[mamech]

hello

I am new to the world of cnc, and I am having a question abut digital read outs (DROs) .

I noticed that DROs are relatively having high cost, even if they do not do any kind of control (just monitoring). for example, the DRO of fagor is in range of 1000 $ . I am wondering because a siemens plc with 3 high speed counters + HMI will be in range of 700$ only, taking into consideration that PLC can make more functions other than just reading the pulses.

can anyone justify to me this contradiction?


I am sorry if I am posting in the wrong forum, I am not sure that this question is in the right place.

[RCaffin]

If I understand you correctly, then DROs are just an antique poor man's substitute for a CNC.
We never bother with them on a CNC.

Cheers
Roger

[mamech]

yes, sure. But still they are products that are sold to upgrade workshops machines to have some kind of monitoring and to be a little smart. I am just wondering why some of them are having high cost relative to their basic function.

[RCaffin]

OK.
On a CNC the transducer itself is fed back into the computer which controls the motors. You might get a DRO display on the screen, but the cost of the computer and the screen are not figured as being part of the cost of the transducer. Typically with a CNC the transducer might be a $50 encoder on the motor. That's pretty simple. We assume the motor drives a low-backlash ball screw here.

With a DRO fitted to a manual machine, the cost of the DRO has to include the box of electronics and the display. Lots of buttons and LEDs and so on. In addition, the transducer itself has to be a whole lot more expensive, becasue it has to actually measure the movement of the table as driven by an ACME leadscrew. with tons of backlash. So a stand-alone DRO ends up a lot more expensive.

Cheers
Roger

[G59]

I am just wondering why some of them are having high cost relative to their basic function.

Well if you had to replace all the encoders on a CNC at once, you'd find it expensive too. Most DRO's use magnetic or glass scales. Very precise and with that expensive. DRO's do more then just show position. You can offset, do calculations, set origin, absolute and relative function and so much more and all that on individual axes if you wanted to. The technology may seem old, but just like a Timex, it does a needed job and very well at that.

With CNC, the DRO is included in the GUI so you can also monitor the axes.