Anyone have an Acu-rite 300 series DRO?

A couple of years ago, I purchased an Acu-rite 300 series DRO for my Monarch 10EE lathe. I didn't support my local equipment distributor, but got it from a company in LA. The manual that came with this DRO sucks, and Acu-rite claims with the on screen tutorial, a person with an IQ of over fity should be able to get this thing to do more than just tell position. I can't get this DRO to do hardly anything. It's supposed to have tool presets, and numerous other features- I've tried for hours to get it set up, and so has another machinist. It would be just so nice to be able to slip in another Aloris toolholder, and have all the offsets dialed. NO SUCH LUCK. I've called Acu-rite on some other problem, of consistantly getting my DRO to read in the correct manner, and I still can't consistantly get it to do that. Move the compound in- my readout should get smaller- not larger. Most of the time it does, but sometimes it just seems to forget which way its going. SO I bought the best one they had, and I can't get it to do a thing. I'm not stupid- I've taught myself to program my CNC lathe in about a month by reading one book.

SO my gripe, is what's with companies documentation. If I was making a $2600.00 DRO, I would certainly write a manual that the average joe could use and figure out my unit. My VersaMil manual is a 150 pages long, and describes just about everything. The accurite manual just refers you to the onscreen prompts, which absolutely are pathetic. So does anyone have one of these DRO's and is able to get it to work like it should? AND if you do have it working, is it as nice as a CNC lathe that just pulls up the tool, and bingo, you're at the right measurement? In theory, it seems like a great unit, but the reality is I should have just got a two channel readout without the frills. Rant over

Brian,

Is it possible to get an update on this venture? I have just requested two quotes for the 300S Acu-Rite DRO.

Raymond

Raymond- So you want an update? Since I'm kind of brand loyal, I bought a basic two axis Acurite DRO for my Bridgeport Mill. Nothing fancy but does bolt circles, with .0005 scales. Again their documentation was pathetic for setting up the bolt circles, and I read and reread the instructions, and finally called them. Again the instructions were poorly written.

My fancy 300 DRO on one of my Monarch 10EE's, has NEVER been used to change an offset on a toolholder, in my supposed library. I run a CNC almost exclusively now, with the Monarch relegated to 2nd ops, and machinist 101 projects. I figured out how to program and turn ball crank handles on my CNC lathe, but I'm obviously not bright enough to figure out an Accu-rite DRO. After getting frustrated a few years ago, not getting any answers, it just got relegated to the FAR BACK BURNER. I've also discovered Newall Readouts are far easier to use, there manuals make sense, and they are accurate. More than I can say about my Accurite DRO on my mill, that's off .003 in 7 inches. Using a 7 inch gage block, a Moore corner block, and an Interapid .0001 indicator, I decided to see how come stuff I was machining didn't work right. Three thou in seven inches is ridiculous. My SIPS repeat and measure to the "10ths" in seven inches. Needless to say I no longer even trust my Acurite DRO's.

So, How's that for an update?

Thank you Brian,

I was leaning towards the Acu-Rite 300S. I wrote to three different Acu-rite reps about getting a quotation for two machines and for clarification on the real measuring length. One answered after a week. My conclusion is that if they are that bad when selling they will be even worse when there is a problem.

Today I requested a quote for the two machines from a Newall installer for two C80 systems. I'll see what happens. I don't know anyone else who can handle vectoring.

You do bring about a point of verifying the accuracy over a longer distance. I'm not certain how and where to get a metre long standard except get a rod measured at a specific temperature.

Raymond

The three thou in seven inches may not be the DRO, but rather where and how the DRO is attached to the machine. In fact, it's probably NOT the DRO.

http://www.neat.com/techinfo/abbe.asp

A error of 3 thou in seven inches represents about a one and 2/3rds degree error in alignment between the critical axis and the measurement axis, provided the error is that you're moving a critical 6.997" for every measured 7". That is a very common kind of misalignment to make.

Another possibility is flex somewhere in the machine as the bed moves is not flexing the DRO the same amount. This is a kind of nondeterministic/kinematic error, as opposed to the above Abbe error scenario.

You'd have to test the DRO by itself, on a test jig, with an interferometer and a mirror on the slide if you want to know exactly how accurate the scale is. Long rods and stacks of gage blocks are not the best way to judge continuous accuracy, since there's no way to tell if you're looking at some kind of periodic error rather than some accumulated error.

Unless you've got a measurement lab hanging around, it's going to be a little hard to truly verify individual machine components to tenths. Which is, unfortunately, the fastest way to see which problem you're actually having.

I can't picture Brian mounting a DRO spar 1.6deg. off parallel.

