Inverter VSD for Myford Super 7 attempting auto destruct

Keith

I am a convert to the inverter and yes, they're dead easy to wire in. Three wires in, four wires out and maybe 4 more for remote control and forward/reverse. I've just bought one for another machine from Clive Steer who advertises on the Homeworkshop pages. If it's as good as it appears (waiting for it to arrive) then for the money it's a bargain.

Regards

Charles

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Normal foot mount in 3 phase will do nicely as they are smoother than the original single phase. Have a look on the web site in my sig line. There are some motors and invertors on there from different people that will fit the bill very well.

The technology is getting better by the day and what used to be a specialised domain is now available to the masses.

-- Regards,

John Stevenson Nottingham, England.

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Charles, John

Thank you for your very rapid replies but as always you have prompted a couple more questions if you don't mind.

Having looked at your site as suggested, I did a "google" on Yaskawa inverters but unfortunately all the pages I found appear to be written in a strange language and I can't find the "this fits a myford" statement!

I had thought that a motor between .75 and 1hp would do nicely - will the 1.5hp inverter be OK with a smaller motor or does it need to have a load nearer the rated capacity? If so will a bigger 1.5hp motor still fit the lathe? The other one I could find on your excellent page, although much nearer to me, I felt might be a little small at .5hp? I'm sorry but you will see from my question I really don't know much about this.

John, my question was not very clear I'm afraid, the foot mounted motor I have spare is a single phase not three phase and although its an old Brooke Crompton I don't want to go to the bother of fitting it if it is likely to produce the old "white finger" vibration and that "lovely pattern" (my wife's description as I showed her what was wrong with my cheap chinese lathe) on the finish.

If I went the inverter route to get the variable speed advantage anyway are motors easy to come by and more importantly does it need to be anything particular. I gather it has to be 230v not 415v but I don't understand what is involved in matching the motor with the VFD or in diving into the motor to change the "windings" (star delta??). If I look at the motors are they easy to identify? I'm happy (I think) to pay for a new motor if necessary but will need to ensure I get the right one. I have already wasted a bit of money on a different machine when I fell for the Machine Mart "quality costs less" and bought a .75hp motor which must have been measured on a very small or very old horse. Unfortunately, I don't have your knowledge to identify bargains even if they stare me in the face, and without the necessary contacts or buying power I can't get anything other than "list" prices. So I need to buy wisely. I suspect I need to read some of your old posts a bit more deeply.

Hope you will forgive my long list of daft questions.

Thanks both for your help, best regards

Keith

Keith

Where are you based. I have a freshly rebuilt 3/4 hp 3 phase motor that keeps getting in the way if that helps?

Regards

Charles

jontom snipped-for-privacy@hotmail.comsaid

Hi Keith,

I've just been down the same route and have come out the other side wiser and with so much more control over my ML7 than I ever imagined possible!

The inverter doesn't have to 'fit the Myford' - I bought a Hyundai N100

1500SF via eBay (once John Stevenson confirmed that it would be 'ideal') along with a .37Kw motor.

The issues that I had were purely to do with the physical size of the motor, the pully that I had on the shelf and the size of the belt on the Myford. The original single phase Crompton motor (1425rpm) had a 1 7/8" pully on a 5/8" spindle driving a 36" O/D belt with a base to centre height of 3.5". The new motor (1380 rpm) has a 14mm spindle with a base to centre height of 70mm, the pully is 19mm bore and 76mm O/D and I need to use the same belt - so, a bush from 14mm to 19mm and packing pieces to raise the motor to a suitable height.

That was one of my questions as well.

The Hyundai has a motor test routine which sets it's parameters to match what the motor is capable of.

I haven't had time to fully test this yet but JS tells me that 1/2 hp 3~ is more powerful that 1/2 hp 1~. Up to now I have found no problem.

Again I had no idea what Star and Delta meant in reality but once I got the motor it all became very clear via the wiring diagram on the inside of the motor connection box. As I now understand it Delta is 240V with three straps linking across the U, V & W connectors and Star is 415V with terminals U, V & W linked together.

As long as the motor is specified as Dual Voltage (240/415) then you ought to have no problem.

I had as many (if not more) - I still have some that I posted to JS last week!

