Author Topic: Cheap DRO for my Seig X2p  (Read 12619 times)

Offline Allen Smithee

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Re: Cheap DRO for my Seig X2p
« Reply #15 on: October 30, 2014, 09:47:04 PM »
This sort of shuddered to a halt because when I came in from the workshop on Monday I realised that I was running a bit of a temperature, and by tuesday morning I was laid up in bed with what my wife thinks is "a slightly heavy cold" (of course we men know better - I still think it's ebola), and I've been here more or less since then. I was feeling a bit better for a while this afternoon, and boredom saw me tinkering with the second of this pair of cheap DROs to explore the options for taking the displays out of the cases to mount them in something nicer, to run them from an external power source and to look at the possibility of fitting backlights. In case anyone's interested this is what I found:

The cases come apart easily enough, being held together with seven small PK screws and a clip feature. Inside this the single PCB is retained with another couple of screws. It will be quite feasible to remove the PCBs and remount them in another box, either cutting holes for the existing membrane switches or bypassing them with other switches.

Fitting backlights will be more problematic because there's no room between the LCD and the board to take the lightflow panel. It may be feasible  to lift the displays onto a header - that level of investigation will have to wait until my temperature drops below 102 and my eyes are back to normal.

I got a surprise when looking at the power supply options. These things are powered by a pair of CR2032 batteries (3v nominal) and I had assumed these were stacked in series to produce ~6v to drive a 5v regulator for the electronics. I was wrong! The batteries are actually connected in parallel (confirmed by the fact that the unit operates quite happily with only one fitted), and the whole caboodle runs off the 3.0-3.4v supply directly. Knowing this makes things very easy, because there are several places within the Seig's control system from which I can easily tap a few milliamps at 5volts, and a single cheap LDO regulator (eg LM3940 etc) plus two capacitors will drop this to a rock-steady 3.3v with enough current capacity to feed all three units.

So I'll be trying this as soon as I have kicked this ebola.

AS
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Offline Allen Smithee

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Re: Cheap DRO for my Seig X2p
« Reply #16 on: November 13, 2014, 12:39:54 AM »
I got around to ordering the other two scales; a 300mm one for the vertical axis and a 500mm one for the x-axis which arrived with Arceuro's customary next-morning performance:



Offering them into place showed the vertical one would be very easy, but the x-axis is going to need a bit more thought. So while thinking I fitted the easy one. At 300mm it has more movement than I actually need (I think the mill has ~250mm vertical travel), but there was room for the whole thing so I didn't bother cutting it down. The quill on the seig X2p drives the whole head, so I didn't have to make a special mount like you would on those machines which have a separate quill shaft. I decided to fit both the scale and the sensor as high as possible to keep them as far as possible from flying swarf, although I'll still be fitting covers at some stage.

The fitting was simple enough - two holes drilled and tapped in the column, so I won't waste space with blow-by-blow photos but for tradition's sake here's the tap shot:



These were fitted with pieces of studding as before, and a simple braket was made from a bit of thin steel sheet (as before) to connect the sensor to an existing bolt that's holding the rod which drives the gas strut (fitted as a mod by the previous owner). The result is tidy enough:



I still haven't made any final decisions on where I'm going to mount the displays, but in my scrap box I fount a chunk of folded 12swg steel which was once an engine display stand. This could be the basis of a free-standing display mount - it will certainly do for now!



I opened up one of the displays to see how practical it would be to take the innards out and mount them in a separate box. Essentially it wouldn't due to the way the LCD is connected to the board - and the same issue precludes fitting backlights, which is a shame. But it will be very easy to plumb in power from an external 3.3v regulator, removing the dependence on CR2032 batteries. I'll be doing that soon while I ponder the options for the x-axis installation.

The case continues...

AS
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Offline Allen Smithee

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Re: Cheap DRO for my Seig X2p
« Reply #17 on: November 13, 2014, 10:59:25 AM »
Meanwhile...

The scale on the vertical fine feed wheel of this mill has always confused me. The major graduations are labelled "0.1, 0.2" etc every ten minor divisions, but there's a label saying "0.025mm" on it. Now that I have the DRO I've been able to cross-check it easily, and I've discovered that the 0.025mm label is right for each minor division, so the "0.1" (ten minor divisions) actually means a movement of 0.25mm. SO the dial is *actually* calibrated in thou with a fairly meaningless pseudo-metric labelling. This alone has justified fitting the DRO. The X and Y axis dials have normal metric markings, just to confuse matters further.

I think when I get my rotary table and dividing head one of my first projects will be to make a new dial which is actually labelled in true metric divisions...

AS
« Last Edit: November 13, 2014, 11:28:44 AM by Allen Smithee »
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Offline Tjark

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Re: Cheap DRO for my Seig X2p
« Reply #18 on: November 13, 2014, 02:40:20 PM »
Allen I have the same scales on my mill.
Have upgraded them with the caliper2pc box.
After the upgrade I am very satisfied with them.
The repeatability is now 0.01 mm on all the scales.
Maybe this is an option for you to.
You can find more information at the next link;   http://www.caliper2pc.de/en_index.html
P.S. I have no connections to this guy, only a satisfied customer.

     Tjark.

Offline Allen Smithee

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Re: Cheap DRO for my Seig X2p
« Reply #19 on: November 13, 2014, 03:54:28 PM »
Allen I have the same scales on my mill.
Have upgraded them with the caliper2pc box.
After the upgrade I am very satisfied with them.
The repeatability is now 0.01 mm on all the scales.
Maybe this is an option for you to.
You can find more information at the next link;   http://www.caliper2pc.de/en_index.html
P.S. I have no connections to this guy, only a satisfied customer.

