Another PM1340GT Lathe VFD Control System Build with a Twist

[mksj]

As a hobbyist and "amateur" machinist, I am always learning and trying new designs for the things I build an my VFD control systems, which I occasionally make for others. I am always trying to optimize the builds through better deigns, safety features, use of good quality components and trying to make the installs easier. I have posted a number of VFD control systems designs and programming recommendations. Some I have built, other I have not, so their use is at your own risk/responsibility but are good starting points/information. At this time if someone is building their own lathe VFD system, I usually recommend they go with a single relay design. It works well and most people feel comfortable with that level of build/installation. Programming the VFD is a challenge, but suggestions for the parameters files on the WJ200 have been previously posted which should help with the intimidation factor of the manuals.The single relay design is specific for use with the Hitachi WJ200 VFD and should not be used (nor will work) with other VFDs.

When I do a build for other hobbyists, I use a more complex VFD control design system that I have evolved through the years, which uses a 4 relay design: a control system power relay, Forward/Reverse relays and a coolant relay/contactor. I use the 4 relay system with an external power supply, so the majority of the VFD input switching is done in the control box, and there are 2 to 3 redundant safety logic events for any control to operate. The E-Stop kills the power relay, which shuts down both the VFD inputs, and the other control relays. It also issues a fast stop command to the VFD and prevents restart if power is lost. I feel this is better than disconnecting the VFD input power. It is also possible to program the VFD output section to shut down, but you would lose the benefits of the quick braking. The coolant circuit can be 24VDV, 120VAC or 240VAC with fusing or a thermal overload. I always fuse or use a thermal motor relay for a 120/240VAC coolant pump, something that is not done on the stock 1340GT machine with this option. The other main limitation with the PM1340GT lathe is a tinny control box on the machine, which is very limiting space wise. I have found only one 24VDC 100W power supply that will fit in the control box. I also use a step down converter to provide 12VDC for some of the sub systems. On some VFD builds I put the power supply in the VFD cabinet. I have been wiring 4 wire power to most of my machines, I pull off a neutral and 120VAC which goes to a separate breaker in the VFD box and then can power 120VAC sockets. On the mill this is very handy for the DRO, drives and lights if they use 120VAC.

I have wanted to make installation of the VFD systems easier, and have long toyed with the idea of using cable sockets as opposed to a terminal block to make the many connections when installing these systems. The main limitations has been cost, finding a 12 pin bulkhead socket that mounts from the back of the cabinet and a cable that has the appropriate gauge wire but is not too big. Most socket/cables of this variety can be around $100, so on my most recent build I decided to do all the cable connectors/fabrication from parts. The positive side is it worked very nicely, the down side is it took hours to assemble and connecting twelve 22g wires/insulating on both sides was a chore. My eyes were not happy either. I did use a premade bulkhead socket for the proximity sensor cable, I will keep this for future builds. When I benched tested the system, it went together very quickly and worked as expected, but I do not plan on doing anymore this way unless I can find a premade assembly that is inexpensive.

I have attached two schematics for the 4 relay system, one is setup for a 24VDC coolant circuit with a OFF-ON twist switch designed to be used with a 24VDC air solenoid coolant system. The coolant only runs when the spindle is turning. The other design is similar but uses the factory 240VAC single phase coolant pump, the ON-OFF-ON maintained switch either will run the coolant continuously or only when the spindle is turning.

I have included some pictures to show the basic layouts schematics and basic programming parameters for the WJ200 using these system designs. The wiring, cabling is fairly detailed, and I primarily use shielded cable with a star ground system at the VFD. Sourcing parts can be a problem, but a lot of this is planning and getting everything you think you need. I use Automation Direct for a number of parts, good quality at reasonable prices. Hope this information is useful to others.
Mark

240VAC Coolant system with fusing.

24VDC Coolant system with control system disconnects being tested on the bench.

Installed system with 240VAC coolant contactor and Breaker. Not much space leftover.

 

[jbolt]

Excellent work as usual Mark. Thanks for sharing all your hard work with us!

 

[tweinke]

Mark I hope you know that with out your help and guidance many here could not do a VFD install that is so carefully thought out. I have no machines to do this to at this time but in the future your work is a reference that I will use. Thank You !

 

[qualitymachinetools]

Mark, are you sure that I can't convince you to move to Pittsburgh for a full time job here? Someone like you is exactly what we need! Haha

 

[Alan H.]

Mark,
I am always interested in your reports on your latest design evolution and approaches.

I would really like to have one those systems with the 24VDC coolant circuit variant and the eezy peazy install with the fancy connectors.

 

[vogeldp]

He was quiet an inspiration for my project, I owe it all to Mark, Thanks for all your help and input especially the patience.

