# VFD conversion via solid state electronic components.  PM1440GT, VFD, 3-phase



## B2 (Sep 11, 2021)

VFD conversion using solid state electronic components.

I finally finished documenting my PM1440GT lathe VFD conversion and want share it.   It took me longer to write this up than it did to actually build the new electronics! (Are these sorts of things every really finished?)

I apologize upfront for its being so long.  I just wanted to make it complete before I posted it so that most of it was at the same posting... but it seems there is always something else to add.  Also, this is my memory document... so I can fix or improve the installation after I have long forgotten what I did!

I replaced all of the original mechanical relay controls with discrete solid state components.   I have not seen any other post where people got rid of the mechanical relays in this lathe conversion, but surely they have so on others.  In doing so I was also able to also eliminate the large power transformer.  Hence, the space requirements significantly decreased and I was able to get everything into the original lathe enclosure with room to spare.  It even includes a homemade, inexpensive, 50 Ohm 400 watt (or a 37.5 Ohm by 300 watt) braking resistor.  So there are no external cabinets or enclosures.  Only a power switch at the wall.   The value of this braking resistor can easily be changed to other values if so desired. Additional features such as proximity sensor, drive frequency display and RPMx10 display, alternative e-breaking rate, auto/manual coolant, +-Jog, etc. are included along with more safety factors.   It has been completed and being used for several months without any observed problems or failures.  I have made enough machining mistakes to believe it is quite safe. 

There are two separate Parts to the document.   Skip Part 1 if you do not need to know how the original factory built 3-phase power system was constructed and operated.  Part 2 is the detailed description of the new VFD system.  Part 1 contains text, figures, tables and photos, but there were too many photos to include them in Part 2.  There is also a list of parts and suppliers near the end.     Part 2 has a table of contents with links to the text, hence you can quickly jump to the text points and the figures at the end.

The technical description is long so it may be faster to get an idea of things by just looking at the figures, which are included in the document, and the pictures, which are separate due to their size.  If you think you are serious about doing a similar conversion, then have a read!  I have tried to put enough details in it to allow even someone who has not worked with transistors for a while to understand what is going on.  I have also tried to provide a limited description of how this VFD works and is set up.  You may not need these.

I wish to thank  the HM folks for their many posts. Since I had hardly worked with inverters, or designed for one before, these posts were very helpful. Mark's (@mksj) posts, especially in suggesting the VFD model and its program settings are much appreciated.  Private discussions with @ptrotter were very helpful and also appreciated.

Let me know, what you think, concerns, what I did wrong, etc.  I welcome ANY question.  

Dave  

PS.  I am not for sure if I can post all of this in one try so it may take a few attempts.  I also have other photos if any body needs to see them.
PSS.  I also apologize for the obnoxious footer on the document.  This is driven by the HM Rule #15.  The folks at HM say that they will be making this rule more friendly in the future.


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## B2 (Sep 11, 2021)

More pictures ...


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## B2 (Sep 11, 2021)

More Pictures 2


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## B2 (Sep 11, 2021)

More Pictures 3


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## RJSakowski (Sep 11, 2021)

What an ambitious project!  I am in the process of writing up my d.c brush motor conversion on my lathe but you just set a very high bar.  Well done!


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## graham-xrf (Sep 11, 2021)

@B2 
You sir - deserve our thanks, and admiration. This stuff so generously shared is a resource for folk to learn from, and it it useful beyond the set of PM1440 owners.


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## B2 (Sep 12, 2021)

Thanks Guys,  I appreciate your feedback and your "Likes".  
Dave


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## Reddinr (Sep 12, 2021)

Well done!  Love the point-to-point wiring on the breadboards!  True hacker stuff there! 

Reminds me to dust off that RPM display and VFD still in a cardboard box awaiting my attention.  I like to age my parts for about a year for some reason.  One thing that I considered was to have two braking levels.  One would be your normal everyday "stop" brake and a stronger "OMG" brake.  I have not completely planned that out yet.


