Measuring device some of you may find useful

frank freedman

Finally at the end of my first week on the frozen mid-western tundra where I have been sentenced to 3 weeks of device service training. Seems that the table positioner uses the Sony SL-130 xxx digi-ruler. This is a flat strip of magnetically encoded material and its resolution can be set from 10um to 100um with strip length from 200mm to 30000mm. For y'all doing CNC or other linear positioning projects, there is no guessing due to gear lash as with the rotary shaft encoders, the reading is where the pickup device is. If you wanted to go with a direct drive from a servo loop controlled motor you may be able to get a highly accurate positioner. Of course, the application here is a medical device, may cost quite a bit more than the shaft encoder. Don't know since currently I have only downloaded the data sheets on the device.

Two more weeks then back to Phoenix to thaw out.

Have fun y'all,

Frank

Just saw some pricing
Tape $5.00 to $6.50 per inch,
Reader assy $520.00 to around $700.00 depending on cable length.

idbruce

Thanks for sharing Frank. Nice find.

frank freedman

@Bruce Thought of you and your endeavors when I posted it.

Can't justify the price for playing around with but who knows, maybe find one as salvage parts.....

FF

Mickster

The Digi-ruler is fitted as standard to every machine I build or rebuild and I have installed, literally, thousands since 1993. However, the specified (0.030"?) gap between the reader-head and the tape must be maintained or the controller unit will get upset and fault-out. I think it is Schneeberger (sp) that makes something similar but they have the scale embedded in a linear rail. Where we can't be sure of maintaining the gap, we use something like a Celesco string-pot (aka: Yoyo) encoder tied to the slide mechanism.

We have had issues, also, where a maintenance tech can't be bothered to RTFM and assumes that the Digi-ruler is some kind of linear slip-ring dveice and 'adjusts' it accordingly (!!!!)

frank freedman wrote: »

For y'all doing CNC or other linear positioning projects, there is no guessing due to gear lash as with the rotary shaft encoders, the reading is where the pickup device is. If you wanted to go with a direct drive from a servo loop controlled motor you may be able to get a highly accurate positioner.

Hmmm, but the problem here is that the backlash will now cause the servo-loop to go unstable.

Wherever I have a gear-reducer or other potential cause of lost-motion, I utilize feedback from both the motor AND the load (aka: dual-loop feedback). P and I terms are fed by the Digi-ruler and the D term by the motor's integrated encoder.

Cheers.

Mickster

Mickster

The Digi-ruler is fitted as standard to every machine I build or rebuild and I have installed, literally, thousands since 1993. However, the specified (0.030"?) gap between the reader-head and the tape must be maintained or the controller unit will get upset and fault-out. I think it is Schneeberger (sp) that makes something similar but they have the scale embedded in a linear rail. Where we can't be sure of maintaining the gap, we use something like a Celesco string-pot (aka: Yoyo) encoder tied to the slide mechanism.

We have had issues, also, where a maintenance tech can't be bothered to RTFM and assumes that the Digi-ruler is some kind of linear slip-ring dveice and 'adjusts' it accordingly (!!!!)

frank freedman wrote: »

For y'all doing CNC or other linear positioning projects, there is no guessing due to gear lash as with the rotary shaft encoders, the reading is where the pickup device is. If you wanted to go with a direct drive from a servo loop controlled motor you may be able to get a highly accurate positioner.

Hmmm, but the problem here is that the backlash will now cause the servo-loop to go unstable.

Wherever I have a gear-reducer or other potential cause of lost-motion, I utilize feedback from both the motor AND the load (aka: dual-loop feedback). P and I terms are fed by the Digi-ruler and the D term by the motor's integrated encoder.

Cheers.

Mickster