LittleMachineShop bluetooth DRO on PM-932M installed

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Harlock
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LittleMachineShop bluetooth DRO on PM-932M installed

Post by Harlock » Tue Aug 22, 2017 1:35 am

This weekend I installed the bluetooth-based DRO being offered by LittleMachineShop.com on to my Precision Matthews PM-932M (a large bench-top mill, RF-45 clone)

This setup uses a wireless bluetooth connection between the processor box for the scales and a 7" android tablet. You can use any android based device you like, but I purchased the one they offered on the site for $70. The advantage of this setup vs. a standard DRO display is that the feature set on your DRO is limited only by the software. The basic software that came with it has the usual hole pattern calculators and not much else.

The scales are of the magnetic variety, and comes in a single 1 meter length. To size it to your mill, just saw it off where you want it and install an end cap. There was enough to do both X and Y with liberal overshoots, so I will hit the ends of travel on the machine before the scale runs out, including accounting for the thickness of the read head.

There was potentially enough left over to do the Z-axis, but since the PM-932M has a built in digital scale on the quill feed, I didn't feel that was necessary. I may do it later as a matter of unifying all my axis to one screen.

The scales read in increments of two tenths (0.0002) which is fine for me as I only need accuracy within .001.

For the X-axis, there is a dovetailed slot on the front of the mill, which is GREAT. No hole drilling needed on the bed there. I fabricated two dovetail nuts and mounted the scale to those. Very easy. I removed the automatic stop setup for the X-power feed to do this. I've never needed it and won't miss it. I don't leave the mill traversing unattended, ever, and no kids or pets to accidentally set it off.

The old mounting bracket for the power feed stop buttons in the center became the item I attached the X-read head bracket to, which I fabricated out of scrap aluminum. The head comes with little side wipers and I put the red gasket rubber on top as a temporary chip collector, which I intend to improve upon later.

There seems to be no spec for how close the head needs to be to the scale, basically as long as the wipers are touching or closer, then it's within range. I put it fairly close in any case, within fifty-thou. It is adjustable as the holes in the read head are slots.

The Y-axis is opposite - the scale sits still and the read head moves, due to the arrangement of the bed castings. It was difficult to work below the table and drill holes, but I was able to use my regular cordless drill without clearance problems right below the X lead screw to mount the head bracket. I used a piece of right-angle scrap and an aluminum spacer to bring the head down to the scale.

The little processor box that receives the scale data and translates it to bluetooth has magnets in it and you can just stick it to the side of your mill stand down below. I forgot to take a picture of that.

I bought a tablet armature / holder from Amazon to hold the tablet - clamped to an adjacent table, and it's very adjustable. The only problem I ran into is that it is only designed to hold a 7" tablet vertically, not horizontally. I have to make a little spacer to help it clamp down on to the top of the tablet. I like the armature overall so I'm not going to return it, and just adapt it instead. Here is the link on Amazon: https://www.amazon.com/gp/product/B00D3205WU/

Total cost out the door was about $500.00 for everything. They did not have a kit for 2 axis universal, only 3 axis, so I put it together from component parts. They sell everything individually.

Here is the three axis kit not including the tablet: http://littlemachineshop.com/products/p ... 1536942993

And here is the tablet: http://littlemachineshop.com/products/p ... =132430212

By not buying the third axis read head, I saved about $100 as shipping and tax would have brought it to about $600 including the tablet, etc.

So far I'm very happy with it, and there is no lag or delay in the bluetooth connection, which was the only thing I was mildly worry about. As responsive as a regular DRO display.

Sorry I didn't take any installation photos, but here is the manual which shows the basic process. http://littlemachineshop.com/instructio ... versal.pdf

Setting up the DRO itself is trivial and takes no time. All the time was spent measuring for, designing and milling various brackets and the dovetail nuts. :D

As a last note, it called for metric fasteners to do all the mounting. I don't have metric taps, so 4-40 was substituted for M3 and 6-32 socket cap head screws were used for the scale brackets. Both seemed to be a great fit. I had to drill out the holes on the plastic scale ends just slightly.