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## B2 (Sep 12, 2021)

Hi @Reddinr

Thanks.  Yes, some electronics do need a burn in to assure that they are going to last.  So far I have not had a problem so the burn-in is happening real time.  I built more than one of these circuit boards before I settled in on this approach.  The real issue was how to fasten the board in and  the electrical connectors.  I tried other connectors and many of them were intermittent.  The board carrier and the screw down, push on connectors seem to work well.   Now that it is all working well and values are set one could make a neat custom circuit board.   I either use tinned wire ends or ferule crimps to go into the elevator style screw connectors.  After putting them in to a reasonable torque I wait a day or so and then tighten them again.  The wires or ferules or the screws seem to compress and relax a bit.  So the second time around they are very secure.   You also will see the LEDs on the board.  Not neccessary, but nice to know what is happening.  One could also design for a much smaller voltage than 24V.  

The Hitatchi VFD has two programmable e-braking rates.  I put these in and programed one to 3 seconds (called CH2) and one to 1 second. This is switched at the left side on the front panel.  The E-stop invokes which ever the switch is set to.  However, on the PM1440GT there is a foot break that really stops the spindle fast.  Faster than 1 second.    When that is hit you want to the e-brake to NOT happen as that would be a conflict between the two rates, electronic vs manual.  So the VFD is programed let the spindle free wheel (coast) when the foot brake switch is tripped.  I also consider the foot brake to be an "OMG" situation and so it is set up to cause the VFD to go to an interrupted mode, where you have to Reset (USP) it completely before you can run the motor again (safety).  There is a Reset (USP) button on the front panel that is recessed actuated... to make it hard to get to.  

Dave


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## Just for fun (Sep 12, 2021)

Holy cow Dave,  That's quite a write up!  Thanks for sharing, I'll have to check it out more when I'm at the house.  To much info for my phone.


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## Reddinr (Sep 12, 2021)

My electronics aging has more to do with procrastination, thinking about buying a better 3-Phase motor, and other projects getting in the way than burn-in.  I'll have to have a look at the Yaskawa drive I have to see if it has two braking inputs.  Great idea with the foot-switch tie-in.  I'll have to keep that in mind too because my G0505G has a foot brake.  My thought was to have a switch on the foot brake that tells the VFD to turn off the output immediately about halfway through the actuation of the foot brake.  Not sure about how well that will work though.

For little projects, I use ExpressPCB for prototype quantity boards.  It will import netlists from schematic capture programs and you get the boards in about a week.  Who do you use for boards?


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## Cletus (Sep 12, 2021)

I also use ExpressPCB here, very happy with their service.  Mainly for custom industrial and medical equipment, I don't really need production quantities.  I'm mainly involved in industrial and medical equipment support throughout the Caribbean and the shop is setup to facilitate troubleshooting, repair, refurbishing and calibration of such and also to design and manufacture custom equipment.


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## B2 (Sep 12, 2021)

Hi @Reddinr and @Cletus

Yes, I realized what you were really saying about 10 seconds after I hit the send button!  Isn't it always that way.  Anyway, if aging makes electronics more valuable I could sell off some of my  50 year old investments!  I think I purchased some of my first transistors in the early 70's and probably still have some of them.  Old carbon resistors made back then seem to change value over that time period!  I also remember rebuilding my Dynaco 120 Stereo Amp. about that same time.   I was still in graduate school.  Shortly after that I had a job for a couple of summers where I designed electronics.  One project was to built a multi output power supply for a company, Hendrix Electronics, Londonderry NH, who was building and selling text editor machines to the news paper industry.  We worked out of some old air force barracks.  Later I think they moved to Manchester, NH and got a real building.   This is before there were any PCs around, think PDP-8.  But we made our own pcbs.  I even used tape layout to do the board layouts which were then imaged down at about 20x scale, before they made the boards for me.  No auto routers back then. 

LSI components were ICs with a couple of flip-flops in it!  At that time there was a brand new device that could be had.  It was called a 4 bit up counter with carry.  No such thing as a down counter yet, so in one project I had to build my own up-down counter from discrete components!  We have all come a long way since then.

Yes, my graduate students used ExpressPCB or something like them, but I have not for a long time.  To tell you the truth it is nice to have a pcb built, but I prefer to debug circuits where I have lots of room to work and see.  The eyes are fading along with other things!   Once, they are working then why not a pcb.  Surface mount is even harder to work with, but I have the equipment.  So I just get down my old supply of discrete components and go at it.  In this case once I had everything working I just quit.  But a pcb would make things smaller and maybe more reliable. 

