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Author Topic: Success! Mini Machining Center under Mach3 control - Video link  (Read 331531 times)

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Offline nava

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Re: Success! Mini Machining Center under Mach3 control - Video link
« Reply #270 on: January 09, 2015, 04:04:23 PM »
Thanks mike,
                  I have also got a new harmonic drive for this project but was thinking it probably wont be any good for any fast spindle work. I will probably use the HD mounted to the back of a vertex 6 inch rotary that I have to do some pretty precise work. 

I would have thought that a stepper can actually spin pretty fast if programmed correctly though perhaps im wrong there.

Any chance you know what servos Simpson is using anyway so I can spec things out a little more?

Offline nava

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Re: Success! Mini Machining Center under Mach3 control - Video link
« Reply #271 on: January 09, 2015, 04:41:21 PM »
I do have a few older electrocraft e240 motors with some heds encoders but may be a bit less torque with these

http://www.ftp.cnchungary.com/Varsanyi_Peter/CNC%20vezerles%20-%20szervoval/ElectroCraft_E240_Motor/electrocraft%20E240.pdf

Offline simpson36

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Re: Success! Mini Machining Center under Mach3 control - Video link
« Reply #272 on: January 09, 2015, 04:53:01 PM »
You can use any servo motor, really. The difference between Stepper and servo is what makes the difference. Which servo is important, no doubt, but not nearly so much as the fundamental technology of the motor type.

Steppers have great holding power and the torque rating is at zero speed and it drops off quickly as the speed increases. Whether a steppers holding torque is adequate for the task depends on the task. No stepper will hold as well as a spindle lock. If you are not going to use flood cooling, you can rig up an inexpensive spindle lock with a 4" band brake and hub for a mini bike or go-cart.

In considering servo motors, one should look at how they are rated. Hobby motors (Keling, etc) are rated at 'just prior to self destruct' levels whereas industrial servos are rated extremely conservatively. Usually at the power level they can sustain 24/7 at for 20 years without a break. Typically an industrial servo can pump out between 2.5 and 3x the torque rating in an 'intermittent' basis.

So, the numbers tell us that a 400watt rated industrial AC servo is equivalent to a 1,200 watt rated (calculated from the power draw) DC brush hobby servo.

A decent used 400 watt industrial AC servo motor and drive set can be had as cheaply as the equivalent new hobby DC servo setup (if you include a decent encoder for the hobby setup)
http://www.ebay.com/itm/MITSUBISHI-MR-J2S-40B-HC-KFS43B-AC-Servo-Drive-Motor-400W-Brake-Set-a18-/160880697451?pt=LH_DefaultDomain_0&hash=item25753ca06b

http://www.ebay.com/itm/CNC-Machine-YASKAWA-AC-220v-Servo-Motor-Driver-400w-Replace-Step-Motor-Tested/321620537287?_trksid=p2047675.c100005.m1851&_trkparms=aid%3D222007%26algo%3DSIC.MBE%26ao%3D1%26asc%3D27675%26meid%3D871f20ebd6ed4b699b2af883250a6825%26pid%3D100005%26prg%3D11378%26rk%3D4%26rkt%3D6%26sd%3D160880697451&rt=nc

I would buy these in a heartbeat over a new hobby setup and never look back.




« Last Edit: January 09, 2015, 04:55:45 PM by simpson36 »

Offline nava

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Re: Success! Mini Machining Center under Mach3 control - Video link
« Reply #273 on: January 09, 2015, 05:14:42 PM »
thanks sound advice and solves my hum har about the steppers. 
Ive been thinking a lot about your awesome brake and how and if you can actually calculate "drag" for continuous milling?
Re: Success! Mini Machining Center under Mach3 control - Video link
« Reply #274 on: January 09, 2015, 05:19:42 PM »
I would have thought that a stepper can actually spin pretty fast if programmed correctly though perhaps im wrong there.

*Please anyone feel free to correct me if im wrong here*

I believe, that if you are running Mach at 35,000 mhz kernel speed, that implies that it can make 35,000 pulses per second, meaning 35,000 steps per second, which at a full step would be 175 rotations per second which is 10,500 RPM. Now, the caveat is, that is a 1:1 ratio which obviously wont work, and 10,000 is probably beyond the rated RPM for a stepper. If you throw an 8:1 ration on there, you're looking at 1312 RPM (at the 4th axis) with the stepper running 10,500 RPM. Also, as Simpson mentioned, the faster a stepper turns, the more torque/holding power it loses. So basically, you'd be at the point where it would be pointless not to do a Servo if you are planning to do high speed operations.

That all being said, I still went with a stepper because of cost, ease of setup, and I didnt need to do lathe work on my mill. Its all about what your intended use is for the machine.

Offline nava

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Re: Success! Mini Machining Center under Mach3 control - Video link
« Reply #275 on: January 09, 2015, 05:31:56 PM »
My 4th axis I guess at the moment is planned for a wide variety of work.  The initial stuff im doing is small diameter 1/2 inch with lathe operations and some 4th axis milling with slitting also.  Gears and timing pulleys I want to do as well as some special collet making for carbon fiber robot arms say up to 20mm.  Ill add another independent linear rail latter for small hobby servo internal splines as a type of shaper operation after general lathe milling to hold bearings so that its all as an inline operation as I can get. 
I built medium sized robots and parts for artworks

Offline nava

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Re: Success! Mini Machining Center under Mach3 control - Video link
« Reply #276 on: January 09, 2015, 05:35:54 PM »
For example here is a small 30cm robot I made a little while back on my bf20l converted to cnc

http://adamdonovan.net/files/Adam_Donovan_Work_2_Multiplexing_Tautophone.html

Offline nava

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Re: Success! Mini Machining Center under Mach3 control - Video link
« Reply #278 on: January 11, 2015, 05:55:34 PM »
Ok not meant to be ebay spammy here but poking around all day for different deals and came across and AC servo with 4NM and a driver from china that seems quite decent for the near 500usd price.  Cool thing about this driver is that its power supply is 220 240 which means for me no additional power supply needed and should be pretty easy to hookup.

I just asked them for the curve sheets and data now..will post it when I have them if anyone is interested.

http://www.ebay.com/itm/271735479951?_trksid=p2055119.m1438.l2649&ssPageName=STRK%3AMEBIDX%3AIT

Offline simpson36

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Re: Success! Mini Machining Center under Mach3 control - Video link
« Reply #279 on: January 12, 2015, 02:47:29 AM »
I just asked them for the curve sheets and data now..will post it when I have them if anyone is interested.

The thread has been read 108,500 times because of the technical content and shared expertise and experience.

Please do not hijack this thread by posting ebay bargains on components you have no experience with.  >:(