What's new
What's new

Best practice: vertical axis DRO scale on a surface grinder

ballen

Titanium
Joined
Sep 25, 2011
Location
Garbsen, Germany
Dear Metrology group,

I have a question about mounting a vertical axis scale/encoder on my surface grinder.

I'm adding a digital readout (DRO) to the vertical axis of my 1986 Jones and Shipman 540APR surface grinder. I'm the second owner of the machine, which was apparently only used for a few months by the original owners, and then shoved in a corner and forgotten for the following three decades. The ways on the machine are pristine, and I've mapped the grinding footprint (150 x 450mm) comparing it to a slightly larger surface plate. Within this rectangle the total deviation from planar is at most 2-3 microns (and might be better, since that's comparable to the accuracy of the surface plate). I've had the machine for several years and really like it. The only shortcoming of the machine is that it doesn't have a DRO.

So I'm adding a three axis DRO to the machine. The long and cross axes are easy enough. But for the vertical axis I'm trying hard to do it as well as possible. I'm more interested in repeatability and resolution than in absolute accuracy. Total range of vertical motion is 280mm. Total cross section available is about 12 x 60mm, which is not enough for a sealed encoder.

I'm using Renishaw parts for an open non-contact system: an RGH25U optical read head, an RGB25Y interpolater, and RGS20-S scale tape. I've used this system in the past for the long axis of my cylindrical grinder, and it works very well. The tape is 6x0.2mm, with a 20 micron period, accurate to +- 3 microns/meter and within +-0.75 microns in any 60mm section. The interpolator provides 10 counts per micron, so a 0.1 micron resolution. That makes sense here: the machine hand wheel scales have 1 micron divisions, and with care, it is possible to work to micron precision. So another order of magnitude in the resolution is justified.

I'm mounting the scale inside the machine, almost directly over the vertical lead screw, and close to halfway between the two vertical guide rails. The measuring tape is attached to a strip of annealed ground O2 steel (thermal coefficient ~11.2e-6/K) 50 x 10 x 360mm, which in turn is mounted to the cast-iron carriage (thermal coefficient ~10.7e-6/K) that carries the grinding spindle and motor. The 50x10x360 strip is attached only at the top and bottom ends, not along its length or in the middle. The optical read head is mounted to the cast-iron machine chassis with steel blocks, bolted in place over an epoxy "shim".

Because of this mounting location, and the slow change in machine temperature in that area, I expect that the O2 carrier strip and RGS20-S measuring tape will be in good thermal contact, and will have a temperature similar to the cast-iron body of the machine. The RGS20-S tape is "mastered" to the O2 strip (glued down at both ends) so will expand and contract with that strip. However there will be some differential expansion between the O2 strip and the cast-iron spindle/motor carriage. Probably this will be less than 5 microns but might be as much as 20 microns if the carriage and scale differ by 5C in temperature.

My question concerns the attachment of the O2 strip to the cast-iron carriage. I can either fix the strip (secure datum point) at one end, and leave the other end free to "float", or I can fix the strip at both ends. I am about 90% sure that the first choice would be best, in part because I have no good way to attach a 10 x 50 mm cross section strip well enough to ensure that the strip rather than the fasteners would deform. My question, how to decide between fixing the strip at the top or at the bottom? Is there a better choice? Mechanically, either is OK. The top of the strip is the region that is in use when the grinding head is near to the grinder table. This might argue for the top being the secure datum point, and the bottom of the strip being allowed to float. But I'm not sure.

I can provide some photos if that would help.

Cheers,
Bruce
 
Last edited:

ballen

Titanium
Joined
Sep 25, 2011
Location
Garbsen, Germany
I finished the hard part of the installation yesterday, and this is now working well. I got no feedback for my first post, so decided to fix the top of the scale (area that is used when grinding thin parts) and to leave the bottom of the scale "floating". Here are a few photos for the next person doing something similar.

