DIGITAL READ OUT 3 Axis - DRO MILL
(2007)
JOB DONE MAN!!
It is not easy to install the digital scales (linear glass etched scales).
Installing the scales means to plan the best way to mount them, to get best precision available keeping far away axial errors which can cost precision on final task.
I have thought for few days how to install these scales and the following photo will show you how I solved this big problem!!!
X axis:
for this axis I use a 642 mm overall length ( 500 mm travel) etched scales with 5 um precision.
The X3 table is not able to travel free on 50 cm since the left leadscrew clamp needs to be trimmed, please see this page to know how to...
I have made "free to move" my X3 and my table can move + - 25 cm , for a total of 50 cm...
The scale must be mounted with two clamps on the sides, because the mill table is not so long as the scale which is 642 mm.
check out few steps to make the 0.01 precise blocks...
threading M4..
drilling, and milling for M5 allenhead screws...
positioning the block on the mill table to drill the table..
yo yo... the block is mounted and the scale is holded perfectly..
please think about this: The scale is mounted few millimeters lower then mill table surface , because during machining operations or objects moving on the table, any contact on the scale will move or damage it, with precision loss.!! so, this is why the scale is at -5 mm from table surface!!
the lower view shows how to fix the sensor to the lower table base.. (saddle)
the left part of leadscrew clamp must be trimmed down few millimeters to allow the Y axis to move free... and also must be drilled and tapped M5 to hold the left X axis block... (same as right, shown above here)
the next level in scales precision is to measure the scales to tight bolts when the 0.01 precision of axis is achieved.
I have fixed the DTI on the mill head and then I have moved the X axis back and forth until scales surface runs 0.01 left to right and front to back..
Please note that all the clamps made , are made with bigger holes than M5 sitting, to allow the block to be moved (and then to move the scales ends), this is to be able to move in any direction the scales helping the 0.01 run true procedure...
the sensor must be mounted with 1.00 mm precision... one way to cheek is with caliper, or with thicknesser..
Y Axis:
the x axis is more complicated because there is a really tight space to fit the scale
the scale used is a 342 overall length (200 mm travel), 5 um precision.
few cuts on the band saw to prepare gross blocks..
and few cuts with the slitting saw
.. machining the main block which will hold (move) the sensor...
screws sittings..
drilling and threading the sensor block holes.. M5
the sensor block is in place.... fixed
the scale is mounted to.. and the sensor is trimmed to 1.00mm distance with ticknesser... (both ends)
again, the scale is checked for a smooth 0.01 mm true run over is axis
to show you how tricky was this installation, check out these few shots. (main X table top runs 0.6 mm on top of the scale which is steady on two blocks, to allow the sensor to move free 0.6mm far from mill body.. !!)
.. and inside of this.. the sensor block hold the sensor , running few millimeters far from other things!!!
I think is a really nice installation of Y axis on the X3 !!!
a closer view shows the X and Y cables tied together....
note that all scales surfaces are covered with alu tape to improve wear.
Y axis:
Y axis is the longest. in the reality the X3 head moves up and down for 35 / 40 cm max... but I have used a longer 792 overall (650 travel) scale.
This is because the x3 column cover is an unstable surface and it is impossible to hold in place at 0.01 true the digital scale.
another point where to put the scale is inside in the mill column, but in this case the movements are made on the other end of the head (the back of), which tend to shows false values due to machines flexibility. (up to 0.05 mm).
So, the best way is to use a longer scale (which wil be only used 35 - 40 cm of 65 total), but this scale will be held firmly on top and on the bottom of the column, assuring a 0.01 strong clamp-..
anyway, let's show the job...
from the block I got few parts....
which I machined to desired dimensions...
these are all the parts for vertical axis...
the mill head cover must be cut to allow the top block to sit perfectly on the mill column "milled" top surface
the top block is mounted. it is made with 360 ° ability to correct scale top trimming, on any direction. this will allow me to trim the scale 0.01 vertical true with mill head...
the L shape of the clamp is because the mill head must travel higher than column highest surface, this is because the head cover is higher that the head itself...
the photo shows the head on its maximum tallest position. perfectly surrounded by the L shape block...
bottom view of top block.
for the lower block I have made a simple small block with M5 sittings, and M5 side thread to hold in o place the scale.
the scale is mounted...
to move the sensor I had to make a small plate with 6mm thick aluminum.
the plate is attached on the head left side...
drilled and tapped M5
once that sensor is mounted, is must be trimmed at 1.00 mm true from scale body, upper position and lower position must be checked
Display and cables..
The display is mounted on the right side, directly on the mill column, with its own factory clamp. the main cable is wired directly on the mill core, to get power when the mill is on, and rest when "she " is off...
The scales cables are grouped together in the easiest way, to prevent unwanted mess.
