[lyonsronnie1]

Hi folks;
I'm building (or retrofitting) a pretty heavy duty table i'm going to be using to cut 3/4" particle board with (Melamine). The table has a cutting area 4X8. I'm cutting cabinets out of it, and at the moment I'm using a more lightweight Zenbot table that honestly works great but it just takes way too long to cut. So I'm doing 5 passes at .16 or so and 100IPM. Some of these sheets are taking two and a half hours to cut which just doesn't work for what we're trying to do.

So as my next step up I've bought an old table I'm fixing up, I have no idea where this thing was made but it's rigid as heck and I think I can probably get some speed out of it. Here's the specs so far, it has 3/8X3/8" gear racks on the side, and although the motors are missing, it was a Nema34 setup with I believe a 5 to 1 gear reduction (12 tooth gear to 60 tooth gear) connected with a belt. It looks like it got about half an inch travel on the machine, per revolution.

i'm shooting for 300ipm CUT speed, and I'd like to cut my 3/4 melamine in 2 passes (just so it's a little cleaner) in some spots and then in other spots that don't need a finished edge, maybe try for a 1 pass cut at 300ipm.

So my motors I believe will be moving at 600rpm or so.

This is a fairly bulky table, the gantry is aluminum but it still weighs probably 100 pounds with everything on it... there are two motors on the X though so maybe i'm overthinking the weight. It has linear rails on the sides so it moves easily.

I'm reading and reading and reading, and I as I understand it to get any speed out of these Nema34's I'm going to have to stay away from the high induction heavy motors and go with lighter ones, but I don't want to get them so light that I can't cut at speed. I've got two motors on the X one on the Y and I think the Z is a Nema23.

So I'm staying away from the cheap 1600oz ones.

I'm thinkin 60v power supply probably using a toroid , and 60v drivers.

I'd rather not break the bank, but does anybody have any suggestions on a decent mid grade motor that could handle what I'm trying to do? Also suggestions on drivers, I'm going to be running Mach III (it's running my other machine) and may try a smoothstepper ethernet breakout board. I also want to add proximity switches and maybe some relays to turn on vacuum and dust collection...

Thank you for any advice, I'm thinking I need something in the 900oz range, and try to keep it under 4mH inductance if possible, from what I've read around the forum.

[automationtechinc]

I would suggest you to use closed loop stepper motor, It will be much better

https://www.automationtechnologiesin...que-1128-oz-in

Power supply:
https://www.automationtechnologiesin...0vac-duplicate

Ethernet Board:
https://www.automationtechnologiesin...pindle-control

[joeavaerage]

Hi,
if you want power and speed don't mess around with steppers, they are good at low speed but crap at high speed, and closed loop changes that not a jot, get servos.

750W Delta B2 series kits (servo/drives/cables) are $438 and they will eat any stepper ever made, I have several of them.

Craig

[dazp1976]

Hi,
if you want power and speed don't mess around with steppers, they are good at low speed but crap at high speed, and closed loop changes that not a jot, get servos.
750W Delta B2 series kits (servo/drives/cables) are $438 and they will eat any stepper ever made, I have several of them.
Craig

^^^^THIS^^^^
Automationtec is just trying a sales pitch.
You need AC servos all the way.

[lyonsronnie1]

I'm reading up on the differences between the torque on the servos and the steppers and trying to decide if I want to afford the servos or not. I'm still trying to learn before I spend any money, I did buy the bearings/spur gear for the pinion (One spur gear was broken off the shaft when they crashed it, all the bearings are old).

The only thing that teases me, is I'm seeing what Avid has done. These guys appear to be running normal Nema34 steppers and they're getting crazy speeds out of them... I've seen Daz your posts on here (thank you sir) talking about how you used the heavier Nema34's and they were slow as molasses, Avid is using 960oz Nema34's at 48vdc, and apparently getting 1000ipm rapids and 500ipm cutting. I thought maybe it was just a sales pitch but I found a video on youtube of a guy running an avid machine clearly cutting 1/2" mdf, 1 pass at 400ipm.

So that's kind of my only hiccup, that's a fairly decent sized stepper and it's induction is apparently 2mh, 7amp. They're running 3.2/1 reduction and the calculators I'm seeing online are saying it's impossible for those motors to be turning that fast at 48v. So that's confusing a little bit.

So I'm thinking the steppers can't handle what I'm trying to do... .but then I see AvidCNC as the aberration and can't figure out why their's work like that.

Thank you folks for any continued advice, and Daz thank your previous posts for explaining that those huge ones are crap.

[TMToronto]

I had saved a few video links from a time when I was considering the Avid machines. Not sure if you have seen them, and if not, they might be of interest as they test axis speeds, etc.

https://www.youtube.com/watch?v=mUlBGCdNzGI

https://www.youtube.com/watch?v=YF5aFfWBYy8

[lyonsronnie1]

I had not seen those videos, thank you for the links they're very helpful!

[dazp1976]

I'm reading up on the differences between the torque on the servos and the steppers and trying to decide if I want to afford the servos or not. I'm still trying to learn before I spend any money, I did buy the bearings/spur gear for the pinion (One spur gear was broken off the shaft when they crashed it, all the bearings are old).