The parts I am using are from Renishaw:

RGH25U non-contact optical read head (produces an analog signal)

attachment.php


RGB25Y interpolator (produces an RS422 incremental digital quadrature signal). The output from this goes directly to the SINO DRO SDS6 display, which has RS422 inputs.

attachment.php


RGS20-S scale material (gold-colored strip) which has a 20 micron period. I really like this stuff. It makes it possible to built an accurate open high-resolution optical encoder at reasonable cost, which occupies very little space. The only constraint is that you need to find a location which provides good protection from dust, dirt and coolant.

attachment.php


There are only three parts: the scale carrier strip, the metal T that carries the head, and the block that carries the metal T. All three are visible in the photo above, and are made from steel, to more-or-less match the temperature expansion coefficient of the machine itself. All of these are stiff and chunky to reduce motion from vibration.

The block that carries the T is bolted to the machine with two M6 SHCS, with a metal-filled epoxy shim between it and the cast-iron chassis of the machine. Those bolts are not visible: they are underneath the metal T, and angled 10 degrees outwards so that I could drill and tap them with hand tools. If you look closely, you can see the fillet of gray J-B Weld epoxy to the left of the block, which squeezed out during installation.

The scale is located almost directly over the vertical lead screw, which attaches to the lower part of the carriage, shown below. The two round vertical rails that guide the carriage and make the vertical ways are on the left and right of this carriage, so the scale is close to halfway between those.

attachment.php


The readhead must ride 0.8mm+-0.1mm above the scale. By tuning the four M4 corner screws, I was able to get this within 10 microns over the entire scale length. Then I injected a metal-filled epoxy shim (J-B Weld) behind top of the scale, so that the M6 mounting screws could be torqued down. This shim is very important, because the cast-iron carriage beneath the scale carrier has a rough and uneven surface. The shim provides a uniform level support, so that I can torque down the bolts hard without distorting the scale carrier.

attachment.php


The bottom of the scale carrier is retained with screws that have lockwashers under them. These screws are not torqued, so that the bottom of scale carrier can move with expansion and contraction.

attachment.php


I was happy and surprised to see how stable the measurements are: even with all of the hydraulics and spindle running, the 0.1 micron digit (4 millionths of an inch, about 1/5 the wavelength of visible light!) is stable. The combination of the scale location and machine design help a lot with this. I can push down hard on the wheel housing without shifting that final digit!

I still need to glue on the top and bottom "end clamps" that fix the RGS20-S scale material to the substrate. This ensure that the scale material expands and contracts with the substrate. I'll wait a few days before I do that, to ensure that the scale has settled after installation. I'll also attach some soft vibration-damping material (self-adhesive bitumen sheet, used for auto-body damping, about 3mm thick) to the back of the scale carrier, in the area around the pulley.

Note: the entire metal scale carrier (with scale attached) can be removed and replace via the 4 screws that hold it to the carriage, so I can still access the pulley and spindle behind them. I coated the back of the scale carrier with mold release compound before injecting the epoxy shim behind it.

Renishaw make a small magnetic reference mark indicator, which provides an electronic reference mark at maximum resolution (here 0.1um). In principle this could be added, but I decided that it didn't make sense here, since every time you dress the wheel, the zero changes.
 

ballen

Titanium
Joined
Sep 25, 2011
Location
Garbsen, Germany
Nice job. Seems you have it well thought out. Looks like a lovely machine in good condition.

Thanks. I have never tried to do a DRO with better than 1 micron resolution before, so I did research and thought about this carefully before proceeding. The machine is wonderful, here's a photo taken some time ago, after I had fixed an oil leak and was inspired to clean it up.

attachment.php


One of these days I'll have to do another "cover shot" with the DRO.

Since I wanted to ensure that the scale extended to the very bottom of the vertical axis travel, I had to take off the chuck. Fastest and easiest way was to remove the entire table and chuck together, which only requires taking off four screws for the cylinder rods, and unplugging the chuck.

attachment.php


attachment.php


I bought this machine within seconds after seeing a photo of the ways (the table ways are equally good).
 

ballen

Titanium
Joined
Sep 25, 2011
Location
Garbsen, Germany
Here's how it looks with the DRO. Front view:

attachment.php


and back view

attachment.php


The interpolator and cabling are inside the column, to the left of the upper access panel. Behind that panel is the gold-colored optical scale and readhead.

