PDA

View Full Version : Verry Verry god price on DRO



GEP
06-01-2013, 09:39 PM
I have bean looking at DRO's for some time and all i got was diverant awnsers and realy didnt know what to buy. The DRO Pro,s recommend magnetic over glass. I fund a member on another forum that sells magnetic DRO's only to forum members. I am buying 3 readouts that will handle 12" travel for $69.00 + shipping and can be cut to fit . If any one is interest pm me and i will hook you up. I am not connected in any way with the seller

Elninio
06-01-2013, 09:53 PM
Magnetic is cheaper but glass is better.

GEP
06-01-2013, 10:08 PM
Glass was the first one. yes maby i agree glass has proofen it self. There are china made glass systems glass rails are made in 10mm increments only one problem they are huge but no problem if you have the room. If one wants to install a DRO system in a limited space machine magnetic is the other option.
Believe me i did a lot of research and have not fund any negative statements on any type. I figure this if magnetic dont work i am not out much. The cheepest glass rail DRO i fund that i would buy is close to $500.00

gcude
06-01-2013, 10:48 PM
If one wants to install a DRO system in a limited space machine magnetic is the other option.

This is why I went with magnetic for my lathe ... my Bridgeport has glass scales though.

lakeside53
06-01-2013, 10:49 PM
Times have changed; the latest magnetics are very good... Check out the specs on DRO-Pros scales.

GEP
06-02-2013, 12:12 AM
DRO-PROS promote magnetic with a 6 year warranty.Dont have no idea hoo makes thers

flylo
06-02-2013, 09:09 AM
#1 DRO Pros told me magbetic are more durable than glass, (as glass is breakable) but in the $6-700 price range glass is much more accurate.
#2 Where would you use 3-12" scales & are they this type Rbay #310224430119 ? Why don't you post a pictue?
#3 I wake up to this e-mail from you Quote "Carma is a bitch it's gettng you GP" At least this one I can read. The last few page long ones were almost impossible because of spelling, grammer & punctuation. Thanks for using spell check.:)

oxford
06-02-2013, 11:20 AM
I was kind of wondering where the 3rd 12" scale was going to be used as well? It seems way short for an X axis.

GEP
06-02-2013, 11:52 AM
Oxford
I have another machine to use it on, may cut it

MaxHeadRoom
06-02-2013, 12:35 PM
Magnetic is cheaper but glass is better.

Maybe define 'Better', magnetic has the ability for the same resolution, down to 1Ám. Magnetic is impervious to contamination, the only down side to magnetic is the possibility of expansion, but so far I have not seen any adverse reports of this?
Max.

flylo
06-02-2013, 01:23 PM
Can you post a picture of these?

macona
06-02-2013, 03:51 PM
Those are not magnetic scales, they are capacitive, like digital calipers. That's why they are so cheap. They suck... Well compared to magnetic and glass.

Magnetic does have it's issues. It's resolution is determined by interpolation of the magnetic field between the poles in the magnetic tape. The two main issues are collection of chips and metal dust and interpolation lag in acceleration and deceleration. The last is really only significant on CNC and that is why you will only find optical scales on CNC equipment. I learned this recently dealing with feedback and tuning problems on my laser cutter.

GEP
06-02-2013, 03:57 PM
I research them a lot fund no negative reports so i figured for the price i have to try them. I may have more time in them to mount them then they cost.
Max you mean the expansion of the scale ? I have not fund any reports on that. DRO Pro's dont mention that. I am wondering how this product compares to the DRO Pro's i am sure looking at the cost diverence there must be a diverance in the product. I do have photos of the product, would be happy to e-mailmthem to your private address

GEP
06-02-2013, 04:04 PM
macona
Shields are a must that i know the problem is they have to be fabricated. I am planning to bend some on the metal brake. So now tell me why dont the so called experts mention what you are talking about

flylo
06-02-2013, 04:04 PM
Thats what I thought when I posted the Ebay link.:(

macona
06-02-2013, 05:53 PM
macona
Shields are a must that i know the problem is they have to be fabricated. I am planning to bend some on the metal brake. So now tell me why dont the so called experts mention what you are talking about

These cheap scales are NOT magnetic. They are capacitive. Capacitive have a very slow refresh rate which makes them not fun to use. I have one on my quill of the mill.

DROPros are not experts by any long shot, they are resellers. They dont design, they just sell someone else's design. Interpolation follow error is a known issue for magnetic and capacitive encoders. Sine output optical encoders dont really have this problem as the period of the scale is so much shorter, usually a maximum of 20um. Capacitive and magnetic encoders have a much larger period, 5 to 6 mm. When you accelerate the circuitry of the reader has to calculate the position, in doing this there is a time lag of displayed position and actual position until the encoder reaches a constant speed. Like I said before, it is not until you see CNC level acceleration that this problem crops up.

