Shizuoka ST-N - plastic gear and knock

Hi, I went to look at a Shiz ST-N today that was pulled off the line a few weeks ago, so not under power. It was used in a ligher production shop and i get the idea it was occasional use -for at least the last 20 yrs.

There were two key issues that were said to be wrong with it.

A)Maybe encoder error? Occasionally the X or Y axis would jump forward and break a tool - sounded like it was a controller issue.

B)Plastic Gear? They said it made a thump/knock sound as it started up that was related to "a plastic gear" in it? And seemed to think it diminished at higher rpm (they weren't really positive on this!) but was the most prevalent at low rpm during rpm ramp. I believe they were told it was a plastic gear by their machine mechanic.

Can anyone shed light on what this may be wrt plastic gear?

is it common issue?
parts available?
does it show up on the AN-S?
any insight would be helpful.

Does it look like these are steppers or servos - they didn't know?

I would be purchasing this with likley the idea of Gecko / mach 3 conversion. Probably abort the Bandit even if is currently works.

Thx for you thoughts on it - trying to make a decision tomorrow - go or no go.

Paul G

Is there a plastic sleeve in the Vari-Speed drive?
Similar to a common wear item in a Bridgeport variable speed head?

Looks like the original stepper motors. We had the same mill with an old Autonumerics control on it. Scrapped the control and made it into a manual. Unless something has changed, I wasn't impressed with the Z axis servo arrangement. The machine we had used the anti rotation key in the quill as an attachment point for the ball screw giving limited Z travel and a not very strong mechanical setup.
The table gives a good clue as to the overall machine condition and it appears that this one hasn't been used very much. A good machine but with the limitations of a knee setup.

Unless that machine is free, or they are paying you to dispose of it, you should just spend a little bit more money and buy a usable machine like a Tree Journeyman 325 or a Mori Seike MV-JR. By the time you strip that thing down, fix the mechanical problems, buy new servos and drives, and figure out how to do a retrofit, you'll be way upside down on the machine.

I owned an AN-S, went far with it. I put a Centroid control on it, 3 new motors, rewired some stuff, built a new Z ballscrew, and did the spindle.

The Z-axis drive arrangement is very flimsy and breaks easily if you are not careful. I sold it with zero backlash in the new Z screw, I got a call about 2 owners later with > 20 thou of slop in the Z, clearly it had been crashed hard numerous times. I never crashed it that hard!

The ST-N is the smaller brother of the AN-S, same head, different body. The AN-S takes a nice cut and is a rigid knee mill, with exception of the Z-axis issues.

In 2004 I paid $6k for the machine working, in retrospect that was a little high, probably $5k was more like it. I then spent about another $6k on the machine, on retrofit and various upgrades/parts. I had somewhere near $12k into the machine when I sold it, for $4k.

I made a bunch of parts on that machine, so it was useful with the Centroid control.

All that said, you're looking at a lot of time and money to make that machine useful. I had to replace the motors because Centroid didn't support resolvers. I kept the motors for 11 years, until I ended up using them to replace all 3 on my Fadal (the motors were rebuilt when I bought the Shizuoka).

I would consider myself experienced with a Shizuoka AN-S and I agree that something more modern can be had for less money.

You can buy a used Fadal and fix it up, for less than it would cost to get that ST-N working nicely. Changing tools by hand SUCKS really bad.

I should point out that parts are basically unobtainium for a 37yo CNC knee mill. I once got a digitized PDF of the entire head from Shizuoka in Japan, but that was the extent of it. You have several vendors to choose from for Fadal parts, and for a machine nearly as old, you can still get new parts. The "farm tractor simplicity" (as I heard it stated in another thread), and the parts longevity, make for a much better choice.

I still think the Centroid control is better than any of the original Fadal controls, but you immediately double the price of a machine when you put one of those on. The NXGEN control is close to the same cost as a set of -4 boards for a Fadal.

If I were spending money, I think I'd rather spend $6k on an NXGEN control than a set of -4 boards, but that's just me.

Hi All -

Thanks for your insight to this - some really good points. I guess the downside of these is part availability and a not so rubust Z axis.

I probably should have mentioned that i'm a hobbiest and this is my entry to CNC (beyond my very small 6x20" Intellitek CNC) -
but i've always thought CNC was the coolest thing and I've always wanted to be able to make something when I need to.

The other part as a hobbiest, of course, is the self justification of what i'm spending - when it gets used a dozen times a year. So would like to keep total investment under $2K - Gecko simple BOB and Gecko controllers.

There is also a AN-S that I looked at that is about the same use factor as this ST-N. In the 3car garage of course the ST-N has its advantages of weighing in at a nimble 3000lbs vs. AN-S at 5300 lbs. But of course that 51x13" AN-S table is pretty impressive to handle a good range of odd things i will want to do.

So I'm weighing the intrepidating "heft" factor and the AN-S, and perhaps it this isn't really and issue from garage jockying (pipe rollers or a set of wheels on a cradle) teh AN-S maybe is a better choice than the ST-N (servo and strong Z Axis). I wasn't quite sure if a low cost Gecko drive will handle the servos - they are max 8.6A rated.

Oh yes - machines aren't free or paying me (sadly) but maybe in the $5-$800 range. Quite honestly i don't think i've seen an inexpensive way to compete with these machines in price (not including elbow greese and production shop lost time i don't factor in). Even a basic manual mill seems to fetch $3K and aren't nearly as robust - given they have their place. So given this do they make a good value?

I do appreciate your thoughts and experiences, as you can imagine - its hard to grade w/o any practical experience in these bigger machines - but i've considered them for a few years while not seen other machines in the price range.