I'm planning to add a 1 micron resolution encoder to the long axis (490mm total travel). Because that environment is dirty (coolant spray and splash) I am going to use a magnetic scale made by RLS (an affiliate of Renishaw) called the HiLin. The scale is 6 x 18mm in cross section, and is completely encapsulated inside a welded stainless steel cover. The magnetic read head (rated IP67) is non-contact and "flies" 0.2mm over the surface of the scale. I should be able to fit it on the rear of the table, where there is a ~12mm gap between table and column. If you look at the photo just above, it will go to the right of the "90-degree elbow drain fitting" attached to the rear of the table. That area is not quite flat enough for the scale, so I'll pull off the table, bolt it to the mill, and machine a flat seat for the scale. I will probably epoxy a 2mm thick aluminium piece onto the table under the area where the scale will attach, and will then machine that flat. That way the rear side of the magnetic scale will be a little bit more distant from the (ferromagnetic) cast iron table. That should help maintain the magnetic field strength of the scale and its long-term accuracy.

Edit: I was asked offline about the planned location for the RLS magnetic scale. This is shown below, in red:

attachment.php
 
Last edited:

priitm

Aluminum
Joined
Dec 28, 2014
Location
Estonia
I am skeptical regarding all kind of tape scales. Not sure, how much they stretch during gluing. I have some experience with installation lika and sony tapes, they seem too soft and unstable to be precise near 1 micron.
 

ballen

Titanium
Joined
Sep 25, 2011
Location
Garbsen, Germany
Hi Priitm,

I am skeptical regarding all kind of tape scales. Not sure, how much they stretch during gluing. I have some experience with installation lika and sony tapes, they seem too soft and unstable to be precise near 1 micron.

I was concerned about exactly the same thing, so I was surprised that the Renishaw tape is specified at the micron level, because Renishaw is a metrology company with a good reputation for honesty in their specifications. For the RGS-20S tape that I am using here, the spec is +-0.75 microns in 60mm and +-3 microns/meter.

Like you, I was very skeptical, so I worked out the numbers myself, because it's simple physics. My piece of tape is 300mm long, so the question is, how much force is needed to stretch that by 1 micron? How does that compare with the forces applied during installation? Let me repeat the numbers for you, because it interesting, and shows that Renishaw is not deceiving us.

In my case, I was applying the tape using their application tool, which replaces the read head so it lays the tape down in exactly the correct spot. Since I was working alone, I did this in short cycles. I raised the grinding head by about 10mm, then walked behind the machine, and used my fingertip to smooth down the tape, which was hanging from the applicator under its own weight. Then I pulled off another 10mm of the backing paper from the adhesive, and repeated 30 times. The tape was never under any force greater than its own weight, even when I was doing the smoothing. The stainless steel tape has a cross section of 6mm x 0.2mm, so a cross sectional area of 1.2 mm^2. The total mass of the piece that I was applying (length 300mm, volume 360 cubic mm of stainless) was about 2.7 grams, so the force of its own weight is about 0.03 Newtons.

Let's compare this with the force needed to stretch my L=300mm piece of tape by dL=1 micron. That is a fractional deformation dL/L = 3e-6, and since Young's modulus for stainless is about Y=2e5 N/mm^2, and the cross-sectional area is A=1.2 mm^2, the force required is
F = Y A dL/L = 2e5 x 1.2 x 3e-6 N = 0.72N
which corresponds to a weight of about 70 grams (3 ounces for those in the USA). I never applied that much force to the tape, or anything near it.

My conclusion: if the Renishaw tape is applied carefully, it will not be stretched enough to break the spec.