Since I have already been down this route and have built a remote control unit which gives me Forward and Reverse at the touch of a button as well as three selectable fixed speeds plus fully variable, I would be happy to talk you through any issues you may have.

JG

Hi there

I have just fitted a Newton Tesla CL 750 to my Myford 254, dead easy to do and I can't believe the how quiet the motor runs. No wiring for you to do at all just plug it in and off you go.

Kit came with a 1hp motor (old one 3/4 hp)

And a ten year guarantee on the inverter!

George Newton is always there for any advice you might need, I asked if I could chop the 13 amp plug top off so I could wire into the main switch on my lathe, no problem and no effect on the warranty either.

Perhaps not the cheapest way to go but a class bit of kit, with the back up of a company that really knows their shit!!

Rich

Charles

Thanks for your kind offer, certainly sounds as if it might have helped. Trouble is I'm located in South Wales and based on the location in your advert for your Clarkson Drill Point and Tap Lead Grinding attachment, I suspect there may be a few too many gallons of that expensive fluid between us to make it sensible. Pity as I've just spent the afternoon clearing a space for the Boxford I need to pick up tomorrow night and there seems to be an excess of floor space at the moment. I suspect it will soon escape though. However, in the longer term and if I can sort this Myford successfully there is always the new boxford to "improve". Do you frequent any of the exhibitions? At the moment I can't think of anything that I visit that is remotely close to you. Thanks again.

Best regards

Keith

JG

Thanks for your reply you have clarified things greatly. With most engineering issues I always find that once you can get past the basic "daft" questions and start to talk and think the new/different language things start to make a bit more sense. The other advantage for me is obviously it is much easier to follow than lead. I really wish I had found this group earlier I might have bought more of the "right stuff" and less of the accumulated junk in the garage. Still these days I think "junk" has been redefined as "Ebay treasure" although thankfully, as you have identified, when equipped with the right shopping list the real goodies are certainly there.

One of the issues I have with the Newton Tesla option is that if I repeat the process for the bigger lathe and the mill it makes a big hole in my modest budget. From what Charles, John and yourself have described it looks as if I could improve all of my current machines and also still save the cost of another "essential" machine. Sounds good to me.

I must admit that I hadn't even thought of the mechanical differences between the motors although I should have as I can remember being told that 3 phase - more efficient - smaller motor for similar output. If you don't mind I will certainly take you up on your kind offer to talk me through the issues just as soon as I have gained enough of an insight to know what they are. I suspect some of you guys on here must be kept very busy "sharing" with us less experienced individuals.

The facilities you describe on your remote control unit seem very appealing; to build such an animal do you need any "electronic" skills or is it the more (for me) understandable switches pots etc? The other question currently in mind how long does this buying and building process take? Despite the high cost at least the Newton Tesla package is available quickly and with the Myford totally dead at the moment I'm missing all the fun! Still if I can get the Boxford I'm picking up tomorrow running perhaps the Myford can wait a while. Sorry thinking with my fingers on the keyboard again.

Anyway, JG thanks for your very helpful reply and if you don't mind I will certainly shout when I know what the (first) problems are for me. Thanks again.

Best regards

Keith

Rich Hi,

Thanks for your message it certainly confirms what others have said about this company. It is pleasing to hear that a top notch company can still thrive in these days of "mediocre" service. I suspect that we get what we deserve when we buy just on the "bottom line". You will see from my other answers that I am getting quite excited by the prospect of learning about this developing technology. Much more excited than when I think about having to change belts all the time; having the right speed available at the touch of a button seems a huge advantage to me. With my Myford completely dead and your excellent recommendation I might follow you to get up and running quickly and then follow the other guys in slower time to convert my other machines.

Talking about new technology I must really master the art of posting a reply, I seem to have got out of sequence and have ended up with three separate responses to the help you are all providing. I suspect that is "bad form" but no doubt someone will be able to put me right.

Hope you enjoy your CL750 and your 254, must admit one of those has been on my wish list for some time. Still we all have to have something to dream (and drool) about and I'm sure my boat will come in soon.

Best regards

Keith

Without taking anything away from Newton Tesla they are only assemblers of off the shelf items, invertors, switches etc.

