# PM-949TS VFD Full Build Control System with Auto Reverse and Back Gear Sensors



## mksj (Dec 14, 2017)

Normally I do not like to do full VFD build systems, they take way too much time and cost. But I was asked to do two full system builds one for a PM-949TS mill and an second for PM-1440GT lathe. I kinda of caved, figuring I hadn't done builds for either machine and I wanted to see what I could be be built for both. This is the a review of the PM-949TS mill build. First there was the wish list which grew over time, I started out with thinking I would build a basic control board build and then the auto reverse for threading would be nice, and also a back gear sensor to reverse the VFD inputs when engaged. I decided to build the full system as a plug and play because there were just too many variables in the build process that needed to be addressed. The other major challenge that was also requested by another PM-949TS owner was developing a low profile spindle tach system,  and I decided to also included a LED Halo light built into the tach sendor ring.

The Tach/Halo LED light needed to be have a very low profile magnetic NPN pickup, the one I chose is only and 1/8 thick by 0.30" wide. I turned a light ring assembly out of 4.25" aluminum stock, which slides up on the ram and extends below the ram about 1/4". The NPN pickup  sensor is fitted between this 1/4" and all the wiring brought out through the back of the ring. A small set screw holds the rings in place. I normally embed the a neodymium magnet into the aluminum spindle ring, but it did not work in this case. This NPN sensor has a very short sense range (like 0.050" or less), so I embedded the magnet on the outside of the ring with a very narrow gap between it and the sensor. I milled an outer ridge so the Halo LED snaps on, but also attached it with some silicone sealant to prevent oil contamination. Some pics as follows:



















The mill control system was a new ground up design as it was a total build, I did use some of the design and features that I incorporated into my knee mill. I use proximity sensors to detect the back gear, so forward is always forward, and a second proximity sensor which triggers an auto reverse for threading. On my mill this is triggered by the spindle stop adjustment ring, I also have an auto start function. In this build we decided to put the following controls in a knee mounted pod, stop, run, forward/reverse, auto reverse, and coolant (with indicator lights for each function). The E-Stop, tachometer and speed control are mounted in a enclosure mounted to the mill head. I used a precision 3 tun speed pot which gives very fine motor control which is set to operate from 20-120 Hz on the 4 pole motor wiring. I used heavy diecast aluminum enclosures, and also polished the unpainted mill head enclosure face. The main VFD enclosure, I decided to go with a larger 20x12x8 NEMA 4X/12 cabinet, so I would not need any vents or fans. It also includes a main power disconnect, VFD fusing, breaker for a dual gang 120V box, brake resistor, 120W 24VDC power supply with 12VDC step-down converter and control system. Everything fit nicely, although a lot of wiring. When completed it ended up working as designed, which made me happy. It was a 3 week build, plus development and sourcing parts. Needless to say I will not be building another one of these systems.

Building the VFD/system control board.








Mounting the electrical box and 120VAC sockets





Control Pods (including the smaller one which is for the 1440GT)













Programming the VFD and bench testing. The two proximity sensors are the small squares attached to the cables. All the control and motor cables are shielded, and a star ground is used on the back plate.





Next will be the 1440GT VFD system build, along with a basic VFD conversion for the PM-1440GT which uses the stock control board.


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## jeff_g1137 (Dec 15, 2017)

Hi
Nice one


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## Alan H. (Dec 15, 2017)

Mark, an interesting and very nice piece of work.  You need to open up a panel shop!  

Hopefully the lucky recipient of this build will post some photos and videos of it in operation.


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## davidpbest (Dec 17, 2017)

Wow - Mark, you outdid yourself yet again.    That ring light with sensor is really slick.   Great job.


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## zmotorsports (Dec 21, 2017)

Awesome work as always Mark.