Cheers,
Bruce

PS: for the record, the adhesive that Renishaw uses for these scales is made by 3M. If you apply the scale to a clean and smooth metal surface, it's remarkably difficult to break the bond.
 
Last edited:

ballen

Titanium
Joined
Sep 25, 2011
Location
Garbsen, Germany
Here is the encoder installation for the cross feed. This is a KA-200 ML180 mm 1 micron resolution scale from Sino Germany, cross section of the scale is 16 x 16mm and the read head 14 x 16mm, so the scale and head fit into a 16 x 32mm opening. The scale came with a calibration chart, showing maximum error of +-1.3 microns over the range.

The scale is mounted on the right side of the saddle, next to the ways, under the saddle. It's mounted to a piece of 20x20mm aluminium L extrusion, 3mm wall thickness, which is epoxied to the bottom of the saddle. If you look closely you can see that I'm milled a drip-lip onto the machine side of the L extrusion, so that any oil or coolant will drip off the extrusion rather than running onto the scale.

attachment.php


attachment.php


The scale head is mounted to a blued steel bar, screwed onto the machine chassis in two spots:

attachment.php


Then I added a cover, and reinstalled the trips that flip the feed direction:

attachment.php


attachment.php


attachment.php


This is a well-shielded location, on the non-spray side of the grinder, so I expect the scale to work trouble free for many years.
 

ballen

Titanium
Joined
Sep 25, 2011
Location
Garbsen, Germany
The final axis which needed an encoder was the long (nominally 450mm, actual travel 487mm) axis. This is much less important than the other two axes, but from time to time it is useful to have it on the DRO. This axis is a challenge for several reasons:

(1) The only sensible place to mount an encoder is on the back of the moving table. The front of the table is occupied with the end-stop toggles, and the bottom of the table is cluttered with hydraulics and gearing.

(2) When the cross feed moves the table as close as possible to the vertical column, there is only 12mm of clearance between table and column. That's not enough for even the skinniest enclosed glass encoder (Sino KA-200, 16 x 17mm).

(3) The traverse speed goes up to about 10 traverses per minute and can run for hours. That's enough to wear out the rubber sealing lips on a traditional glass-scale encoder. So a non-contact encoder is called for.

(4) These points above argue for an open optical encoder, such as the Renishaw RGH24/RGS-20 combination that I used on the vertical axis. But the grinder environment is messy with coolant spray, which will easily contaminate an optical encoder.

For these reasons, I decided to try something new: a magnetic encoder. There was not enough space for a Newall Microsyn, so I decided to try a HiLin scale, from a Renishaw associated company called RLS, which is based in Slovakia, HiLin high-accuracy linear magnetic encoder system .

One problem with magnetic scales is that the magnetic strip is generally a polymer embedded with magnetizable particles, and after coolant exposure, the polymer swells and distorts. The HiLin scales are available in a completely sealed version, where the magnetic strip is enclosed in a completely welded-shut stainless steel carrier, so is impervious to coolant. The scale has a 2mm pitch, but the company literature claims accuracy at +-5 microns/meter with hysteresis and repeatability errors under 1 micron.

I was able to order the scale and head online, with delivery to Germany about one month after placing the order. (Full disclosure: I got a 30% discount after saying that I planned to write a report here.)

Here's a photo showing the scale, head and mounting hardware, as delivered. The scale has a measuring length of 500mm and an overall total length of 560mm. It is 18mm wide and about 6mm thick, and is delivered in a fitted wooden box. The stainless steel foil cover appears to be laser-welded to the body of the scale. Note that the foil cover is quite thin, so be careful not to dent it during installation.

The scale head is 18 x 20 x 50mm in size, and has an LED that turns green to indicate good orientation and signal strength. Output is EIA-422A, differential TTL, compatible with my Sino DRO.

attachment.php


In the past, all of the precision encoders that I had purchased came with calibration certificates, but this scale did not. (I asked the company if a test/calibration certificate would be provided, and they told me that it was available at additional cost. I asked how much that would cost, but they did not reply.) So I decided to do a crude accuracy check myself. Later this year I will borrow a laser interferometer and do a more precise check myself.