Technology has gotten to the stage where once you get past the terrible documentation sent out with these magic boxes it's really easy.

There are basically three terminals strips in an invertor. Single phase in, usually marked L&N or L1,L2 and sometimes even L3 which you ignore. If it's the L1, L2 marking it doesn't matter which way is live unless the book says. Then you have the three phase out, usually marked U,V,W, again it doesn't matter which wire go where to the motor as long as they do all go there. If the motor goes the wrong way just swap any two.

These two terminal blocks are at mains potential so normal care and safety apply.

Last is a smaller terminal strip for the start stop and speed pot. These are low voltage connections 10v to 24v at around 10 mA depending on model so very safe. These are the wires you need to bring out to the remote switches and can be on thin alarm type cabling.

The default wiring for most invertors in industry is for the invertor to be switched on with contactors and locked on until stopped. This is usually handled by relays as part of the machine package.

We can do the same but need other safety procedures to prevent it auto starting after a mains failure. The best procedure for the home shop guy is to use what is known as 3 wire operation. This used two switches a start switch that needs to be made to start the motor and a stop switch that needs to be broken to stop the motor. he idea of the broken stop switch is a series of them can be daisy chained together for things like guards and limit switches. The three wire configuration gets it's name form the three wires, one common, one start and one stop.

How these are wired in depends on the manufacturer, many have a quick connection cheat sheet if you ask.

-- Regards,

John Stevenson Nottingham, England.

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My view is that I just didn't want to learn the electrical side of getting a "home brew" up and running, obviously John knows his stuff, and when you do it all seems so simple.

But frankly I just couldn't be bothered, I just wanted something to bolt on and get on with things.

I'm sure I could have done my set up given time, but I work away half the year and just couldn't justify the time spent sourcing the bits and pieces.

The Newton route was (is) best for me, like I said not cheap, but an excellent package, it's still a novelty to switch on the lathe and for it to be so smooth and quiet. It's not that the old motor was worn, I have owned the lathe from new and it's done sod all up to now.

In back gear, with the speed control turned right down the chuck crawls round, I will get round to marking it and use a stop watch to count the revs, the old Smiths mechanical tacho I have won't resister the speed it's so slooooooowwwww.

On the other DIY front I think I will have a go that these DRO's:

They seem to be the same a this dude is selling:

But at a knock down price, I'm a bit worried that I will get shafted for Vat as they come into the country tho.

I was a Harrogate on Friday, enjoyed the show, it's the first ME exhibition I've been to since the days of Wembly Conference Centre!

I even managed to shag deal out of Myford! That must be a first....

Rich

John

Many thanks for the information you have a real gift for making the complicated appear quite straightforward even logical. I believe with your and the other guys help I'm now getting a basic picture of what a VFD Inverter consists of and how it is connected. I build computers for a hobby and many people have a "blind spot" that convinces them that it is some sort of "black art", of course it isn't you just need to know what plugs into where. I suspect after your excellent description that I have the same problem with these inverters.

I'm getting the idea that at my sort of level once you have identified the individual components (inverter, filter? / keypad?) required it is just a matter of connecting them up and sorting out a suitable location/ housing and adding the various control switches/pots either in the same housing or remotely if more convenient. I had originally thought that some sort of programming interface was essential to adjust to the motor parameters but from what JG said and the RS web site am I right in believing that this function is already built in to some inverters? At least to a sufficient level to look after my basic needs for motor speed control. If this assumption is correct is it safe to accept their "default" parameters? Do I also understand correctly that a "filter" is required? I notice that some inverters claim to have these built in, is this the same thing or are additional filters always required.

Having had a quick look at the RS web site I'm guessing (top of my head stuff) that something like the Siemens 420, Telemecanique IP55 or Mitsubishi E520 is the sort of thing I would be looking for. Am I in the right "ball park" or have I got it hopelessly wrong (wouldn't be the first time). I did find an Ebay supplier that sells the Hyundai N100 that JG mentioned but can't see his specific model. If this guess is somewhere handy they all appear to be about =A3200 (0.75Kw) to which I need to add a few pounds for the switches/pots etc. Although both sites talked about selling suitable motors I can't see any prices listed so would guess about =A3100 off the shelf? With a bit of care I'm guessing that I could put a system together for under =A3300 using new components and my buying power of 1. I've also noticed that RS sell one under their own name for quite a bit less but I am always wary of "own brand" as I can not tell who put it together for them.