Mike


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## uncle harry (Dec 21, 2017)

mksj said:


> Normally I do not like to do full VFD build systems, they take way too much time and cost. But I was asked to do two full system builds one for a PM-949TS mill and an second for PM-1440GT lathe. I kinda of caved, figuring I hadn't done builds for either machine and I wanted to see what I could be be built for both. This is the a review of the PM-949TS mill build. First there was the wish list which grew over time, I started out with thinking I would build a basic control board build and then the auto reverse for threading would be nice, and also a back gear sensor to reverse the VFD inputs when engaged. I decided to build the full system as a plug and play because there were just too many variables in the build process that needed to be addressed. The other major challenge that was also requested by another PM-949TS owner was developing a low profile spindle tach system,  and I decided to also included a LED Halo light built into the tach sendor ring.
> 
> The Tach/Halo LED light needed to be have a very low profile magnetic NPN pickup, the one I chose is only and 1/8 thick by 0.30" wide. I turned a light ring assembly out of 4.25" aluminum stock, which slides up on the ram and extends below the ram about 1/4". The NPN pickup  sensor is fitted between this 1/4" and all the wiring brought out through the back of the ring. A small set screw holds the rings in place. I normally embed the a neodymium magnet into the aluminum spindle ring, but it did not work in this case. This NPN sensor has a very short sense range (like 0.050" or less), so I embedded the magnet on the outside of the ring with a very narrow gap between it and the sensor. I milled an outer ridge so the Halo LED snaps on, but also attached it with some silicone sealant to prevent oil contamination. Some pics as follows:
> 
> ...




WOW .....super build.


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## Ramblerman68 (Jan 7, 2018)

Oh sure Mark, now that I've decided to get the same mill, you aren't gonna build any more?!!  Hahaha.  Awesome  work as always sir


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## Kamloopsendo (Mar 31, 2018)

mksj said:


> Normally I do not like to do full VFD build systems, they take way too much time and cost. But I was asked to do two full system builds one for a PM-949TS mill and an second for PM-1440GT lathe. I kinda of caved, figuring I hadn't done builds for either machine and I wanted to see what I could be be built for both. This is the a review of the PM-949TS mill build. First there was the wish list which grew over time, I started out with thinking I would build a basic control board build and then the auto reverse for threading would be nice, and also a back gear sensor to reverse the VFD inputs when engaged. I decided to build the full system as a plug and play because there were just too many variables in the build process that needed to be addressed. The other major challenge that was also requested by another PM-949TS owner was developing a low profile spindle tach system,  and I decided to also included a LED Halo light built into the tach sendor ring.
> 
> The Tach/Halo LED light needed to be have a very low profile magnetic NPN pickup, the one I chose is only and 1/8 thick by 0.30" wide. I turned a light ring assembly out of 4.25" aluminum stock, which slides up on the ram and extends below the ram about 1/4". The NPN pickup  sensor is fitted between this 1/4" and all the wiring brought out through the back of the ring. A small set screw holds the rings in place. I normally embed the a neodymium magnet into the aluminum spindle ring, but it did not work in this case. This NPN sensor has a very short sense range (like 0.050" or less), so I embedded the magnet on the outside of the ring with a very narrow gap between it and the sensor. I milled an outer ridge so the Halo LED snaps on, but also attached it with some silicone sealant to prevent oil contamination. Some pics as follows:
> 
> ...


Chevy mentioned that you had built his tach and light ring so Iwent looking for this thread.  VERY nice work once again.  
Alex


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## davidpbest (Mar 31, 2018)

I completely agree.  Mark Jacobs does meticulous work.


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## mksj (Mar 31, 2018)

Thanks Alex and David, I think David has me beat by a mile when it comes to meticulous work. The challenge on installing a tach on machines with a back gear is that the speed sensor needs to be attached to the spindle in order to get the correct RPM. Factory VFD systems with RPM tachs take the VFD  analogue output (0-10V) and use a scalable voltmeter to display a calculated RPM, and use a back gear sensor to change the scaling range.


