# Odd behavior in "MX-210V" forward/reverse/power switches



## Tomzo (Nov 2, 2021)

I know, I know - I bought a cheap Chinese lathe, but I am not dissatisfied with the machine overall.  I am still tuning things up (when I get time) and I expect to have it performing as well as it can pretty soon.  This model has a 1100W brushless DC motor and controller on it.

One thing that is odd is related to the power switch and the forward reverse switch.   When I power the unit up it comes on and the RPM display and speed pot work fine.   If I hit the red button, the display stays on for about 5 or 6 seconds, then flickers with a "tick, tick, tick" sound coming from the controller board.   It then shuts off, but the fact that it does this kind of bothers me.

If I have the late on and in the forward position, if I turn the speed down to zero and then switch into reverse it does the same thing as if I had turned if off with the on/off switch.   This is annoying as I am fitting an electronic leadscrew to the machine and it has no thread dial (metric leadscrew) and I will be running the leadscrew backwards to move the carriage back without disengaging the half nut.

The direction switch is one of these:  https://www.aliexpress.com/item/33006912928.html

The power switch is one of these:  https://www.ebay.com/itm/3332428042...z%2BbRFYoKNdGbsICbnc|ampid:PL_CLK|clp:2047675

Assuming the color conventions from the main power inlet to the lathe are correct, the common goes to the rotary switch as well as to the main power switch.   Three leads from the direction switch go to the motor controller board and are plugged in there.   On the power switch, two of the pins are jumpered together.

I have a couple of questions:

-  Is the whole lathe supposed to lose power when in the "0" position in the forward reverse switch?   I thought that would just kill power to the motor but leave the rest of the system functioning.   I suppose if it just turned off instantly without the delay, ticking sound, and flashing display it might not be an issue, but I would rather not have to open up the little cover and hit the green button every time.
-  It seems to me that there is some power discharging somewhere that keeps the display alive for a while - I presume one of the capacitors on the main board.   There are two large and a number of smaller ones on there.   I noticed that there is a ground wire from the main power that gets sandwiched between the back cover and the main body from one of the panel screws.   Both surfaces were painted so I scraped off all the paint thinking that there was no ground to dissipate the cap - no change.  My electronics experience is pretty weak so this was just an idea I had for something to try.
-  There are no identification markings on this controller board and it has a number of unused connections on it so I am pretty sure this was some excess controller they had laying around so they plopped it into this frankenlathe - the paint color varies in some of the components so I know it was cobbled together from the parts bin.   I have half a mind to find a BLDC motor controller and just replace all of this stuff, but would like to see if there is some reasonable fix first.

Anyway, thanks in advance for any information any of you might be willing to share with a newbie machinist.

Tom


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## Tomzo (Nov 2, 2021)

After reading my post I figured more information is needed.   The jumpered connections on the on/off/estop switch are the A1-14 terminals which, if my understanding is correct, is used to hold the contactor in when the green button is depressed - otherwise it is a momentary switch.   

I looked a bit more closely at the board with the back panel off and found that it is (unsurprisingly) a relay that is clicking.   There is an LED on the board that after power is cut stays full brightness and then flickers and dims with the relay.    There is another LED on the board that stays lit for a long time (I waited about 5 minutes) - even with the entire lathe unplugged.

I think this tells me that the power is coming from the capacitors.  My understanding is that most circuits have some sort of bleeder resistor to drain down the caps.   If only this no-name board had some identifying information on it so I could get a circuit diagram....


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## markba633csi (Nov 2, 2021)

I suspect that rather than a malfunction, the controller board may be mis-adjusted.  What I would try is first putting a mark on each trimpot on the board then one at a time readjusting the pots and watching the effect of each.  You can always return to the original settings
It sounds like the behavior you are seeing is some sort of safety feature, either for you, the motor, or the electronics but perhaps working too well?
Does the spindle stop instantly when you hit the red stop button or is there a delay and relay ticking?  I would put more importance on how the spindle motor behaves rather than the rpm display
-Mark
It would be a simple affair to add a bleeder resistor across the main supply cap(s)- post some closeups of the board


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## KevinM (Nov 2, 2021)

Tomzo said:


> I know, I know - I bought a cheap Chinese lathe, but I am not dissatisfied with the machine overall.  I am still tuning things up (when I get time) and I expect to have it performing as well as it can pretty soon.  This model has a 1100W brushless DC motor and controller on it.
> 
> One thing that is odd is related to the power switch and the forward reverse switch.   When I power the unit up it comes on and the RPM display and speed pot work fine.   If I hit the red button, the display stays on for about 5 or 6 seconds, then flickers with a "tick, tick, tick" sound coming from the controller board.   It then shuts off, but the fact that it does this kind of bothers me.
> 
> ...


