Machsupport Forum
Mach Discussion => General Mach Discussion => Topic started by: Tef9 on February 10, 2009, 06:08:09 PM
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I am about to buy a Milling Machine, I have selected which one I want however due to its lack of CNC I plan to convert it almost immediately.
It is an Eastern Mill so I was planning to replace the leadscrews for ball screws and then fit ... servo motors on each axis.
Two questions:
1) I am only looking at Servos due to our 'workshop guy' at work recomending them over steppermotors...is there a real gain?
2) Can mach3 controll Servos? If not what would be a good set of stepper motors? (I am in the UK)
Thanks,
Andy
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I am about to buy a Milling Machine, I have selected which one I want however due to its lack of CNC I plan to convert it almost immediately.
It is an Eastern Mill so I was planning to replace the leadscrews for ball screws and then fit ... servo motors on each axis.
Two questions:
1) I am only looking at Servos due to our 'workshop guy' at work recomending them over steppermotors...is there a real gain?
2) Can mach3 controll Servos? If not what would be a good set of stepper motors? (I am in the UK)
Thanks,
Andy
Mach is perfectly happy with either steppers or servos, as the interface between the PC and the motor driver is the same for either.
How big is the mill? For small (table-top) machines, steppers are every bit as good as servos, and generally a bit cheaper. For large machines (knee mills) servos *may* make more sense. But, really, outside a production environment, it's more a religious question than anything else. Up to and including a Bridgeport-sized machine, you can get perfectly acceptable results with either. There are pros and cons to both, but the functional differences are generally rather minor, and often not good for much more than bragging rights (My mill will rapid faster than your mill!). By far the most important things, no matter which you use, are to size them properly, gear them properly, and power them properly. Most beginners tend to start with steppers, and grossly under-size them. Then based on the poor outcome, they decide steppers are inherently no good, and will always lose steps. This is simply not true. Mariss Freimanis, the owner of Gecko (www.geckodrive.com) has a good rule of thumb: Up to 100W, use steppers. Above 200W, use servos. Between 100W and 200W, use either. You'll find some good information on stepper sizing, and power supply spec'ing on his site as well. Whichever you decide on, I'd strongly recommend Gecko drivers - they are first-rate, reasonably priced, and well supported.
Regards,
Ray L.
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Well said Ray, I couldn't agree more!
I run a Lagun knee mill, (Brigdeport clone) every day powered with steppers and it works absolutely great! The knee is powered for the Z with a rapid speed of 25 IPM, X and Y rapids are 100 IPM. That's plenty fast enough for the milling we do so selling me the idea servos are needed for big iron would be tough, especially when I watch that super heavy knee zip up and down.
I purchased my steppers from www.homeshopcnc.com after Rick LaLonde, who i think may be the owner there, advised me what sizes to buy. Like you I was really unsure what to do since that was my first conversion but decided to trust Rick's advice and I am 100% satisfied. Matter fact I just recently purchased steppers for my upcoming lathe conversion based again on his advice.
As for drives, again I agree with Ray. Gecko G203V drives have been happily powering my steppers and I have yet to have even one problem.
My suggestion would be to contact Rick and see what he recommends for your application. Bet you won't be sorry.
Good luck on your conversion.
Kerry
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Well said Ray, I couldn't agree more!
I run a Lagun knee mill, (Brigdeport clone) every day powered with steppers and it works absolutely great! The knee is powered for the Z with a rapid speed of 25 IPM, X and Y rapids are 100 IPM. That's plenty fast enough for the milling we do so selling me the idea servos are needed for big iron would be tough, especially when I watch that super heavy knee zip up and down.
I purchased my steppers from www.homeshopcnc.com after Rick LaLonde, who i think may be the owner there, advised me what sizes to buy. Like you I was really unsure what to do since that was my first conversion but decided to trust Rick's advice and I am 100% satisfied. Matter fact I just recently purchased steppers for my upcoming lathe conversion based again on his advice.
As for drives, again I agree with Ray. Gecko G203V drives have been happily powering my steppers and I have yet to have even one problem.
My suggestion would be to contact Rick and see what he recommends for your application. Bet you won't be sorry.
Good luck on your conversion.