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## Kamloopsendo (Aug 21, 2018)

Mark:  I'm interested in using a proximity sensor off the back gear lever (high/low) so that forward is always forward and reverse is always reverse.  I'm assuming you mounted the sensor to identify lever position so as to know when the back gear was engaged.  Don't think I'm up to worrying about an auto reverse set up at this point.  I've yet to build the control panel but do have the power supply enclosure completed and did go with 15 amp breakers as per your suggestion for the 12 and 24V supply.   I also wondered about the choice of an NPN sensor rather than PNP - was this simply availability/size issue?
Thanks again Mark
Alex


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## Rickwjenn (Aug 21, 2018)

Excellent information and super professional work.  Thanks for sharing.


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## mksj (Aug 24, 2018)

Alex,

I use PNP proximity sensors because all my systems use logic diodes which require source (PNP) wiring configuration. Most proximity sensors come in PNP and NPN configurations, but there are other factors such as NC and NO contacts and shielded vs. non shielded. They typically have a maximum switching current of 200-300mA, there is also some voltage drop (around 1V).  The type and configuration is specific to the application and how it is wired into the system. On the back gear one could use a simple momentary switch which would reverse the VFD forward/reverse inputs when the back gear is engaged. 

You had a previous question on the location of the mill controls, I find having them in a pod at the front of the mill makes them much more user friendly, the stop starts are momentary. Direction can also be switched while running by just flipping the direction switch. On a more recent mill build I added an addition set of momentary for/rev buttons so for tapping in/out. These systems use 2 wire control with latching relays as opposed to 3 wire control, this is adapted to the design of the systems I build. I do put the E stop and speed controls along with the RPM display on the head.
Mark


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## Kamloopsendo (Aug 25, 2018)

Mark: Thanks for getting back to me, I had asked about the NPN because you indicated you'd used an NPN unit as the tach sensor earlier in this thread - I'm assuming now that was a typo.  I have a basic wiring diagram that I believe I got from David in Langley a 3 wire mill control set up that I think originated with you.  I'm having some trouble trying to understand how it works.  I've attached a pic of the diagram and would really appreciate if you'd take the time to clarify this for me.






 The way I read this the power (source wired is the term I believe?) is from P24 and what I don't understand is when the 3 position switch is in the neutral (Off) position there should be no power to the momentary RUN SW and thus no signal to the logic terminal on the VFD (terminal 1 on the logic inputs).  In either of the "ON" positions for this 3 position switch there is power for the signal (I presume thru the diode when in the R position).  
As you I'm sure are aware my understanding of this stuff is pretty basic so suspect I'm simply missing something and I'd really like to understand what's happening here.
Thanks again.
Alex


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## Kamloopsendo (Aug 25, 2018)

Mark:  I also 'ment to ask why you chose to place the emerg stop switch up high beside the head rather than on the box off the knee.  I'm short so would kind of like it REAL easy to reach - is there a problem with this?
Alex


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## mksj (Aug 25, 2018)

Different sensors are used depending on the application, the tachometer is independent of my control system, they usually come with an NPN NO induction sensor which is triggered by a magnet. They are also sensitive to the polarity of the magnet, so you need to check that you have a N-S orientation to the sensor. This can be checked by powering up the tach/NPN sensor and running the magnet across the sensor, in the correct orientation the red LED in the sensor should flash when the magnet runs in front of the sensor. The sensors I use for back gear and auto-reverse are PNP NO shielded proximity sensors which sense metallic objects, there are many different types and sensing ranges. I am using them as a non-contact switch, in the case of the auto-reverse it is a small square shielded sensor with a 3mm sense range. This triggers a relay which reverse the F/R VFD inputs using 2 wire control.

On the schematic I have several versions, so send me your current email via PM and I will send you updated schematics and parameters. The one you have is based on 3 wire control of the WJ200 VFD but are dated. As wired with P24, the VFD 24VDC input power supply is powering the LED indicator lights in the switch, so no external power supply is needed. A 3 way switch is used for the direction with the center being off. This is fairly typical of the way most mills work. When you use VFD input 4 programmed for USP unattended start protection, the direction switch must be in the stop position when the machine is powered up otherwise the run command will not work. Cycling the switch through the stop position once powered also does the same thing. If you use the schematic without input 4 then you can use a 2 way F/R switch. Typically most mills with VFDs also have a separate safety start button that will only power up a latching run relay/contactor when the run direction switch is in the stop position.