I have an Accu-rite Turnvision DRO and have similar complaints except for the inaccuracy. It uses the older B&L scales. The manual is nearly incomprehensible, like a software manual written by the programmers. Some of the instructions are flat out wrong, and some of the features simply do not work, or work incorrectly. For example, in the teach mode, if you make a move in only one axis and push the button to enter the move, that move is ignored - you have to move both axes for teach mode to work. So teach mode is useless. The key pad and the series of key presses needed just to zero an axis is completely counterintuitive, and worthy of a digital security system for complexity and difficulty. We call it the 'User Hostile' DRO. It can do a lot of neat things but it's so hard to run, no one uses it here except for simple DRO function. I called Accu-rite for help and was told "that's an obsolete unit, no one here knows anything about it" in exactly those words. Once we figured it out,we made up our own instruction sheet so we could use it. One of the machinists flat out refused to use it after a certain point and would take an older display off a mill, set it on top of the Turnvision and connect the cables just so he could use the lathe.

I bought a Newall to replace it but haven't installed it yet, I guess I'm waiting for the Accu-rite to burn out first so we can take it out back and use it for target practice.

I don't think its limited to DROs: The Starrett 742 Data Logger manual sucks big time, too. And I've got microscope filar eyepiece (think of it as a DRO hooked up to microscope crosshairs) from Lasico that vies with the Starrett manual for worst of show.

You'd think that they'd write these things from a user perspective.

Damned engineers.

Jim the Engineer.

Bosleyjr,
I doubt that an engineer wrote the manual.
These days, companys hire technical writers to do manual writing. (Lots of technical writers are journalists that couldn't get jobs with news media or English majors that couldn't gejobs as teachers.)
As I recall from my days as an engineer with Texas Instruments, I wrote the instructions for the equipment I designed. Customers never had any trouble, becuase the typical engineer would have an inexperenced person try his directions, after 1st product unit was built, and make changes if there were any ambiguities.
That changed in the late 70s or early 80s, when the technical publications department hired technical writers that would meet with designers and then would independantly interpret and write what they thought applied.
Bob N.

Boy I must be blind or something to install my scale on a Bridgeport mill, and get it off by almost two degrees. The scale mounts on a fully machined tablepart of the table, a side you can use for checking your table for runout, and the other half of the scale is attached directly next to this surface. Frankly it's hard to screw this part up. This isn't like installing a DRO on a Devlieg Jig MIll, or on a Sip (especially on a Sip). No the Bridgeport installation is machining 101. The Dro is probably as perfect as the supplied instructions on how to use it.

Frankly these days, I don't TRUST any machine tool to be accurate. I qualify just about everything I use, because there's parts I make in my machine tool line, that virtually have to be perfect or they don't work- period. There's no room for error in location, or perpendicularity. I don't use the Bridgeport for super precision parts, but still I expect a year old DRO to give better results than what I get from mine. I took for granted that once installed, the DRO would be accurate. Not so- so I check all of my dro's now- not just the acu-rites. I'm not trying to split tenths here, but I sure would like to know if I have a scale that reads to two tenths, that it's accurate. Using gage blocks and a .0001 indicator may not be the NAtional Bureau of Standards, but it sure gets me in the ballpark, for checking distances. For checking long lengths, I'm not wringing a pile of gage blocks together, but I have several sets of qualified rods that are in increments up to 12 inches long. Again, maybe not up to ToastyDeaths standards, but certainly accurate enough to determine whether the machine is capable of positional repeatability to at least under a thou.

I just quickly read the article referred to by post by toastydeath. Certainly in a situation where a ballscrew or acme screw is attached to a rotary encoder, angularity of the screw to the actual movement of the table has a serious effect in accuracy- BUT the Acu-Rite does not use a rotary encoder, it's a glass scale attached directly to the casting of the machine.It doesn't care whether there's five miles of backlash, it doesn't care whether the feedscrew is mounted crooked- it just measures movement. If the table moves, it's supposed to tell how much, and in my low precision Bridgeport, it has half thou scales. Someone should re read their article and tell me how it applies to a machine with glass scales firmly mounted to one of the most accurately machined parts of the machine. In this case angularity has NOTHING to do with the three thou discrepancy in locational accuracy. Maybe in the seven inches of movement, the TABLE of the Bridgpeort mill is flexing three thousanths?? I doubt it. I didn't test it at the extreme ends of the travel. but right in the center. The reader and the scale are in perfect alignment, with both pieces mounted solidly. Sorry, but I stick with my story- the DRO is not reading correctly. I did the same test on one of my Moore Jig Bores right after checking the DRO on the Bridgeport- The Moores spectacularly accurately ground leadscrews, are still as accurate as ever, on my 1964 Moore #3. Moving it's table using the same setup, I get EXACTLY 7 inches- well okay maybe not exact, but within a tenth or two taking in varying temperatures, blah, blah ,blah.

