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Clausing 8520 TouchDRO

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Briney Eye

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#1
Now that my recently-acquired mini-mill is up and running, I've started using it to make the mounting hardware for digital scales. I'll be installing a full set of Shars scales and using Yuriy Krushelnytskiy's "TouchDRO" hardware and Android app. I've already set up my Logan Model 200 lathe with TouchDRO, and love it.

I started with the quill scale, figuring that it would be the most difficult given the limited space. First to go were the factory mounting brackets. There simply wasn't room for them. After a lot of measuring and sketching I came up with a scheme for two L-shaped brackets, and only one needed to be bent. A flat "moving" bracket would attach the read head to the quill stop, and a "fixed" bracket with one 90-degree bend would attach the top end of the scale to the mill's head. The bottom end of the scale would float. I had already successfully used a similar approach on the X axis for my lathe DRO.

I milled and bent the brackets from 1/8" mild steel, and this shot is of the initial fit check, to make sure things aligned properly and to mark the length of the top bend in the fixed bracket:

IMG_1454.JPG

I can only use 3" of travel, so I cut the Shars 4" stainless vertical scale down using a cutoff wheel in my Dremel, then squared it up on my 6" x 48" belt sander. Piece of cake. After the fit check I milled the top end of the fixed bracket to align with the back face of the scale and drilled and tapped it.

So much for the easy part. I don't own a drill bit that will touch this hardened stainless, so now I'm waiting for the cobalt and carbide to be delivered. Once I have the tooling I will be drilling the top end of the scale to match the fixed bracket.

Marking, drilling and tapping the quill stop, in place, was a delicate hand operation, but went well. You can see the 2-56 cap-head screws that attach the moving bracket to it. To mount the fixed bracket the head was drilled and tapped for a single 10-24 cap head screw that you can see here just peeking out from underneath the moving bracket. After aligning and tightening the fixed bracket I drilled for two 1/8" anti-rotation roll pins, one of which you can just barely see here.

Once everything is assembled, aligned and tight I will install 1/16" roll pins in the moving bracket/quill stop and the fixed bracket/scale so that the 2-56 screws aren't shear-loaded and to stiffen things up.

I apologize for the verbiage. Pictures will be much easier to understand, and I'll be posting more detailed shots over the next few days if life doesn't get in the way.
 

Briney Eye

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#2
Here's a shot showing how I made the brackets. I will be drilling and tapping a hole to relocate the thumbscrew to the left side at some point:

IMG_1458.JPG

I'll probably "streamline" them a bit more. I plan to give them a black oxide treatment. I might also make a hairline indicator to attach to the left edge of the quill stop bracket.

I'm afraid that I have to wait a couple more days for some carbide drills. Cobalt drills won't touch the scale. I'm a little surprised by how easily I cut it with my wimpy little Dremel.
 
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34_40

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#3
Thanks for sharing the effort and the pics. maybe someday I'll get up the nerve to do this to mine.
I'll be "watching" for the next installment.
 

Briney Eye

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#5
Z axis is installed and aligned:

IMG_1473.JPG

I'm going to do a chip guard as a separate thing.
 
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tweinke

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#6
Looks like a nice clean install so far! I added TouchDRO to my PM727 earlier this year using one of the premade boards and used the W axis combined with Z so that the head movement and quill are combined. So far I have been very happy with my choice because I can move either the head or quill and still keep position on my tool. I do not know if this is normal on a mill but it sure seems to be a nice feature to me.
 

Briney Eye

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#7
Looks like a nice clean install so far! I added TouchDRO to my PM727 earlier this year using one of the premade boards and used the W axis combined with Z so that the head movement and quill are combined. So far I have been very happy with my choice because I can move either the head or quill and still keep position on my tool. I do not know if this is normal on a mill but it sure seems to be a nice feature to me.
That's what I intend, and I'm assuming that the quill readout puts out a compatible format. I need a Micro-to-Micro USB cable to test it with one of the read heads, though. On my list. (UPDATE: The digital output from the quill works with a display from one of the other scales, and is ALWAYS ON even if the quill display has turned itself off. This is good.)