For the crude check, I mounted the HiLin scale on the table of my cylindrical grinder, so I could compare its readings with the non-contact Renishaw optical encoder below the table. The optical encoder has an accuracy of +-3 microns. Here you can see the optical encoder in the Y axis of the DRO display and the RLS magnetic encoder on the Z axis of the DRO display: they differ by 6 microns (499.079 mm versus 499.085 mm).

attachment.php


I then set up the DRO to display Y-Z, and ran along the full range of travel:


The largest deviation I see above is 19 microns, which makes me confident that the RLS magnetic scale errors are under +-10 microns.

Here is the scale installed on the rear of the grinder table:
attachment.php


I had planned to leave the scale open/exposed, but in the process of drilling and tapping the mounting holes, discovered that this was not a good idea:
attachment.php


You can see that the cast iron dust from the mounting holes I am drilling has been attracted to the magnets in the scale. This will also happen if coolant containing iron or steel dust lands on the scale. So I decided to retrofit as much of a cover as possible.

Before fitting the cover, I finished mounting the scale and head:
attachment.php


The shim strips under the scale bring it to a height that is constant to within 0.04mm = 0.002". I am going to replace the ones visible here (steel) with stainless steel shims, and will mount them and the scale with some removable gasket sealant, to prevent coolant from migrating behind the scale and leading to corrosion and displacement.

The head is mounted to an aluminium block held to the saddle with three M6 SHCS.

The splash covers are made from anodized aluminium L-angle, which is non-magnetic, so won't disturb the magnetic field of the scale. The fixed cover started off as 30 x 60 x 2mm and the moving cover started off as 20 x 20 x 1.5mm material. The cover consists of a part that is fixed to the saddle and intended to block coolant that bounces off the column, and a cover strip that is fixed to the table over the magnetic scale and rides above the fixed part of the cover. These covers are non-contact: there is no contact between the fixed cover and a moving part, or between the moving cover and a fixed cover. The fixed cover extends upwards about 3mm into the moving cover, so is sealed by gravity. The scale is not directly protected to the right of the read head (as viewed from the back of the machine).

attachment.php


The cover is not ideal, because it does not cover the scale to the right of the head (as seen from behind). However I think it will work well, because the coolant spray will be coming more or less in a straight line from the contact point of the grinding wheel, and bouncing off the machine column. So these covers and the table should ensure that the magnetic scale is always in the "coolant shadow" .

Here is a view from the other side. When the grinding head is high up, this is the worst case, because the grinding wheel is almost directly over the scale, and the "coolant shadow" comes quite close to the scale. (If you look closely, you will see two aluminium "ramps" fitted below the fixed part of the cover. They are also visible in the previous photo, above. These ramps are needed because the telescoping splash shield for the vertical axis has two stop tabs. The ramps ensure that these tabs will slide up over the fixed part of the cover and don't catch.)
attachment.php


and showing the closest approach to the column:
attachment.php

Roughly speaking, going out from the table, one has:
scale: 6mm
air gap: 1mm
fixed cover: 2mm
air gap: 1mm
moving cover: 1.5mm
air gap to column: 1mm

Here is the overall rear view:
attachment.php


attachment.php


and a final photo showing all three axes on the display:

attachment.php


So far the scale is working well. If the covers do a good job of keeping steel and iron swarf from landing on the scale, I'll pull them off later this year and spray them green to match the rest of the machine. If not, back to the drawing board. I might be able to mill a recess into the bottom long edge of the table.

Cheers,
Bruce
 
Last edited:

ballen

Titanium
Joined
Sep 25, 2011
Location
Garbsen, Germany
I've done some grinding and the scales have all worked well. I was concerned that the magnetic X-axis scale might attract steel or iron swarf/dust and get contaminated, but that's not happened, it has remained clean. So I went ahead and finished the install, meaning cleaning up the details and painting the new parts.