Before I retired I taught and did research at a major university,  EE, Physics, and Materials.  There was another process that is available to actually made ICs, called the MOSIS service.  It was set up by our military to enable them and everyone else to make small quantities of ICs, before committing to full production runs. You do a full production run and made a mistake it is very expensive.  Even small IC masks are multiple $10,000.  So doing everything over can be 100Ks just to get the masks made.   Several of my colleagues used this service.  I only used it once.    https://themosisservice.com/  Anyway, if you need small quantities of ICs, logic or analog, one can sign up.  They call the service multi-project wafer design.  The service takes lots of folks different designs and merges them on to a single wafer for processing.   They use a hand full of commercial IC companies to process the wafers and when they are done they package your ICs and send them back to you.  Actually affordable, a few $K, if you really need this.  Even less for a student. However, you need some computer tools to do the modelling and the layouts.  You send them a Gerber file and they do the rest.   If you need speed this is the only way to go.  There used to also be a service via them where you can even do MEMS devices.  You can imagine it takes a while to get the devices back. 

Sorry for wandering off topic.  Thanks for looking at my post.

PS.  @Cletus , do you make it to the Caymans? My wife and I have been scuba diving there for about the last 15 years. Really nice. We usually go in the summer when the crowds are smaller. Anyway, they closed down during covid so it has been a while since they would let us in.


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## Cletus (Sep 12, 2021)

Well, I've been going to Grand Cayman to support one of the private hospitals there, but I have not been there in about three years. I miss that place and the copious amounts of beer hanging out at "Peppers", I even ended up on-stage playing guitar there one night in a drunken stupor 
I started my EE career back in the 70's here where we used to manufacture Ferrite Core Memory systems for Dataram Corp and United Telecontrol Electronics.  Two years ago I built myself a Dynaco 120W stereo amplifier using KT88s.  So, we do have similar interests, although I never did get to scuba dive!


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## B2 (Sep 12, 2021)

If you can still swim you can scuba dive.  However, if you are over 70 or not in good shape I would not advise it.  Over 70 seems to be the point where instructors are hesitant.  Take the week course in the states so that you can actually dive when in the Caymans.   The courses are all about safety.   You have to have a certification card to rent equipment.   We have been using Ambassador Divers for years.  Nice folks.  

Ferrite Core Memory!  Wow, it would seem you have been around for a while too.  I did R&D in Hard Disk Drives for years.  Lots of magnetism and magnetic materials.


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## Reddinr (Sep 12, 2021)

Wow, interesting careers!  I feel like a relative newbie.  My EE training was in the early '80s.  Spent much of my career at small companies and then my own consulting business for the last 15 years.  Did magnetic design, power design digital design, and firmware/software for industrial, military, and medical applications.  The components do keep getting smaller.  I ended up with a binocular microscope to aid in putting together SMT prototypes.   I usually just go for a PCB right from the start and cut/jumper as needed to save time and because of ego (this time I'll get it 100% right!).  I gave up on assembly for anything below 0603 parts and .025 spacings or any quantity >2 pieces.  Now that I'm nearing/at  retirement I guess I need to figure out what to do with all the test equipment I've accumulated.  I also probably need to part with the old UV EPROMS and 68000 processors and 78xx etc. parts I have laying around.


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## B2 (Oct 8, 2021)

Hi Folks, 
 If any of your are interested in how I made the Lathe Front control Panel or the Hall Effect magnet mounts in my VFD conversion...  I just posted a bit about a backer board that I made for my PM940M-CMC.  In this posting I included photos of the making both.  









						Milling Nylon Backer Board
					

I recently posted my description of my PM1440GT lathe VFD conversion. https://www.hobby-machinist.com/threads/vfd-conversion-via-solid-state-electronic-components-pm1440gt-vfd-3-phase.95058/     (  VFD conversion via solid state electronic components. PM1440GT, VFD, 3-phase  )  In this I showed...




					www.hobby-machinist.com
				




Dave


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## Cletus (Oct 23, 2021)

Very, VERY, *VERY COOL! *


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## B2 (Oct 23, 2021)

Thanks Cletus! 
With the addition of the spindle counter circuity I should probably update the files for this VFD conversion one of these days.  First I must make a new front panel plate to hold the extra counter display!  In the counter design addon I have a switch that allows me to also count the spindle rotations after the proximity sensor has been tripped i.e while the ebrake is doing its thing.   That is, it will allow me to determine how many spindle turns occur after the ebrake is applied.   Hence, I hope to determine exactly how far out a proximity detector needs to sense in order to know where to position it so that one can turn threads right up to the point where the tool might be very close to the spindle etc without hitting.    

