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Best way to add a DRO to a Jones and Shipman 540 APR?

ballen

Diamond
Joined
Sep 25, 2011
Location
Garbsen, Germany
I've been fixing up a 1986 Jones & Shipman 540APR surface grinder. It's a nice machine. Now I'd like to add a digital read out (DRO) with glass scales to it. My question is, what's the best way to mount the scales onto the surface grinder?

[From the literature that came with the machine, I know that a factory-installed Heidenhain DRO was an option; it would be good to where those scales were installed.]

Here's what the machine looks like:

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Not long ago, a friend gave me a defunct Heidenhain ND770 display, rescued from the trash, which I've repaired. This is a 3-axis display, really intended for a lathe, but will work fine here. I also got a set of LS803 scales the same way, which happen to be the correct length. These are working well, though they need new lip seals. But that's easy, I've done it before. The scales have a 40 micron grating, but together with the display will display to 1 micron resolution. The scales are about 18 x 30mm in cross section, the head adds about another 16mm to the long direction, making them 18 x 46 mm.

So regarding the three axes:

(1) The cross-feed direction is not difficult: the scale can be mounted to the right-hand side of the machine under the saddle, with the head fixed to the saddle. It might also be possible on the left side, but that's more exposed than the right.

(2) I'm less sure about the long (transverse) axis. The logical place to attach the scale would be to the back of the table, with the head fixed to the saddle. But since the saddle runs right up to the column, that would reduce the 150mm cross travel. I don't want that. Currently when the table is run as far back as possible, there is only about 12mm of space between the back of the table and the column. So unless I mill a slot in the back of the table (which I don't want to do) I would lose at least 6mm of travel in the cross direction (and probably more like 8mm). The other option would be to attach the scale to the front of the table. But that would get in the way of the adjustable trip dogs and the speed control lever. So neither option works well.

(3) For the vertical axis, there seem to be two options. One would be on the front of the column, facing the operator, on either the left or right side. The main disadvantage is that the scale is somewhat exposed to coolant and grinding dust. It's also far from the "ways", by which I mean the vertical steel bars and rollers which allow vertical movement. The other option (but I am not sure it is feasible) would be to mount the scale inside the column, in the space in between the body of the column and the moving internal frame that carries the motor and grinding spindle. It would be good to know if this is even possible: has someone out there done this or seen it?

Advice and photos would be greatly appreciated!

Cheers,
Bruce
 
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No one responded to my post above. I'd still like to do this, perhaps using a Renishaw RGH24 head and RGS-20S scale for the long travel of the bed. If you have a J&S 540 with glass scales or encoders, could you please post a couple of photos showing where/how they are installed?
 
Yer pretty much on the money to how there intended to be mounted.

For the height axis they are normally fitted on the front of the column to the right hand side with the main body of the Encoder moving with the spindle.

And for the cross feed they are fitted in the gap under the cross slide, we have two 540s at work with 2 axis readouts, if I remember I’ll get some photos.

I never seen a longitudinal read out on a grinder, nor have I ever needed one? But I’ve not done it all either...

Also, I’ve never seen a green J & S, only the old blue ones or current white ones, where is it from?
 
For the height axis they are normally fitted on the front of the column to the right hand side with the main body of the Encoder moving with the spindle.

On the internet I have seen some pictures of J&S 540s that have DROs but I can't see any encoders visible for the vertical axis. So it must be possible to put them inside the body, which I think must be better, since there is less dust, grit and coolant there.

And for the cross feed they are fitted in the gap under the cross slide, we have two 540s at work with 2 axis readouts, if I remember I’ll get some photos.

Thank you!!

I never seen a longitudinal read out on a grinder, nor have I ever needed one? But I’ve not done it all either...

The modern "digital age" grinders I have seen have them on all three axes.

Also, I’ve never seen a green J & S, only the old blue ones or current white ones, where is it from?

