[tas99]

I'm in the process of installing a 4th axis I recently purchased from Novakon and would like information from anyone who has installed one. In particular, is there anything in the setup process other than enabling the A axis in the configuration that needs to be done? Does the motor movement profile need to be modified?

Any information or problems encountered would be appreciated.

Tom

[JoeBean]

I just finished setting up my 4th on my NM-200s2, so not exactly the same but similar enough. Here's what I can tell you:
A was already enabled for me,

Don't forget to fill the rotab with oil! I use vactra, but it isn't critical. And don't forget to unlock table rotation and lock motor position before starting.

Mine had been configured with a 5 pin connector at the mill, but the cable had 7 pin connectors (they had switched between when I bought my mill and the 4th axis shipped). So Khai shipped me a new 7 pin connector. So check that.

The original 5 pin connector didn't have ground attached, so it wouldn't have worked anyway. After rewiring the connector I added a ground to one of the mounting screws for the PC power supply as it had a good connection. Be careful with pulling ground from the aluminum plate the connector is mounted to as it doesn't usually provide avgood ground.

The wiring for me was pin1 ground, 2 A, 3A-, 4B, 5B-. On the nm200s the aluminum plate that hold the axis connectors, amongst other things, and sits over the geckos is hinged on the left side so you can open it and see the wiring colours for A,A-, etc. This was a nice touch that I hadn't noticed in my teardown.

The spacing of the mounting holes in the rotary table didn't line up to my mill table. Khai said to go ahead and enlarge them which I will do when I get the next opportunity.

Now, as for settings... Mine came with the A axis steps per rev in the motor config set to 200. The correct value was 500 IIRC. For top velocity I tried different multiples of 360. 720 was too slow, 1440 was too fast (for me, though it didn't miss steps unloaded). So I set to 1080.

The stock settings allowed me to turn the axis but needed adjustment. So here's how I figured those values out, in case you have a problem:
IIf you have a pendant, or if you open the mpg in mach once you hook up the rotab, you should be able to spin it by moving by steps. Positive should travel in the pos degree direction (if it doesn't, swap A and A-)

Start by turning to some easy to remember degree on the table's ring, such as a multiple of 10 (eg. I'll assume 110 for the purpose of simplifying this explanation). Noting what the dro reads vs how much you actually moved should give you an idea of how close it is. Then set dro to 0, and issue in mdi "G0 A120". Compare the actual location with what was called for (120) and adjust the motor setting accordingly.

Once that's done, adjust velocity and acceleration to something you're comfortable with.

Hope that helps!

[tas99]

I appreciate the detailed response and I have a couple of comments and questions.

I had the same 5pin / 7pin connector issue and in addition to having to wire in the new connector it was larger than the old connector so the plug and screw holes had to be reworked. I found a ¾” Greenlee chassis punch is just the right size for that and made easy work of enlarging the hole but just to be safe I wrapped all the components (relays, etc. ) that are attached to the back plate in stretch wrap to protect them from any stray chips.

I was given the same information regarding the ground on pin #1 but when I looked at the connector wiring to the 4th axis there was no ground on pin #1 so I saw no benefit in grounding pin #1 on the mill connector and when I talked to their support guy he said it wasn’t necessary. I’m always leery of adding ground wires and causing ground loops. There was a problem when I added my probe so my axis remains ungrounded and I hope it’s not going to be a problem.

The motor setup is a different issue. I have a 4th axis on another machine and although it’s not running Mach3 I have an understanding of the principles involved. Our machines and 4th axis are different but I doubt there would be a significant variance because of it.

You said to unlock table rotation and lock motor position before starting. I’m not sure what those are and I see nothing on my device that would lock or unlock either. My default steps per is over 12000 which is also what it’s set to for the X,Y and Z axis. You stated that the correct value was 500 IIRC. I’m not sure what you mean by IIRC and I’m surprised that out values would be so different. Then again, different models may be the reason. The default acceleration value on my X,Y,Z and A axis are in the 70’s.