Dave



B2 said:


> Ok. Here is what I measured, so far, for the TPI and then the mm/turn for my PM1440GT. This also displays the lever positions not listed on the PM manual or front of the lathe for available TPI. Note I use my Hall effect spindle counter, which makes 10 counts per revolution (10 magnets), to count the number of turns over a 10 inch travel distance. So the numbers should be pretty good....assuming


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## Cletus (Oct 23, 2021)

Oh yeah, I like it!


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## B2 (Dec 26, 2021)

Hi Folks,  
As I mentioned before I was adding a counter to my VFD converted PM1440GT.  I finally got around to writing it up.    Since I took the time to work up an Excel Workbook to generate the Gcode I posted that process at https://www.hobby-machinist.com/thr...strument-panel-gcode-in-one-quick-pass.97099/   I put some pictures there too.  


B2 said:


> Here I am sharing my efforts to automate some Gcode generation via the use of a Excel Workbook (multiple spread sheets).



Here a couple of final pictures of the spindle turn Counter mounted in the lathe's front control panel.  There is also a small three position switch located just under the counter (the center display) where one can either use it to reset the counter, to just let it run, or to have it only run after some trip event such as the Proxi. stop or Estop etc. to determine how many revolutions the spindle turns after the event.  Since my Hall magnet for the RPM pick up has 10 magnets/revolution rather than just one the count is really 10x.  That is the first digit on the counter display is a fraction, 1/10, of a revolution. 

 Also, I am attaching a circuit drawing of how the counter was attached to VFD control that I have already written up and posted.  Comments are welcome.  The counter has 4 leads. +power, Gnd or low, Signal in which connects to the Hall Effect sensor on the spindle (same one as used for the RPM display) and finally a reset input.  If the reset input is low then the counter is set to zero. If the reset is high or disconnected then the counter starts counting.  So the approach I took to using it with the proxi stop is that a signal holds the reset low until the proxi or other similar connection is interrupted.  At that point the reset goes high and the counter is allowed to count.  So it counts until the spindle stops.  Due to my VFD Latching circuit design it works for other events such as manual breaking or Estop etc.  

I will try to post some data on some data on how fast the VFD breaking works later.

Dave


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## B2 (Jan 8, 2022)

Hi Folks,   
If anyone is interested, I improved my Panel Excel Gcode generator that I used here.  It will now also do D-Sub connectors of the standard sizes.  This should pretty much cover all of the D-Sub connectors.  


B2 said:


> New Template is added to the spread sheet. Are there any other connector templates that would be of value to folks?


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## ColbyB99 (Mar 24, 2022)

Hey, this has been an interesting post. I will be doing a similar project myself for my 1440gt.
I currently have the single phase version. I honestly did not think I would need to run this off a vfd. But after running my lathe for a year. I can see the benefits. 

I am not wanting anything as in depth as what I am seeing here. However, this was a well thought out project and i give kudos to the people involved. I need to get a 3 phase motor and a drive. I mainly started interest in a vfd setup because of the harsh startup on my lathe when in low to medium speed range. Also speed control would be an added benefit. Also if i decide later to add other features I can expand. I will build a separate control box to mount behind the lathe.

I will likely to do most of my controlling from a plc maybe mitsubishi, omron or similar controller, just whatever I have laying around, hopefully eliminating extra relays and or wiring. Also, most of the time changing logic or additions are quicker that having to rewire.

Can someone help me through this project. 
I mainly want to be able to soft start. I do not need a break function from the drive currently so that could possibly eliminate the need for the breaking resistor and I'm fine with the motor coming to a coast.