Also, an important correction to my earlier post: the company that makes the X-axis scale (RLS, which stands for Rotary and Linear motion Sensors) is based in SLOVENIA not in Slovakia. My apologies for mixing this up, geography has never been my strong point.

Here are some final photos and a few notes.

For the magnetic scale itself, I made up nice shims, 40 x 12mm, with two 4mm holes at 28mm offset, in the necessary thicknesses from 0.04mm to 0.15mm, to shim the scale parallel to the travel within about +-0.01mm. These are under the clamping screws, so not really visible in the photo anymore. Before screwing the scale into place, I also coated the back of the scale and both sides of the shims with gasket sealant (the kind that doesn't fully harden but gets rubbery). The idea is to prevent any liquid from migrating behind the scale and encouraging rust to form which lifts the scale.

You can see that I also machined away a bunch of the excess aluminium from the head mounting block, so it's a bit sleeker looking.

attachment.php


Here is another view, with the lower cover and read head installed, but the upper cover not yet in place

attachment.php


Here's a view from another angle, with both covers in place, but the coolant drain gutter not yet installed:

attachment.php


Here's a rear view of the X axis scale, with the coolant drain gutter added

attachment.php


and from another perspective

attachment.php


Here the saddle is fairly close to the column. (I's not as close as it can get, because in that case there is only about 1mm of clearance between the top cover and the column.)

attachment.php


If anyone has further questions about any of the three axes, please ask!

Cheers,
Bruce
 

TGTool

Titanium
Joined
Sep 22, 2006
Location
Stillwater, Oklahoma
Interesting project. What sort of parts do you intend to grind that you need this level of accuracy? Gauge blocks perhaps?
PS, none of your photos are visible in your posts (at least I can't see them).

Photos have been showing up just fine here. Nice pics, by the way.
 

ballen

Titanium
Joined
Sep 25, 2011
Location
Garbsen, Germany
Interesting project. What sort of parts do you intend to grind that you need this level of accuracy? Gauge blocks perhaps?

The grinder itself is accurate to a few microns over the 150 x 450mm work envelope (I checked the geometry against a surface plate when I first got it). So on small parts I can work to micron precision, if I pay attention to temperature and take a lot of care.

I have always read that a good rule of thumb is that the measuring system should have an additional factor of ten accuracy (or precision, depending upon the situation) compared with the accuracy you are trying to achieve. That's why I wanted a 0.1 micron scale for the vertical axes.

Yes, I have made some custom "gauge blocks", shown here. I first machined and stamped these, then hardened and ground them. There are used on my cylindrical grinder to set tapers. You first set the table to grind cylindrical (constant diameter) then use these "blocks" plus an indicator to set the table over a specific amount. For example the block I am holding is exactly the right size to grind a precise SK40 taper.

When I first tried to grind some tapers, I made up the right lengths by wringing gage blocks together. But there were two problems. First, the blocks got messy with coolant and grit and I didn't like having them in that state. More important, the fixture that accepts these set over blocks has an inner corner, and if that has any dust or grit, it prevents the blocks from seating correctly. (I found this out the hard way when some tapers came out wrong.) So my custom blocks are exactly the right length, no need to wring them together, and they have a corner broken to prevent offset from dust or grit in that inside corner. There is one for a 10 degree taper (used on my Studer grinder hubs) one for each Morse Taper size from 0 to 5, and one for SK40, and some spare unhardened material in case I need another one for some other angle.

attachment.php


attachment.php
 

Conrad Hoffman

Titanium
Joined
May 10, 2009
Location
Canandaigua, NY, USA
Really nice job. Those Renishaw tapes are very good, though I've never used one that long. Floating the end of a long piece is the only way to go unless you want to reinvent the oilcan. A very small length change can give a shockingly large bow if you tie both ends.
 

