[charlieslasher]

Choosing new drives and motors,

I want better acceleration and more speed.

i have nema 23 381oz kelling steppers motors with g540 drive and 48volt power supply.
ball screws are 1605

my machine can just handel 5000m/min in two axis. its a moving table 500x600mm work area setup to to cut 7075 all day long.

i think i want servos and new drives and dont mind spending $300-$600 per axis what the options?

Also Vector drives?
i got the hitachi inverter for my 2.2kw spindle but i didnt get the vector drive... version sj200 or something?
What difference will the vector drive have on the 2.2kw Chinese spindle with bigger tools at lower rpms?

thnaks charlie

[BanduraMaker]

Switching to 1610 screws would speed things up considerably and I imagine at a much lower cost than servos. Plus, you can probably pawn off the old screws. I've got the same motor and drive setup on my machine with 10mm pitch screws and can get 400ipm (about 10kmm/min) on my heavy and long axis.

Not to say I don't day dream about servos and 1000ipm rapids

[charlieslasher]

True, but will i lose power to cut? i have not stalled a steper from cutting 7075 yet but if i double the pitch i might be getting close. Even if i do go to servos do i need to increase the pitch anyway and use the power of the servos to make up for the increased pitch?

Any idea on what drives to look at? So much stuff to learn still. I just got steppers understood.

[BanduraMaker]

Well, of course your mechanical advantage will go down by 50% at a given cutting speed but I'd say that doesn't mean that it will be a problem. Consider that steppers have max torque at zero RPM and it goes down from there. For a given feed rate, your stepper will be spinning at half the speed it was with the 5mm screws.

What feed rate, spindle speed and DOC are you using to cut aluminum? If you know that, you can find websites to calculate your required cutting force.

I'm pretty sure I've seen a document somewhere with the torque curve of those motors, possibly when it was still Kelling but I just checked and can't find it now. With that torque curve, you can calculate the cutting force with 5mm screws and 10mm screws and compare it to the cutting forces calculation above and see how it works out.

With a quick google search I found this site: Force, Torque, and Power and with a 7075-T6 with a brinell hardness of 150, 1/4" endmill at .1 DOC, .004" chipload @ 1000sfm (2 flute bit) recommended spindle speed is about 15k, feed rate is still only 122ipm and force required at the tool is only .3lbs. - I know for a fact that my machine with the 10mm screws is well above that at 122ipm! (and please, this was a quickie calculation so there's definitely a possibility that I entered something wrong)

Unfortunately, I know little about steppers and even less about servos so I can't help you there. Though my old college engineering TA just hooked up with me on linked in and it turns out he works at Baldor. I asked him if any nema 23 servos happened to have fallen off the delivery truck

[rowbare]

DMM DMM has some multi axis packages that might do the job for you. There are several threads here discussing their servos.

bob

[Fenza CNC]

Defiantly want to take a look at DMM. Their 400W motors will be ideal for your machine, directly driven to your 5mm screws should give you around 3 times faster acceleration at only the rated torque, remember these can go to 3 times the rated torque for rapids and can spin 3,000 rpm so 15m/min rapids.

Although the 750w package looks better on paper in reality your machine will need to be 'even more beefy' to handle these, besides to 400w package is far cheaper and still just as good for your application. If your current setup can stop and change direction in 0.3 seconds the 400w servos will do it in 0.1 and they will even take you to 15m/min.

I didn't see which ball screw end supports you used, but if it is the ones linearmotion on eBay sell then these aren't up for the job of servos. Take a look at Support Unit, Nanosmith these are more of the real deal, may even improve accuracy and surface finish while handling the force of the new servos. You will need the Standard-Heavy preload bearings, Economic-Universal is what LM on eBay use I believe.

Hope this helps, Fenza