The only thing that teases me, is I'm seeing what Avid has done. These guys appear to be running normal Nema34 steppers and they're getting crazy speeds out of them... I've seen Daz your posts on here (thank you sir) talking about how you used the heavier Nema34's and they were slow as molasses, Avid is using 960oz Nema34's at 48vdc, and apparently getting 1000ipm rapids and 500ipm cutting. I thought maybe it was just a sales pitch but I found a video on youtube of a guy running an avid machine clearly cutting 1/2" mdf, 1 pass at 400ipm.

So that's kind of my only hiccup, that's a fairly decent sized stepper and it's induction is apparently 2mh, 7amp. They're running 3.2/1 reduction and the calculators I'm seeing online are saying it's impossible for those motors to be turning that fast at 48v. So that's confusing a little bit.

So I'm thinking the steppers can't handle what I'm trying to do... .but then I see AvidCNC as the aberration and can't figure out why their's work like that.

Thank you folks for any continued advice, and Daz thank your previous posts for explaining that those huge ones are crap.

Right. Some insight.
I've got nema34, 1080oz, 4mh inductance on my Z axis on the mill.
Using 60v I can get 400rpm before it starts to become unreliable. That's with 5mm ballscrews making 2000mm/min.
Upping to 80v I can get 3600mm/min stable which makes 600rpm. (I reckon I'd get 700rpm on 80v)
This metric 3600mm/min converts to 142ipm for me.
Convert these rpm's to what you need and see where it gets to in terms of ipm.

Getting true reliability from a nema34 using 48V is frankly bollox afaic!.

Steppers massively drop torque as they speed up.
Servos have continuous torque throughout their range.
Steppers can max at 1000rpm (barely).
Most servos are rated to 3000rpm.
If you have gear reduction you need more rpm which is why we suggest servos.

Torque values increase/decrease as the gaer ratio changes.
If you have a 3:1 reduction for example you want 3x the rpm for the max amount of gear rotation required.
If the Servo has 3mn of torque that would increase to 9nm on the reduction.

Now remember: we're talking PROPER AC servos here NOT those gimmick hybrid ones.
I reckon if you go the stepper route in your case, you'll get pi**ed off with the performance and rip them off.


When it comes to seeing others videos on the Web claiming this/that and the other, you have to watch yourself. Many are 'sponsored' and the machines not quite 'true to spec' if you catch my drift.

[joeavaerage]

Hi,
steppers are very torque dense at low speeds. For instance the 34 size steppers you are interested in are 1100oz.in or about 5Nm. The 34 size 750W Delta servos I have
suggested are 2.4Nm rated.

So the steppers have more torque, but of course this is only at low speeds. The steppers have likely lost 50% of their torque by 500rpm, say 2.5Nm whereas the servos are still 2.4Nm and
will retain that 2.4Nm right up to rated speed namely 3000rpm.

If you can achieve the axis speeds that you want with say 400-500rpm then steppers are probably entirely adequate, but with a heap more than 48V. If however you want that more speed that requires the motor
spin over 1000 rpm then the servo wins out.

Second area that servos outperform steppers is overload performance. When a stepper gets overloaded it misses steps or stalls, no if or buts, it just stalls. When a servo gets overloaded it just digs
in, the current goes up, but it produces three to four times its normal torque and can do that for several seconds. Thus the 750W servo might be rated at 2.4Nm (continuous) but it can at overload produce
7.2Nm. Its this overload capacity that really makes the servo seem much bigger and more powerful than the numbers suggest. Its not a good idea to design to the overload rating but its really good to have
up your sleeve.

Your choice really comes down to speed. If you can get want you want from your machine (speed) with motor shaft speeds of 400-500 rpm then go with steppers, but if you need more then go with servos.

Note that there are lots of Chinese made servos that are cheaper than the Delta ones I have suggested, and they seem to work fine, but have really poor documentation, questionable support and
no set up and tuning software. If you've had no experience with servos don't be tempted with the cheap prices, you'll tear you hair out trying to get them to work. Delta is a Taiwanese brand made in China
and DMM is a Canadian brand made in China, both work well, have great support and documentation and most tellingly free set up and tuning software at fair prices.

Craig

[lyonsronnie1]

Thank you Craig, and Daz, i'm going to keep looking at the specs of the servos and what they need and the steppers before I spend any money, you've given me a lot of useful information.

[lyonsronnie1]

So after researching for awhile, I decided to go with Steppers after all, and also that my torque 'heavy' stepper motors were a bad idea. I read and read and read and came to the conclusion that low inductance is likely much more important... so I chose an Oriental Motors PKP296D63AA stepper motor, and installed one on the Y axis of the machine after finding all the gears and belts and everything this originally had.

I messed around with Mach 3, couldn't figure out why it wasn't moving properly, and kept using my old CNC. Well last week I started messing around with it again and figured out why it wasn't moving properly. I had the native units in Mach 3 as MM and not Inches, but some other setting as inches, and everything moved super slow.

So long story longer, I got it set up in Mach 3, with an Ethernet Smooth Stepper and a C11 BOB, a 77volt power supply and a Gecko G201x. It's easily moving (in the air) at 600ipm, and if I put all my weight against the trolley I can't get it to skip or stall, this thing seems crazy powerful for what ultimately is just going to be cutting plywood or melamine like my Zenbot, which I have cutting at nearly 200ipm no problem.

So i ordered the pieces to do the other axis (Axi? Axises? Axis's?) the same way but haven't cut anything yet, I'm going to have to decide on a Spindle before that...