Right now I have everything installed and when I try to get rotation with the MPG it seems to want to move but doesn’t. All I get is a chattering noise. It may be the table or motor is locked but I can’t be sure. I have a call into their tech support but a response could be long in coming.

I’m flying completely blind here since my mill came with very incomplete documentation (they say it’s as good as it’s going to get since they have newer models now) and the 4th axis came with no documentation whatsoever so any help would be appreciated.

Regards,

Tom

[JoeBean]

I had assumed it was a 5 wire stepper, thus my comment re: the ground. But thinking about it that would be a unipolar stepper, which obviously isn't the case here as we're using Gecko drives, so you're right re: groud. Sorry about the confusion.

Here's my rotab:


As you can see it has 2 table lock levers, one on either side. And you can see a thumbscrew of sorts in front of the motor. That locks the rotation of the motor for whem it's vertical vs horizontal. Without locking it activating the stepper in one of the directions, depending on how it's turned, will essentially spin the stepper instead of turning the table.

I'm guessing your values for step per unit were set to steps per inch, correct? And I'm guessing the value was 12700 steps per inch, right? I'm assuming that based on the following:
I assume your stepper is similar to mine, with 200 steps per revolution and 10 microstep resolution (=2000 microsteps per rev).
And i'm assuming your ballscrew pitch is 4mm (which was list for the nm135, as opposed to 5mm for the nm-200s2).
Steps (or, technically I guess microsteps) per inch, then = 2000 *(25.4/4)=12700

For mine it's 10160. Anyway...

Those values can't transfer to a rotab as, obviously, the screw pitch for your axis has nothing to do with a rotab. So at the 12700 value the stepper (assuming it's essentially the same, with the same # microsteps per rev, which it should be) for each single "unit" move on the rotary table (ie. 1 degree) the stepper would make 6.35 complete revolutions. That doesn't make sense.

But at the 500 value 1 degree would require a move of 1/4 revolution, and the rotab would have a resolution to .002 degrees.

In short, it's safe to err on the low side of this value and add more as required. It'll just mean at the worst that issuing, for example, g0 a1 will move less than one degree., whereas if your current value is wrong it'll completely revolve the table 25.4 times per degree.

hope that helps, and IIRC = if I remeber correctly.

[tas99]

It looks like we’re dealing with two different devices. I remember reading that the NM-200 had a 6” device while my NM-135 had a 4”. I’ve attached a picture and as you can see, it doesn’t look like it has any locking devices for either the table or the motor. There are 4 screws (2 of which can be seen in the picture) that extend into the motor shaft, I think, but I’m waiting to hear from Novakon on what might be my problem. It sure sounds like the motor is trying to turn but is locked up for some reason.

BTW, I haven’t cleaned the grease from the unit yet. I wanted to make sure I could get it working first.

I understand your logic in determining the values and your assumptions in determining those values are correct but until I feel more comfortable applying step commands to the motor I’ll have to wait on that.

As for IIRC, ok, makes sense once you tell me.

Thanks for the information and I’ll let you know the results after I talk to Novakon; which could be quite a while. If it weren’t for Khai I think they’d lose many of their customers. He’s always there, trying to help.

Regards,

Tom

[JoeBean]

The info re: steps is universal, ie. "applying it" can't hurt anything. The calculations are taken straight from Mach3's manual.

As for whether the table is stuck disconnect the cable going to the motor to free it (otherwise it'll lock up) and try turning the table by hand. If it won't turn you've got something holding it. It should turn easily and smoothly.

If it does turn by hand buy seemingly not with the stepper (by the way you can remove that large plug and watch the shaft of the motor to see if it's spinning even a little) you've almost definitely got the wires connected incorrectly. Try switching one of the A wires with one of the Bs.

But as Aleister Crowley would say, "Do as thou wilt". Obviously don't do something you're not comfortable with.

[StillLearning]

Tom,

I have a 4th axis for the NM-135, but it looks completely different than yours. Square and ground metal. This one had a 5 pin connector so all I had to do was pull it out of the case, plug it in and it spun around... Mind you I have not had an opportunity to use it much, but I hope to get to that point.