I believe that I can make a nicely-sealed Z-axis chip guard using some aluminum angle and door sweep weatherstripping. Also on my list. I should be able to pick up something that will work at the hardware store. Maybe I can get a picture up today. If I'm not happy with it I'll order a brush-type sweep from McMaster-Carr. (UPDATE: I bought the brush type and it looks like it will work well. Eventually I will post a picture.)
 
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Briney Eye

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#8
I was wondering why the Y axis wouldn't lock up:

IMG_1475.JPG

I don't remember it, but I just went through the bits and pieces again to make sure. At some point in this machine's life, the "645-012 Rod" went missing. So I made a new one. Right behind it you can see the 1/16" spacer (UPDATE: actually needed 1/8") under the mounting plate to provide some clearance when I install the chip guard:

IMG_1478.JPG

... and now the Y Axis scale is installed. Shimmed up the outboard end 0.023" to get it aligned:

IMG_1487.JPG

Hey, what's one more hole under there, anyway? I made the mounting plate 1.125" wide, and it butts up tight against the underside of the cross slide. I don't know how to make it any stiffer. There's just enough clearance for a box end wrench on that gib screw locking nut to the right.
 
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Briney Eye

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#9
All the scales are installed, with just the Z axis cover to go.

I made some Y-axis cover mounting blocks to replace the temporary washers:

IMG_1489.JPG IMG_1490.JPG

Laid flat in the front, I can still use the 1/4" t-slot, and I don't lose travel on the Y axis (where there's not that much to begin with):

IMG_1492.JPG

IMG_1493.JPG

I had to order some 2-1/2" aluminum angle from McMaster-Carr and cut it down:

IMG_1495.JPG

Looks pretty clean, I think:

IMG_1497.JPG

Also from McMaster-Carr, to keep the chips out of the Z-axis scale:

IMG_1500.JPG
 

Briney Eye

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#10
Hooked all the scales up:

Clausing 8520 TouchDRO Board.jpg

Everything works!

Clausing 8520 TouchDRO First Power.jpg

Just have to button up, mount the box, make the Z axis cover, do some cable management, and calibrate!
 
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tweinke

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#11
That looks mighty fine! Have you calibrated your scales yet? I remember reading something about the W needing to be done separately but no info how to do that. I decided to just plug it into x and figure the correct counts. If I may ask, what are you using for a tablet mount?
 

Briney Eye

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#12
I figure this ought to work:

1. mount a test indicator in the spindle
2. extend the quill fully and lock it
3. lay a 1-2-3 block flat on the table to provide a good reference surface (or just use a good spot on the table)
4. zero the test indicator on the top of the 1-2-3 block using the knee, and lock the knee
5. zero the DRO Z axis
6. stand a second 1-2-3 block on top of the first one
7. unlock the quill, zero the test indicator on the top of the second block, and re-lock the quill
8. scale the W axis CPI so the DRO says 3.000 inches (I suppose I should measure the block and use that number)
9. remove the standing 1-2-3 block
10. unlock the knee and crank it up to zero the test indicator on the flat 1-2-3 block
11. set the Z axis CPI so the DRO reads 0.000

The articulated arm is a CAMVATE camera mount, and the tablet holder is an ASICS.
 

tweinke

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#13
Sounds like a plan to me. Thank you for the info on the tablet mount. It might sound silly but I have been putting my tablet on the mount I made for the lathe and having to look over at it which is not very handy or even possibly unsafe as I now think of it. Never thought of looking at camera gear.
 

Briney Eye

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#14
Mounted the Big Box O'Lectronics on the column today. I wound up switching to a normal USB connector for the W axis. There must be somebody online who carries cables with micro connectors on both ends, but I couldn't find them (Argh! Digi-Key has them, and I've been ordering from them for 30 years!).

The power consumption of the Mixed Scale board is so low I didn't bother with ventilation. It might get a little warm in there, but it won't get hot enough to be an issue. I simply notched the edge of the enclosure with a rat tail file for the cables:

IMG_1527.JPG

Buttoned up:

IMG_1532.JPG

I just bent some 1/16" aluminum from the hardware store to make the brackets, and drilled and tapped the column for 10-24 button head screws.
 
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rlschow

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#16
Hi Jon, I watched your YouTube about this also. Your DRO installation looks great, Thank you for posting this. I am seriously thinking about using the same system on my 8520. I have a few questions.