My lathe looks similar to yours.  When I received my PM1022 I thought that certainly it was not working correctly.  Stopping the machine would completely shut it down.  When turning on the machine it would not start until moving the speed dial to minimum. That is a pain due to having to reset the speed at every start.  Shutting off the power switch would stop the lathe but if the speed was set to minimum it would still be powered for about 8 rotations before shutting down completely (I believe that the capacitors are responsible for this). Not exactly ideal when threading to a shoulder. Moving the F-O-R switch to O would stop the lathe quickly and turn the machine completely off. I called PM and they said that it was normal.  I have gotten used to the unusual setup but may someday dig in and see if I can make it behave as I want.  I hope you find a solution.  It really sucks for CNC.


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## Tomzo (Nov 2, 2021)

Mark - I searched the board and there are no trim pots on there - likely due to the BLDC design.   I did take it out completely and found what appeared to be a part number (EP-SM9088-C) but this returns no hits on Google.  I have not powered it down while turning to see if it stops immediately but will try that - once I get it put back together.

Kevin - at least that is one bit of information that says this is "normal" for this class lathe - SMH.   

The lathe works and all, but these little glitchy things bug me quite a bit.   It really makes me want to build or buy a new controller setup if nothing else so I will know what I have.  I have seen BLDC controllers for e-bikes and the like that look interesting to me but I am not sure if something like that would adapt to this application.  I have a buddy who is an EE and will be pinging him shortly.

Thanks

Tom


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## markba633csi (Nov 2, 2021)

I'm sure you could sub a different controller- BLDC motors are really just 3 phase ac motors with a permanent magnet rotor, but your system may use a speed encoder on the motor shaft which talks to the controller
If you think bleeding down the power supply would help I could give you a hand there- need to identify the main storage caps, and read the capacitance value in microfarads (uF) to select a suitable bleed resistor
Use care


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## Tomzo (Nov 2, 2021)

Thanks Kevin - much appreciated.   The lag time in the control system turning off is annoying but I can probably live with it.   I do want to figure out how I can get the direction switch not to kill all power when it gets to the 0 setting.   It may cost me a round of golf but I think I will have my EE friend take a peek before I start really digging in to the controller.   Also, if I do start soldering stuff on there I want to identify a source for a BLDC controller so I know I have a fallback before I turn this lathe into a very heavy brick....


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## Tomzo (Nov 2, 2021)

Since a BLDC motor operates like a three phase motor, I was wondering if I can run it off a 120V VFD - something like this:



			https://www.amazon.com/Variable-Frequency-Inverter-Converter-HUANYANG/dp/B0775QGLVJ/ref=sr_1_5?dchild=1&keywords=120V%2BVFD&qid=1635906592&qsid=147-4069641-6391201&sr=8-5&sres=B0775QGLVJ%2CB0899T3QQ4%2CB00UCGM8A2%2CB07RT898TW%2CB00LODGP2E%2CB01DKJWM62%2CB01EJ38RDA%2CB01AOCLIEU%2CB07CJXQWVT%2CB0972MCVV5%2CB073TVHH5H%2CB092YZS5R3%2CB07JMK63LP%2CB08KCSX85J%2CB0775BKKNJ%2CB07ZT12CY9%2CB07H4FNLR3%2CB077KY3W2P%2CB08PKP1493%2CB087JBGHXG&th=1
		


The price is right for sure and my guess is that it is probably built better than the no name controller that came with the lathe.


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## RJSakowski (Nov 2, 2021)

Is your lathe still configured  as the OEM lathe or has there been some modifications.  The type of switch illustrated in your first link comes in many different configurations.  

I used one with my sdc brush motor but I have mine wired between the controller output and the motor so that I reverse the leads going to the motor or break the circuit for FWD/REV and OFF.  I use the red eStop button for the main power switch.  I only shut it off when I am done machining as it kills the power to the controller.  I have the Clough42 ELS but it is on a separate power supply and I generally don't shut it down.


