[spoiledbrat]

For my 4 meter axis (that's how they sold the rails), I had originally wanted a ball screw for accuracy. I am able to achieve the level of precision I need with my ground helical racks. I have since learned that ballscrew loads are way easier to tune... If I could do it all again, I may have considered a shorter table (still overbuilt, though!) with ballscrew drive on all axis.

That would have been one hell of an expensive ballscrew, though.

Rob

[spoiledbrat]

Jsheerin,

I think that in all cases, you will need some torque overhead for the PID tuning to control the load... that is, if you are accelerating really fast, and the drive/controller detects an undershoot, it will need to have additional reserve of torque to apply to the motor/load to correct this.

Rob

[jsheerin]

Related to your ballscrew comment, do you know what your inertia ratio is?

On my design I'm using about 1/3 or so of the continuous torque for accelerating. Then I have about 3x the continuous torque available for peak loads similar to your motors, but I would only be using about 1/2 of the peak torque due to motor controller current limitations so the time I could use peak torque should be longer than normal.

[ger21]

Our machine uses a ballscrew, about 15ft long, with a rotating nut.

[spoiledbrat]

Jsheerin,

X axis inertia was calc'd to be approx 5:1. The y axis was 5.46 (single motor), and the Z axis was 0.97:1.

[spoiledbrat]

more pics can be found here:

Login

Rob

[xclr82xtc]

i read this thread...and im so confused. lol.. i have no idea what all these rates and numbers you guys are talking about are..

[xclr82xtc]

57k to date. still need the second spindle, though. This includes the Becker vac pump, water cooling setup, and everything else.
Trying to finish up before end of month January. Thank you all for the guidance and assistance.

..i dont know much about these...but couldnt you buy one for less??

[mactec54]

xclr82xtc
..i dont know much about these...but couldnt you buy one for less??

Not at this level, he has the best of everything in it, the gearbox's alone are $2,600each

[spoiledbrat]

Ok, got back to the states a couple of months ago, and finally got my machine running a little better.

I could not get the Galil DMC-4080 to work for me. Main reason, I cannot tune the servos in galil to save my life. Just never happened. I did pay for the autotuning software, and it did allow my machine to make some disturbing noise. Not much more than that. Once I did achieve stable results, I found that the card was not very adept at fast 3D motion. I was trying to send 130 lines of code per second at the galil from Mach, and it choked. This was displayed as stuttering motion for the most part, with super fast (and graceful) multi-axis moves every now and then. I would use the galil for a milling machine in a heartbeat.

I Purchased an MCB-1 card from Industry Controls, and started my learning curve all over again. The MCB-1 uses a USB board, and then transfers information to the main board (in the control cabinet) via 2 each shielded cat6 cables. I cannot state plainly enough that this card can handle fast 3d carving. I have yet to choke this card with data. I plan on running my 3D carving routines at 600 ipm after I get my hands on metacut pro/finish software.

Rewired everything, and even made some custom CN1 cables for my servos.

Video is here:


Cheers!

Rob

[spoiledbrat]

Running some test cuts. 0.250 depth of cut, programmed at 500 ipm. Circles are 0.500" up to 5.000". Smaller circles, of course, never got up to speed.

[ktb100]

Looking pretty awesome !!

[joshendy]

Good god thats impressively cool. When the CNC was travelling back to change tools I was thinking "yeah but isn't this dust shoe going to get in the way?" and then up it goes! Very neat. Would love to see some more videos!

[harryn]

Very nice. The atlanta drives engineers told me that helical rack is pretty quiet, and your build proves it.

I am impressed how quiet your router actually is in general, of course an enclosure is always nice, but even cutting it is not bad at all.

Harry

[spoiledbrat]

Agreed on the noise. The racks are pretty quiet. The spindle is a low power (2.2 kw) watercooled. I think my my enclosure fan is the loudest component...

[mactec54]

spoiledbrat

I like the speed now, Looks close to what you wanted

Well done, now you are ready for production

[thegolfer]

This is a very impressive build! I'm sure you're over the moon at it's performance

I have a quick question: what tolerance was the base and gantry machined to? I'm interested in building a small format machine (1200mm x 900mm x 150mm) with a welded gantry and base (and am interested in getting these elements manufactured overseas), but I'm struggling to get a good idea of what tolerance the mounting surfaces for my linear rails/ball screws should be machined to.

Your insights would be much appreciated!

[ktb100]

The base was machined on our double column bridge machine. Rail and rack surfaces were machined in the same set up to hold as close as possible tolorance. The machine itself repeats within 0.001" over 10'.

[steve123]

Awesome build! Can you give a link for your spindle, tool holders, ATC?

[spoiledbrat]

Golpher,

Sorry for the delay. I did not see your post until yesterday (5 months later!). Kirk, at Majesticmachinery.com, is the way to go to get a heavy frame custom fabricated and machined. I am bery happy with the results.

As for the ATC, spindle, etc.:

Toolholders were purchased from Majestic. Tool forks were fabricated in house. The ATC spindle was purchased with the help of a broker, direct from china. Works will so far. I did forward the spindle info to Kirk; I believe he was thinking of carrying them in the future. Definitely worth a shot if you want to know who you are dealing with when sending out thousands of dollars.

If Majestic does not carry the spindle, pm me, and I will get the info to you.

Cheers,

Rob (happy heavy CNC router frame owner)