Emcoturn 120 lathe retrofit

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LutzTD wrote: Would you suggest I put it in the housing behind the lathe and just run ac power and the signal out to it there?

I am no expert on electrical noise. But as far as I can tell the main problem with a VFD is the noise they send back down the power inoput to the other components, rather than radiated noise from the output side.
Many VFDs have an input filter, some don't. Input filters are surprisingly cheap, and also easy to find on eBay, just search eBay for "rasmi".
Be aware that many input filters have a 30+mA leak to earth, and that will trip domestic RCDs. There are 3mA leakage variants to avoid this, but they may not work quite as well.

I would like to get shielded wire for the motor, the wire in your picture looks like it has a braided jacket, do you have a source for that? Thanx again

The wires in the photo are just generic Multi-Flex SY, nothing super special.
www.tlc-direct.co.uk/Main_Index/Cable_In...ulti-Flex/index.html
However in other places, especially in the drag-chain I have found rather more exotic cables. This is a nice cable for Modbus:

For smart-serial (which is on RJ45 connectors, so CAT5 / CAT6 is needed) I am using
www.rapidonline.com/lappkabel-2170489-un...2mm-od-6-3mm-49-1790
For servo power I am using:
www.rapidonline.com/Cables-Connectors/La...able-4-x-1mm-63-4337
And for encoders and resolvers I have 50m of a cable like this:
www.rapidonline.com/lappkabel-00277131-6...m-4-x-0-14mm-63-6881
Except the 3x2 + 2 + 4 version:
picasaweb.google.com/1081645046564043805...#6217838146609796818
It's a super complicated cable, the 3x2 cores are inside the overall sheath and braid, and then they have their own sheath, shield, drain wire and kapton layer.
I am actually planning to sell my spare 40+ metres of it.

andypugh wrote:

LutzTD wrote: Would you suggest I put it in the housing behind the lathe and just run ac power and the signal out to it there?

I am no expert on electrical noise. But as far as I can tell the main problem with a VFD is the noise they send back down the power inoput to the other components, rather than radiated noise from the output side.
Many VFDs have an input filter, some don't. Input filters are surprisingly cheap, and also easy to find on eBay, just search eBay for "rasmi".

And for encoders and resolvers I have 50m of a cable like this:
www.rapidonline.com/lappkabel-00277131-6...m-4-x-0-14mm-63-6881
Except the 3x2 + 2 + 4 version:
picasaweb.google.com/1081645046564043805...#6217838146609796818
It's a super complicated cable, the 3x2 cores are inside the overall sheath and braid, and then they have their own sheath, shield, drain wire and kapton layer.
I am actually planning to sell my spare 40+ metres of it.

Although the current in the output side is reasonably smooth due to the inductance of the motor windings, the voltage is certainly not. Each phase voltage varies from -ve DC bus to +ve DC bus at the PWM switching frequency (usually in the 2-10kHz range), with switching times of the order of 1us or faster. And when connected to single phase, the bus itself is wobbling up and down by 340Vdc at mains frequency, so the final waveform is complicated. You can pick up the edges easily in adjacent wiring, particularly if you have some means of accidental capacitive coupling, eg the cable is close to something sensitive. Screened wires on the motor connection will eliminate that tendency but there will be an induced voltage in the screen that needs to be conducted to ground at the VFD end of the screen. The motor needs to be firmly grounded too but the advice is usually to leave the motor end of the screen floating to avoid a ground loop. If you connect it at the motor end too and are unlucky, you may find that the motor screen develops a nice resonance. Yes, I've spent many hours doing EMC testing on drives, motors and PSUs....

The input filtering is required to meet the various mandated EMC standards which can be very challenging. If the VFD is sold unfiltered, it's a good idea to fit one as Andy says. The reason some are sold without is that the actual filtering required depends very much on the particular installation. I've just bought a very nice Yaskawa drive for my Milling machine and the supplied filter is a large fraction of the size of the drive itself...

Andy - I have a shopping trolley open in Rapid Electronics at the moment, full of drag cables, boot ferrules etc. If you are interesting in selling some (or all) of the fancy cable, I'd be very interested.