I can perform all work needed. I have experience in all the related work that was described in the project. I pretty much do this type of stuff for a living. I have 10+ years of experience in automotive manufacturing. Which puts me around industrial robots, servo drives, electrical motor controls as well as electrical safety control systems. Most of my motion controls experience is with 480v 3 phase. I have never worked around 1 phase to 3 phase motion controls. It may not be that different, I'd just like to see what everybody thinks in a setup for this minimal design and recommended parts.


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## B2 (Mar 24, 2022)

@ColbyB99 

Thanks for the compliment.  I did put a lot of thought into my design and am glad I put it all in the original enclosure so that there is no external box.  

I am a pretty busy and tied up through April, but afterwards I would be happy to try to help you.  Mean while you can message me with questions or post them and I will respond when I get a chance.  

If you are going to purchase a new motor (3Phase) you should get one that is made to run at variable speeds. (probably set you back about $600) The stock motor that I got from PM with the PM1440GT is OK and seems to work ok at any speed for me, but not specifically designed for variable speed.  Hence, while mine seems to work reasonably well, others have complained that it stutters during start up.  There are several discussions on HM about which motors work well.  

With the Hitachi VFD you will find that many of the functions, like brake essentially come for free.  You just program them in.  My circuits for the control interface to the front panel is actually very simple, but I spent quite a bit of time in my write up trying to explain the basics of the circuits for those who have less background in electronics.  )I should just layout a PCB for folks and then they would not even have to worry about the circuits!)  For example, when you switch Forward/Reverse/Neutral switch to Neutral the VFD can be programed to brake or to coast(free wheel) to a stop with code or via wires.  I think I have mine to program to brake to a stop in less than 3 seconds.  (actually 3seconds * Operating Freq/Max Freq).   I really do not think you even need the braking resistor most of the time as there is some heat dissipation capability in the VFD its self.  It all depends on the load and how you are operating.  Anyway, you can see from my description I put in a resistor but built my own rather than getting one of those big sea slug like resistors that are really designed for use in VFDs used in control environments such as paper mills etc.  

Dave  L.


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## ColbyB99 (Mar 27, 2022)

B2 said:


> @ColbyB99
> 
> Thanks for the compliment.  I did put a lot of thought into my design and am glad I put it all in the original enclosure so that there is no external box.
> 
> ...


Hey Dave, thanks for the reply, I guess I just mainly need help finding a motor that will work with little no mods to my lathe to make it fit.

I have to say, I'm an electronics engineer by trade, your setup looks similar to what I would probably do. Its impressive. Your write up on your project was equally impressive. You spent way more time than I probably would have.

I will likely not go in depth with the controls, being I will do it all mainly in the PLC. However the safety side of the lathe cannot go through a PLC. It can, but it must be a safety PLC and they are not cheap. One safety relay for the estop and side gear cover safety switch will be enough. I'm not even sure if this lathe came with a safety relay. I dont remember when I hooked up power seeing one inside.

I will try to keep everything basic and use everything I can that is in the lathe. We have some vendors at work that we get a lot of our stuff from to do projects and repairs. Hopefully they can help to track one down and give me a good price.


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## B2 (Mar 27, 2022)

ColbyB99 said:


> One safety relay for the estop and side gear cover safety switch will be enough. I'm not even sure if this lathe came with a safety relay. I dont remember when I hooked up power seeing one inside.


I found a quite moment to respond.  

You do not need a relay to get the safety features if you follow my electronics design. I built them in.  In the original factory design this was done by a  latching relay.  Hence, I did the same but with transistors.  See my electronic control circuit drawing and see how the e-stop, gear cover interlock etc are all in series with my latch.  When current is broken the VFD is turned off and will not start again until put in to neutral, which resets the protection latch.    Leaving out the VFD, the entire total cost of my system is far less than the cost of the factory design.   

WRT to your motor issue, I do not have a solution for you as I simply have not researched it.  I think it is a long shot to use the factory 3PH motor but maybe Matt could help you out.  A single phase motor costs more than an equivalent 3 phase.  Maybe you can trade/sell it off to someone.    Mine works reasonably well, but other folks complain.  Maybe I just got lucky.  As far as a slow start up is concerned you can set the ramp up time in the VFD programing just as you can the braking time. If the motor will handle it you can also change the ramp up profile (plot of rpm vs time).  Or you can just set the speed via the speed pot to a low value and then turn it up after it starts.  You might want to download the Hitachi VFD manual in pdf format and search on these items.  I mention the best version of the manual in my write up.  But it is very long.  