It was delivered new, to a company in Germany, in 1986. Apparently there was a period in German manufacturing where some studies had shown that green machines had a calming effect and led to fewer work-time accidents and injuries. So a lot of shops would only accept green machines. This particular machine has factory paint, but under some parts of it there is a blue layer. So I think it was a factory special paint job for Germany.
 
Nice grinder!

I would not waste any time on the longitudinal axis scale. You will not need it, just a hard stop.

A good place to look for scale mounting ideas are used machines with scales. If you find one ask the dealer to send photos.
 
On the internet I have seen some pictures of J&S 540s that have DROs but I can't see any encoders visible for the vertical axis. So it must be possible to put them inside the body, which I think must be better, since there is less dust, grit and coolant there.





Thank you!!



The modern "digital age" grinders I have seen have them on all three axes.



It was delivered new, to a company in Germany, in 1986. Apparently there was a period in German manufacturing where some studies had shown that green machines had a calming effect and led to fewer work-time accidents and injuries. So a lot of shops would only accept green machines. This particular machine has factory paint, but under some parts of it there is a blue layer. So I think it was a factory special paint job for Germany.


Hi Ballen, have you got an email address so I can email you some photos?
 
Could you post them here? I'm sure others would like to see them.

Hi, yer I want to but I can’t work out how to do it on the mobile version? I’m on an iPhone. Ill keep trying...
 
Here are the photos that Luke provided. The machine has scales on the vertical axis and the cross axis. Actually I think two machines might be pictured here, because the cross slide is done in two ways, once on the right side near the cross feed stops, and once under the saddle in the middle.

Vertical axis:

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Cross Axis:

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I will do the cross axis in the same way as shown in the photo where it's on the right side near the stops. I'd prefer to put the vertical axis inside the machine, and am curious to see if anyone out there has such a setup and can show photos. I'd also like to instrument the long axis, and again would enjoy some photos from others who have done this.
 
Yes they are two machines one is a standard 540 one is the high rise version
 
Do you actually find the scales that useful? Sure i get the need on a mill and could not imagine life with out them now, but for a surface grinder im not kinda sold on the benefit? Or is the z scale - cross slide nice for nailing slot widths? My grinder actually has a locking bit for the saddle on that side, but i have never felt the need to lock the saddle. Hence sticking a scale there makes good sense. Not so sure about the verticle scale on the micrometer height stop bracket, but on a non powered rise and fall grinder i spose thats the natural spot to stick it. That said, on the front column were the button head screws are in the cover is a nicely machined surface that's square and true you could also mount it off.

Ballen, on a std quadrature encoder, your 40 micron line grating only gives you 10 micron positioning, sure the display may show a third digit, but i kinda don't get were its coming from. 10 microns is less than the J&S dials give you as std. IMHO you really want a finer scale for the vertical spindle rise and fall on a grinder. Only having 4 tenths of a thou resolution is not going to get any were near good enough.
 
I’ve only ever seen them at my current toolroom, they are all okay up to half a thou but generally grinding is required for better then half a thou so the read outs are used as a guide then the dials are used to graduate in tenths
 
Do you actually find the scales that useful? Sure i get the need on a mill and could not imagine life with out them now, but for a surface grinder im not kinda sold on the benefit?

I could not easily get by without them on my lathe and mill, and just finished adding them to my cylindrical grinder (another thread here). I already used that a couple of times, and having scales on both axes is helpful. So I think I am going to do all 3 on the surface grinder.

Ballen, on a std quadrature encoder, your 40 micron line grating only gives you 10 micron positioning, sure the display may show a third digit, but i kinda don't get where its coming from.

I've explained "where it's coming from" at the end of this post, please see the final paragraph below.

Regarding my cylindrical grinder, the grating on the two scales I am using is 20 microns, not 40.

The scale on the cross slide (Sino KA-500) interpolates by a factor of 10, so two counts per micron. That scale came with a laser interferometer calibration curve showing that the max error over the entire travel is 1.5 microns. (I know the guy who calibrated it and sold it to me and he is OCD about these things, so I believe it.)

