# DRO for G0704



## Transformer (Feb 17, 2015)

I am considering adding a DRO to my mill.  From reading here and elsewhere it seems most use magnetic scales, yet poking around on Ebay the glass scales seem cheaper and accuracy seems to be a toss up.  The biggest negative for glass seems to be that they require more space, they are bigger.  Has anyone installed glass scales on a G0704 and how did it work out?  Or if you have experience on glass vs magnetic and have an opinion I would love to hear it.


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## brav65 (Feb 17, 2015)

I have a PM-25MV which is almost exactly the same machine.  I have installed a DRO Pros DRO with glass scales. Here is a thread where I posted some pictures, page three has pictures of the completed installation.  

http://www.hobby-machinist.com/threads/pm25-mv-from-the-beginning.26618/


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## GSWayne (Feb 24, 2015)

I installed a set like the Promo 2i from the DRO store http://www.thedrostore.com/
and I have been happy with that system.   I think the magnetic scales are better, but the glass ones appear to be good enough and cost less.


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## snocatfun (Mar 2, 2015)

I really like using the magnetic scales as they are smaller and more compact on the machine. I have a Grizzly G0722R milling machine and I installed a 4 axis EL-700 DRO PRO with magnetic scales, I can combine my Y (head) and U (quill) axis for a single readout or have them display separately this is an outstanding DRO system. I had to come up with my own mounting system for the U (quill) axis and it worked out great. The magnetic scales I think are more robust and less likely to be damaged over the glass scales... I'd like to add a picture but I don't have enough posts on this site, maybe in the future.


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## wrmiller (Mar 2, 2015)

I have DroPro glass scales on both of my mills (PM25 and Charter Oak) and they work fine, and I have no intention of using flood coolant. No problems installing on either machine.

I will be going magnetic, i.e., DroPros EL400 on my big lathe as I may eventually use coolant on that and the mag strips are supposedly coolant proof.


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## MontanaAardvark (Mar 2, 2015)

Transformer said:


> I am considering adding a DRO to my mill.  From reading here and elsewhere it seems most use magnetic scales, yet poking around on Ebay the glass scales seem cheaper and accuracy seems to be a toss up.  The biggest negative for glass seems to be that they require more space, they are bigger.  Has anyone installed glass scales on a G0704 and how did it work out?  Or if you have experience on glass vs magnetic and have an opinion I would love to hear it.



I've been going over the exact same question  for my G0704 (also trying to decide if I'm going to CNC it instead).   

I've seen mention of these iGaging systems, and swear I saw a YouTube video about them.  They look like a good approach.  
http://www.amazon.com/iGaging-Magnetic-Remote-Digital-Readout/dp/B003JULE4Y/ref=pd_cp_hi_0

There are different lengths available.  This one is the X-axis, 24" long.  


Bob


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## MAlcocer (Mar 2, 2015)

I am currently installing glass scales. I bought ditrons and the one I have finished is working superbly. I am running them to a custom built board with a Bluetooth card. I use the touch dro app on my android. Only $325 in to the setup. Magnetic scales are nice for the reasons mentioned above. The igaging scales are good but very bare bones. You will not get any of the handy features that come on the dro interfaces. They also suffer from interference from what I have read. They have two models. The one most buy were designed for use on table saws. Their model designed for mills is only slightly less than a glass scale.
If you are going to go CNC you can attach stepper motor and controllers running through mach 3 for the same price as a good dro (if you make your own mounts). Just use it manually until you are ready to go full on CNC and it will act as your dro. Then upgrade to ball screws and the rest later. In hind sight I should have went this route. The experience setting up the steppers would be nice. And in the end I may just be getting rid of the dro anyway.


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## Suburban (Nov 11, 2017)

I know this is an old thread, but I'm trying to figure out what to do with my G0704.

"If you are going to go CNC you can attach stepper motor and controllers running through mach 3 for the same price as a good dro (if you make your own mounts). Just use it manually until you are ready to go full on CNC and it will act as your dro. Then upgrade to ball screws and the rest later. In hind sight I should have went this route. The experience setting up the steppers would be nice. And in the end I may just be getting rid of the dro anyway."

I'm a total newb when it comes to CNC, so I'm a little confused by this part.  There is backlash in the stock Grizzly/Chinese screws, which I understand that the ball screws do not have, and I thought that was a requirement.  Without a DRO scale to provide actual positioning information, I don't understand how stepper motors and Mach 3 could be a replacement for a DRO.  Can somebody set me straight here?


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## richl (Nov 11, 2017)

The dro is only display the position information to the screen that it records, the stepper/servo motors are  able to know and use the position information that they are creating as they travel. This is all done internally with the servo/stepper and it's controller board. It does not need the dro to know where it is, it works fine without that information, it generates it all internally.
Simple right, the mach3 software than acts as the display device and displays this information (the information generated by the stepper/servo controller combination) on the screen for you


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## Eddyde (Nov 11, 2017)

Suburban said:


> I know this is an old thread, but I'm trying to figure out what to do with my G0704.
> 
> "If you are going to go CNC you can attach stepper motor and controllers running through mach 3 for the same price as a good dro (if you make your own mounts). Just use it manually until you are ready to go full on CNC and it will act as your dro. Then upgrade to ball screws and the rest later. In hind sight I should have went this route. The experience setting up the steppers would be nice. And in the end I may just be getting rid of the dro anyway."
> 
> I'm a total newb when it comes to CNC, so I'm a little confused by this part.  There is backlash in the stock Grizzly/Chinese screws, which I understand that the ball screws do not have, and I thought that was a requirement.  Without a DRO scale to provide actual positioning information, I don't understand how stepper motors and Mach 3 could be a replacement for a DRO.  Can somebody set me straight here?


Getting table position through the stepper motor encoders will not be accurate with a standard lead-screw. It would work ok with ball screws but not as accurate as a DROs linear encoders, mounted directly to the table. Also you don't necessarily have to abandon the DRO encoders when you go CNC, if you get a motion controller like a Galil that accepts dual encoder input, you can achieve very precise positioning even without ball screws. Though my CNC conversion is temporarily on hold, I am going that route.


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## MAlcocer (Nov 11, 2017)

It will not be as accurate as a DRO. But a G0704 will not be able to hold the tolerances down to the level that a good DRO can read anyways. Backlash of a leadscrew can be compensated for via the software and you can use techniques similar to how you would is a mill manually to improve this further (planning cuts all in the same direction at one time). My original statement was meant for those who were thinking of cnc for their G0704.  And my advice is to skip the DRO. Yes the scales can be used to verify the position to the cancellation controller but the G0704 has too many other issues that will affect it's ability to repeat tolerances. You are just adding to the costs at that point and getting little in return.


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