-M
Attachments
15-07-06_duke-SPNG-slide-carousel-5003.jpg
Closer view of the android tablet that is the display.
15-07-06_duke-SPNG-slide-carousel-5012.jpg
close up of X-axis read head without chip cover.
15-07-06_duke-SPNG-slide-carousel-5018.jpg
Close up of Y-axis read head without chip cover.
15-07-06_duke-SPNG-slide-carousel-5021.jpg
overview of X-axis and display.
15-07-06_duke-SPNG-slide-carousel-5025.jpg
close up of Y-axis with chip cover.
San Lorezo Flume & Lumber Co. #2 - "Felton"
Live Steam Photography and more - www.mikemassee.com
Contributing Editor, Live Steam Magazine
Webmaster, Allen Models of Nevada

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SteveM
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Re: LittleMachineShop bluetooth DRO on PM-932M installed

Post by SteveM » Tue Aug 22, 2017 8:42 am

Nice.

Do you know if those type of scales will work with other DRO's?

Steve

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WesHowe
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Re: LittleMachineShop bluetooth DRO on PM-932M installed

Post by WesHowe » Tue Aug 22, 2017 8:58 am

I like the pictures. I have a similar Grizzly RF45 clone (G0755) with a glass scales DRO installed, 3 axes (Z on the head). I have about the same invested in that, but the head reading, while it works, has not proven to be of much use... I use a separate quill DRO all the time. When I do arcs on the XZ or YZ plane I zero the head and lock it, and set the quill to match what the DRO says to move it to.

Your scales look a lot less intrusive and disruptive than the glass ones.

As a side note, I place my vise on that first T-slot as you did. I found that when it is on the middle one you run out of Y travel sometimes.

Thanks for the post, it was informative.

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Harlock
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Re: LittleMachineShop bluetooth DRO on PM-932M installed

Post by Harlock » Tue Aug 22, 2017 11:14 am

SteveM wrote:Nice.

Do you know if those type of scales will work with other DRO's?

Steve
No idea unfortunately. I would contact LMS and ask them. Many other DROs use magnetic scales and read heads, but I don't know anything about compatibility between brands.

Best,

-Mike
San Lorezo Flume & Lumber Co. #2 - "Felton"
Live Steam Photography and more - www.mikemassee.com
Contributing Editor, Live Steam Magazine
Webmaster, Allen Models of Nevada

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Harlock
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Re: LittleMachineShop bluetooth DRO on PM-932M installed

Post by Harlock » Tue Aug 22, 2017 11:33 am

WesHowe wrote:I like the pictures. I have a similar Grizzly RF45 clone (G0755) with a glass scales DRO installed, 3 axes (Z on the head). I have about the same invested in that, but the head reading, while it works, has not proven to be of much use...
The guy at LMS was trying to convince me to put a third axis on the overall head travel, but I thought about it and decided that would be completely useless. If you have to move the head up to change tools (say, going from an endmill to a drill chuck) and then put it back, it won't matter if you put it back in the exact same spot because the endmill will be a different height, whatever's in the drill chuck will be at a different height, etc. when you put it all back in. I don't have any tools that are a single tool permanently mounted on an endmill holder, like a CNC turret would have. I have regular collets and a drill chuck. I tend to use the quill travel for all Z movement while machining, rather than use the head as a substitute for a knee. The locking and unlocking procedure for the head moves it around quite a bit and is much slower than doing it with the quill. It's not as accurate as a knee, as depending on the force applied to the two locking bolts, the tip of your tool may be in a wildly different location.
WesHowe wrote:As a side note, I place my vise on that first T-slot as you did. I found that when it is on the middle one you run out of Y travel sometimes.
Yea I ran into the same problem. THe first slot seems perfect. Other than that the vice seems to be just the right size for this mill.
San Lorezo Flume & Lumber Co. #2 - "Felton"
Live Steam Photography and more - www.mikemassee.com
Contributing Editor, Live Steam Magazine
Webmaster, Allen Models of Nevada

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WesHowe
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Re: LittleMachineShop bluetooth DRO on PM-932M installed

Post by WesHowe » Tue Aug 22, 2017 3:50 pm

Harlock wrote:The guy at LMS was trying to convince me to put a third axis on the overall head travel, but I thought about it and decided that would be completely useless.
Exactly.

