New PM-940V

I think you are right Mark, although the fan does not show up on the wiring diagram. Below are pictures of the motor, motor plate and the 2nd connection.

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I have finally figured out the wiring diagram, however there is one component I don't understand. There is are 2 devices called "H3Y" that seem to be a time delay relays that are in the FWD/REV circuits and seem to add about a .5 second delay in the FWD and REV connections to the VFD. I'm not sure why these are needed. Maybe someone has seen this before and know why they are needed. The wiring diagram is below. The components in question at KT1 and KT2. For some reason they are installed in different locations on the FWD and REV circuits but look like they have the same effect. This is the diagram that comes with the machine from China, not a PM updated diagram.
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On another note, I am moving along with the disassembly. I haven't decided whether I will repaint it or not. After I get it all cleaned up I'll make that decision. It shouldn't be too hard as there are only about 7 parts. The hardest thing to take off is the box with all the electronics. This requires removing the panel where everything is mounted to get to the screws. I'm not sure this can be done without disconnecting wires inside the box and I don't really want to do that unless I decide to remove it all and control everything via the Acorn board.
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Single phase 240VAC fan blower motor. Motor nameplate I assume is the for the fan. I have to say that the paint job on these machines is pretty bad, but I guess at the end of the day it isn't going to matter. On the control cabinet, you may end-up not using the control relays if directly interfaced with the CNC control system to the VFD, but if that is later then you may want to get it all up and running and then take that step. Meed to be careful with electrical noise issues and wiring. Looks like you are moving along.
 
Nameplate says 3 phase and you are right about the paint job. I'll probably keep the existing controls for now in order to get it up quicker. If I go the other way I can get rid of everything in the cabinet except the VFD. That would give me plenty of room for the motor power supply and Acorn board. As it is now, I will need to put the motor power supply somewhere else. Any idea why they have the time delay relays in the FWD/REV inputs to the VFD? At some point I will power up the VFD and look at the programming.
 
The schematic does not give any description of the components, just seems like a number of interlocks. If there is a particular component then maybe post a photo of it. The schematics are also quite lacking as well as the part descriptions. Only figured mine out by tracing everything. My mill has a main power relay, it cannot be energized if the for/rev switch is not in the stop position. Most VFD's will not run if say the for/rev input are both activated, but I still use 2-3 levels of interlocks in case a switch fails closed. The motor cooling fan looks to be single phase 240VAC, runs off of the R and S terminals and there is a start/run capacitor.

Just read you comment on the time delays of 0.5 seconds, not sure what that is about. A VFD will ramp down and then reverse if given an opposite run command.
 
It took me awhile to understand the wiring diagram but it ended up making sense. There is a main contactor that is energized by the power button that provides power to the VFD and to the other relays. The FWD/REV buttons energize relays that latch and lock out the opposite direction, pretty standard interlock. There is a stop button that de-energizes both direction relays, also straight forward. What I don't understand is the need for time delay relays. These are part number H3Y-ST6P which can be googled. There are in series with the FWD and REV inputs to the VFD and are set for about .5 seconds. As I think about it, they may be to provide a slight delay in the directional input to the VFD to ensure that the relay for the opposite direction has had time to open. If one were to push the opposite direction button while the spindle was running, it could send signals to both inputs of the VFD if the relays were a little slow to open. Actually kind of elegant.
 
With a relay interlock, one relay has to completely release to provide power to the other relay (break before make). It may be the timers have something to do with the motor blower. Most VFD's have a hierarchy as to input controls and which override other controls, if F/R are both active the VFD would not run until one went open, not aware that it would generate a fault condition. There is an issue with relays in that as the coil snaps open that it generates a significant voltage spike that can feed back into the control system wiring, typically these are dealt with an AC snubber network or reverse diode for DC. On a 24VDC control systems I use, the spikes can be in the order of 160VDC, which can damage other electronics shared with the same power supply. So if you used the same 24VDC to trigger the VFD inputs they could be damaged. I use reverse diodes to prevent this and also if someone connects the power supply backwards, the diode will present as a dead short and prevent damage to the other components. This is a common practice, but the diode needs to be sized so it will not be damaged if this was to occur and also handle the peak spike voltages. Possibly the relay delays have something to do with the voltage spikes and the relay release, don't know.
 