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## Tomzo (Nov 2, 2021)

Well if by OEM you mean it is wired the way it came from the manufacturer then yes it is. I am thinking that since the neutral basically gets cut off when the direction switch is on 0, I am thinking that the "latch" on the main power switch releases and kills all power. Since the off switch and estop should cut the hot wire I wonder if I wire the neutral to the main switch directly from the power source in addition to the selector switch. If my theory is correct this would keep the controller "live" without affecting the circuit that tells the motor which way to turn.

Sound plausible?


Sent from my iPhone using Tapatalk


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## markba633csi (Nov 3, 2021)

There may be a reason the factory did that, but I don't know what it could be.  You obviously don't want to smoke the controller finding out
It may be that they want to be sure the motor comes to a full stop before changing direction to prevent damaging the motor driver output stage
-M


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## Tomzo (Nov 3, 2021)

Yeah - that is always the concern.   The way I see it the neutral goes to the controller from the same location either way - from the on/off switch.   Routing it through the selector switch - when the 0 position is off - just adds another on/off switch.   The selector sends the neutral to the board to tell it which way to turn either way and the board should not "know" that the neutral goes to the main power switch with my proposed "solution".  I will mull this one over a bit more.


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## markba633csi (Nov 3, 2021)

My point being if the motor is coasting to a stop and you slam it into reverse with power applied is that going to break anything? 
Maybe that's what the factory was trying to avoid.  With the machinery coming in from overseas, it's often hard to tell between a malfunction or a feature.
Anyhow, a bldc motor and a 3 phase motor are different enough that a vfd might have difficulty with the former even if there's no rotary encoder providing feedback.  Make sure you can return any vfd you buy if it doesn't work out with your motor


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## Tomzo (Nov 3, 2021)

Good point! I suppose that under the current setup if I were to (stupidly) rotate from forward through off to reverse while it is still spinning as soon as the switch goes to reverse it will do about the same thing I would think. The controller gets the reverse signal either way - it just is running on the capacitors in between direction signals now but with the change it would just stay on.


Sent from my iPhone using Tapatalk


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## Tomzo (Nov 8, 2021)

I did some additional sleuthing on how this switch is wired up and found some details on a listing on Ali-Express.   In the diagram below the common wire is wired to positions 9-10.   This switch is independent of the three wires that send signal to the motor controller for direction and serves, apparently, just to cut the common when it is at the 0 position.   It would seem to me that simply bypassing this extra switch by taking the wires out and connecting them with a simple wire nut would prevent the controller from powering down when the direction is changed.   the safety cutoff switch and on/off buttons would still work as normal.   Of course, slamming the switch from forward to reverse with the lathe running would be a bad idea, but that is a bad idea either way IMHO.


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## Tomzo (Nov 20, 2021)

Update - I finally got time to take the panel off and rewire the common to bypass the switch and it worked perfectly.   Now to complete my other projects on this lathe : rebuild of tailstock, removal of compound in favor of a solid block, backplate for 4 jaw chuck, and finishing the Cough42 ELS.


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## gregreid (Jul 30, 2022)

Hey Tomzo, I wanted to say a sincere THANK YOU for researching and posting this.  I also own an MX-120V with the same aggravating "power off everything" behavior when switching spindle directions, and also implemented a Clough42 ELS, so the powering off between cycles of ELS thread cutting was SUPER annoying.  

I'd pulled my switch out of my lathe to find its part number and was Google searching for its wiring sheet so that I could disable that power-off "safety" ... when I happened across this thread in the Hobby Machinist, which solved the problem.  Simply disconnecting the red and orange wires from posts 9 and 10 and connecting them together in a wire nut keeps the power on through direction changes.  (Of course, we now need to be diligent to ensure that the spindle is completely stopped between directon changes, but that's simple enough.)

After finding this thread, I registered on this Hobby Machinist forum just so that I could say THANKS to you. (It took overnight to be approved.)  And now that I'm here, it seems like a great resource for other things too, and I'm sure I'll stick around.  

I was about to post a link to my own thread in the ELS "Issues" section in Clough42's GitHub, but remembered that the Hobby Machinist acceptance requires that I make at least three appends before linking anything.  Anyway, I'm sure you can find my issue #224 thread there.  And in it, you'll find a link to a video that I posted to show my ELS setup to introduce the problem.  (I also show pics of the before and after switch mod.)  I'm sure you must've completed your own MX-210V ELS setup by now, but if not, you might be interested in seeing my implementation.  And of course I'd be happy to share the 3D printed designs with you (encoder bracket, ELS display mount, gears) if they'd help.


