New member from Trinidad

[njhussey]

Hi and welcome to the forum Trini. To send a PM to someone you have to left click on their name and select private message (that is if they have set their profile to allow private messages!) Best thing to do is as you are currently doing, look around, see what others have done. I'd suggest looking at Kingcreaky's build here as that's the size you want. once you've had a look, made some notes etc. get your pen and paper out (or better use Sketchup or similar) to do some rough drawings. put them up on here for people to critique/advise and then go for there. Don't even think of sorting the electrics until you've got the basic frame designed as the electrics will depend on your design....

Good luck and welcome to the forum!!

[JAZZCNC]

Welcome trini,

Don't let me put you off but if this is your first CNC machien then starting with a large machine isn't always a good idea.
While it may seem like not much more work for large machine compared to smaller size this isn't the case in reality. There's hell of a lot more work and it's much harder to get a large accurate machine. Design and build quality become much more important.

Every thing Neil suggests is good advice you should listen too but please be aware of the scale of machine your undertaking. Just because others have built large a machine doesn't mean that machine performs good or couldn't be better with just a few small tweaks.!! . . . So Research then research some more then a little more for good measure before starting.

[Trini]

hi

Thanks for the welcome. Yes I will go through Kingcreaky's build. I have downloaded the sketch up program. I was getting ahead of my self with the electronics. But after many reviews of others I see that the frame has a lot of work also.

So thinking about where to start, I was wondering how much over the dimensions should I go. Eg. I am designing for an 8'x4' cutting area so recommended dimensions should be just a one or two inches over 8'x4' or must the top area be to exact 8'x4'? Also I would like to know the different rails to use. I would like to design up to the rails. I see that many people used the SBR bearings. What are your taught on this calibre of machine.

regards

[Trini]

hi.
I have a sketch from sketchup. How do I change it to a photo too upload?

[njhussey]

Under "File" select the "Export" option and then "2D Graphic" and it will export whatever is shown on your screen.

[Trini]

ok here goes.
I have played around a bit with sketch-up. This is what I have so far.. I would like for you all to over look it and add any suggestions. My plan is to design around the equipment I would use on it.
Plans on using
1] 4 pcs Nema 34 stepper motor 1600 oz.in bipolar with single shaft 4 pcs Stepper motor driver DM860A, peak 7.8A, 24-80VDC 4 pcs Power supply 350W 60V 1 pc Breakout board & 1 pc parallel cable. [ will buy from amazon]

2] CNC KIT FROM AMAZON LIST BELOW

1 x RM1605--300mm ballscrew ball nuts + end machined for end support bearings(BK/BF12)
1 x RM1605--1750mm ballscrew ball nuts + end machined for end support bearings(BK/BF12)
2 x RM1605--3000mm ballscrew ball nuts + end machined for end support bearings(BK/BF12)
4 x BF12/BK12
4 x 6.35*10mm coupling
2 x SBR20--300mm liner rail
2 x SBR20--1750mm liner rail
2 x SBR20--3000mm liner rail
12 x SBR20UU
Note: The ballscrew kit is C7 standard with standard machine end.
All the length of the ballscrew and liner rails kit can be cut at any length.

I have not pick the spindle yet, to design around it. So any design ideas you fellas have would be nice to hear them. Also I would like to know what other electronics I would need, so I can budget my spending and source them while I do the rest of the build. I was thinking about appox $3000 to $4000 U.S.

[njhussey]

OK, frame looks not a million miles away, I'd make sure that the top rail has a thick wall otherwise it'll resonate with high frequency vibrations from the spindle. Bed looks like it could do with a bit more bracing.

Electrics, don't buy a "kit" of parts from one seller as they're always compromised in at least one area. If you're going to use Nema 34 motors (Z axis won't need it unless you're planning a monster?!!) then they need at least 100V to make them perform, best to use a 230V driver to get the best performance. If you're determined to use lower power drivers then use ones that can take 80V and build your own power supply to get the best performance.

Ballscrews, for wood you'll need speed so I'd use 1610 ballscrews on your X & Y axis and 1605 on your Z only. But at this length you'll need rotating ballnuts on a fixed (clamped both ends) 1610 ballscrew. Otherwise you'll need to go up to 20mm ballscrews and possibly 25mm, couldn't say which without doing the calcs for speed etc.

Couplings, use belts, this enables you to swap pulleys to increase/decrease the speed/resolution and more importantly it stops resonance being transmitted to the stepper motors.

Spindle, you can't got wrong with a 2.2kW water cooled spindle with inverter, the type you get from eBay....I've got one and they're great!

Other electronics will be things like relays and other electronic components (fuses, din terminals etc. etc.) to build your control panel, limit switches what controller are you thinking of?