Taking the CNC Plunge

[TomS]

Yesterday I removed the spindle cartridge and disassembled the spindle. Bearing cups looked OK with just slight discoloration on the rolling surfaces. No scratches or grooves which was better than I expected. But what I did find was metal chips packed inside the lower spindle bearing end cap. This was because my mill didn't come with a lower spindle seal (part 75) as shown in the parts diagram. Anyone else missing the seal? For those that haven't checked it's very easy to unthread the end cap. There's three small dimples in the end cap face where you can get the end of a punch into to exert a small amount of rotational force to unscrew it. I recommend that you check it out. It may save you having to change out the bearing.

Here's a screen shot of the PM-932 manual showing the spindle end cap (part 74) and spindle seal (part 75). Mine didn't have part 75.


And here's a picture of the interior side of the end cap. The counterbore is an odd ball dimension something like 62.1mm. I'm going to make an insert to reduce the bore to a standard dimension like 55mm or there abouts then buy an off the shelf seal to fit the spindle OD. For info my spindle OD is 1.650" (41.9mm) but because I'm going to spin this thing up to 9000 rpm a contact seal won't live at that speed. I can get a seal for a 1.655" shaft which gives me a small amount of clearance which keeps from frying the seal and will keep out most of the chips and coolant.


Tom S.

 

[jbolt]

Mine didn't have a seal either. I put a thick o-ring on the spindle behind the cap to cover the gap.

 

[TomS]

Mine didn't have a seal either. I put a thick o-ring on the spindle behind the cap to cover the gap.

Interesting that the manual shows a seal but they ship the mill without one. I like your o-ring fix.

Tom S.

 

[TomS]

Update on my PM-932 belt drive conversion. Got my angular contact bearings and the Kluber bearing grease is on the way. Thanks jbolt for helping me sort out AC bearing suffix codes. Ordered my VFD (Hitachi WJ200-015SF). Should be here early next week. Then the fun begins.

Tom S.

 

[TomS]

My VFD (Hitachi WJ200-015SF) arrived this past Saturday. The first order of business was to mount it in the enclosure. Got that done today and will mount the enclosure on the control cabinet tomorrow after putting in air flow vents.



My approach is to get the VFD and motor wired and finish up the belt drive conversion so I can use the mill. The second phase is to upgrade to a ESS and spindle control board. My current motor wiring setup should make it fairly simple to get up and running quickly. This is where I can use some help. I have 240VAC single phase coming into the control enclosure. This powers a 24VAC transformer that feeds the motor contactor coil. When I push the power button the contactor latches sending 240VAC through the For/Rev switch to the motor. The attached wiring diagram represents my current wiring with the exception that the head elevation circuitry has been removed as has the X axis power feed circuitry. And my E-stop is now wired into the limit switch circuit.

I have four wires coming out of the For/Rev switch. Can I/should I connect these to the VFD input? If yes, how would I do that? Connecting the motor to the VFD seems simple enough using the attached diagram. L1 connects to U/T1, L2 connects to V/T2 and L3 connects to W/T3 on the VFD. Correct?



Not sure how to connect P1 and P2 or if I need to.


And last question, at least for now. What Ohm potentiometer do I need? I've seen recommendations for 1K, 2K, 5K and 10K. I have a 50K, a 100K and a 1 megaohm. Will any of these work?

Thanks for your help.

Tom S.

 

[tmarks11]

P1 and P2 are a thermoswitch inside your motor; you are supposed to hook them up so it kills power to the motor if it overheats. The Hitachi WJ200 has connections that are designated for that purpose.
1. Set code C005 to "19" (Page 4-6 "PTC) - (activates thermal protection)
2. P1 and P2 should be hooked between terminal "5" and "L" (page 4-30).

5K or 10K pot will get the job done. You don't want to go much higher than that, since EMI will induce sufficient current to cause unstable response.
1. Set Code A001=00 (Page 3-12) -activates external pot.
2. Connect it between "L" and "O" (page 4-5).