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## gregreid (Jul 30, 2022)

As to your other ongoing projects (which I'm sure you also must've finished by now):

rebuild of tailstock: I'd be interested in some detail about what you're doing there.  My tailstock is about 2mm too tall and I see no way to adjust it lower ... other than milling down its base, and I don't yet own a mini-mill.


removal of compound in favor of a solid block: I recently did this myself and can confirm that it improves rigidity, especially noticeable when cutting threads.  I made sure that my block is exactly the same height as the deleted compound so that I can easily swap them back and forth without having to readjust quick-change tool heights.  It bolts into the existing compound attachment rotating plate (which I found you MUST do in order to keep that plate "up" so that it doesn't interfere with the cross-slide travel) as well as two other bolts threaded into the cross-slide so that it's very solid. 


backplate for 4 jaw chuck: I recently bought an independent 4-jaw chuck with the proper 95mm register for the original lathe back plate.  The only issue is that the 4-jaw chuck mounts with four rather than three bolts.  Rather than build a new back-pate, I plan on drilling and tapping 3 new holes in the original back plate, which I think will be easier to do and easier when changing chucks.  And BTW, I also bought an ER-32 collet chuck that mounts directly to that same backplate.  It's what I'm using most often now.


finishing the Cough42 ELS: I've finished mine ... with the final touch of disabling the "safety off" between spindle direction changes, thanks to you.
Greg

P.S. I also added a 3-axis DRO, which works great.


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## Tomzo (Jul 30, 2022)

Thanks Greg - I am glad you found the info useful.  I got diverted to doing some projects on a used RF-30 clone mill that I got, so I did not update the things I have done on the MX-210V.  I did complete the ELS project and that system is awesome.  I made a solid block (aluminum for now) to replace the compound and it does make things more rigid.   I have not tackled the entirety of the tailstock's issues as there are a few, but I have been able to get it adjusted so that I am not turning too bad a taper.   It is not perfect by any means.   I also got a 4 jaw chuck with the right register and did as you suggested - drilled and tapped holes to fit the existing backplate.  I also ordered an ER32 collet chuck from Ali Express (my first purchase from that site) and while it fits, I am still fiddling with it trying to get it to run true.  Whether it every will or not is anyone's guess.   I have been moving both of my kids over the last few weeks and have been slammed, so I have not had much time.

I would be interested in the DRO you used on the lathe - what did you go with?


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## gregreid (Jul 30, 2022)

FWIW, here's the ER32 collet chuck I bought.  It fit perfectly and runs true ... but it cost almost as much having it shipped here (Florida) as the collet itself.  https://www.ebay.com/itm/304319402090

And here's the DRO kit that I purchased: https://www.ebay.com/itm/384487676170   I had to shorten one of the scales (for the Z-axis used on the tailstock for drilling depth), which was easy enough to do.  I'll take some pics to share with you shortly.  But I'll note right now that it's not a perfect setup:

Due to the location of the Y-scale on the left-hand side of my cross-slide, it can interfere with the chuck if the chuck jaws are opened significantly (the end of the opened jaws would crash into the scale mount!).  No big deal for MY needs, as I'm usually making small parts in the ER32 collet.  If I need big parts in the 3- or 4-jaw chuck and need to get up close to the chuck face, I can add the compound again to give me the additional 1.5 inch reach to the chuck face without interference of my Y-scale mount.  So it's a bit fiddly, but there's really nowhere else better to mount the Y-axis scale on the cross-slide.  If you were to mount it on the right, it'd block the gib screws and you'd lose X range to the tailstock.  And...


You lose the ability to mount a follow rest there.  I never found the need for a follow rest anyway.
The X-axis is the easiest, mounted on the rear.  And my Y-axis (cross-slide) mount serves double purpose in also holding the X-axis scale slider/reader.  I didn't put a scale on the compound, as I was planning on deleting the compound anyway.  Instead, my 3rd DRO axis (Z) is on the tailstock for drilling depth.  This was the trickiest to mount, but I think I came up with a reasonable solution, as you'll see in the pics once I take them. OTOH, I've only used it once and could easily live without it.  I was just looking for an excuse to use that 3rd DRO axis somehow.

Greg


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## gregreid (Jul 30, 2022)

Back home from a trip out, I went into the garage and shot a one-take poor-quality unrehearsed video of my DRO setup: https://photos.app.goo.gl/8KNkeqqKyxiSiQjH7    I hope you can get the gist of it from this; feel free to ask any questions.


