[Source] Lm10 Renishaw Mag Linear Scale Replacement Vendor Spec.

While I cannot speak to the magnetic side, I have recently purchased a Ditron 11F (1um) optical scale, and was somewhat of a mixed bag. Although advertised as having an index of 50mm per piece, the actual received spacing was double that, at 100mm between zones. In addition, the zones were not centered around the nominal midline of the scale, but offset. Both were confirmed to be factory current practice. Having said that, the scale does seem to operate to the other specifications. It made me wonder about others experiences, so it will be enlightening to see what you get, Jim.
 
JimDawson said:
OK, I have a Ditron 1um read head coming, should be here mid next week. I'll get it tested and post the results.

Stay tuned.........:)
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heyO, any chance we can get a link to what you procured? I'd like to see the specs. I still have not gotten anything setup for mine.

_Dan
 
The attached PDF is all I have. There is no internet link that I can find.

The specs really make no sense, a poor translation at best. Once my testing is complete, I'm going to send them new specs that are actually readable in English.;)
 

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JimDawson said:
The attached PDF is all I have. There is no internet link that I can find.

The specs really make no sense, a poor translation at best. Once my testing is complete, I'm going to send them new specs that are actually readable in English.;)
Click to expand...
Dawson Controls Translation Services, INC. ???

That is some poor technical describing ...
Thx!
 
My Ditron MR200 read head just arrived! From the outside it looks good. The finish on the head is not as nice as the Renishaw, they could have used a bit finer emery cloth to finish it. Also the sensor surface does not appear to be flat, I'll check it with an indicator later. Has a 3M armored cable with a 9-pin D-sub connector. I wanted it with flying leads with a color code, but I guess this is what they had. I need to figure out the colors so I can wire it in after I cut off the plug.

upload_2017-4-4_15-42-20.png

Now out to the shop to build a mount and get it onto the router so I can test it.

Stay tuned..........:)
 
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OK test time.:cautious:

I ordered this with flying leads, but they shipped it with a 9 pin D-sub. No problem, I have wire cutters. :grin: The wiring looks very professional. The cable is high quality with 4 twisted pair, with both foil and braid shielding.

upload_2017-4-5_13-7-54.png

Here is the setup. First find a hurricane tie and modify to become a read head bracket. Fortunately I had enough extra length on the tape to accommodate the extra head.
upload_2017-4-5_13-13-2.png

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I had a bit of trouble setting the spacing, the Ditron head is a bit more sensitive to spacing than the Renishaw. I wired the Ditron into the W axis on the machine, that way I could read it on the DRO.

The test consisted of running the router from 0 to 96 inches and back for a bit over an hour. Then will compare the Ditron position to the Renishaw position on the DRO. I don't actually know it either encoder is reading the absolute position correctly, all I can do is compare the readings.

I do have a high degree of confidence in the Renishaw reading because I have been able to hold +/- 0.001 on machined parts on the router, and < +/- 0.0005 on the mill. On Alloys Shizuoka, equipped with the same Renishaw readers, we were able to achieve 1um roundness in circular interpolation, on a 4 inch circle. This was checked with a 1um resolution CMM. In that case we were looking for deviation rather than a specific size, but as near as I could measure it with calipers, it was exactly on size.

I zeroed out both encoders, and pressed Go
Here is the test G-code
%
G0 Y96.0
G0 Y0.0
M47 (repeat)
%
The best speed I could maintain reliably was 150 IPM, but I did take it to 200 IPM during the test, I really need bigger motors on my router.:(

So at the end of the test, about 10,000 total travel inches, the Renishaw was reading -0.0001, and the Ditron was reading -0.0007. Yeah, I can live with that.:cool: I'm going to call this a success. :encourage:

I'll leave the Ditron connected and do some comparisons on the next job I run on the machine.
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$90 + $28 Fedex shipping from China.

A little update, I ran an air cut of a large job, and the Ditron seemed to track just fine. Within 2 0r 3 tenths of the Renishaw, and that's at 140 IPM. Close enough for me.
 
OK, need an opinion here.
Should I go with something like this on the mill or look for a glass scale solution?
Is there a chance in hades that this 9-pin would work with my old Mitu Digimatic Display Head or are the signals totally different?
I'm still leaning towards doing TouchDRO, just trying to get by on a tight budget right now.

Now for the Kicker - Step Son is in China for a couple of days next week, Bejing. hmmm, wonder if he'd like to do some shopping for a DRO. :)
 
middle.road said:
Is there a chance in hades that this 9-pin would work with my old Mitu Digimatic Display Head or are the signals totally different?
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I can just about guarantee that the pinouts would be different, so a bit of rewiring night be needed. You just couldn't get that lucky.;)

The other issue might be the output of the read head. I depends on what signal the Mitu wants to see. It could be single ended, or push/pull quadrature, or it could want a 1v P/P sinewave. All of those outputs are available from Ditron. You are going to have to figure out what the Mitu wants. Also you will need the resolution that the Mitu will accept.

Overall I'm a real fan of mag scales. Easy install, maintenance free, bullet proof, and very compact.

EDIT: It looks like the Mitu uses a Gray Code encoder. That is basically a serial data comm system. Nothing from Ditron is going to work.
 
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