The diode in the schematic is such that there is both a sustained reverse command and also powers the run/stop inputs. The diode band end is connected to the F switch block. The purpose of the diode is to prevent back feed when the switch is in the F position. An alternative would be to use an extra switch block on the switch, but then it would require a bigger control box because of the stack height of two switch blocks needed for reverse and run command.

There may be a bit of confusion as to the E-Stop, you already have a Stop button on the control pod, I use a unguarded momentary red button for the stop and a guarded green momentary button for run. So in a panic stop you just bang on the red momentary stop button, the E-Stop on the head is redundancy for the stop function, but is in addition a locking off out button for the VFD run controls. This is typically a push, and twist to release type E-Stop. On my mill it came with a digital head which had the F-S-R switch already in the head, on my builds I put that switch in the lower control pod. My mill is an amalgam of the stock VFD system fused with a new control system and I have automatic reverse and auto start based on sensors on the head, in addition to the back gear. 

I do find having the run buttons as momentary and down at around the table height, that you will more often turn the motor on/off frequently when doing operations then leaving it running with the typical controls on the head. With the typical non-VFD switch is is very clunky to constantly turn the switch ON/OFF/Reverse, this can lead to being more careless and safety issues if one is not careful.

Lower control pod on my mill.




Upper control pod on my mill.





Stop, Run, F/R, Auto Reverse, Coolant. The enclosure is only deep enough for a single set of switch blocks.


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## Kamloopsendo (Aug 26, 2018)

Mark:  Thanks for the explanation.  I misunderstood how that system worked not realizing that the momentary Stop and Start switches are THE start stop switches and that the forward reverse switch was for direction only.  Seems obvious now and can't fathom why I read it the way I did, just learning I guess.  I do like the idea of a separate stop/emerg stop switch, so will likely wire that into the panel on the mill head as you and Chevy have. 
Thanks again for taking the time
Alex


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## scott55 (Nov 25, 2019)

Any chance of getting the settings file for the Hitachi VFD?
I have been running my 949 on a Fuji VFD which just failed on me and I just ordered the Hitachi.
A head start on the setup parameters would be very welcome.


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## mksj (Nov 25, 2019)

The parameters will vary depending if you are using 2 wire or 3 wire control and how everything is wired. I typically prefer 3 wire control as opposed to 2 wire for safety reasons  unless you are using a latching relay design. I recently did a build for a PM-935 which would be essentially the same as yours. I ended up using a 2 way switch for forward/reverse so one can flip the rotation switch for threading without stopping. The way that these switches work on the 2 way is such that you need a NC switch block and a NO switch block (3 way is two NO). This also has a back gear switch which is a limit switch that is mounted so it is engaged in back gear. This keeps the spindle rotation always the same when switching to back gear. I added a tach and light ring to the spindle, we are still working out some details of the system. The 1 and 2 switch is for different braking speeds, 1 is ~ 1 second, 2 is ~3 seconds, if you hit the E-Stop it reverts to 1 second. A 1 second deceleration time may be used for threading. I use a single shielded cable between the control head and the VFD cabinet. The system was just installed, and we are working out a few details, so this is a starting point.

One thing I forgot to mention as to the differences between the 935 and 949, the latter uses a 2 speed constant Hp motor which runs at 4P (~1750) and 2 P (~3500), the motor needs to be wired as 4 pole and the upper max speed is set to 120 Hz which will give you the same top speed as the 2P setting. You will get much better torque with 4P and the motor has constant Hp from 60-120Hz. I have a parameter file for an older 949 build, I ill need to dig through my files to find it.
PM-949 4P motor connections


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