 

[Alan H.]

Yes, Mark knows his stuff and his willingness to help us all is beyond compare. I had emailed Mark on more than one occasion and he always shared a wealth of information. I started out thinking about using the existing contactors but quickly shifted my focus to a single relay system per Mark's recommendation. The more I evaluated alternatives, I finally became focused on the "full monty" so I contacted Mark and he agreed to build one for me.

So I am the fortunate recipient of his latest design that he posted about here. I have it in hand and I am putting it together this weekend. Here is a photo of the lathe's control box with Mark's control system fit in it and the front panel from the lathe with all new switches and hardware ready to install on the lathe. Notice the new connectors Mark spoke of.

I hope to finish it today if all goes well with other commitments.

Thanks Mark!

 

[ptrotter]

Mark, I am just about ready to order a PM1340GT lathe which I initially will run off an existing RPC while I complete a VFD setup. My primnary reason for the VFD is to expand the speed range somewhat as well as add some of the cool control features that you have in your VFD setup. I have been studying your schematics carefully and I believe I finally understand what it is all about, however I have a couple of questions. I am basing these questions on what looks like your latest version with the joystick jog and the 2 way coolant switch (very cool).

1. I believe you are using the aux 24VDC power supply to power everything (relays, LEDs, proximity switch), while using the relays to switch the VFD's 24V power source for the fwd/rev/stop signals to the VFD. Very nice, this keeps all the signals to the VFD referenced to itself while minimizing the load on the VFD power.

2. It looks like you are using the LED in the E-STOP switch as a power LED and that it goes on only when the fwd/rev lever is in stop position. Am I correct?

3. What happens when you are not using the proximity switch? Could it accidently shut off the machine? Might it be useful to put a switch on the panel that would disable the proximity switch when it is not in use?

4. The WJ200 documentation specify a speed control pot at 1k-2k ohms. Is there a reason you are using 5k ohms other than the availabilty of a 22mm 5k unit?

5. What are you using for a 24DVC to 12VDC converter?

6. Do you know any source for small quantities of shielded VFD cable? Everywhere I look only sells full rolls.

7. What are you using for terminal strips?

Thank you for all the effort you put into this and sharing it with the community. When I started looking at this I had absolutely no knowledge of VFDs and now I feel confident that I can build a system that will meet all my needs. I have probably spent over 6 hours just following every wire in your designs so that I was sure that I understood exactly what it was doing. In order to save space in the control box, I will probably mount the aux 24VDC power supply in the VFD enclosure. I am trying to figure out how to avoid bringing 240VAC into the control box at all. Perhaps add contactor on the coolant pump and control it with the coolant relay in the control box. This would prodvide better seperation of high and low voltage. I like your proximity switch set up. I may have to buy a mill just so I can make one like it!

Paul

 

[mksj]

See comments below.

Mark, I am just about ready to order a PM1340GT lathe which I initially will run off an existing RPC while I complete a VFD setup. My primnary reason for the VFD is to expand the speed range somewhat as well as add some of the cool control features that you have in your VFD setup. I have been studying your schematics carefully and I believe I finally understand what it is all about, however I have a couple of questions. I am basing these questions on what looks like your latest version with the joystick jog and the 2 way coolant switch (very cool).

Yes, many people ask for a 2 way joystick jog, and the coolant switch in some cases they want the ability to run the coolant continuously or just when the spindle lever is engaged. The Joystick jog is probably a holdover for threading without the proximity sensor, but probably not needed if using the P sensor.

1. I believe you are using the aux 24VDC power supply to power everything (relays, LEDs, proximity switch), while using the relays to switch the VFD's 24V power source for the fwd/rev/stop signals to the VFD. Very nice, this keeps all the signals to the VFD referenced to itself while minimizing the load on the VFD power.

The VFD WJ200 power supply can only supply 100mA, so you one is very limited as to what it can power. It cannot supply enough power for multiple relays, but the primary reason for using a separate power supply is that the the relays switch the VFD controls, not the switches. This means less wiring that is exposed to electrical noise and allows a combination of interlocks so that if a spindle switch failed closed, the control system would still stop the VFD when the spindle switch in in the stop position. On some system builds using 3 wire controls, one relay locks out the other direction relay, similar to contactors.The proximity sensor used is limited to 200mA, so one needs to be mindful of the total system draw. The coolant relay/contactor is powered separately otherwise you would exceed the P sensor mA rating with 3 relays on.

2. It looks like you are using the LED in the E-STOP switch as a power LED and that it goes on only when the fwd/rev lever is in stop position. Am I correct?

