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DRO -- Educate Me Please

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Rick_B

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#1
I am leaning strongly towards a DRO purchase for a Bridgeport mill. The mill is a Series 1 J head with a 9 X 32 table and X axis power feed. With the power feed the table movement is 16-1/2" in the X direction and 12" in the Y. I know VERY little about DRO's so I thought I'd start a discussion relating to some high level questions and working down into the details. Please don't consider any of the following as factual statements - they simply represent what I think I know today. At a 50,000 foot level:

What a DRO isn't - it is not a CNC type of functionality. It cannot be programmed to perform a series of steps that can be executed by the push of a button.

What a DRO is - in simple terms it is a tool to measure and monitor table movement but the movement is executed by either manually using the the lead screw or a power feeder in one or more axis. In other words a DRO replaces the standard lead screw dials as a means of measuring how far the table has moved in any of one, two or three directions (depending on what you buy). As a result, any lead screw backlash is no longer significant because the DRO is measuring only actual table movement where as the dials are factoring in any backlash in the lead screw/nut configuration as well as table movement.

If the above is correct then let's drop down to 5,000 feet
the DRO uses a scale on each axis to measure movement and reports that back to a display - Question - how does the scale actually measure the movement?

When using a DRO I believe you can set a zero point and then measure from that zero point and return back to the zero point. question - does the zero point represent the tool center - in other words can the tool diameter be reported to the DRO and then it compensates for that diameter or is that an operator calculation?

What can I do with a DRO beyond the elimination of backlash issues. Some examples - touch off the end of a work piece and measure the distance a slot has been cut, touch off the work piece and find its center, touch off a work piece with a hole and find the hole center. Are these typical DRO features? What else can be done with a DRO before you need to consider full blown CNC functionality?

That's probably enough for now - thanks for any thoughts/comments you may have.

Rick
 

Cobra

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#2
Try looking at DROPros.com for a good introduction into the differences between glass and magnetic.
They are very helpful in selecting the DRO that best suits your needs and equipment.
 

cathead

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Well, for starters, it is more accurate than the mechanical scales. I know there are two basic types, the magnetic and the glass
scale type. Supposedly the glass scale is slightly more accurate. You can set your zero point anywhere you want to to establish
edge surfaces or hole centers. Most will do bolt circles which gives you numerical coordinates of each bolt hole center. I often use
an edge finder to set my DRO. You find the edge of the enge finder tool and then move the table half the diameter of the edge finder and
you are at the edge of the part. Then you can reset the DRO to zero. You can also edge find both ends of a part and determine the
center. I do that a lot and work from the center for easy symmetry. I'm not an expert on this subject, just having learned from doing.
 
Last edited:

RJSakowski

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#4
The DRO scale is typically optical, magnetic, or capacitive. It consists of a repetitive pattern on a linear scale and sensor which can detect that pattern. The frequency of the repetition determines the resolution of the DRO scale. Generally , the DRO uses a detection scheme which can determine the direction of movement.

The DRO simply determines the position relative to a reference position. It doesn't compensate for tool diameter. On a mill, the table moves underneath the spindle. Setting a zero reference position can be any point. Typically, one would refer to the spindle axis but you could just as easily bring a tool up to the edge of the work and set a zero there. Substituent milling into the work on that axis with that tool would be relative to the edge.
 

Bob Korves

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#5
Many better DRO's have functions for bolt circles and step measurements. After the first position you push a button, and the next position will then become zero, zero. Go there. Repeat until done.
 

brino

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#6
Rick, you seem to have a good handle on the use and benefits of DROs.

Personally I have not made the jump to DROs yet.

Many people like the little igaging LCD units, and the price is certainly right.....
12 inch: http://www.busybeetools.com/products/digital-remote-readout-0-12in-in-metric.html
24 inch: http://www.busybeetools.com/products/digital-remote-readout-0-24in-in-metric.html
36 inch: http://www.busybeetools.com/products/digital-remote-readout-0-36in-in-metric.html

However I have two things I do not like about those:
1) the small size of the LCD, and
2) the lack of bolt circle and other functions because the axes are independent.

Sure you can work-around those issues by mounting them on a swivel arm with a light and you can work out the coordinates of each manually or with the help of your Machinery Handbook, but if(when?) I pay for a DRO unit I want to realize the biggest benefit!

-brino
 

Rick_B

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#7
Thanks for the info guys - this may be a short lived discussion. I just took a look at pricing and now have sticker shock. If I can't get into the DRO game in the $300 range I will likely seriously reconsider the jump to DRO's.