Obviously I need to learn a lot more about the various functions etc but would this get me a reasonable system that should be reliable and give me basic control of the motor without any longer term reliability issues? I have also got the feeling that this approach is rather "throwing" money at it and is not likely to produce the best bang for my pound. In comparing these inverters is there anything in the spec that I should particularly look for? It all gets a bit technical for a non electrician (as they intended of course) and I wouldn't want to miss a critical factor.

John, I really appreciate the time you spent preparing your earlier detailed advice and I certainly am not looking for hours of "free training" but could you give me a clue to confirm (or not) that my initial thoughts are at least on the "right planet". I hate it when I get all excited about a project only to be shot down in flames later because I hadn't grasped the basic concept. Particularly if it is after I have already spent some money. I'm off to pick up my "new" Boxford tomorrow so I promise I won't hit you with any more "multi-question papers", thanks again for your patience and help, very best regards

Keith

Rich

I was just off to bed but now you've got me all excited about my next "learning programme" - a DRO set up for the mill. I have already fitted the mill with a couple of the cheap Chinese scales but this of course only really gives a digital handwheel scale with a zero ability and instant metric/imperial conversion. Even this limited I find them a great help and get quite cross when the battery is flat and I have to revert to reading the old collars.

I have spent a little time looking at the Shumatec system and am hoping that John will come up with a "long term report" on the one he fitted a while ago. My only concern and the weak point for me is the actual scale, I know from my own experience these cheap scales are not forgiving of cutting oils. I believe that you can fit better scales but this adds considerably to the cost. John's description of his fit included a good picture of how his scales were protected and I would be interested in how they have performed. The glass scales appear to have better resolution and I would have thought better reliability but they will still need to be kept clean.

I enjoyed Harrogate on Sunday but of course all of you early guys had stolen all the deals. Anyone who gets a deal out of Myford must be on a roll; I hope you bought some lottery tickets at the same time. To be fair I got a good (reasonable) deal out of them on a milling vice a couple of years back at Bristol. The box looked unloved but the vice was perfect and has a decent bronze nut. I suspect that they just didn't want to take it home again.

I looked at the Chester DRO and the system offered by Warco as additions to their machines. The Newell system from Chester appears to be a fully sorted and well regarded industrial system at not as great a price premium as you might expect. If you can catch them on a good day it has got to be worth consideration and avoids having to build/import it. It also doesn't rely on cheap imported scales. I have been thinking of a VMC type mill and the Chester offer of machine, power feed and DRO for less than =A32K looked tempting. Must mean that either the pound is very strong or customers with money to spend are in short supply. The Warco equivalent looked well finished as usual but I haven't yet had time to research their DRO system, the scales were Chinese but the controller was German. Unfortunately they had run out of information leaflets by the time I got there.

Make sure you don't tell John S that we are about to start asking DRO questions or he will put his prices up. In my past (working) life I have been asked to pay very considerable "fees" for advice that was no where near as good as John's. Still I'm sure he knows we appreciate his time and excellent advice.

Best regards

Keith

My Draper Tools mill is metric, can't stand the thing, well that's not strictly true, the machine is actually quite good, it's the metricness!! that bugs me.

I have had a couple of replys from the Ebay seller, a bit of a langauge barrier as you might expect, I knew I should have stuck in at school and learned Chinese.

I picked up a flyer on the Chester stand for the Newall Dro's Their B60 system 3-axis is £1095, way too expensive for an amateur user, well this user anyway!

The trouble is it a pro system and it will be very good,but hard to justify on a machine that cost me about £500 'ish 15 years ago.

I am still toying with going the full size Bridgeport route, I just watched a very nice one fail to sell at £3.5k on Ebay this morning, power feeds all round and what looked like a 2-axis dro. For me apart from the price is that I am in Lanarkshire and nearly every machine I have spotted on Ebay is well South of the border.

