The "Elite" CNC design

[RiseUp]

I've been researching, reading, looking up terminology, and trying to figure out/deduce everything I possibly can about the aspects and advantages of CN. While I've seen many designs, some are far too complex(expensive) while others simply don't fit my needs. One design that, for some unknown reason, just seems most logical to me is the mobile gantry. Inspired by Probotix's "cnc prototype",http://http://www.probotix.com/deskt...ter_prototype/, I give you the "Elite" CNC machine design.
It has a work area of 12"x12"x4".
The undriven side of the X axis does concern me though, as I'm not sure it will slide too smoothly. I've thought about adding another rail and screw to drive it, along with a gear and toothed belt synced to the stepper motor, or just drive another stepper as a slave.
Another option, I could use the bearings on gaspipe idea instead of the linear bushing to remove the "stick" problem. I'm just worried that the whole X axis will be hindered by the "stick" of the undriven side.
Any feedback is much appreciated.

[svenakela]

I like that you try out new ideas, but unfortunately I don't see how this will make a better machine than the already tried out constructions for machines in the same size.
Don't reinvent the wheel, so to speak.

[RiseUp]

Originally Posted by svenakela I like that you try out new ideas, but unfortunately I don't see how this will make a better machine than the already tried out constructions for machines in the same size. Don't reinvent the wheel, so to speak.

Not exactly reinventing, just redesigning, lol. I threw a few concepts together and came up with this. The mobile gantry design allows a larger work area/footprint area ratio, so to speak, and that's what I'm looking for. I don't want a machine that takes up a lot of space yet has a small work envelope.

[MrWild]

I like utilizing the same space for the motors. I'd pulley and belt the X axis though so the drive was centered. If left like it is, I'd triangulate the gantry.

[RiseUp]

I figured I'd have to do that so the X axis won't "stutter". No big deal though, so long as I get the screws on both sides aligned with each other right. Just as a side question, how strong would my motors have to be to lug this thing around decently? I plan to use aluminum and UHMW for almost the whole thing. I bought some Vexta unipolars a while back.(at $5.00 for NEMAs you just CAN"T PASS them up) They're rated for 6V 0.8A 2 phase 1.8deg/step model number PX245-02B-C8. I can't find the datasheet, but I'm pretty sure they'll do the trick. Any quotes on torque required?

[ZipSnipe]

Originally Posted by svenakela I like that you try out new ideas, but unfortunately I don't see how this will make a better machine than the already tried out constructions for machines in the same size. Don't reinvent the wheel, so to speak.

I agree!! I see too many times where people try to reinvent the wheel when really the wheel rolls just fine. Not that there's anything wrong with trying something new. But I think the tried and true designs are just better. I changed my original design back to the more common design for example.

[budP]

These are very small motors 43 in/oz unipolar.
Your machine will be really slow with these motors

budP

[Kipper]

I was hoping to see a super new design.....Keep doodling!

[RiseUp]

Originally Posted by Kipper I was hoping to see a super new design.....Keep doodling!

Continue doodling I shall! It's not exactly new, but has undergone some revisions to conform to the trends that seem to work really well, like the rails of the Y axis being aligned with each other vertically instead of horizontally,etc.
I'll probably go hunting for better motors soon. 100 in/oz should be good enough,right?

[budP]

100 in/oz should be good enough,right?
Reply With Quote
In my opinion NO the absolute minimum i would go with is 150 and that is pretty small.

budP

[RiseUp]

Well, considering as this IS a benchtop design, DIY, and the most 'precise' components on it will be the linear rails, I guess I'll go with 150 oz/inchers. I have those little Vexta's as of now and I'll certainly try them out, but I figured I'd have to get beefier motors. Thanks for the input.

[FandZ]

I think it looks purdy but like you said I'd worry about the "stuck" problem. If you are worried about saving workspace, I think the best idea is to mount the motor below the tray area. In all reality you are not freeing up any space. You simply are shifting the rails from being narrower on two equal sides to thicker on one side. If you really think about it, you are using more workable room since you need two rails on the motor side to give it questionable stability.

Check out this build. http://www.glacialwanderer.com/hobbyrobotics/?p=17 I'm not too crazy about the z axis but how can you argue about X and Y?