Rick
 

ch2co

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You might take a look at Yuriystoys.com He has a do it yourself system that comes as a parts only system or he also provides fully built modules
for reading out DRO's on large (inexpensive) tablet screen. His site talks about the differences and accuracies of the various sale types.
 

mksj

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There are many 2 axis Sino DROs in the $200-300 range, a 3 axis is not much more. You could get by with a 2 axis with a a separate spindle DRO (about $50). I consider the Igaging Absolute scales much less affordable these days and there accuracy is not up there with comparable glass scales. Glass scales work just fine, I do recommend a scale cover for longevity of the scale. Glass and newer magnetic scales have comparable accuracy, the magnetic scales are less prone to fouling and a bit easier to install, but much more expensive.
http://www.ebay.com/itm/2-Axis-digi...ne-with-precision-linear-scale-A/291767846797
http://www.ebay.com/itm/2-Axis-digi...ne-with-precision-linear-scale-m/331859638720
 

Bob Korves

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#10
For the best prices, go to Aliexpress. There are the same three axis DRO's there for less than $250, shipped.
 

Holescreek

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#11
Thanks for the info guys - this may be a short lived discussion. I just took a look at pricing and now have sticker shock. If I can't get into the DRO game in the $300 range I will likely seriously reconsider the jump to DRO's.

Rick
I took delivery this morning of my third DRO from a seller in China (Enpod), this one is a 3 axis with glass scales. $313 delivered, received it in 5 days. My other two are two axis units that are on lathes.
http://www.ebay.com/itm/182295304583?_trksid=p2057872.m2749.l2649&ssPageName=STRK:MEBIDX:IT

The seller is very communicative, meaning they are very interested in making me happy. We exchanged 4 emails before they shipped this one. I've tried to help them understand some of the confusing parts of their ads relative to scale lengths but to be honest they are just selling the same thing as everyone else - but much cheaper. It's important to let them know you want the "english" model when you give them the sizes, my first unit was a chinese model and it was a PITA to get set up, but the seller worked hard as a go-between with the factory to get me what I needed. When I bought the second unit (english) I was able to get the first one straightened out quickly.

I have a thread or two here on installing the units on my Cinci Traytop lathe and Clausing lathe. The new setup is going on a 9x42" Bridgeport.
 

Bob Korves

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#12
I took delivery this morning of my third DRO from a seller in China (Enpod), this one is a 3 axis with glass scales. $313 delivered, received it in 5 days. My other two are two axis units that are on lathes.
http://www.ebay.com/itm/182295304583?_trksid=p2057872.m2749.l2649&ssPageName=STRK:MEBIDX:IT

The seller is very communicative, meaning they are very interested in making me happy. We exchanged 4 emails before they shipped this one. I've tried to help them understand some of the confusing parts of their ads relative to scale lengths but to be honest they are just selling the same thing as everyone else - but much cheaper. It's important to let them know you want the "english" model when you give them the sizes, my first unit was a chinese model and it was a PITA to get set up, but the seller worked hard as a go-between with the factory to get me what I needed. When I bought the second unit (english) I was able to get the first one straightened out quickly.

I have a thread or two here on installing the units on my Cinci Traytop lathe and Clausing lathe. The new setup is going on a 9x42" Bridgeport.
What are the differences between the English and Chinese models?
 

Holescreek

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#13
The words on the readout when you are in setup mode are in chinese. Other than that, nothing. It is rather hard to set the unit up for a lathe (changing scale resolution to go from radius to diameter readout for example) when you don't know what it says, and the manual is hard enough to understand without that little speed bump.
 

coffmajt

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I installed a DRO Pro 3 axis system on my mill two years ago and love the way it works. You can input your tool diameters and it will compensate from an edge if that's what you want. Makes centering easy and checking angles even easier, but as some have reported with the magnetic scales, not cheap. I did not want the glass scales due to concerns with coolant and chip fouling, which have not been any problem with the magnetics, == Jack
 

Rick_B

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I took delivery this morning of my third DRO from a seller in China (Enpod), this one is a 3 axis with glass scales. $313 delivered, received it in 5 days. My other two are two axis units that are on lathes.
http://www.ebay.com/itm/182295304583?_trksid=p2057872.m2749.l2649&ssPageName=STRK:MEBIDX:IT

The seller is very communicative, meaning they are very interested in making me happy. We exchanged 4 emails before they shipped this one. I've tried to help them understand some of the confusing parts of their ads relative to scale lengths but to be honest they are just selling the same thing as everyone else - but much cheaper. It's important to let them know you want the "english" model when you give them the sizes, my first unit was a chinese model and it was a PITA to get set up, but the seller worked hard as a go-between with the factory to get me what I needed. When I bought the second unit (english) I was able to get the first one straightened out quickly.