Thx,

Paul

Well, i made a decision to take a chance on the ST-N. Of course attacted to that modetsly nimble 3000lbs vs. 5500 for the AN-S and the ease of converting the steppers rather than replacing servo motors. I know servos are better but... machine size is something to be reconed with in limited room.

This mill does have a head noise as stated earlier - think it is the belt squeeking like mad (stiction!!!!), possibly and hopefully not the "alledged" plastic back gear - jury still out. But if i change tension on the belt, momentarily until the reeves drive retension it, the noise changes drastically kind of goes away. Could it be the belt gets to a condition of super stiction?

Granted this is a 1980 - 37yr old mill (at least according to a driver board tag in the Bandit - some observations:

1. Ball screws don't appear to have gross backlash in them judging by hand, we'll see when i get a dial indicator on the bed.
"Y" is smooth as silk and silent
"X' is smooth but appears a bit more friction (could be the dovetail ways vs box ways on teh "y") and not completely silent but a uniform sound - could be scew axial bearing I did pull the spring guards back best i could an it appears there was light oil residue on the screw and didn't see any scoring - but that is really a ters inspection method
"Z"-can't access that until i remove some parts or power it with a driver - suspence builds.

Knee "Y" way.
- looks relatively clean - some evidence of few small rust spots that were spot removed previously.

Bed:
No cutting tool marks that i can find, but of course a lot of micro dings that ruin the pride it would like to have - but hey its a 37 yr old mill7
- Oil in galley bolow the X screw -Any easy way to drain this - drain plug? ncidently there is an allen plug on the non-motor end of the table that i thought was the drain - but not the case. Looked like it held a "pin" in or applied a pressue to a pin - though not sure what it may be fore it that is the case.

Spindle:
I haven't been able to move this yet, hopefully there is no scoring - jury still out.
I can't feel any movement in it up, down or sideways.

So after i recoup from the mill move for a few days - goal is to complete mechanical inspection an hopefully it fairs well enough to invest in the Gecko control upgrade.

I'll inspect the axis ball screws condition by removing the steppers so i can turn the dials easily by hand (instead of training for the thumb wrestling olypmpics) put a dial indicator on them and see what backlash really is. Probably should have done this on the inspection!

Motor belt noise - any thoughts on that one, probably need to lower the spindle down - see what it looks like. Need to look at the noise source - hopefully it is the belt and not more - well hepfully this can be dealt with with a bit of enginuity.

Well lastly - im into the machine for $500 and an $80 trailer rental so thought it would be worth a risk - theres not much to choose from in my area. I did get about 10 NMBT 40 tool holders with it, one with a nice 5/8" drill chuck. Now that the moveing stress is over - i can one element at a time validate mechanical condition fully before investing in drivers etc. Looking at low cost Gecko's (G214?), beakout board, Mach3, and PS if i can't use existing (existing could be 3 phase?).

Well hopefully I can make a decent mill out of it if it is worthy of the Gecko retro cost and the effort.

Any thoughs advice are certainly welcome.

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Paul

Here is a link to the PDF I got from Shizuoka. It's a diagram/parts breakout of the AN-S head, which should be the same as yours.

The back gear is a phenolic composite resin gear, fiber reinforced -- it's not plastic.

http://apsoft.com/download/AN-SW_sp.pdf

BTW, those are DC brush servos on it now, not steppers.

Thank you Perry - downloaded and helpful!

I'd probably be pleased if these were steppers on teh ST-N. Though were you viesing the AN-S with the resolvers on the end of the motor cans?

These motors look like the steppers that were on y friends ST-N - found here. http://www.buildyouridea.com/cnc/Shizuoka/retrofit/retrofit.html


Is there a way to tell for sure - inspect the driver card - maybe it will say stepper or Servo".

Thx,

Paul

I was looking at the AN-S pictures.

It's simple to identify, take the end plat off the motor. If there is a red/black large gauge wire, it's DC. If there are 4 or more wires going to the motor, then it's stepper.

Those look like DC motors to me.

Perry Harrington said:

Here is a link to the PDF I got from Shizuoka. It's a diagram/parts breakout of the AN-S head, which should be the same as yours.

The back gear is a phenolic composite resin gear, fiber reinforced -- it's not plastic.

http://apsoft.com/download/AN-SW_sp.pdf

BTW, those are DC brush servos on it now, not steppers.

Click to expand...

I now this thread is old, but checking in anyways.
Do you have any more Shizuoka docs? ST-N and/or AN-S?

Thanks!

Paul G said:

Thank you Perry - downloaded and helpful!

I'd probably be pleased if these were steppers on teh ST-N. Though were you viesing the AN-S with the resolvers on the end of the motor cans?

These motors look like the steppers that were on y friends ST-N - found here. buildyouridea.com


Is there a way to tell for sure - inspect the driver card - maybe it will say stepper or Servo".

Thx,

Paul

Click to expand...

How goes your retrofit?
What hardware did you choose to use?

Nope, no more info. I contacted Shizuoka in Japan directly and just received that PDF, quite helpful.

I haven't laid eyes on that Shizuoka I had in about 10 years. Dunno who has it now, but about 2 guys after I sold it, someone called me and said there was 20 thou backlash in the Z. I rebuilt that screw with a new rolled screw and original ball nut, with custom sized balls, zero backlash nut. The yoke was a little flimsy IMO and tended to flex if pushed hard. I'm guessing the follow-on owners must have crashed the Z hard a few times and broke the yoke bolts or buggered up the Z screw or something. It was a good machine, plenty more rigid than a Bridgeport, however the Z was a little flimsy and tended to cause chipping of expensive endmills. I found that it worked best with some cheap HSS 3/4 EMs when slotting Al plate stock. They wore out quicker but didn't chip and would end up lasting longer for that type of workload.