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21st Mar 2011, 02:39 PM #1Intermediate Member
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A little help with my first milling machine
Hi all,
After months of searching for the "right" milling machine, I finally settled on one the other day. This is the first mill I've owned, and the plan was to get one that would also be my last.
For some reason, finding a good machine that was within my meager budget turned out to be quite a challenge
Please forgive me if I get some of the terminology wrong, my knowledge of mills and milling is pretty much zero at this point. I did a bit of reading up before I started shopping for a machine, but don't assume I know what I'm talking about here
What I ended up with is an Anayak FV-something-or-other with a #40 spindle, a 3hp varispeed head, power x and y with a 12-530mm/min gearbox, a Sony LH30 2 axis DRO, coolant pump, and power quill (via gears, not a separate motor like the x/y axis).
The reason this machine was within my <$1000 budget was that the varispeed head is completely stuffed. I bought it on the assumptions that a) the head internals were not repairable, and b) I wouldn't be able to source spare parts for it.
My assumptions seem correct so far - most of the splines in the various pulleys and shafts are gone, and I'm pretty sure there's a bunch of parts missing - not that I have found a diagram, so can only guess what it's meant to look like in there at the moment.
So, why did I buy a broken mill that I didn't think I could repair, you ask?
My plan is to gut the head and install a single speed pulley between the motor and spindle, and use a VFD. The head has a 2 speed gearbox, offering 1:1 and 9:1 ratios.
The mill originally offered speeds from 50-3200rpm, with a motor speed of 1420rpm.
I don't think I'll be able to cover quite such a range with a VFD, but should hopefuly end up with something usable.
So a couple of questions to the collective forum wisdom if I may:
1) Does anyone know what model my mill is? The serial number starts with 79- if that means anything? There doesn't seem to be any identifying marks on it other than the "Anayak" badges.
2) What sort of speed range should I be aiming for? My intended use is probably 50/50 light machining of steel and Al. I've calculated a few speeds for different scenarios with steel and come up with rpms in the low hundreds, but could be doing it wrong.
3) I know VFDs can eat motors that aren't designed for them, but this one will only get very infrequent use (an hour or two a month) - is it worth using this motor, or will it die a very quick death? If a VFD will certainly wreck it then I'd prefer to save the motor and use a different one, but if it might last a few years of light use, I can avoid the cost of a new motor for now.
Sorry for the bad pic, my phone doesn't have a flash, and the lighting in my shed isn't what it could be It looks a bit funny without the motor up on top.
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21st Mar 2011, 03:39 PM #2Dave J Guest
Hi and welcome to the site, you will find a good bunch of guys here.
I think you got ripped off, so I will come and pick it up and give you a few extra hundred for your troubles. LOL
Seriously, good score for the price I am not sure about parts but their are manuals online for a lot of different mills. You can start at Grizzly but there are a lot of other manuals around.
Have you had a look at what is broken and if it can be fixed?
Speed for mills is usually somewhere around from 200 to 3000 and I see your type of mill go up to 4500rpm on some models. You would get by with a 3000 speed limit.
To check the motor see if it has 6 terminals on it. If it only has 3 I think there are some VFD's around that will power it but there more expensive.
Dave
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21st Mar 2011, 03:50 PM #3Intermediate Member
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Thanks Dave,
The motor is a "Reivaj" brand and has 6 terminals.
I'd assumed you just connected the 4 wires used in the existing setup to the VFD output. I think I better do some more reading, as I'm new to the world of VFDs too.
I was planning on using something like a Mitsubishi A740-2.2K drive, but budget may mean I end up with a used A540, or an ebay special.
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21st Mar 2011, 03:55 PM #4Most Valued Member
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There is a similar mill on ebay at the moment at Auburn,the seller is a trader,he lists his ph no and states that he has a full book on the mill,might be able to get a photo copy of what you need with a little bit of universal currency.
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21st Mar 2011, 04:00 PM #5Most Valued Member
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Hi festy and welcome
First up do you have 3 phase in your shed?
Stuart
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21st Mar 2011, 04:08 PM #6Intermediate Member
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@pipeclay - there were two identical mills at the auction, one working (now listed on ebay) and one in pieces (mine).
Is that a realistic price he's asking? I know what he payed for it a week ago...
@Stuart - yes, I have 3 phase. I don't think I'd get too far with this mill without it
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21st Mar 2011, 05:19 PM #7Most Valued Member
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Don't worry about how many terminals the motor has, it is largely irrelevant as the star point can normally easily be picked out of a motor and it modified for delta (ie 230V 3 phase) use. I've had to do all 3 of my motors on my machines, and the job takes about 15 minutes if the star point is easily accessible, roughly double that time if you have to strip the motor and start digging around for it. If you don't feel confident to do the job yourself, a motor rewinding service will do the job for about $60.
Likewise, don't believe all you hear about VFDs "eating" motors, that is largely untrue. If you operate an old motor at high load and low RPM you could run in to cooling issues, but really it's just plain common sense. You may also find old motors are more noisy when operating on a VFD compared to more modern motors, but that sometimes comes down to the peculiarities of the motor itself.