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## Tomzo (Jul 31, 2022)

Very nicely done!  I have TouchDRO on my mill, so when I get around to this project I will probably use the same tablet for the lathe.


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## gregreid (Aug 1, 2022)

Tomzo, you motivated me to tear down and rebuild my MX-210V tailstock -- and I'm glad I did.  Here's a list of things found and fixed:

The lubricant (if you can call it that!) in the tailstock spindle was horrible.  A heavy smelly sticky dark brown substance more resembling moldy molasses than grease.  It took a lot of work and acetone to clean it out, and then I lubed it with some moly. 
The steel "flange" that the side-to-side adjustment setscrews push into was actually two pieces of crap metal held together by a 5mm cap screw.  I welded the two pieces together, filled in the gaps, then belt-sanded smooth square faces.
The above 5mm screw as just barely long enough, and threaded into the aluminum base, which showed signed of thread wear.  I drilled it and tapped it (and the metal "flange") to accept a 6mm cap screw instead, of proper/longer length, and used red locktite when reassembling.
There's also a 5mm clamping cap screw towards the front bottom that rides in a slot to allow some pivoting motion.  I also drilled and tapped it to 6mm as well for extra security.
One of the side-to-side adjustment setscrews was a proper 1-ish inches long, while the other was only a 1/2-inch long.  I replaced them both with longer 6mm cap screws that make the adjustment much easier to do.
I put a good hard washer under the tailstock spindle lock, which makes it easier to get tight clamping.
I mentioned earlier that my tailstock centerpoint was about 2mm higher than the center point of the spindle.  I corrected this by carefully filing down the front of the tailstock main body ever so slightly and also adding a .012 shim to the rear when reassembling the body to the base.  The top of the tailstock spindle is now properly parallel with the ways, and the centerline is now the proper height.
And, not related to the original tailstock but to my DRO addition, I cut/ground down the bracket that I mentioned in my earlier DRO video so that the tool post can no longer interfere with the bracket at full extension.  I can now reach a choked-up tool to the point of a dead center.  I also trimmed the top of the aluminum scale mounting bracket a tad so that there's more clearance with the spindle lock handle.  
Finally, I took my time with a tailstock alignment bar to get things aligned very closely, and then followed up by cutting down my own 3/4-inch bar at both ends to the same DRO diameter indication, a bit at a time, to get them within .005 of each other over a 12-inch span.  It took a lot of fiddling and very gentle tapping of the tailstock at the end, but I'm very happy with the result.  Then I tightened everything up and re-checked that all is still aligned nicely.  All's good.


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## Tomzo (Aug 1, 2022)

Most impressive!   That 5mm grub screw in the slot on the bottom is lousy - I may follow your lead there.  Five thousandths over 12 inches is pretty darn good for this class of lathe!

Question:   How much work did you put into leveling out the ways?   That can introduce taper as well, correct?


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## gregreid (Aug 1, 2022)

Tomzo said:


> Question: How much work did you put into leveling out the ways? That can introduce taper as well, correct?


Not much, to be honest.  The garage cabinets underneath my bench (https://www.homedepot.com/p/Husky-H...n-W-x-32-in-H-x-21-5-in-D-HTC100007/306903547 ) are heavy steel with adjustable feet, and I took a good long while when installing them, a year or so ago, to get them very level in all directions, bolted to each other and bolted to the wall and then re-adjusted a tad more.  The bench top is a solid 1.5" thick (3/4" oak on top of the 3/4" oak tops that came with the cabinets) with plenty of screws fastened into the cabinets and with a heavy "back splash" tapcon'ed to the block wall and bolted to the cabinets.  It's super rigid, flat and square. 

But I did nothing special with the lathe installation/leveling.  It's bolted to the bench on both ends with as big of a bolt as would fit into the supplied lathe mounting holes (I think 5/8-inch but may be wrong).  As you know, on this MX-210V lathe there are only the two mounting bolts, and the ways sit on a sturdy column rather than having four separate feet, so I think that there's less chance of introducing (or fixing) twist with this setup.

I did purchase a precision level ( https://www.ebay.com/itm/303797138722 ) while waiting for my lathe delivery, and used it to check that the amount of deviation from perfectly horizontal shows the same at the chuck and tailstock end, so I didn't have to do any shimming.  Just lucky with that, I guess.


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