I should note that we purchased a different computer for running the Mach3 and after installation and using the supplied NM-135Universal profile, everything seemed to work just fine.

The documentation is exceptionally poor. The only ones I have ever seen from Novakon were marked "Draft" and were missing all of the diagrams and a good portion of the required information. I read somewhere (probably in this forum) that the NM-135 is close to the Smithy 622 - of which the manual is pretty good and seems to be a pretty decent reflection of the structural parts of the mill. You can download it from the Smithy site easily.

As JoeBean mentioned, if you can reach the spindle opposite the stepper motor, then you should be able to turn it completely round using your fingers when it is not powered up. If not, then it is locking up somewhere and needs a different approach.

Good luck

By the way - you can check out some of the other web acronyms here: Web Abbreviations - WebAcronyms.com
The silly things are probably a result of trying to reduce the number of keystrokes. They can be quite confusing though.

[tas99]

I thought I’d give an update on my progress in resolving this issue.

I talked to Novakon and they gave me their recommended settings for the A axis and I’ve included them here in case anyone wants this information in the future.

I learned from them that the worm gear comes disengaged from the spur gear and the 4 screws that surround the shaft housing have to be loosened and rotated to engage the gears. In doing that I found that mine were already engaged so that didn’t get me much other than information about its operation. I only mention it to help anyone with questions in this area in the future.

I was able to remove the motor from the assembly and when connected found that I could drive it forward and reverse with my pendant so the wiring and motor were not the issue. I also learned that I could rotate the A axis from the keyboard with the F and R key; something that’s probably in the Mach manual that I hadn’t discovered.

Novakon then suggested that I add oil to the unit and let it stand for a while. They don’t ship the units with oil because of some regulation. I was then able to turn the shaft although it took quite a bit of effort and certainly requiring more torque than the motor could deliver. The net of it is that with a little more manual turning I was able to get it to a point where it turns quite easily with my fingers.

Ok, the motor turns, the shaft and table now turn so I should be able to marry the two and get the motor to turn the table but before I do that I’ll let the oil percolate through the system over night, top it up in the morning and then finish the reassembly.

I’m surprised the lack of oil would cause the unit to freeze and I suspect there may have been more factors involved but I have no way of determining what they might have been and the units seems to work freely so I’ll leave it alone.

If they had supplied some documentation I might have been able to work the problem through on my own but it came with absolutely none. Adding oil, engaging the drive, how would anyone know? BTW, there is no convenient oil fill like I think I see on JoeBean’s unit. This one has one innocuous little screw on the bottom that’s used for the oil fill. I also have the same documentation as StillLearning, more pages blank and all with “DRAFT” watermark. When I talked to Khai about it he said they abandoned all work on the NM-135 because they now only sell the newer NM-145. Nice if you have a 145 but those of us with a 135, well, we have a 135, what can I say. I will try and get the documentation from the Smithy website for future reference.

Thanks all for the help. I hope to have this completely resolved by tomorrow.

[tas99]

It looks like my problems are resolved but I'll share a few things I learned in case others have similar problems.

The motor/shaft and associated worm screw can be pivoted away from the spur gear for transportation. It can also be pivoted to tightly against the spur gear causing the unit to bid; which was the situation in my case. The screw - outlined in yellow in the picture should be loosened to allow the entire motor/shaft,worm gear assy to be pivoted into or away from the spur gear. Rotating the table while pivitong the assy allows for proper engagement and adjustment of backlash. It's something you just have to do and get the feel of but it's not difficult.

I had to replace the connector on the back of the mill and in doing so I dislodged a pin on the spindle power plug so the spindle wouldn't work. With help from Novakon I got that corrected and the system operational. It's real easy for the pin(s) to dislodge so before screwing the back plate in place take a minute to check each of the wires. A visual inspection is all that's necessary since it's pretty easy to spot if you look for it.

Thanks for everyones help and the assistance from Novakon.