Hello from Cardiff!

[Jonathan]

What would you recommend as you guys know best? is the LC spindle really needed over a cheaper alternate such as the kress.

The Kress is in the end still a router, not a proper spindle. It will have more run-out, be noisier etc and won't last forever. The minimum rpm is 5000 ... whereas you can go lower with the water cooled spindle. That's good for cutting metals.
Maybe get a really really cheap router to start with then save up for the spindle? I started out with a router for about £6 from the car boot sale ... one of the ones from Aldi. This is what I have now got:

http://cgi.ebay.co.uk/2-2KW-WATER-CO...ht_7977wt_1139

For an A3 size machine the only reason to get the 2.2kW version is because it takes bigger collets. The extra power wont be required.

is 40mm Alu Profile ok to build a machine of my needs with?

Do you have a drawing of it, or better know its second moment of area?

is making the leap to 25mm supports really needed for a A3 machine?

It's not needed, but every little helps. The more rigid the machine is the faster you can cut whilst still maintaining a good finish. I regret not getting 25mm for the Y and Z axis, but then my machine is much bigger.

what Force Nema 23 motors will I get away with?

These 3Nm ones are popular/economical:

http://www.ebay.co.uk/itm/3-X-3Nm-St...#ht_1617wt_905

You could use less, but the price per Nm goes up if you do. The main thing is to look for motors with a low inductance and run them on a high voltage as that gets more torque at higher rpm. With those motors 70V will work well, which means you'll spend about £40-£50 on each driver.

[jcb121]

So would these Stepper motors with these Stepper drivers hooked up to this breakout board with this 48v PSU or this 36V PSU

and that would be the electrical side done apart from the spindle?

[Jonathan]

Steppers good and drivers are ok but you will find equivalent much cheaper on eBay internationally and 75 volt would be nice.

The breakout board you have chosen is opto-isolated which would be good except the drivers you have chosen are already opto-isolated ... that makes it slightly more difficult to wire up and can lead to issues so it's best and also cheapest to use a breakout board which is not isolated or even just connect them directly.

The 48V supply is ok, but again 70V would get higher torque. It's also very expensive ... so go for this one if it's still availably and you stick with the 50V drivers:

http://cgi.ebay.co.uk/ws/eBayISAPI.d...ht_1179wt_1139

Though it looks like Zapp might have bought the lot to sell them for three times the price:

http://www.zappautomation.co.uk/ep00...b64aaf46d5274f

I dislike the way they are making so much on those bye claiming it's a good price by saying the RRP is £280.

[jcb121]

are there any benefits to having the cutting bed move along the x axis?

I know it will take more room in my workshop but surely it's more stable?

[Jonathan]

Swings and roundabouts...

Moving bed is bad if the part you are machining is heavy, or if you've got a heavy vice etc as the steppers have to accelerate that mass quickly. If however the mass of what your machining+bed+clamps is less than the gantry then moving the bed will get better acceleration/speed.

How rigid the machine is depends on how you configure either option, so it's difficult to compare. Having the gantry stationary is good in that you can make it as strong and heavy as you want want ...

Not sure what other pro's/con's there are as I never really considered it ... other than space as you say.

[jcb121]

what do you guys think so far? the cutting are from the outside of the 10mm bit is 420x290

so just under A3. this is with 20mm clearance on each side of of gantry when moving in all directions.

so the actual cutting are is 40mm bigger both ways.

I need to re-think my Z axis though, it's too big and won't give the spindle enough depth.

I'll be limited to the thickness of the sheet not be the length of the supported bar.

[Jonathan]

The way you've orientated the X-axis linear bearings will make them difficult to align parallel - you would have to cut the frame they attach to extremely accurately or have some adjustment. If you rotate them by 90° then it's easy to align them as you can fix down one and use it to get the other parallel.

Having the Y-axis ballscrew close to the bed is a good plan as that reduces the overhang... which will reduce deflection parallel to the Y axis. Similarly to the X-axis you've not got a way to adjust the spacing in the Z direction of the Y axis bearings. That orientation is good .. you just need to have the plates in the YZ plane bolt to/overlap the plates in the XY plane. Look at how I did it on my machine if that's not clear.

Where's the X-axis ballscrew(s)?

Putting the rails on the moving part of the Z-axis is stronger than having the bearing blocks moving when it's at the upper limit. Be careful with making the Z-axis too long. It will make the machine much less rigid. I had that problem (400mm Z axis!) so I ended up eliminating the gantry sides:

http://www.mycncuk.com/forums/showth...ding.../page11
(only need to look at the last few pages...)

Mounting the stepper motors on posts has poor torsional stiffness. A 'solid' mount would be better.