The scale on the long axis is a Renishaw RGS-20s with an RGH-24X head. This is again a 20 micron grating, with x5 interpolation in the head so you get one count per micron. Renishaw specs this as accurate to 0.75 microns over any 60mm stretch and accurate to 3 microns over a length of up to 1 meter when slope-corrected with 2-point calibration.

I may fit the vertical axis of the surface grinder with a Renishaw RGS-20s scale and a RGH-24W (0.2 micron resolution) or RGH-24Y (0.1 micron resolution) head. This is more precise than me or the machine, but it's nice to have a measuring system which has higher resolution than one can work to.

10 microns is less than the J&S dials give you as std.

Sure. On my J&S 540, the vertical axis dial is 200 microns (0.2mm) per revolution, with 200 tick marks. The tics are 1 micron increments. I want a DRO that has at least that resolution (and perhaps a factor of 5 or 10 more).

IMHO you really want a finer scale for the vertical spindle rise and fall on a grinder. Only having 4 tenths of a thou resolution is not going to get any were near good enough.

Agreed!

Educational note:
You are correct that if you have a 40 micron grating scale which gives two TTL quadrature signals with the same period, then the best you can do is one count per 10 microns. That's because the signals are just -1 and 1 and have no other information. But if you have a 40 micron grating scale with two ANALOG sinusoidal quadrature signals with the same period, then these can be used to get much finer than 10 micron resolution. That's because the sin and cosine curves go smoothly from -1 to 1, and so from the exact values you can (in the absence of measurement and instrumental noise) deduce your location exactly! In modern TTL scales that additional "interpolation" is built right into the scale head. So the scale head constructs a "continuous" analog signal from the light reflected from or transmitted through the scale, then uses that to create two quadrature TTL signasl with a period that is shorter than the scale grating period by factors which range from (typically) 5 to 100. Here is the spec sheet for the Renishaw scale, if you want to read more about it: http://resources.renishaw.com/en/download/data-sheet-rgh24-encoder-system--103378 . See page 4 for a listing of the head types and resolutions. This system offers resolutions from 5 microns to 10 nanometers (not a typo, that is 0.01 microns!). In the semiconductor industry that's just the starting point for precision measurement.
 
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If you have a solid 1 micron real world read out, im really not sure your going to need better than that, hell im really not sure a J&S540 or pretty much most other std surface grinders could even go sub micron with any real certainty. That said, my experience of my J&S 540 is that tenths as well as i can measure them is about equal to milling to about 2-3 thou on the Bridgeport effort - accuracy wise.

Sorry did not realize thoes kinda heads were available, i knew the technique, just did not realize you could actually easily find them in the wild as it were!

For the longitudinal - table travel stroke though, im really not sure were you could sensibly mount the scale, if you put it on the back of the table your going to lose the saddle travel. Me im often using all the travel i have that way to grind as wide as i can using the saddle travel, that said its the stuff i kinda do, equally theres little harm in buying a 3 axis readout and simply just not plugging the third scale in. Then you have the option down the road. I have never seen a J&S 540 with anything but the table travel stops for stroke length control, to my knowledge none even had anything graduated at all on that axis, its kinda hard to see how you would need it and equally do to how a J&S 540 works the reversal is not exactly a precise distance - repetitive at all either. Hence your kinda fitting a scale to a axis you have no fine control on, your losing travel doing so and i realy question the benefit to it?

Don't get me wrong, if you end up with like a cutter grinder which does have accurate travel controls, or a cylindrical grinder i totaly see the benefit in having that readout. Wanting that axis to be precise!

But on a table only moved by a rack - pinion and no calibration or a hydrulic ram running a direction change over bump valve arangment, sorry i just don't see how you can really use that readout for anything? Other than possibly a read out speed testing method because thoes microns are going to be passing fast at grinder speeds!
 
If you have a solid 1 micron real world read out, im really not sure your going to need better than that, hell im really not sure a J&S540 or pretty much most other std surface grinders could even go sub micron with any real certainty. That said, my experience of my J&S 540 is that tenths as well as i can measure them is about equal to milling to about 2-3 thou on the Bridgeport effort - accuracy wise.