Yeah, I was down with a pal, and he was cringing at my bargaining skills at the Myford stand, having a 254 is like the Betamax of the Myford world :-)) So my stance was that they should be glad to get rid of the stuff, seemed to work to!

Going for a "package" deal on a VMC with Dro and power feed to the table might be the best option for me, then stick my mill on to Ebay. Not sure about Chester as a company going by some of posts on there, there aftersales seems to be a bit dodgy. Where as Warco seem to be quite well thought of. I took a picture of the Warco Dro while I was there, more to see how they had mounted it then anything else.

I've got a Shumatech DRO on my lathe and the DRO is very good although the scales have been troublesome. The US boys on the Shumatech Yahoo group have used Jenix glass scales which do sound more reliable but I don't know of a decent (ie cheap) UK source. Either that or I need to find some redundant quadrature scales and use them.

Regards

Charles

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What's the problem with the scales ? Would sufficient shrouding fix them or do they have other problems ?

I bought a chinese scale on Saturday, mostly because they've got so cheap (18 quid !) it was worth a play. I was pleasantly surprised to find that it works like an absolute scale although it doesn't say so on the casing. However, it appears this is achieved by never really switching it off (if you turn it off the display goes blank but the data doesn't stop). Is that how they all work, or do the expensive ones like Mitutoyo have true absolute measurement ?

-adrian

Charles

You have me worried now; as soon as I have the inverter sorted I planned to go the Shumatech route on a to be acquired VMC type mill. While I felt the scales were a bit of a compromise on resolution I thought they might work OK until better scales became more readily available. What sort of "trouble" have you had, is it an inherent reliability problem or the dreaded "contamination" issue?

I have always suspected that these scales sell by the millions to amateurs like me who don't use them very much and seem to be very accepting of their little foibles (don't work!). I'm sure many are fitted to give an appearance of "professionalism" to our little machines and will operate successfully when kept spotlessly clean. I know I am a lot happier having "real" tools when I can afford them and Snap-on have made an empire out of selling the "image". However, now I have retired and am planning to use the things daily the functionality and reliability becomes a critical issue.

I have used some very cheap ones on my mill and have had the occasional (50% of the time) blip with the buttons getting dirty and the auto-off that doesn't. Found out the cause for that one was a bit of miss-alignment in my mounting which flexed the scale a little. I also thought the wiring was a bit vulnerable and am not convinced that the "no cutting oil" restriction is acceptable to me. Are you happy with their function when working? Given a second chance would you have still gone that route or "dug deeper" for industrial scales?

Best regards

Keith

I have a Shumatech on my small TOS lathe, a 14 x 40 model in US speak. One scale, 8" is on the Chinese one and the long axis was going to be an encoder running on a knurled wheel on a machined un used portion of the bed. If I could have got a couple of thou resolution on this long axis I would have been happy but have decided not to bother. I feel that these are more useful on a mill than a lathe as on a mill they are direct reading to a published 1/2 thou, in reality probably 1 thou. On a lathe you have the x 2 problem of working with diameters when feeding radius so that 1 thou is now 2.

As many have pointed out scale quality can vary from supplier to supplier so there is no base to work from. The Jenix scales seem to be an answer but not with the Shumatech readout as it's missing the last digit to take advantage of the extra precision.

It's now got to the stage where the genuine read heads and scales are undercutting what was a hobby market.

Taking the ones advertised on Ebay at £246 for a lathe setup, even if you get hit for VAT and handling it will come to around £310.

The BW Electronics ones with 2 thou advertised resolution are over £437. Ortec are about the same.

I have a BW as well as the Shumatech. The Shumatech is far better than the BW but I have a feeling that as prices steady the imports ones will be the way to go.

-- Regards,

John Stevenson Nottingham, England.

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Quite probably. The X axis scale just stopped working on Saturday hence my grumble. John S has a bigger lathe and could cover his really rather well but I couldn't (5.5" centre height). The Z axis, being 24" long does suffer from flex a bit but that may well be dues to my fitting rather than the scale. As John has said less accuracy can be lived with here so I'm not that bothered.

No. Overall I think that the Schumatech and chinese scales have been a good buy for me and Lester Caine (the UK sipplier) is a good guy. However some "professional DRO's are getting close-ish in cost and better in resolution.