Halcohead

Stainless
Joined
Apr 10, 2005
Location
Bay Area, Ca
Beautiful work and grinder. You even went so far as to paint the covers! It's cool the tables come off so easily on these grinders. Is the manual table feed via a manual hydraulic pump rather than rack and pinion or cable drive?

Are you using a generic DRO readout with these various scales? I guess so long as they output quadrature signals of the right voltage, you can connectorize the scales to the standard DB9 if they don't already come that way?

Interesting project. What sort of parts do you intend to grind that you need this level of accuracy? Gauge blocks perhaps?
PS, none of your photos are visible in your posts (at least I can't see them).

I used to have a B&S grinder this size with a 0.1um scale on the vertical travel. That resolution was very nice for holding tight tolerances grinding cylinders. With a good condition grinder, temp control and careful work, holding 0.5um on size for small flat parts is reasonable and the 0.1um DRO really helps with that.
 

ballen

Titanium
Joined
Sep 25, 2011
Location
Garbsen, Germany
It's cool the tables come off so easily on these grinders. Is the manual table feed via a manual hydraulic pump rather than rack and pinion or cable drive?

The drive is a rack and pinion under the table. The gear is in the "shadow" pocket in the top left of this photo, partly visible to the left of the end of the cylinder.

attachment.php


attachment.php


Are you using a generic DRO readout with these various scales?

It's a Sino SDS6-3V. It's not quite generic because the scale inputs are EIA-422 (balanced differential) rather than RS-232 (often called "TTL") which is unbalanced/single-ended.

I like Sino DROs and scales, because I've corresponded for many years with the main guy behind Sino, Peter Wendlandt. He really knows his stuff. Note that Peter has cautioned me against buying gray-market versions direct from China, and so I purchase scales and display stuff from authorized German resellers.

I guess so long as they output quadrature signals of the right voltage, you can wire the scales to the standard DB9 if they don't already come that way?

That's right, both the X and Y axis scales came with "flying leads" (meaning, no connector).

The Z (cross) axis uses an out-of-the-box Sino KA-200 scale, which already has the correct connector but has an RS-232 output. So for that, a small RS-232 to EIA-422 converter box is needed. It hangs out the back of the DRO. It's hard to see in this photo:

attachment.php


but is plugged into the Z connection between the scale connector and the DRO itself.

The vertical (Y) axis uses a Renishaw interpolator which has a native EIA-422 output. Here, I just had to compare the Renishaw datasheet connection diagram with the Sino one, and solder the leads in the correct order to a DB9 connector.

The long (X) axis was the same story, because again the readhead has an EIA-422 balanced interface. Again, I needed to compare the RLS datasheet to the Sino one, and solder the leads in the correct order to the DB9 connector.

I used to have a B&S grinder this size with a 0.1um scale on the vertical travel. That resolution was very nice for holding tight tolerances grinding cylinders. With a good condition grinder, temp control and careful work, holding 0.5um on size for small flat parts is reasonable and the 0.1um DRO really helps with that.

Good to hear that!

I haven't had enough experience yet using the DRO to see the degree to which it will help me. But I have already discovered that the backlash in the vertical axis doesn't behave quite like I thought it would. So it should be easier to shift height settings if for example there are steps and then get back to where I was.

Cheers,
Bruce
 
Last edited:

RJT

Titanium
Joined
Aug 24, 2006
Location
greensboro,northcarolina
We have used readouts on grinders for 30+ years, but never on the longitudinal (long table) axis. I can't think of a single time I would need it. What am I missing? We set a mechanical hard stop if we need to repeat to a certain position to grind something in a spinning fixture, but I don't need a readout for that. Use readouts daily for cross (saddle) and down feed.
 

michiganbuck

Diamond
Joined
Jun 28, 2012
Location
Mt Clemens, Michigan 48035
I have used grinders with verticle and cross DRO..and travel stop on the long travel with s stack of shims to place in to change the long travel stop. Many Tc grinders have a screw adjustment on the long travel stop.
that can be very handy... one example is when the OD of the wheel goes farther long as you go deeper with the verticle.
 








 
Top