I crammed all my electronics (incl VFD) into a relatively small box on the side of my machine in order to save space and get the machine through doorways. I was very careful to keep the VFD and it's wiring as far from the rest as I could. When I first got things running I had what appeared to be bad noise issues and spent a bunch of time trying to diagnose and correct it. I ended up installing a Rasmi input filter (Andy's suggestion) and large ferrite beads on the output cable to the motor. Neither of these things fixed the particular problem I was having. I borrowed a friends spectrum analyzer to see if I could trace the noise to tie it to some event and while I could see plenty of noise and where it occurred in the cabinet it didn't help to find how to eliminate it. Ultimately I found the problem as I began to re-route various wires to provide further isolation and I discovered that the USB keyboard I was using was unusually susceptible to noise on its input wire and was generating spurious characters. Simply replacing the keyboard solved the problem.

I am not sorry I put the filters on the VFD, it did reduce noise overall according to what I could see on the spectrum analyzer and is suggested practice in general and also specifically shown in the automation direct manual for the VFD. I recall that the Rasmi filter and ferrite beads I found only added about $50 total to the build. But in the end it was other random issue that bit me. Just be as careful as you can with routing wiring, shield where appropriate, and you may be fine.

My last resort was going to be to move the VFD out of the electronics cabinet but it didn't come to that and the lathe has been working great.

-Tom

Muzzer wrote: Andy - I have a shopping trolley open in Rapid Electronics at the moment, full of drag cables, boot ferrules etc. If you are interesting in selling some (or all) of the fancy cable, I'd be very interested.

The spec is here, style 0027131
edgecdn.lappgroup.com/fileadmin/document...lex/DB00277101EN.pdf

I want to keep some for future projects, but I could sell 20m or so for half the Rapid rate, say £2.50 per metre + postage?

Incidentally, for bootlace ferrules look at tlc-direct:
www.tlc-direct.co.uk/Main_Index/Cable_Ac...html#Ferrules_French

Much cheaper than Rapid or RS. Also, I am very pleased with this crimper:
www.amazon.co.uk/Self-adjustable-Ratchet...rminal/dp/B00IR7A3ZU which works a lot better than my RS uk.rs-online.com/web/p/crimp-tools/0464482/

Andy - that would be rather excellent and would save me some beer vouchers. £50 + postage would be great. If you could let me know how much, I could pay you with Paypal if that suits.

I had my eye on one of those assorted kits with crimp tool for £30 as I have a variety of wire sizes. Of course, I have loads of ferrules and a large box full of proper crimp tools somewhere at my mother's so feel reluctant to fork out all over again. However, I don't want to use Toytown tools either. Do you know if yours is better than the thing that comes in the kits?

As ever you can't get everything you want from one source, so I will have to get some stuff from RS, some from Farnell and some from Rapid, even connector shells from the same series have to come from multiple sources. I've also managed to find useful stuff on ebay and Amazon. Most of the mechanical stuff is direct from China.

tome wrote: I crammed all my electronics (incl VFD) into a relatively small box on the side of my machine in order to save space and get the machine through doorways. I was very careful to keep the VFD and it's wiring as far from the rest as I could. When I first got things running I had what appeared to be bad noise issues and spent a bunch of time trying to diagnose and correct it. I ended up installing a Rasmi input filter (Andy's suggestion) and large ferrite beads on the output cable to the motor. Neither of these things fixed the particular problem I was having. I borrowed a friends spectrum analyzer to see if I could trace the noise to tie it to some event and while I could see plenty of noise and where it occurred in the cabinet it didn't help to find how to eliminate it. Ultimately I found the problem as I began to re-route various wires to provide further isolation and I discovered that the USB keyboard I was using was unusually susceptible to noise on its input wire and was generating spurious characters. Simply replacing the keyboard solved the problem.

I am not sorry I put the filters on the VFD, it did reduce noise overall according to what I could see on the spectrum analyzer and is suggested practice in general and also specifically shown in the automation direct manual for the VFD. I recall that the Rasmi filter and ferrite beads I found only added about $50 total to the build. But in the end it was other random issue that bit me. Just be as careful as you can with routing wiring, shield where appropriate, and you may be fine.

My last resort was going to be to move the VFD out of the electronics cabinet but it didn't come to that and the lathe has been working great.

-Tom

Hi Tom,

I found the Rasmi filter for about $60 that will fit. Can you give me some info on the ferrite beads?

Hey Andy,

For control cable I am using shielded cat6a or the cable that was on the component from the lathe. For example, the steppers, the home switches, the tool changer already had very long cables so I assume they are of adequate quality. The new encoder will be a cat6a run as well. I'm going to look at the DC motor cable and see if it is OK, If not the motor cable will be the only one I need to source.

thanx