X3 servo conversion questions

[JB_in_Fla]

Assuming I stick with NEMA 23 & NEMA 34 sizes to match the mounting plates on the cncfusion.com X3 conversion kit - can I use the gecko 320's to drive servo's attached directly to the cncfusion adapters w/o gear reduction? The servo kits I've seen all have belt reduction drives.

Also, with the 5tpi ball-screws what is the approximate positional speed one can expect using servo drives? Faster than the 60ipm most are getting with steppers? Will the accuracy go down, and how much, without the typical reduction belt drive? Thanks.

[dneisler]

I don't know about the servos, but on my X3 with 425's and a 640, G203's I am getting easy 72IPM cutting, and 120+ rapids with no loss.

I made a part yesterday for a guy cutting 72 IPM. Found out real quick I need to secure my enclosure better for that speed.

[skullworks]

I have seen video of an X3 with Nema 23 servos on the CNC Fusion 1st generation kit and it moves...

I'm building up mine currently using "slow" (1200rpm) servos in a direct drive config on X/Y and 1.5:1 on Z and I expect to have 200 IPM rapids... Which makes this the slowest CNC machine I have used since 1986. ( That record belongs to a Bridgeport usind a Bandit CNC with 100 IPM rapids.)

( I'm NOT using the Fusion kit, I want more travel and know how to get it. )

[ViperTX]

skullworks....well you peaked my interest...."not using the Fusion Kit.." What you doing?

Paul

[skullworks]

Well if I find I have more money than time when I am ready to get serious about finishing my X3 conversion... I will contact John Stevenson and order the ballscrews and hardware only from the conversion kit developed for ArcEurotrade ( won't be needing any of the electrics since I'm going servo )

I had allready emailed John and he needed some additional info I needed to draft up when my hobby got rudely interrupted by real life events... I found I had structural damage to a part of my roof, and repairs so far have cost $11,700 but the job is not finished yet... Insurance company has been less than helpful, they have taken the position it was pre-existing and therefore not covered.

On the other hand I do have access to a nice Mori Seiki SV50 VMC and plenty of other sweet toys I can use to make any required conversion parts, problem is, they are not mine, in MY garage subject to My Whims if you get my meaning.

I have SolidWorks to work out some of the concept design issues. If I do it like I have envisioned my conversion won't be a simple bolt on, (which IS the best feature of the Fusion kits) I will do some machining to the column ( internal Z axis limits) (top ballscrew thrust bearing mount).

One option I am exploring is about a 6" riser for the column which mounts the Y axis servo on the rear and uses a telescoping tube ballscrew cover. No motor out in front. The riser also allows for more effective use of the columns full length dovetail ways.

More later, when I can't see the moon thru the living room ceiling.

[JB_in_Fla]

So is it safe to say that a servo drive kit will get you faster rates? I know machine limitations apply, but apples to apples will the servo system give you faster speeds or is the spindle HP the limiting factor? Thanks

[neilw20]

Stepper motors are quite OK on the X3.
How fast do want to move and why.
When you are machining with a 1KW spindle steppers are more than powerful enough to shear off a 1/2" cutter, without losing steps.
Why complicate such a small machine. You will need a cabinet for the control gear instead of just a hump in the back.
As for rapid feed, the limits with most small cutters is their strength.
Do you really want the cutters to be bending much during cutting?
Even on wood, the SX3 with steppers can get be fed ultra fast with smoke coming off the cutter. Gives a nice burnt effect for engraving but hard on HSS cutters.

Bottom line. Do you NEED the speed.
I slowed mine so my brain can keep up with it.
If it had a tool changer, and was rushing around like a mad ant, then you might gain a bit of time. Have a coffee while it is working.
If you intend cutting lots of air speed is a definite advantage.

[skullworks]

I'll agree up front that for 95% of the people Steppers are the clear choice.

I am one of the 5% odd balls who will use "stepless" servos to get the most out of my hardware. (meaning no Step/direction type commands)

1st off the spindle drive itself will be a servo - the machine will be able to rigid tap as needed.

One prime use for me will be to machine 3d models for casting patterns from plastics and wood, also Polystyrene for lost foam type casting patterns.

I have done this on a CNC knee mill (4200rpm) and it took nearly all day. The program ran via DNC and had over 703,000 lines in it.

The speed between cuts adds up. Trust me on this, I started with a Bandit control programing by a teletype to punched tape... Top speed was 100 IPM. (circa 1980)

The machines I get paid to setup daily now have rapids in the 1200+ IPM range.

I know the limits of the X3 chassis, I know I can machine at outrageous speeds... In styrofoam.

[neilw20]

Yes. I agree in your case you have a lot of air to cut.
Make the CAM program zig-zag and stop the stupid seeking.
Cutting air is like foam. Go with 500 IPM and up.
Should be spectacular.
Full enclosure that sucks for the bean bag swarf?

[Kelinginc]

I think Stepper Motor system is good for X3. We have more customer using Stepper packages
http://www.kelinginc.net/Three34XCNCPackage.html
http://www.kelinginc.net/CNCNEMA23Package.html

[JB_in_Fla]

the reason I was curious about the faster speed is that some of the things I'd like to do involve wood cutting/carving and with the lower density of the wood it would be nice to be able to pick up the speed and not watch paint dry. My expertise, and a big tool in my career, is in the CAD side and I already have a half dozen projects ready to go once I get a control system!

[cadmonkey]

One option I am exploring is about a 6" riser for the column which mounts the Y axis servo on the rear and uses a telescoping tube ballscrew cover. No motor out in front. The riser also allows for more effective use of the columns full length dovetail ways.

I want to know what you come up with on this - I considered something similar but need to keep the mill close to the wall for valuable floor space (hence all the electronics came out of the column 'hump' already) so a stepper out the back was ruled out but until JUST now I hadn't considered a sidemount motor on a belt drive. Could get a lot more travel on the Y if the nut is stationary to the saddle I believe...Damn, I've got my XY parts already done and ready to install and I'm already questioning the design...oh well, I guess that can be a possible "Service Pack 2".