Congratulations on a good find, that sure is a heck of a first milling machine you have there! While it may be a bit of a challenge to initially get going, if the rest of the machine is otherwise in good condition you've probably bought your first and last mill
Pete
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21st Mar 2011, 05:39 PM #8Intermediate Member
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Thanks Pete,
I have no intention of running this on 240v - the power feed and coolant motors are also 415v so to keep it simple I was just going to leave the wiring as is, and put a 415v VFD on the spindle motor, along with disabling the motor reverse switch.
Am I right in thinking that the delta/star wiring issue is when you're rewiring for 3ph 240v operation?
I've read about the cooling issues when running motors at very low Hz and would fit a cooling fan to the motor if it became an issue, but between the 9:1 gear reduction and the light, infrequent use this thing will get I'm hoping it's not an issue anyway.
The "eating" motors I was referring to was the insulation breakdown from the high energy spikes that the VFD's inverter produces. Apparently the pulses generate minute amounts of ozone inside the motor, which breaks down the insulation on the motor windings - whereas "VFD safe" motors have more/better/different winding insulation which is more resistant to this?
I've built a few small inverters and have seen the high voltage pulses on the output waveforms so know what that's about, but just not sure how bad it is in the real world.
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21st Mar 2011, 05:58 PM #9Most Valued Member
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Well you could, but as you have 3 phase you don't have to.
With 3 phase you don't need to worry about how many terminals your motor has as you can run it in 415V star.
I guess it comes down to which one VSD is cheaper.
Good luck getting it up and running, keep us posted
Stuart
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21st Mar 2011, 06:16 PM #10Intermediate Member
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Some Anayaks were also sold under the DoAll badge at one stage, and from what I can tell mine was probably the FV-2V model - except the listed top speed is a bit higher than mine.
I've seen lots of references to 42"x9" sized mills, so seeing it listed as a 49"x12" puts it's size into perspective a bit for me, and explains why it took me 3 hours to move it 10 feet on the weekend
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21st Mar 2011, 06:55 PM #11Most Valued Member
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Yes that's right. Sometimes these messages get a little crossed if a lot of people are active at the same time, and I posted my response before learning you had 3 phase available.
I'm not sure where you have that information from. How did you "see" the high voltage pulses? A CRO?
While you've built them yourself, for the benefit of others, a VFD essentially works by taking the raw AC input, turning it in to DC, and then turning it back in to square wave AC again. The frequency of this square wave is varied to vary the speed of the motor. In theory the voltage of the square wave is never more than the DC voltage. In addition the VFD uses the inductance of the motor windings themselves to turn the square wave into something very close to a sine wave.
That's the theory, but in practice the same inductance and capacitance effects can cause the voltage to "over shoot", leading to momentary voltages higher than the DC voltage. I'm afraid I find the ozone story a little hard to believe, as for ozone to be generated you'd need arcing to occur. If that's happening in this type of motor you're about to see the appearance of the smoke genie in all his glory. Instead, the higher voltages stress the insulation and may be enough to cause it to break down. If you're operating a dual voltage motor on 230V 3 phase the overshoots are unlikely to be a problem, since clearly the windings are capable of 415V anyway. However if running at 415V and then adding the overshoot, yes it MAY be a problem. Having said that, if it were me I wouldn't throw a perfectly good motor in the bin simply because it wasn't inverter rated! I'd just run it on the basis that you really have nothing much to lose, and if it fails as a result of the overshoot voltage you just replace it then. The VFDs themselves are typically quite robust if a good brand, and can take a significant amount of abuse. Not to say they can't be damaged, and I guess that would be your call on the day.
I hope that makes sense and helps a little?
Pete
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21st Mar 2011, 07:05 PM #12
Hi Festy,
Welcome to the forum, I've seen similar issues with voltage spikes from vfd switching, breaking down insulation, mostly with submersible pumps. Not so much with regular motors, the usual remedy is to fit dv/dt filtering, if you think it's going to be a problem. But in the case of your mill, I wouldn't be too fussed about it. Running long periods with inadequate cooling is probably more of an issue. Something to keep in mind when you are sizing the pulleys for the belt drive.
That is a serious bargain you got for under $1000, I look forward to seeing the restoration as it progresses.
Regards
Ray
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21st Mar 2011, 07:11 PM #13Most Valued Member
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Agree Ray, I believe it's really more of an issue with long cable runs and the associated capacitance. I can imagine that would be precisely the situation you describe with the submersible pumps. As you say, filters can be installed between the VFD and the motor, but for the type of application described here I wouldn't sweat it. Of course if the motor windings are already a bit dodgy, this won't do them any favours!
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21st Mar 2011, 07:49 PM #14Intermediate Member
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Thanks guys, that's exactly what I was hoping to hear!
I know that seeing nasty spikes on a DSO screen doesn't always equate to real world problems, but some of the things I've read on the interweb recently left me unsure.
I'll charge ahead with this motor and cross my fingers
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21st Mar 2011, 08:26 PM #15Senior Member
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Villawood auction?
Sounds like you've kept the purchaser to a minimum margin, by the time the rip, gst and transport figured into it!
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