Just curious, Mark, why is the hex rod better then round rod? Is it less costly?

 

Morning Mark,

I went to have a look at Phlatboyz.com this morning (AEDT). Have you been cybersquatted? Ouch.

Dorsal,
Was that you on the T-shirt forum? If so, are there any candidate inkjet modules for the Mk III? I keep looking at an Epson R1900 on the local ebay - still around $1K down here. If we could get an inkjet module on the Mk III, do you think there is enough height clearance for a folded t-shirt or even windcheater? Trying to make a choice now the baby bills are almost paid and the Aussie dollar is rather high.

ciao,
Scott

 

Ahhh. Much better than what I saw this morning.

 

Good stuff guyz! The cut you did on the live show (even though the settings were wrong) was pretty cool. It's amazing how the bit can travel hundreds of inches and somehow end up at the exact same place (you mentioned this when it cut the fuse - you could not even tell where the cut started or ended). How does the machine know how far it's moving? Of course the computer is sending coordinates to the driver board, and the board to the motors, but how does it measure units? Do the motors literally have "steps" like servos do? That is, for example, 100 steps of the motor = 1 in bit movement.

- Jeff

 

Jeff, that is exactly how all the PP s work, with stepper motors. Each machine will have slight variations, but there are approximately 2000 steps per inch with the gearing that's in place on my MK1.5, and I expect the MK2 and III are very similar.
The magic is to get the machine "tuned" properly so there are no rough or tight spots in the axis travel, so the steppers don't miss any steps. Once that's done, they will repeat steps within a couple thousandths or less.

 

Actually, rc servos don't really have steps. They are closed loop, meaning they get position feedback from a potentiometer. So they can be commanded to go to any position and they will go to the same spot each time. On the other hand stepper motors actually, only move in steps. They are open loop, meaning they don't have any feedback device to tell them their position. So the cnc machine doesn't really sense it's position. It relys on the fact that stepper motors are designed to move a precise step, each and every time. And it just counts the steps and assume it's at so and so position. Hence the term "missing steps", which means the cnc machine is not where it expects it to be. So why use stepper motors. It's because it's cheaper and less complicated. And as you have seen, they work very well, for our needs. And yes, you need to calibrated each axis. You set this in the control software, X number of steps/inch for each axis.

-Kwok