

[Norgmonster]

Got it :-)

I should be looking to make something like this then:

[JAZZCNC]

Could you also have a look at my new designs and let me know what you think (smaller bed, lower gantry and less rails)?

It's Ok for general layout and better than last but lots of very important details missing or not thought about.! . . Like. How do you fasten the bearings to the Gantry profile.? . . . Z axis .?? Well no detail there at all.!!

Now given the Short length and to be honest even the Gantry isn't massive wide then suggest you use Ballscrews and save lot of hassle. You'll get much better accuracy and far better reliabilty. Won't cost much more money either.

Personally I'd drop the profile that sits on the bearings and increase the height using taller profile or 2 pieces. Then sit the Gantry profile directly on the bearings fasten to a plate.
I'd also have stiffer gantry. 2 pieces arranged in L config is very stiff. Like this

[Norgmonster]

It's Ok for general layout and better than last but lots of very important details missing or not thought about.! . . Like. How do you fasten the bearings to the Gantry profile.? . . . Z axis .?? Well no detail there at all.!!

Now given the Short length and to be honest even the Gantry isn't massive wide then suggest you use Ballscrews and save lot of hassle. You'll get much better accuracy and far better reliabilty. Won't cost much more money either.

Personally I'd drop the profile that sits on the bearings and increase the height using taller profile or 2 pieces. Then sit the Gantry profile directly on the bearings fasten to a plate.
I'd also have stiffer gantry. 2 pieces arranged in L config is very stiff. Like this

Thanks for the feedback on the new design.

I was thinking to fasten the bearings to the gantry profile using bolts and t nuts that slot into the profile groves.

The x axis will be around 100cm and the gantry (y axis) will be around 150cm. Is this considered small?

No z axis because i wanted to address what i had so fare.

I'm using 80x120 on my x axis. To increase the height, the only larger profile is 80x160 in that range. This would add 40mm. Should i go with two 80x80, one 80x160 or somewhere between?

The L shaped gantry in your photo looks to be using two lengths of 80x120 making the gantry 200mm high. Is this right?

My original plan was to make a router that could be upgraded in size (4'x8') when the time came. That's why i was going for R&P and not ball screws. Is this a practical approach considering that the alternative would mean starting from scratch?

Ill make some alterations and post them soon. :-)

Thanks again,

Norgmonster

[JAZZCNC]

The x axis will be around 100cm and the gantry (y axis) will be around 150cm. Is this considered small?

Not small but still within acceptable range of ballscrews without taking special measures.

The L shaped gantry in your photo looks to be using two lengths of 80x120 making the gantry 200mm high. Is this right?

Yes ITEM 80x120

My original plan was to make a router that could be upgraded in size (4'x8') when the time came. That's why i was going for R&P and not ball screws. Is this a practical approach considering that the alternative would mean starting from scratch?

In theory all sounds great but in practice theres that much work and setup goes into machine to start with that you'll probably not want the hassle of converting.
Personaly I'd build with the intent of building another machine when want larger. You'll then be able to put all you've learnt and design changes into the new improved larger machine. Use the First to build second then Sell it complete and working. If do this right you'll make money rather than costing money converting.