That is correct in the joystick jog version of the design, if only a forward jog button is used, it has a green light to indicate the machine is running, red when stopped, both lights out when there is a fault condition or the E-Stop is pressed.

3. What happens when you are not using the proximity switch? Could it accidentally shut off the machine? Might it be useful to put a switch on the panel that would disable the proximity switch when it is not in use?

The proximity sensor needs a sufficient mass to trigger it, I have never had it engage with swarf, etc. Since the engagement distance is 8 mm it is very unlikely that anything will trigger it. On my machine I have the ability to bypass it for machining purposes only, and I can tell you that you can easily forget that the sensor is bypassed and crash the lathe. This is why there is an additional limit switch that engages at about 2 mm from the stop face. If someone is not using it, the stop can be placed on a shelf or one can use a bypass plug that goes into the cable socket. In this way the micrometer and the cable are completely disconnected from the system.

4. The WJ200 documentation specify a speed control pot at 1k-2k ohms. Is there a reason you are using 5k ohms other than the availability of a 22mm 5k unit?

The WJ200 will work fine with a 5K pot, the main reason for this value is there are very few speed pots that will directly fit a 22mm hole, and the usual values is either 5 or 10K. I have seen some that are 1 and 2K, and they are very expensive. On a few installs where cost has been an issue, I have machined a 22 mm plug and mount a standard 2K pot in the center.

5. What are you using for a 24DVC to 12VDC converter?

Many auxiliary items require 12VDC, such as additional LED lights, Tachometers, etc. I also install adjustable step down converter if a specific voltage is needed. Some Tachs, like the MachTach specify 6-9VDC, unless you add a heat sink to the voltage regulator.

6. Do you know any source for small quantities of shielded VFD cable? Everywhere I look only sells full rolls.

No, not really. You can check Wolf Automation. But usually they have minimum quantities. I uses shielded motor cable on my systems, but for short lengths, you could get by with 600V unshielded cable. The cable needs to have 3 conductors plus a ground.

7. What are you using for terminal strips?

I use various terminal strips depending on the build. On the multiple relay systems I use 20 terminal block small DIN rail type, these are available through some of the Asian sellers, but they often arrive broken because of poor packaging. My newer builds still use terminal strips for certain connections, but the front panel control cable and proximity sensor all use sockets. This makes for easier and quicker installation with less chance of a wiring error. If you are building a system you should use wire labels and some color coding schema so you can verify your connections (see picture below).

Thank you for all the effort you put into this and sharing it with the community. When I started looking at this I had absolutely no knowledge of VFDs and now I feel confident that I can build a system that will meet all my needs. I have probably spent over 6 hours just following every wire in your designs so that I was sure that I understood exactly what it was doing. In order to save space in the control box, I will probably mount the aux 24VDC power supply in the VFD enclosure. I am trying to figure out how to avoid bringing 240VAC into the control box at all. Perhaps add contactor on the coolant pump and control it with the coolant relay in the control box. This would provide better separation of high and low voltage. I like your proximity switch set up. I may have to buy a mill just so I can make one like it!

There is no issue with bringing 240VAC into the control box, must control systems use a combination of low voltage like 24VAC and high voltage 240VAC. Since the coolant relay or contactor interfaces with the other relays, it should remain in the control box. If you are space limited, then you can move the power supply to the VFD enclosure. I usually provide 24VDC back to the VFD enclosure for a fan. Technically if you are running a 120/240VAC single phase coolant pump, you should have it fused or on a breaker that supplies power. If using a mini-contactor, I will wire in an overload relay to the output of the contactor. It is also possible to build the complete control system and fir it in the VFD enclosure. I am doing that currently for a Jet Lathe system. Most coolant systems are using a 24VDC solenoid with something log and air or drip system like a Fogbuster. The wiring to the coolant relay is setup so the relay output can easily be changed from 24VDC to either 120/240VAC single phase. On three phase builds, I always use a coolant contactor with a thermal overload relay and it is wired to a 3A 3pole breaker in the VFD enclosure. The thermal overload relay protects the motor, the breaker protects the wiring.

I do machine bolt on proximity sensor systems that you can attach to the micrometer, more recently I machine the stop and build the holder into the micrometer stop. Always tinkering.

Alan's system installed, the 240VAC comes in on the far right side. The coolant relay power wires can be switched to the N and L terminals for 240VAC. Adding a mini contactor and a thermal overload relay requires a different setup:

Bolt on and integrated P sensor holder assembly:

Wired with limit switch:

 

[jbolt]

You can buy shielded cable by the foot from Igus. McMaster also sells some by the foot or in small increments. I found the price from Igus to be reasonable.

Sent from my SAMSUNG-SM-G900A using Tapatalk