1. What are your thoughts about the TouchDRO-bluetooth-to-tablet setup now that you've (presumably) had some time to use it?
2. Are you happy with the accuracy and consistency of the readout?
3. Any bugs or problems to report?
4. Does it ever lose the BT connection?
5. Are you fully satisfied with the Fire tablet for this application?
6. What length scales did you purchase for your X and Y? Did you cut them down to final length?
7. Did you maintain full travel of your table?
8. Anything else that you'd do differently if you did it again?

It looks like you installed everything so not to lose access to original locking handles or gib screws on the table and carriage, which is nice.
If I install this system I want to try to replace the USB cables from the reader heads with metal armored cable to make the installation more durable. Who knows, it might help with electro-magnetic shielding too.

Roger
 

Briney Eye

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#17
Hi Jon, I watched your YouTube about this also. Your DRO installation looks great, Thank you for posting this. I am seriously thinking about using the same system on my 8520. I have a few questions.

1. What are your thoughts about the TouchDRO-bluetooth-to-tablet setup now that you've (presumably) had some time to use it?
2. Are you happy with the accuracy and consistency of the readout?
3. Any bugs or problems to report?
4. Does it ever lose the BT connection?
5. Are you fully satisfied with the Fire tablet for this application?
6. What length scales did you purchase for your X and Y? Did you cut them down to final length?
7. Did you maintain full travel of your table?
8. Anything else that you'd do differently if you did it again?

It looks like you installed everything so not to lose access to original locking handles or gib screws on the table and carriage, which is nice.
If I install this system I want to try to replace the USB cables from the reader heads with metal armored cable to make the installation more durable. Who knows, it might help with electro-magnetic shielding too.

Roger
1. I've used it much more on the lathe at this point. Love it. Now that the holidays (and a family funeral) are past, I hope to get back on the mill and finish up some things there. I highly recommend adding decoupling capacitors in the read heads. I still haven't gotten to it on the mill, and it's flickering in the least-significant digit. On the lathe it didn't work at all without them.
2. Accuracy-wise, the aluminum scales are good enough for what I'm doing, and had maybe 0.001" of hysteresis when I checked with a test indicator.
3. No actual bugs, but I wish the Preference Banks could be named and were "smart" enough to remember which Bluetooth connection to use.
4. The connection on the lathe started out finicky. It was particular about which wall wart I powered it from. Luckily, I've saved a big box of them over the years. Adding the decoupling capacitors in the heads also seemed to make it more stable in that respect. It's rock solid now, and only loses the connection when we lose power. I used an old transformer-based supply for the mill, and it seems happy other than that last-digit flicker which I expect to go away when I add the decoupling.
5. The Fire works great. It just requires some finagling to get the Google Store installed on it first. PITA in that respect.
6. I cut the 4" stainless scale that I installed on the quill and the 24" aluminum scale for the X axis. As I say above, you will need carbide if you want to drill stainless scales, but a cutoff wheel in your Dremel will hack through it. Try not to get them too hot, since the scale is just glued to the beam. I could have left the X scale longer and shifted the mounting blocks out flush with the ends of the table and it might have looked a little better. I had a reason for making it shorter, but I can't remember what it was now. Old age :).
7. I have full travel on all four scales.
8. I keep wondering if I could have figured out a way to mount the X axis inside the table. I've seen it done with magnetic "tape" scales, where people have buried all of them inside the machine. You have to have a second mill to make the modifications, though. Other than that, it's made for a great setup.

-Jon
 

rlschow

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#18
Thanks for the information. Good to know about putting bypass caps in the reader head. Putting the x scale under the table is a neat trick for protecting it, but for me more work than I want to budget for the task.
 

Briney Eye

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#19
Thanks for the information. Good to know about putting bypass caps in the reader head. Putting the x scale under the table is a neat trick for protecting it, but for me more work than I want to budget for the task.
Here's a head with a 0.1uf ceramic decoupling cap installed between VDD and GND. I could have trimmed the leads a bit :):

IMG_1208.JPG
 

rlschow

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#20
Leaving them long means they're still usable for something else if they don't work out there. I think I'll install them in preemptively, because once I get the scales aligned on the machine I won't want to take them off to make mods to the boards
 
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