I have a thread or two here on installing the units on my Cinci Traytop lathe and Clausing lathe. The new setup is going on a 9x42" Bridgeport.

What is your impression of the accuracy and repeatability of the DRO's you are using? Also - they see to have all of the features of the more expensive models - would you agree with that or are there things/features that you don't get?

Thanks
Rick
 

Bob Korves

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What is your impression of the accuracy and repeatability of the DRO's you are using? Also - they see to have all of the features of the more expensive models - would you agree with that or are there things/features that you don't get?

Thanks
Rick
Rick, the technology used for glass scales should give the same accuracy regardless of brand, if built to the same nominal accuracy. The issues with the imported stuff is the quality of the mounting and supporting equipment, which are often not made to the same robustness as the best made ones. Repeatability can be impacted by loose mounting hardware and less rigid construction over the longer term. Then again, hobby machinists are not usually as rough on equipment as commercial shops are. You pay your money and take your chances.
 

Rick_B

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Thanks bob - that brings up a good question - how do the 3 scales mount to a Bridgeport - is hardware generally included? I suspect that it depends on where you get it - like you said the more you spend the closer it will be to plug and play I'm thinking?

Rick
 

Bob Korves

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Thanks bob - that brings up a good question - how do the 3 scales mount to a Bridgeport - is hardware generally included? I suspect that it depends on where you get it - like you said the more you spend the closer it will be to plug and play I'm thinking?

Rick
I am the wrong person to answer that question. I don't have a BP, and I have not looked critically at many installations. A careful installation of any DRO, with additional protection added where needed, pays dividends long term. It is really important to keep the oil and swarf out of glass scales, and to not let them get bent or otherwise physically damaged. Hardware is usually included, but quite often it must be modified or new parts made to achieve an accurate, protective, and robust mounting.
 

mksj

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that brings up a good question - how do the 3 scales mount to a Bridgeport - is hardware generally included? I suspect that it depends on where you get it - like you said the more you spend the closer it will be to plug and play I'm thinking?
When it comes down to it there are many different variations on mounting, I purchased the DRO Pro EL700 with 4 axis, and used only one bracket for the X-Axis mount. If you need to modify or fabricate the brackets it is easy to do with some aluminum stock. The alignment of glass scales is more critical then the magnetic so you need to spend the time to make sure they are aligned properly. The cheaper glass scales may not be as coolant proof as better ones, but in the hobby environment this should not be an issue if they are properly installed. There are lots of references online as to mounting DROs on knee mills. I assume your Z-axis would be the knee, which is easier to mount than the spindle scale. As I mentioned you can get an inexpensive battery operated spindle DRO, which comes with brackets and are easy to mount for around $50.
 

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British Steel

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#21
I am the wrong person to answer that question. I don't have a BP, and I have not looked critically at many installations. A careful installation of any DRO, with additional protection added where needed, pays dividends long term. It is really important to keep the oil and swarf out of glass scales, and to not let them get bent or otherwise physically damaged. Hardware is usually included, but quite often it must be modified or new parts made to achieve an accurate, protective, and robust mounting.
I've fitted a few to Blidgepolts (Chinese ones), not that difficult but most of the supplied hardware went in the scrap for melting... it's important to ensure the scales are EXACTLY parallel to the movement, I run a dti gauge along the scale to check horizontally and vertically, aiming for zero to a few thou" divergence, with the dti mounted where the read head is going.
You will probably need to make adjustments so mounting on pads with grubscrews at their corners will give fine adjustment on castings with draft and allow fitting the scales more neatly than the supplied hardware (clunky cast ally angle brackets).
Leave the plastic shipping shim between scale and reader in place until you get to mounting and shimming the reader to ensure the right alignment and spacing. If you can, make removing the shim the last step (you may need to remove its retaining screws while you can get to them though, and tape it in place - bloody awkward!)

Dave H. (the other one)
 

Holescreek

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What is your impression of the accuracy and repeatability of the DRO's you are using? Also - they see to have all of the features of the more expensive models - would you agree with that or are there things/features that you don't get?

Thanks
Rick
Long story short, my first DRO was bought from a fellow in Hong Kong maybe 13 years ago for about $480 shipped. It's a Meister Top 10 3 axis unit. In all the years since I've barely dipped a toe into the included features the unit has built in. I've never even tried the calculator function since there's a stack of them on top the tool box. I have used the bolt circle and straight line hole layout and chop milled a large radius in using the programmable function. Mostly I set zero and watch the numbers.