The chances of a glass scale breaking once installed is so remote it is not worth mentioning. You would have to have a major crash of some kind before you would have to worry about it and even then it is usually the read head that breaks.

MaxHeadRoom
06-02-2013, 06:42 PM
There is basically 3 types, Inductive, Magnetic and optical.
If you get a quality magnetic type like this, http://www.newall.com/technology/ there should be no problem.
Max.

Mcruff
06-02-2013, 09:37 PM
Not sure just how long magnetic scales have been around but I have been using them since 1984 or there abouts. Sony's, and they are nearly flawless and I would put them up against just about anything. Metal chips are not even a concern as the scales are nearly completely sealed. Expansion should be a non issue also.

Davo J
06-02-2013, 11:08 PM
I inquired as I could do with 1 or 2 magnetic scales, but they are Igaging (spelling) type scales.
They wont work with my Sino, Meister, etc sets and the postage would probably be the killer for me.

For those that want this type of scale it sounds like a good deal. Plenty of guys use these and are happy with them and no complaints, I just seem to have enough trouble with my calipers with this type of scale protocol.

Not knocking these at all, but DRO's with glass scales are coming down so much in price so quick it might not be long before these are a thing of the past. If you have a look on Ali Express etc the DRO readouts are down to around $60-$80 and the glass scales are down to around $65 each (both plus post). Like any thing the more they sell the cheaper they get.

As for the quality, well time will tell but they seem as good as what I already have.

Dave

GEP
06-03-2013, 07:07 AM
The of the Dro posted in the 2nd post of Dro's is the same i am talking about. I paid about 1/2 of the cost of that one, they are brand new. I figured what the heck if they dont work my trash can will accommodate them. I will keep you all informed after i mount them. It will be a while i have to many irons in the fire now. Swing arm mounts for the read out are a big topic on many forums, go to the walmart site and search for swing arm mounts. I am going to see if they have the one i was looking at for $ 19.00 or so, no way will i pay $ 140.00 for a swing arm that are sold by the dro pro,s

Doozer
06-03-2013, 07:21 AM
These cheap scales are NOT magnetic. They are capacitive. Capacitive have a very slow refresh rate which makes them not fun to use. I have one on my quill of the mill..

Yes, most I have seen are quadrature capacitive. I have the older square boxy looking Mititoyo DRO on my mill, and the readers inside even have the round hole where the button battery was supposed to go, a direct part ripoff from the Mititoyo digital caliper, which is most certainly capacitive. You mention slow response to update. I have never noticed this. Even with my quill DRO. Seem to update fast enough not to notice it. On thing I will say, brands OTHER than Mititoyo digital calipers (like Starrett and B&S calipers) have a very slow response time and they are a pain in the azz to use. For that reason I always buy Mititoyo digital calipers. Starrett and B&S are real crap and aggravating to use. Maybe other brands of capacitive DROs have a slow update rate, but not Mititoyo as I see it. --Doozer

EVguru
06-03-2013, 07:59 AM
Lots of ignorance here.

The Chinese scales mostly use a capacitive vernier system for position sensing and output data as synchronous serial (clock & data). Both relative and absolute (since power up) positions are in the data.



The Chinese scales do not handshake the data output. The scale data is sent continuously with a fixed, ~300ms period. The serial data stream is 48 bits long and is clocked by the scale at a nominal frequency of 90 kHz,


The usual chip they're based on has fast and slow update modes (fast 50Hz, slow 3Hz) and resolution can be improved by averaging the fast data.

Most calipers udate in slow mode (but can usually be put into fast through the SPC connector), whilst the linear scales seem to be set up as fast mode.

The Shumatech DRO was based on reading these scales.

http://www.shumatech.com/support/chinese_scales.htm

Charles P
06-03-2013, 12:19 PM
Whilst we've got a number of people who know their DRO's can I take the thread in a drift...

I have an Acu-rite D100 DRO and a TTL output scale by Elektra. The reading is exactly twice the read measurement. What's wrong (and no, it's not the radius/diameter function - tried that)

Thanks

Charles

MaxHeadRoom
06-03-2013, 12:45 PM
Hopefully the Accu-Rite dip switch setting has one to suit the scale resolution you are using.
Max.

macona
06-03-2013, 06:53 PM
The D100 resolution is set up from the front panel. You can download the manual and it tells you how to set the resolution. Like Max says, hope it has the right resolution.