Mori Seiki SL2B Z axis Servo Gearbox gear adapter
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  1. #1
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    Default Mori Seiki SL2B Z axis Servo Gearbox gear adapter

    Did a Centroid Retrofit on a Mori Sl1H I had last fall. Been happy with it so far. Don't use it much and am realizing now that I should have done the bigger Mori lathe I've got which has a dead control.

    Anyway been looking it over trying to get a parts list together and finally pulled off the Z axis motor. I knew that the yaskawa motors used tapered shafts and I don't have a plan yet on how to deal with that.

    I've attached some photos of the gearbox (Large spur gear attached to the ballscrew) and the spur gear that was mounted to the motor shaft. I'm already planning on using a DMM 1.8kw AC servo as a replacement but the new motor has a 22mm cylindrical shaft.

    I didn't grab a diameter off the gear last night but its 24 tooth and looks to be about 2" in diameter. (I'm totally guessing here) Wasn't sure if I could just buy an off the shelf replacement.

    A misumi SSG2-24J22 spur gear looks like its probably pretty close to what I'm looking for. Hardened, ground, 22mm bore with keyway etc. SSG2-24J22 | Ground spur gear SSG | KOHARA GEAR INDUSTRY | MISUMI South East Asia

    Does anyone actually know if its as simple as that or is it likely that there is something special about this spur gear? This is a positional system to accuracy of the gear is important. Is there someplace to look for these precision gears?

    Also I'm assuming any gearbox has got to have some running clearance to function reliably. These old Mori's are known for their excellent rigidity and accuracy. Does this work due to backlash compensation? Or was the fit on this gearbox really that close?
    z-axis-motor-spur-gear-2.jpgz-axis-motor-spur-gear.jpgz-axis-servo-gearbox.jpgz-axis-servo-shaft.jpg

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    Quote Originally Posted by wolfenstien View Post
    .......Also I'm assuming any gearbox has got to have some running clearance to function reliably. These old Mori's are known for their excellent rigidity and accuracy. Does this work due to backlash compensation? Or was the fit on this gearbox really that close?
    The gears are very precise and need a tiny bit of clearance. The black ring you show in one of your picture is an eccentric. On assembly, you adjust that ring with the motor mounting bolts lightly snugged to set the clearance on the gears. There's a fine line between just right and tight. If tight the gear whine loudly.

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    Quote Originally Posted by Vancbiker View Post
    The gears are very precise and need a tiny bit of clearance. The black ring you show in one of your picture is an eccentric. On assembly, you adjust that ring with the motor mounting bolts lightly snugged to set the clearance on the gears. There's a fine line between just right and tight. If tight the gear whine loudly.

    I always wondered what those rings were for. All the motor mounts have them I just couldn't understand why. makes sense now.

    Think I'd have any luck purchasing a replacement gear for the motor side or are these specials?

    Existing is:
    39mm OD
    24 tooh
    Pretty sure that means the pitch diameter is going to be 36mm and the module will be 1.5.

    I don't know how to measure the pressure angle. Also not sure which classification (tolerance) this would need on the JIS standard. Misumi is showing JIS class 2 hardened and ground which is quite decent.

    Right now its looking like the motor I want to mount can't fit in this area anyway though so I'd probably need to space it out 3/4" or so to be able to fit a thicker mounting plate over the gearbox. I think I could just make a shaft extension with the appropriate angle and reuse this gear at that point.

    Sound reasonable?

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    I have never replaced those gears, just worked with them when changing ballscrews, and thrust bearings.

    What is the reason for wanting to switch to a different motor? Yaskawa motors are very good. Since you are talking retrofitting I going to assume the motor is older and a DC version. The amp for those should be an analog +/-10VDC command signal design which many retrofit control systems can work with.

    Adding a shaft extension has a strong likelihood of adding some runout to the gear. It, and you, won't like how that works.


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