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View Full Version : After I get my linear scales mounted, what do I do to ensure accuracy ?



hephaestus
08-10-2015, 10:50 PM
I've seen a few videos on youtube about
DRO's but I can't seem to find anything
in detail about indicating them in.

I did see mrpete222's video to check
accuracy but nothing about the installation.

I have the X scale mounted and its
centered in the middle of the table
"on the side anyway", centered left to
right and not off any more than 1/64
and I have it dead nuts level with the
top of the table.
I also have 1 shim "a washer" on each
side to move it away from the table
since the reader is wider than the body
of the scale. The shims that were provided
were not thick enough to make a difference.
I sanded the washers to a close tolerance
but may need to work on those more.

Also I noticed a slight bow in the scale
that crowns toward the table. I used a
Feeler Gauge towards the mounting
points and determined that I needed
a .064 shim to straighten it out.

What else will I need to do ?? Thanks

macona
08-10-2015, 11:02 PM
Almost all the scales out there float and are guided by the glass scale inside the aluminum strip. So as long as you have it on there pretty straight you will be fine. You would have to be pretty far off to actually make a noticeable difference in accuracy and by that point your scale would crash into the reader head.

You dont need to go crazy with these things, as long as the reader head does not rub against the scale housing you will be fine.

hephaestus
08-10-2015, 11:06 PM
So it's supposed to hang down some
"which is the way I have it" rather than
being pushed up all the way against
the bottom of the scale body?

loose nut
08-11-2015, 10:05 AM
Different equipment may need to be set up differently. My Fagor DRO specify an alignment tolerance of 0.008" over the length of the scale, in both planes but less is better, others may be different. It isn't difficult to get the scales within a couple of thou. using a dti mounted on the mill. Also after installment is done your DRO may have an accuracy check that has to be performed to set up the scales to their most accurate condition. Some DROs have a built in accuracy checking function. Should be in the Manual.

loose nut
08-11-2015, 10:11 AM
So it's supposed to hang down some
"which is the way I have it" rather than
being pushed up all the way against
the bottom of the scale body?


If you are talking about the reader head, these "may" have to be set at an specific distance from the scale and have a spacer gauge, bit of plastic, that you set the distance from the scale with. If the manual doesn't say anything about this then it may not be necessary.

macona
08-11-2015, 05:07 PM
You will have to look in the instructions and see what the spacing is. Some scales come with a little plastic clip that you remove once the scale is installed. It sets the proper gap. They should not be touching no matter what.

hephaestus
08-11-2015, 08:40 PM
You will have to look in the instructions and see what the spacing is. Some scales come with a little plastic clip that you remove once the scale is installed. It sets the proper gap. They should not be touching no matter what.
That's just it, there was no instructions.
There is only a manual that tells what
the buttons on the DRO are, it doesn't
even tell how to use the functions or
how to make them work.

Maybe I should call the seller and see
if something was left out.

macona
08-11-2015, 09:42 PM
Ohhh... That's annoying. I would start by looking at the scales at http://www.dropros.com/DRO_PROS_Digital_Readout_Scale.htm and see if they are the same. I am guessing you have a chinese kit?

RB211
08-11-2015, 10:18 PM
The plastic support piece that is used to protect the reader to scale during shipping is a good tool to set the spacing. However with the Chinese scales, its not critical, i'd say within .050

hephaestus
08-11-2015, 10:46 PM
I bought it off ebay from zsinstruments
In Lafayette Indiana
It says "Ditron" for the make assembled
in USA supposedly.

hephaestus
08-11-2015, 10:52 PM
Ohhh... That's annoying. I would start by looking at the scales at http://www.dropros.com/DRO_PROS_Digital_Readout_Scale.htm and see if they are the same. I am guessing you have a chinese kit?
Thanks for that link.
My scales look just like those really.

wierdscience
08-12-2015, 10:06 AM
I bought it off ebay from zsinstruments
In Lafayette Indiana
It says "Ditron" for the make assembled
in USA supposedly.

I've bought from ZS before,they have good service from my experience.Ditron scales are Chinese,but pretty good,we have a couple scales on mills at work,no problems with them.ZS I believe buys the components and assembles systems to the customers requirements.I had an Accurite DRO that had one scale too short for my installation,I bought the scale I needed from ZF and they installed the correct connector on the cable to convert the Ditron scale to the Accurite monitor.

Like mentioned before the reader heads have a good .010-.015"+/- of float.I just install them with the plastic shim in place using a depth mic to get the scale body parallel to the table surface.Once the reader is attached,then take the shim out and it's good.

RB211
08-12-2015, 10:35 AM
I've bought from ZS before,they have good service from my experience.Ditron scales are Chinese,but pretty good,we have a couple scales on mills at work,no problems with them.ZS I believe buys the components and assembles systems to the customers requirements.I had an Accurite DRO that had one scale too short for my installation,I bought the scale I needed from ZF and they installed the correct connector on the cable to convert the Ditron scale to the Accurite monitor.

Like mentioned before the reader heads have a good .010-.015"+/- of float.I just install them with the plastic shim in place using a depth mic to get the scale body parallel to the table surface.Once the reader is attached,then take the shim out and it's good.

My scales and reader head are Ditron as well. Not made or assembled in USA. http://www.drokits.com has far better pricing on the Ditron scales.

wierdscience
08-12-2015, 01:20 PM
I've got some from them too,but from them you get no service nor any retrofit knowledge.They did have on their Ebay page some plain counters that were nice,about $140 for a three axis counter.
I do wish Ditron would get their act together and start producing some long scales,say 6' or better.

RB211
08-12-2015, 06:34 PM
I've got some from them too,but from them you get no service nor any retrofit knowledge.They did have on their Ebay page some plain counters that were nice,about $140 for a three axis counter.
I do wish Ditron would get their act together and start producing some long scales,say 6' or better.

Your right about no customer service, one of my scales were defective. I had to get out my logic analyzer and figure out one of the quadrature outputs was not working. Opened up the reader head, and noticed crappy hand soldering. Re-heated the blobs with my iron and fixed the scale! As for the DRO head, I actually ordered it from Alibabba direct from China, with shipping it was still cheaper than what DROkits wanted. Could not say the same however for the glass scales...

hephaestus
08-16-2015, 02:01 AM
Well I pretty much finished up my X installation. I will be posting some pics in another thread but as far as accuracy goes, since there is a slight bow in the scales I guess it is throwing off the measurement some. I put some feeler gauges in the center, to straighten out the bow and the scales measurement reading changed by like 3 tenths. Once I get an indicator on it i'll be able to tell more about it.

big job
08-16-2015, 04:17 AM
I don't think a little off will matter. I expoxied my scales on 3 yrs ago & still fine today. And they are right on with my dials.
I'm still in the habbit of using both dros and dials.