Can't help with the Acu-rite, but I will chime in on the Newall. I have 2 C80s in the shop. One was installed by MSC on the mill we bought, the other I installed on the lathe. I really like them. I have used an older Anilam and Mitutoyo DRO's and I much prefer the Newalls. Both mine are 2 axis units, but the manual shows vectoring and summing features. The head unit is built nice and solid, the scales and scale mounts are very well made. The Microsyn scales look pretty fragile, but that is what the guard is for (the Microsyn scales are the slim scales for tight areas). Scale cables are solid.

The Mitutoyos worked ok until they got dirty (glass scales) then they would jump. The Anilam was so old, I don't know if it is fair to criticize it, but every now and then it would forget where it was.

Can't give a long term review yet, but the Newall certainly looks well built and engineered. The manual seems decent as well. Don't know how it compares feature wise with the Acu-rite, but it does basic stuff like bolt holes(mill) and tapers(lathe). The one on the mill I have set up as a generic (as opposed to a mill or lathe) setup so it can do sub-datums. The lathe setup can do tool offsets (I think it will do up to 99 different tools). The head unit is the same on both, how you set it up determines the features.

I like the Newall readouts, but I just don't get how a tube full of balls, somehow translates position. I have Spherosyn scales on one of my Devliegs which happens to have EIGHT FEET of travel. I'm a little concerned with it, because the way it's designed, it has no intermediate supports for this scale.So eight feet of scale is just hanging from the two ends. If I lift up in the center, my readout changes two to six tenths. Something tells me that aint right. The thing can't help but to sag in that length, unsupported.

Brian,
In my manual, they say that scales over 2 meters in length should have a support. They have a roller that sits near the reader and travels with it.

Edit: I looked, and it is actually scales over 2.5 meters in length, and it doesn't look like the roller travels with the reader, but is sprung in such a way that the reader can pass over it. The 2.5 meter scale has 2 such supports, with longer scales having more than that. Looks a bit awkward, but they do take that into consideration (maybe you have an older unit?)

The Newall system has End Mounts as well therefore the Encoder helps support the scale on the free end. It is possible that Brian is not seeing "changes two to six tenths" in normal use because the Encoder, when in the middle, helps to support the middle.

I never noticed a wear ring or bushing in the Encoder that could be replaced if worn from this type of rubbing.

The Newall scale tube is stretched by putting the balls in compression. The compressed ball column length changes to achieve the calibrated length. Probably this stiffens the tube considerably.

Raymond

Brian, I have an Acu-rite 300M on my Bridgeport mill. I can't say I've experienced any of the problems you describe.

I've got .0005 scales (ENC-150) on 3 axis' and they are dead on as best as I'm able to measure using standard gage blocks wrung together and it repeats well. The 300M supports linear error compensation tables that can be set up to compensate for errors in each axis. I'm pretty confident that your model will also have this feature. I would first check to see if there are any erroneous entries in the table. If there were, it could cause the sort of error you're experiencing. If it's clear, you could then use it to compensate for the error your seeing.

I have no issues regarding the manual for it. It's pretty straightforward and effectively explains how to use all the features. It must be very different from yours.

One of the nicest features is its ability to store programs. Once I have all the steps for a given part programmed into it, I can save it and recall it anytime I need to run more of those parts. Being able to see the entire layout graphically with the current operation highlighted is also a great feature, especially when I get interrupted in the middle of running a part and come back an hour later.

Marc -

Marc, I have a 300T on my lathe, but on the mill I just purchased the basic readout, with the same scales you have. Whether it can compensate for errors, I haven't had time to figure out.

What do you mean by erroneous entries in the table?? The scale is mounted on the back side of the table, with the reader attached directly to the saddle. I would assume it would just read movement- period.

Brian, by erroneous table entries I was referring to the Linear Error Compensation 'tables' stored inside the DRO, not the physical table of your machine. I don't know if your model uses them. Which model do you have the problem with? I believe some of the simpler models employed a similar error correcting scheme but was limited to maybe 3 segments rather than the 99 of the 300 series. It's a longshot, but if there was erroneous data written in the table it could throw your readings way off. Conversely, if they are clear, you might be able to use the feature to correct the error you're experiencing. Just out of curiousity, are you seeing the error on a single axis or all of them?

Well Brian youre not alone I am a cnc programer
and I am lost with mine bought it new $1500 ,took it off my mill and replaced it with a Fagor and all was well
. a Fagor a all was well.