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ALCOSTEAM
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Re: LittleMachineShop bluetooth DRO on PM-932M installed

Post by ALCOSTEAM » Wed Aug 23, 2017 6:53 am

I read thru the LMS page for this system and it says with a total x,y, and z movement of 32 inches or less. I see no explanation of why the 32 inches or less. Is that something within the software that will not allow it or is it they only send you one magnetic strip. LMS sells one meter long magnetic strips, will the system function with a whole strip say on the x travel and then another strip divided up on y and z travel. We have an old Sargon 2 axis readout on a 3hp Enco mill at the shop with iirc a 54 inch table. For our use I think this system would be a nice upgrade.

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Harlock
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Re: LittleMachineShop bluetooth DRO on PM-932M installed

Post by Harlock » Wed Aug 23, 2017 5:01 pm

ALCOSTEAM wrote:I read thru the LMS page for this system and it says with a total x,y, and z movement of 32 inches or less. I see no explanation of why the 32 inches or less. Is that something within the software that will not allow it or is it they only send you one magnetic strip. LMS sells one meter long magnetic strips, will the system function with a whole strip say on the x travel and then another strip divided up on y and z travel. We have an old Sargon 2 axis readout on a 3hp Enco mill at the shop with iirc a 54 inch table. For our use I think this system would be a nice upgrade.
I am not sure why they say that either, the strip is 39.5" long. I used 24" of it for X (the actual travel is 22.5", left overshoots for the thickness of the sensor) and I think another 9" or so for Y. I have about 6" left.

I don't think there is a software limitation. My thought is that they were extra cautious about people getting it and then realizing they didn't have enough magnetic strip. It is easy to order more and it is cheap.

-M
San Lorezo Flume & Lumber Co. #2 - "Felton"
Live Steam Photography and more - www.mikemassee.com
Contributing Editor, Live Steam Magazine
Webmaster, Allen Models of Nevada

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NP317
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Re: LittleMachineShop bluetooth DRO on PM-932M installed

Post by NP317 » Thu Aug 24, 2017 11:29 am

To solve the Z-axis position changing issues, I installed a 4-axis DRO PROS mill kit on my full-sized milling machine.
Both the Quill Z ("U" on the display) and the table Z have digital measurement, and the readout allows "summing" of those two Z readings.
Result: You always see the tool-to-part distance, regardless of which Z you move.

I had no idea such a solution existed (after working in machine shops for decades...) until I found the DRO PROS web side. (I'm a little sloooowww.)
The working results really make my milling projects much simpler and enjoyable.
And their scales are the magnetic type. Easy to keep clean and functioning. Had I understood their advantages, I would have installed those on my lathe too. It has glass scales, which are bulky and sensitive to chips and dirt. They required careful dirt shielding installation.
~RN

RSG
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Re: LittleMachineShop bluetooth DRO on PM-932M installed

Post by RSG » Thu Aug 24, 2017 12:11 pm

Nice DRO, while I can't really see any advantage to using a tablet, other than to possibly transfer from machine to machine the magnetic scales are a real plus! I have two DRO's from DRO PROS and they utilize magnetic scales. It came with a plastic shim approx .020" for setting the distance of the reader, this might help in setting yours too. As far as cutting the scales, if they are anything like my magnetic scales once cut the rest is useless as it requires the leading edge (left end) as a registration point for encoding.
Vision is not seeing things as they are, but as they will be.

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