Yes, you want to hook your FWD/REV switch into the VFD. You probably also want to buy an E-Stop button and hook that into the VFD too.
1. Set Code A002 =01 (Page 3-13) - activates terminals for control
2. Lead from the FWD switch terminal to "1" (Page 4-16).
3. Lead from the REV switch terminal to "2"
4. Switch power to "P24"

Not sure what on your switch equates to which position. Basically, when the switch is in FWD, it should allow current to flow from "P24" to "1". When in REV, "P24" to "2".

A couple other points:
1. You will want to set up regenerative braking to slow down faster
2. Make sure that your VFD controller box has good ventilation. That thing can be putting out 100W of heat. You notice in the manual they specify installing it in a box that is at least 4" clearance above,4" below, and an 2" on each side. That might be more than needed, but in the little box you have you might end up having to install a fan to keep ventilation flow (page 2-8).

EDIT: Hitachi, not Fujitsu....

 

[TomS]

P1 and P2 are a thermoswitch inside your motor; you are supposed to hook them up so it kills power to the motor if it overheats.

The Fujitsu WJ200 has connections that are designated for that purpose IIRC; let me take a quick look at the manual and check. Ideally you want the thermoswitch to tell the VFD to shut down.

5K or 10K pot will get the job done. You don't want to go much higher than that, since EMI will induce sufficient current to cause unstable response.

Yes, you want to hook your FWD/REV switch into the VFD. You probably also want to buy an E-Stop button and hook that into the VFD too. Let me check the manual and get back to you.

Thanks. For clarification my VFD is a Hitachi.

Tom S.

 

[tmarks11]

typo on my part, meant Hitachi.

Great VFDS; I have two Hitachi WJ200 VFDs: a 2 hp one on my lathe and a 3 hp one on my mill.

Note I went back and looked at the manual and added to my reply above.

 

[mksj]

I would recommend a 5K speed pot, the spec. for the WJ200 is 1K, so anything in the 1-5K should be OK. The P1 and P2 are thermostats (P-Stats), alternatively I often connect them either to the E-Stop circuit or there is the inputs/settings to connect them to the WJ200 as noted above, which will shut down and give you an error code. The connections will differ if you use source vs. sink logic. Consideration should be given to if you want the P-Stat to shut down the motor AND also send a stop single to your CNC program, similar to a limit switch. Shutting down the motor in the middle of a cutting sequence could be problematic. It is also possible to use a simple 2 pole 24VAC relay powered through the motor P stat which also provides power to the main power contactor and connect one pole to the the VFD P-Stat contacts and the other to CNC program stop function. Breaking power to the E-Stop, Power or the P-Stat opens turns off which opens the relay and stops the motor, powers down the VFD (this takes about 30 seconds) and sends a stop signal to the CNC program.

I had previously posted a 3 wire connection diagram that can be used with momentary buttons as opposed to 2 wire sustained on to input 1 and 2. It also utilizes the current machine E-Stop system to power down the VFD. A few people have used this on their PM mills. I am a bit unclear if this machine is going to be used for CNC, then the computer/program would control both the direction and speed of the motor directly unless you are manually going to be doing this.

 

[TomS]

I would recommend a 5K speed pot, the spec. for the WJ200 is 1K, so anything in the 1-5K should be OK. The P1 and P2 are thermostats (P-Stats), alternatively I often connect them either to the E-Stop circuit or there is the inputs/settings to connect them to the WJ200 as noted above, which will shut down and give you an error code. The connections will differ if you use source vs. sink logic. Consideration should be given to if you want the P-Stat to shut down the motor AND also send a stop single to your CNC program, similar to a limit switch. Shutting down the motor in the middle of a cutting sequence could be problematic. It is also possible to use a simple 2 pole 24VAC relay powered through the motor P stat which also provides power to the main power contactor and connect one pole to the the VFD P-Stat contacts and the other to CNC program stop function. Breaking power to the E-Stop, Power or the P-Stat opens turns off which opens the relay and stops the motor, powers down the VFD (this takes about 30 seconds) and sends a stop signal to the CNC program.

I had previously posted a 3 wire connection diagram that can be used with momentary buttons as opposed to 2 wire sustained on to input 1 and 2. It also utilizes the current machine E-Stop system to power down the VFD. A few people have used this on their PM mills. I am a bit unclear if this machine is going to be used for CNC, then the computer/program would control both the direction and speed of the motor directly unless you are manually going to be doing this.