Dave L.


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## ColbyB99 (Mar 28, 2022)

B2 said:


> @ColbyB99
> 
> Thanks for the compliment.  I did put a lot of thought into my design and am glad I put it all in the original enclosure so that there is no external box.
> 
> ...





B2 said:


> I found a quite moment to respond.
> 
> You do not need a relay to get the safety features if you follow my electronics design. I built them in.  In the original factory design this was done by a  latching relay.  Hence, I did the same but with transistors.  See my electronic control circuit drawing and see how the e-stop, gear cover interlock etc are all in series with my latch.  When current is broken the VFD is turned off and will not start again until put in to neutral, which resets the protection latch.    Leaving out the VFD, the entire total cost of my system is far less than the cost of the factory design.
> 
> ...


I'll have to look over your controls a little better as I just glimpsed through to see what all you incorporated. If it were me and seeing some of the things I have seen in the automated industry, I would not put anything less than a category 3 dual channel circuit with monitoring on my lathe If I was going through it and changing the basic controls. A cat2 with monitoring would probably suffice but upgrading to cat3 would not require that much more. It's probably overkill but a possible entanglement is severe enough that it justifies to me. The main reason for this upgraded safety circuit is if a component or safety feature fails then how does your machine/ controls identify it and react. All components react differently during a failure. Most will fail safe and dangerously.  This is what's known as the B10 or B10d value for a component and it should be listed in the components spec sheet online if someone were to be looking for it.  B10 will represent how many times the component will switch/actuate etc... before failing and B10d will represent half that value as a dangerous failure.  So with each device you add, that B10 value gets cut in half. Ex. Like a similar contactor that is in my lathe. The contacts can weld which would likely cause a dangerous failure and that same contactor can have its energizing coil to go bad causing an open circuit condition on its auxiliary contacts not allowing the voltage/current to flow through and out to a motor/device which would then likely result in a safe failure. I want get into it and quote a bunch of functional safety ISO standards. Unless anybody would like to learn more, I can direct them to the proper standards for their reading and guidance. Being that I am around this stuff everyday and i see components fail all the time, it's nice knowing the safety control system saw the fault and reacted accordingly. Again, it's probably overkill for a hobby lathe at home and almost everytime I work on it, I kill power whenever I can but it will definitely make me feel and sleep better knowing when I hit that estop etc... it shuts it down without a doubt. 

Anyways Dave, I appreciate you helping out and your work and write up is the stuff that really helps out people and makes a difference. Hopefully I can find a motor soon and get my project finished. When I finish my project I will likely post the upgrades to the safety circuit if anybody is interested and possibly the motion controls from the PLC.


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## B2 (Mar 29, 2022)

Hi Colby
I agree, almost every fails at some point in life!  However, I am not really familiar your requirement(s):


ColbyB99 said:


> I would not put anything less than a category 3 dual channel circuit with monitoring on my lathe


However, more importantly would be the question: What would you "monitor" and what "conditions" indicate a problem.  If it is just the e-stop, I suppose you could build a big relay system to shut the power off at the wall, but that seems pretty drastic.  What is the difference between a big E-stop switch between the lathe and the breaker box and just having an on-off wall switch (30 Amps/220 Volts).  I have a standard box knife blade switch to enable/disable power then I have a breaker at the breaker box.    The VFD is designed for this very sort of input, but if anything goes wrong with the computer in the VFD then perhaps there are no control inputs that could do anything to straighten the VFD computer out. 

So hit the e-stop and if that does not work then you would just have to throw the power switch at the wall.   In the factory design they simply have a latching relay, which then causes the three phase power relays to drop out.  So it all hinges on the latching relay to be safe.  Yes, its contacts could weld and then you are back to the wall switch.  In my design have essentially replaced this relay with a two transistor latch which provides the control signal to the VFD.

If you analyze this circuit it you will see that if the e-stop is tripped or the cover interlock switch is not conducting then the VFD is turned off. They are in series with the transistor switch and if anything cuts this current the VFD Stop signal is applied.   These mechanical switches do  not depend upon any transistor etc.  They just interrupt the signal current to the VFD.  (The VFD is a current controlled devices.  No current is the off signal to the run condition.   I am not for sure how you would make this "a dual" safe circuit. 

