high speed CNC carving guidance

Hello, I've built several CNC machines all of which are stepper based and run LinuxCNC, so I'm pretty well versed in the area, but I've only ever used them to do 2.5d milling.

I'm now dipping my toes into 3D, and while the machines I have will work they are really slow.

I'd like to begin a build of a high speed carving machine for soft(ish) wood carving. I've built a small 3-axis machine very similar to the shapeoko (but of course without the belts), out of extruded rail, precision rod and 1/2" acme screws.

I've been researching servos but all I've been able to find so far is either really expensive, or ODrive, which is not LinuxCNC compatible.

Has anyone done a build like this and can point me in the right direction? Pointers to specific vendors/parts and/or build logs would be great.

Thank you,

DougM

Thanks Tommylight, I will take a look at this.

Money wasn't actually my biggest concern, I was ok with about $100 for the driver and $60 for the motor, but what I was seeing (unproven on Ali Express) was $275 per node.

So if there's a more off the shelf solution in that price range that can be recommended that would be great.

Also I was hoping for BLDC rather than DC. I was set to buy the Gecko G320X until I realized it was a brushed drive and not a BLDC drive.

Are there any step/dir BLDC drivers out there? Or, am I not understanding how to interface LInuxCNC to a servo? Should I not be using step/dir at all? Clearly I need to research this more.

Thanks,

DougM

I'm looking at this motor

www.omc-stepperonline.com/24v-4000rpm-02...-42bls100-24-01.html

and this driver:

www.omc-stepperonline.com/bldc-driver/

Both are easily within budget, the only question is how to get from LinuxCNC to the driver. Currently I'm using parallel ports, but I could upgrade to a dedicated driver card.

Does Mesa have something that would drive the above?

Thanks for any guidance/experience, I'll keep researching.

I know you are asking about servos , so here is a link to some economy ones i have been eyeballin for a while now,
www.ebay.ca/itm/Lichuan-100W-Nema17-AC-2...1fffe84e36%7Ciid%3A1

www.ebay.ca/itm/200W-400W-600W-3000RPM-A...1fffe84e36%7Ciid%3A1

that should give you a 50% increase over steppers, assuming everything is in order
But I think you should address the issues as to why your machine is not fast, as you would probably benefit more from making those changes, than from servos. Im not saying dont get servos, because servos are sweet, but im saying from a cost/gain point of view, other changes would make more of an impact and be cheaper. since I dont know what motors or the lead on your machine, assuming your 1/2 acme are 10tpi, you should be able to get be able to get like 200ipm assuming 10tpi x 2000 rpm, its hard to find data on stepper motor rpm, but seems average is between 1000-2000 rpm, even at 50ipm, thats still reasonably fast if i got my rough numbers correct, i dont know what speeds you are looking for but i think you should be able to go reasonably fast with your setup assuming a lot of things.
if you arent hitting those speeds or wish to go higher, I think you would get more value out of increasing the leads on your screws, and by using larger motors/drives/power supplies. even doubling your leadscrew to 5tpi, you can still get a good resolution with standard stepper motors, and will give you a bigger increase in speed. using larger stepper motors/drivers/powersupply because that can also be the limiting factor on your top end speed. if the load from cutting/leadscrew resistance/ etc cause you to stall the motor before you can reach max rpm, it will severely limit your machine speed.
None of that will help if you cant actually machine at those speeds, and you then get into a hole in my bucket situation with min/max speeds/feeds where you have zero torque/max vibration resonance in your ideal speed/feed range. its hard to explain, but like where you cant feed fast enough and your spindle cant go slow enough, without loosing all torque or getting unuseable vibrations .

none of my experience comes from woodworking though, but the main point should still be the same, which is design the machine with speed in mind from the start, and everything else that comes with it, such as acceleration/deceleration and center of gravity, leadscrew whip, spindle range, rigidity, etc. you should really consider using rails and ballscrews if speed is your intention. or atleast a higher lead screw. the difference between steppers and servos shouldnt be the limiting factor for speed in your machine

DougM wrote:

I'm looking at this motor

www.omc-stepperonline.com/24v-4000rpm-02...-42bls100-24-01.html

and this driver:

www.omc-stepperonline.com/bldc-driver/

Both are easily within budget, the only question is how to get from LinuxCNC to the driver. Currently I'm using parallel ports, but I could upgrade to a dedicated driver card.

Does Mesa have something that would drive the above?

Thanks for any guidance/experience, I'll keep researching.

for doing highspeed, you should consider using one of the mesa boards, because it will be spitting out lots of steps and if you toss microsteps into it, it will be even more.

I have several of the motors you posted, different brand, but same specs
www.ebay.ca/itm/Free-Ship-from-China-42B..._CLK%7Cclp%3A2334524

the problem with these motors, and its explained here,
www.phidgets.com/?tier=3&catid=64&pcid=57&prodid=1013

the problem being it has 8poles and 3 phases giving it 24 commute per rotation so 1/24 resolution, where a stepper has 1/200 resolution . which you can feel in the motor. they are fast and have a lot of pep/torque, but its like a stepper motor, if a stepper motor only had 24 positions. compared to a fanuc servo, which feels closer to a stepper motor. so as far as i can tell, these motors might not be great for something involving direct drive to a leadscrew without any gear reduction, which would then eliminate the point.

but these motors make real good spindlemotors for mini lathe toolpost spindles, which is the reason i bought them.

Thank you all for your guidance - after spending a few more hours learning I am persuaded that I understand enough to make an initial purchase. The three that TommyLight posted look really good and in price range, I'll get one of them for testing.

www.ebay.ca/itm/Lichuan-200w-dc-3000rpm-...p2047675.c100623.m-1
www.ebay.ca/itm/100W-Integrated-NEMA23-B...047675.c100005.m1851
www.ebay.ca/itm/200W-Integrated-Brushles...047675.c100005.m1851

To the question of why my steppers are so slow it's nobody's fault but my own. Once I got the machines working I had so much I wanted to do with them I didn't take the time to ever tune them or learn how to optimize for speed.

But this is also a learning experience - I've been wanting to get into servos for a while now and this is the perfect opportunity - the machine is quite small (16 x 18" bed) so I don't need a lot of high power equipment to drive it.

I might also get a Gecko 320x and a brushed motor just to see how they do.

I will post my experiences here as soon as the equipment comes in.

Thank you,

DougM