Linear scale: Glass or Magnetic?
Hi experts. I'm thinking of adding feedback to a cnc retrofit and aware there are minuscule magnetic scales for that purpose. I do not have any experience with mag scales, just find them attractive (for now). I am unsure if they even work in an hostile machine-tool environment and so I thought I'd ask for "Pros & Cons" vs glass scales.
Q1: How 'magnetic' those are? Is this something that fills with steel chips every 5min or... how does it work for you?
Q2: What sort of signal those mag scale output? Same as the common glass scale's "A & B"?
Q3: Do they actually work?! Accuracy/integrity wise I mean...
Re: Linear scale: Glass or Magnetic?
Quote:
Originally Posted by
Mecanix
Hi experts. I'm thinking of adding feedback to a cnc retrofit and aware there are minuscule magnetic scales for that purpose. I do not have any experience with mag scales, just find them attractive (for now). I am unsure if they even work in an hostile machine-tool environment and so I thought I'd ask for "Pros & Cons" vs glass scales.
Q1: How 'magnetic' those are? Is this something that fills with steel chips every 5min or... how does it work for you?
Q2: What sort of signal those mag scale output? Same as the common glass scale's "A & B"?
Q3: Do they actually work?! Accuracy/integrity wise I mean...
The main difference between glass and magnetic scales is how they measure the distance:
Glass scales have a precisely etched glass strip with finely spaced lines and an opto-interrupter array that rides on that strip. The scales use Vernier principle to obtain 5-micron or 1-micron resolution from the grid that is spaced at larger intervals.
Magnetic scales use magnetoresistive sensor array (Hall effect) and a magnetic tape with 5mm or 2mm pole-to-pole distance. The sensors produce two analog sinusoidal analog signals 90 degrees apart (sine and cosine), and use a sine/cosine interpolation algorithms to produce 5 micron or 1 micron resolution respectively.
Re: Linear scale: Glass or Magnetic?
Nice one, cncmakers001. Appreciate this knowledge sharing. Who wins in terms of thermal stability? Hands down the glass I would guess, are those magnetic a contender on this aspect?
Also, I can't help but to suspect issues when it comes to magnetic + ferrous metal chips around (sticky?). Pardon my ignorance, I've never seen nor handled a magnetic strip.