The first unit I bought from the current seller went on my Traytop which also had a Trav-a-dial on it and they jive perfectly for accuracy. I checked the second one on the Clausing with gauge blocks and it matches as well.

The unit comes with a small bag of screws, a mount for the DRO , 3 angle brackets and scale covers for each one. I'll get something posted on the installation in a few days, The X and Y are done and I'm finishing up the Z axis tomorrow.
 

bruedney

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#23
I purchased one for my mill and one for my lathe from aliexpress, very nice units and the price was unbelievable for what you get. Plus it was free shipping and came in 5 days to my door.
Those links don't work

I would be intersted in knowing the actual units please.

Cheers
Bruce
 

Rick_B

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So here's a high level question - I have a line on several acu-rite DRO's - both are two axis units. One is an ACU-RITE III and one is an ACU-RITE D200. Both include scales and cables as well as the read out units. I don't believe either of these are currently offered and may not be supported - I'm going to check that out. Cost is sub $400 range.

I can get a 3 axis import unit for a little less money that seems comparable in terms of published specifications.

So the question - is an older used ACU-RITE 2 axis unit a significantly better buy than a 3 axis import - assuming the same price range?

Thanks
Rick
 

Happycamper

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Rick, there are several different brands/names and I'd venture to say the chineses ones are all very similar if not the same. Whatever you get you will be happy with. These are all elctronics and usually if they work when you get them, they'll work for a good period of time. I know that you will find (after installing and using a DRO) that it makes machining a LOT easier and you will wonder why you didn't install them years ago!

Hawk
 

mksj

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#26
Given that an older used DRO unit is as is and lacks some of the newer functions of DROs. I would opt for a new DRO. I have also seen issues with older DRO head units with regard to the resolution of the scales they support. I did have an Acurite View DRO on my last mill and it was great, they offer very good quality DROs, but the two models you are looking at are quite old. Personally at the price range you are looking at, for about $100 more I would seriously look at the Easson ES-12B. This would be a step up on the generic Chinese DROs, a number of us have the ES-12 series and they work great..
https://www.aliexpress.com/store/pr...xis-DRO-system-and-3/1021179_32789719488.html
 

Rick_B

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Given that an older used DRO unit is as is and lacks some of the newer functions of DROs. I would opt for a new DRO. I have also seen issues with older DRO head units with regard to the resolution of the scales they support. I did have an Acurite View DRO on my last mill and it was great, they offer very good quality DROs, but the two models you are looking at are quite old. Personally at the price range you are looking at, for about $100 more I would seriously look at the Easson ES-12B. This would be a step up on the generic Chinese DROs, a number of us have the ES-12 series and they work great..
https://www.aliexpress.com/store/pr...xis-DRO-system-and-3/1021179_32789719488.html
I did/do have a concern with used, older prducts that may no longer be suported. I'm curious about your recommendati regarding why you consider it a step above other imports? Is it functionality, build quality/robustness, customer service?

How is the customer support fromthe imprt dealers?

Thanks
Rick
 

Bob Korves

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#28
DRO Pros are known for providing good service after the sale and for standing behind their products and honoring their warranty. That comes as a cost. Much of their product is Chinese import equipment, and is sold at much higher prices than the cheapest priced stuff from eBay or Ali Express. If you want somebody to hold your hand, they are a good choice. If you want to save considerable money at the cost of manuals that are at times indecipherable and maybe looking for help on the web and here on H-M, then go with the bargain price stuff. Lots of the cheap stuff has been installed quite successfully and is in regular use with good results.
 

mksj

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#29
Easson has been around for a long time, and both from a quality and reliability stand point I would consider to be better built units over the generic Sino DRO. The manuals are in comprehensible English. The DRO head unit is very functionally laid out and the graphical display for milling is a bonus . Alliepress is the cheapest, I would also consider Quality Machine Tools or DRO Pros if you want a unit shipped form the US with better support but at additional cost. The ES-12B/C is about 1/2 to 1/3rd the price of an comparable Acu-Rite or Newall DRO. Other than a generic rebranded Sino DRO, Easson DROs are often supplied with machines for both lathe and mill (ES-8, ES-12).
http://www.hobby-machinist.com/threads/easson-es-12-b-dro-install-on-a-pm-833t-mill.56329/
http://www.hobby-machinist.com/threads/easson-12b-install-details-on-a-pm1340gt-long-post.55949/
 

Bob Korves

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