 I did think about what the failure mechanisms might be and the only one I could come up with was that the VFD failed in some terrible way.   Transistors usually fail open and so I think all of the controls to the VFD tend to shut the VFD "Run" condition off if a transistor for that control fails open.  Should a transistor fail by fusing short then something might not stop when you want it to do so, but it is a soft failure as these are the controls like Forward, Reverse, Jog e-brake etc.  Then you hit the e-stop and the machine stops.  Even if the latch transistors were to fuse closed the e-stop etc. still works, after all it works when the latch is on so that condition is still the same logic.  So if you have to protect against a VFD failure and the wall switch is not safe enough then you may just have to live without the VFD.   However, you will still want a wall power switch to back up the latching relay.   

PS.  A real safety concern is when you get hold of a live wire and cannot shut the power off!  You need someone else to shut off the main!  So I wire my breaker boxes in upside down so that the main switch is at the bottom ......  so that my wife can "reach" the main switch!  (-:

Dave L.


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## ColbyB99 (Mar 30, 2022)

B2 said:


> Hi Colby
> I agree, almost every fails at some point in life!  However, I am not really familiar your requirement(s):
> 
> However, more importantly would be the question: What would you "monitor" and what "conditions" indicate a problem.  If it is just the e-stop, I suppose you could build a big relay system to shut the power off at the wall, but that seems pretty drastic.  What is the difference between a big E-stop switch between the lathe and the breaker box and just having an on-off wall switch (30 Amps/220 Volts).  I have a standard box knife blade switch to enable/disable power then I have a breaker at the breaker box.    The VFD is designed for this very sort of input, but if anything goes wrong with the computer in the VFD then perhaps there are no control inputs that could do anything to straighten the VFD computer out.
> ...


Hey Dave, glad to hear from you again. I apologize to anyone if this is getting off topic and if so please say.

Again, I would have to really look over your schematics.


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## ColbyB99 (Mar 30, 2022)

ColbyB99 said:


> Hey Dave, glad to hear from you again. I apologize to anyone if this is getting off topic and if so please say.
> 
> Again, I would have to really look over your schematics.





B2 said:


> Hi Colby
> I agree, almost every fails at some point in life!  However, I am not really familiar your requirement(s):
> 
> However, more importantly would be the question: What would you "monitor" and what "conditions" indicate a problem.  If it is just the e-stop, I suppose you could build a big relay system to shut the power off at the wall, but that seems pretty drastic.  What is the difference between a big E-stop switch between the lathe and the breaker box and just having an on-off wall switch (30 Amps/220 Volts).  I have a standard box knife blade switch to enable/disable power then I have a breaker at the breaker box.    The VFD is designed for this very sort of input, but if anything goes wrong with the computer in the VFD then perhaps there are no control inputs that could do anything to straighten the VFD computer out.
> ...


Sorry about the last response. Some reason it cut me short and posted that without me being finished. I'm still getting use to this forum.

Like I said, I really need to sit down and go over your design/ schematics to better give you a good answer and example. Just from what you have noted, it seems safe. I thought I would bring this up being that any changes made to a machine, one would need to keep in mind the safety controls and keep them intact. I noted this mainly for someone with no experience and they were doing a similar project. 

I dont want to get off subject from this post and if so please say. If you would like, DM me and I can further explain what I'm talking about as to  monitoring and give you a good example.


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## B2 (Apr 22, 2022)

Hi Folks,   I just posted a new thread on finding all the possible TPI and FEED rates on my PM1440GT as well as on other lathes.  If you are interested look here:  


B2 said:


> TPI Feeds X-Feeds: Generalized Excel file for your Lathe


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## B2 (Jul 10, 2022)

Hi Folks,

Re: PM1440GT VFD conversion Revolution Counter Circuit modification

Sometime ago I found that at high RPM my Spindle Revolution Counter would miss a count or two out of 10,000 etc.  I found that this was due to excessive noise on the Hall Effect sensor signal line/ground when running at high RPM.  I finally got a round to adding a simple pull up resistor to this line and this seems to have fixed the problem nicely.  The attached pdf document shows where this was added in the front panel circuit board circuit drawing and in the board layout. 

Dave L.


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