Kerry
Yup, I bought most of my stuff from HomeShopCNC as well. I did go with servos this time, and don't regret it, but also don't see a clear, practical advantage. With the SmoothStepper, I can get 400 IPM rapids on X/Y, and 75 IPM on Z, but seeing that big sucker flying around at 400 IPM is downright scary! So, I backed it off to 150IPM for actual use.
I agree with everything you said about Rick. He was a huge help in my first conversion (an X2), and on this one. Great products, great prices, and great support. What more can you ask?
Regards,
Ray L.
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Here is a item number on ebay for some crydom solid state relays that
I used to turn on/off my router - dust collector.
They have worked great!
260356186971
Hope this helps!
olf20
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Kerry, Ray,
Mind to say which model motors you used for the X,Y and Z....and the ratios ?
Thanks,
RC
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Kerry, Ray,
Mind to say which model motors you used for the X,Y and Z....and the ratios ?
Thanks,
RC
RC,
I used the HomeShopCNC 850 oz-in servos, with 500 line encoders, Gecko G320s, 70V/20A power supply. X and Y have 2.5:1 GT2 belt reducers, Z has a 4.8:1 XL belt reducer, all of my own design. Were I doing it over, I'd use the 4.8:1 on all three, as I can't get the motors up to full RPM with the 2.5:1. There's more than plenty of power with the 2.5:1, but max rapid speed is >400 IPM, which SCARY fast for a machine this size. I normally run 150 IPM rapids on X/Y, and 75 nIPM on Z.
Regards,
Ray L.
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My HomeShopCNC steppers are as follows:
RHT34-1200 oz/in $258.00 For X and Y. Geared 1:1
RS34-2550 oz/in for Z geared 2:1
RHT34-740 oz/in for A direct coupled to the rotary table shaft so it's 1:1
Are are run with Gecko G203V drives.
Steppers are the most powerfull at slow speeds so that's the reason for the low gear ratios.
Ray, Are you powering the knee or the quill for the Z axis?
Regards,
Kerry
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My HomeShopCNC steppers are as follows:
RHT34-1200 oz/in $258.00 For X and Y. Geared 1:1
RS34-2550 oz/in for Z geared 2:1
RHT34-740 oz/in for A direct coupled to the rotary table shaft so it's 1:1
Are are run with Gecko G203V drives.
Steppers are the most powerfull at slow speeds so that's the reason for the low gear ratios.
Ray, Are you powering the knee or the quill for the Z axis?
Regards,
Kerry
Kerry,
Right now, I'm using the knee for Z, but I'm in the process of designing a quill drive. Once that's on, I'll use the knee for tool length compensation, and the quill for the "active" Z axis.
Regards,
Ray L.
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Thanks guys,
RC
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Wow...thanks for all the responses...I was hoping there was little difference as the cost of servos is so much higher than the cost of stepper motors. I would love to go for Gecko but sadly buying form the USA is expensive atm...sadly as you seem to have all the fun stuff :-[
Here is the the mill I intend to buy:
http://cgi.ebay.co.uk/AMA30LV-Milling-Machine-Variable-Speed-Long-Table_W0QQitemZ360127992736QQihZ023QQcategoryZ12584QQtcZphotoQQcmdZViewItemQQ_trksidZp1742.m153.l1262
and here is the stepper kit I was going to go for:
http://www.motioncontrolproducts.co.uk/product_info.php?cPath=5&products_id=8
I was going to replace all of the motors with this one as it has a higher torque...is that wise?
http://www.motioncontrolproducts.co.uk/product_info.php?cPath=4&products_id=11
I really am a novice at this but it seems to all things required in the kit, including a break out board for connecting upto Mach3 ;D
Any good?
Thanks,
Andy
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Andy,
I have been seriously considering one of those machines,they have excellent travel,and
are more sophisticated than the rf45 types available from:
http://www.engineerstoolroom.co.uk
The only objections I have to it is that it has a MT3 taper which is not really the best for milling,R8
would have been better.Plus he has put the cost up by £200 since the last batch,which takes it over my budget!
As to stepper/servo's do a bit more research before you commit I have built a few systems now and I find
that the advantages of servo's far outweigh there (small) price differance.
Whatever you do you will need a Z axis motor of twice the size of the X&Y because of drilling etc.
Where abouts in the UK are you based?
Tony