Yes, I'm undecided about this. I want at least 1 micron resolution because the grinder is capable of that. The rule of thumb in metrology is that if you want to measure something with a given precision, your tools should have a factor of ten MORE precision.

Sorry did not realize thoes kinda heads were available, i knew the technique, just did not realize you could actually easily find them in the wild as it were!

I've learned a lot from you and your posts over the years, so happy to give something back for a change! The nice thing is that these heads and scales can be had for reasonable cost. Ebay has a large number of RGH-22 and RGH-24 heads, I paid about 90 USD for an RGH-24X head. I paid a bit more than that for 1 meter of the RGS-20s scale material. You can also purchase the scale material directly from Renishaw for about 0,35 Euro/cents per mm. A 600mm strip costs about 200 Euros.

For the longitudinal - table travel stroke though, im really not sure were you could sensibly mount the scale, if you put it on the back of the table your going to lose the saddle travel.

My idea is to put it underneath the table, as I did on my cylindrical grinder. I only need a few mm of clearance.

I have never seen a J&S 540 with anything but the table travel stops for stroke length control, to my knowledge none even had anything graduated at all on that axis, its kinda hard to see how you would need it and equally do to how a J&S 540 works the reversal is not exactly a precise distance - repetitive at all either. Hence your kinda fitting a scale to a axis you have no fine control on, your losing travel doing so and i realy question the benefit to it?

<SNIP>

Sorry i just don't see how you can really use that readout for anything? Other than possibly a read out speed testing method because thoes microns are going to be passing fast at grinder speeds!

What you say makes sense. I better think through more carefully about whether or not a scale on the long axis has any real use.
 
I ran a Parker and a B&S with DRO and found it very handy for step dimensions and coming back to a part after a dress.
Yes, I would read the dress amount on the hand wheel dial, then add that number to the part DRO zero(s).

Originally I thought because of wheel breakdown DRO would not be very useful on a grinder, but after using for a short time I found DRO very handy.
 
Hi Ballen:
The other issue regarding a DRO on the longitudinal axis of a grinder, especially a glass scale DRO is the prospect of wear.
My expectation is that you will find a use for the long axis scale very infrequently but you will wear out the lip seals and the scale itself very quickly unless you're very clever about where you locate it and very anal about keeping it squeaky clean.
Even then, with all the direction reversals and the high rate of travel of the table, I am pessimistic about how long it's going to last.

Cheers

Marcus
Implant Mechanix • Design & Innovation > HOME
Vancouver Wire EDM -- Wire EDM Machining
 
The other issue regarding a DRO on the longitudinal axis of a grinder, especially a glass scale DRO is the prospect of wear.

If I do a scale on the long axis, it will be a Renishaw RGH-24 head and RGS-20s scale. The only "contact" between the two of them is optical. There is NO mechanical contact and no lip seals: the head and scale are 0.8mm (0.032") apart.
 
My idea is to put it underneath the table, as I did on my cylindrical grinder. I only need a few mm of clearance.

How would it like the oil and dust though? Its nothing like a clean environment directly under the table on a J&S 540? Don't have - never been around a cylindrical so don't know how well it compares?

Yeah there a neat little scale, had not seen those before, had seen a magnetic version of it, separate head and tape wise, that may be a better option as its far more immune to dust and oil. Especially as your not going to need micron resolution on the table stoke travel.

End of the day, if you get a 3 axis DRO display, you can really easily leave that one connection off, then its only the scale cost to add.

As to dressing, you want a wheel head dresser, love mine, no coming of the part crap, just dial the diamond down, dress, drop the head that much and carry on. Sure i can get a fractionally better grind from a table diamond, but its still pretty sweet for most of what i do, yeah it did take a while to dial the wheel head dresser in dead nuts to the table, it may still be a fraction of a micron out, but i only had kitkat wrapper tin foil at the time!
 








 
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