Pocket NC specs

[sine...@gmail.com]

Hey guys, I'm thinking about buying a pocket NC but I need to know some basic specs to determine if this little machine will meet my requirements. Specifically I need to know the OD of the B axis work mounting plate; the size of B axis housing square block including width and thickness and what stepper motors are used. I'd really appreciate it if someone could provide me those specs and anything else you want to add.

Christine

[Michael]

Hey Christine,

So for the dimensions of the B disc there is a Fusion 360 model of the B disk and the vise we ship with the machine at this address. (http://a360.co/21mUm81) 

The OD of the B axis disk is approx. 4.9in in diameter. The B housing block is approx. 6in x 6in x 1in. 

As far as accuracy of the stepper motors we are doing 8333.3 steps per degree and have about 0.002in of backlash (at the far edge of the B disc) due to the pulley configuration we are using.

If you want a basic model of the machine for machine simulation purposes you can find one at (http://www.pocketnc.com/s/PocketNC_CAD-4etj.zip)

Hope this helps,

Michael

[sine...@gmail.com]

Hi, thank you for replying and yes it did help. Boy that thing is small but for small parts it's perfect. Are those long rails THK? If so what type come with the machine?

[sine...@gmail.com]

Oh I just saw your description of the stepper motor resolution of 8333.3 steps per degree? Not sure why it requires that kind of accuracy or is it per revolution.

[Michael]

Yeah so the motors have 8333 steps per degree of table movement. there is a gear reduction that causes this. It is mostly so we can get more torque out of the motors.

I'm unsure of the THK rail type. are you wondering from a strength standpoint or what is important about that?

Hope this helps,

Michael

[sine...@gmail.com]

No I was wondering if they were ball or a slide type. I think the ball are more precise but maybe a little more prone to vibration?

[sine...@gmail.com]

Gear reduction: so the steppers are just standard steppers? I was curious as to how stand alone steppers could get that kind of resolution.

[Michael]

So as far as the rails go here is a link to the THK Z rail we use https://tech.thk.com/en/products/thkdlink.php?id=1129 

The other rails are a skinnier version of a similar design. https://tech.thk.com/en/products/thkdlink.php?id=1128

The stepper motors are a pretty standard Koko motion motor, but then the b disk is a big gear that two of the small stepper motors turn. i am unsure on the gear reduction but that is where the high increase in resolution occurs.

Michael 

[sine...@gmail.com]

That makes sense.

[sine...@gmail.com]

When will more of these machines be available? I saw maybe on your website that they are currently out of stock?

[Pocket NC]

They are currently here:  http://www.pocketnc.com/pocketnc/pocket-nc

We currently have an 8 week lead time within the US.  Thanks for your interest!

[Christine LaBeach]

Ok so I did the math and so 8333.3 steps per degree would be about 3,000,000 steps per revolution which would require a gear reduction of 15:1 if my math is correct.

[in...@pocketnc.com]

Hi Christine,

Sorry to say that the information above is incorrect. 

The gear is a 8:1 reduction with 35.55555 steps/degree giving a step angle of ~.028 degrees. 

-Matt

[Christine LaBeach]

Oh well thank you for correcting me. I guess I got confused on the 8333.3 steps per degree. Not real clear on that.