Hi Mark, The time delays are not in the motor blower circuit. They simply seem to add .5 second delay in energizing the FWD and REV inputs to the VFD. On the diagram above, they are labeled KT1 and KT2. You might be right about the relay release, this would allow time for any transient to dissipate before connecting to the VFD inputs. On the reverse side, the delay contact is directly in series with the REV relay contact in the VFD input. Since both relays are energized at the same time, the timer contact closes slightly after the other contact, adding a little delay. On the FWD side the delay contact is in series with the power to the FWD relay so it adds a little delay to the closure of the FWD contact. Same effect, but odd that they would do it differently. I guess it works so I won't worry about it so this is just curiosity as to why they did this. I expect at some point I will remove everything but the power button and the main contactor and do it all through CNC control of the VFD.
 
I have gotten my new mill pretty much taken apart in preparation for the CNC conversion.

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I think I will strip and repaint it since it is apart. It has surprisingly little painted surface, probably less than 15 sq. ft. The head will be a little tricky to paint as I really don't want to take it all apart, so we'll see how that goes. I am having a little issue with removing the Z axis lead screw. It has an odd nut on the bottom that looks somewhat like this:
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I'm not sure what to use to remove it as I have to get at it from the bottom of the column.

I haven't decided what paint to use on it. I'll probably wait until I get it striped to see how it looks, probably some kind of epoxy or polyurethane.

I think I will use the existing spindle motor controls for now and use the CNC system for the axes, then in the future convert those to use the CNC for control. I plan to build out a new control box with everything for the CNC except for the VFD. Initially I will need both boxes hooked up, but when I am ready, I will put a VFD in the new box and I will be able to remove the old control box completely. I received my Clearpath servos so I have almost everything I need, just waiting on the CNC conversion kit for ArizonaCNC.

Lots of fun so far.
 
This thread might be useful to you in paint choice.

That nut would perplex me as well. Can you get into there with a brass drift and hammer on the notches?

I'm toying with what direction to head with my own CNC mill build. I've considered everything from a simple conversion of the 833 or 940, to epoxy-granite stiffening of the same mills, to a ground up granite slab or molded E-G build. I was about to pull the trigger on the same 940 you have, but the "mainland China" paranoia kept me from it. Even Matt at PM cautioned "the 940-V is not up to the standards of the Taiwanese machines" I am accustomed to. I must admit, by the time I get done, I'd basically be after a set of castings with hardened and ground ways, and if the spindle needs rebuilding to gt better speed/performance, that can't be that difficult. So I'm following your build with interest. Very curious about your reaction to the build quality of the 940-V, particularly with my comments in mind.
 
David, The build quality looks ok when you get past the paint. I have very little experience with this type of equipment so I am not a good judge but while the castings look a little rough, the machining looks ok. I think the Chinese do a lot of manual work in building these machines such as using jigs and hand drilling and tapping holes rather than CNC machines. After looking at your lathe and mill rebuilds, I think you would see a significant difference in the quality of this machine vs the Taiwanese machines you have. It is fine for me, but you would probably be a little frustrated with it judging from the quality of the equipment you list in your signature. We'll have to wait until I have it back together to really see how it looks as I will be replacing most of the parts that are not as well finished. With the new ball screws, bearings and motor mounts, about all that is left are the main castings and tables so it might end up better than expected. I think the poor paint work makes it look a lot worse than it is. I'm not a big fan of the Chinese electronic control system. Although the components seem to be good quality, it just has a kind of shoddy feel to it. When I am done, I will have replaced this completely so I am not worried about it for now as it seems to work.

I think I will use the Steel-It paint. There is so little surface area to paint that I can do it with their rattle can version which will make it quite easy. The Steel-It paint does not seem to do well with the HVLP spray equipment I have and I don't want to buy new spray equipment. No equipment cleanup either with the rattle can. I'll probably start the paint striping process in the next day or so.

Now it is time to see what to do about removing that Z lead screw.
 
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