Yes, I saw those. I quite like the idea, but I'm not keen on swapping from the micro-USB connectors to the RJ-45s, and I'm also not keen on having a laptop in the generally messy environment of the machine shop!

AS
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Offline Tjark

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Re: Cheap DRO for my Seig X2p
« Reply #20 on: November 13, 2014, 06:18:20 PM »
Allan, I see what your mean.
I have bought a second hand Pentium 4 and installed this up the wall.
This works great.
About the RJ-45s I have to wait how they will take the cold and hot, moist and dray air conditions in the shop.
I have a workshop with a ½ stone brick wall so not very pleasant in the winter.
Heat the shop with a petroleum heater.

   Tjark.

Offline Allen Smithee

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Re: Cheap DRO for my Seig X2p
« Reply #21 on: November 14, 2014, 09:02:47 PM »
I've made some progress on the scale covers, but I'll cover those when they're finished. In the mean time I've addressed one of the major pains of these cheap units - their appetite for batteries. These units run on a pair of 3v lithium button cells, and they draw current even when notionally switched off, so whenever you want to use them you can be sure at least one will have flat batteries. Which is silly, because the only draw a few milliamps and so don't really need anything "clever". Sorry about the poor photos in this bit - I'd left the camera indoors and so used my phone.

So I got a cheap wall-wart 3v regulated supply (from Maplin, as it happens):



I cut the connector off the end of the cable and (after checking polarity with a DVM) spliced three wires onto each cable, covering with some heatshrink:



I then took the back off each display, threaded one positive and one negative lead through the battery hole in the rear cover and soldered them directly to the board:



The rear cover was then screwed back on with the power leads coming through the battery hole:



Finally I cut a small slot in the lower edged of the battery cover with a diamond wheel in a dremel so that it could be refitted to keeup the crap out:



When all three were done I put a simple switch in the power lead, and here's a quick mock-up of my intended free-standing display mount:



Still needs the wiring tidying away, and a clean-back and repaint of the stand, but you get the idea.

AS
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Offline tangler

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Re: Cheap DRO for my Seig X2p
« Reply #22 on: November 15, 2014, 02:18:38 PM »
Thanks, that's useful information  :ThumbsUp:.  I'm thinking of putting a couple of these scales on my Flexispeed since it has no dials and the screws don't lend themselves to graduation.

Cheers,

Rod

Offline Jo

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Re: Cheap DRO for my Seig X2p
« Reply #23 on: November 15, 2014, 02:37:53 PM »
:o

Rod go for quality readouts pretend it is a Cowells: fit a pair of long reach dials on the two axis. Available in imperilous (if you really must  :disappointed:) or modern measurement types for the same price as these cheap readouts ;)



Jo
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Offline tangler

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Re: Cheap DRO for my Seig X2p
« Reply #24 on: November 15, 2014, 03:04:04 PM »
Jo,

Thanks, I'm still vacillating. Your set up is nice and simple but on the other hand I like the idea of dual reading.  I also still have the old style capacitive scales that I took off my mill which I could try as a stop gap - not so elegant as the remote readout and more difficult to shield.

Cheers,

Rod

Offline Allen Smithee

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Re: Cheap DRO for my Seig X2p
« Reply #25 on: November 16, 2014, 12:38:09 AM »
The X-axis scale installation is nearly complete. It took some head-scratching to make it neat, and I ended up having to mill a mounting block to specific dimensions - this was made much easier by the fact that I had digital readouts on the Y and Z axes to work with!

I've left the camera in the garage, but tomorrow I'll finish the installation and the covers, and then I'll post all the pics (assuming people are interested).

AS
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Offline Allen Smithee

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Re: Cheap DRO for my Seig X2p
« Reply #26 on: November 16, 2014, 10:57:00 PM »
OK, the final leg...

First of all the scale covers. They explicitly warn that these scales are not swarf or coolant-proof, so some covers are a good idea. I decided that the z-axis one was sufficiently out-of-the-way to do without one, but the x and y axes needed something. I was in B&Q a while back and my eye fell on some useful-looking PVC extrusions including a 30x30x1mm angle section. A piece of this was trimmed to fit around the y-axis sensor mount:



...and then attached to the side of the saddle with a couple of M3 screws into tapped holes. I'm bored with the tap-in-hole shots so let's take those as read. This scale had to be spaced out from the saddle, so the cover isn't long enough - I'll come back to that later.



I finally settled on a design for my x-axis installation. It's a compromise because there isn't much height available (the height of the sensor is only a few mm less than the distance from the saddle to the surface of the table). The overall installation looks like this:



I'll have to remove it to adjust the gib, but it only takes a minute and it's an acceptable compromise. To make this work I had to take the front off the sensor housing abd re-route the cable so that it came out of a new hole in the end of the housing rather the the top (the original hole being covered with electrician's tape). I then had to make an adaptor block to extend the table so that the scale could cover the whole range of the x-axis travel (330mm). I made this from the same piece of hot-rolled steel bar I used for the other mount, but it's a more complex part that allowed me to practice some milling. It also increase my confidence in what this game little mill can do.

The block needed two flat, square faces to sit on the machined surfaces of the underside of the table. It then needed the corner joining these surfaces notched back by 2.4mm to clear the radius of the table. It then needed the lower portion relieved back to allow for the sub-flush fit of the table against the saddle, and then it needed a 3.5mm rebate to clear the gib screws and locknuts. Then it just needed two holes - one tapped M3 for a stud and the other 3mm dia with a 5.5mm counterbore for a flush-fitting mounting bolt. I had lots of "fun" making this, with the need for most of the above features only being discovered during trial fittings. The result looks like this:



...and it fits here:



It was whilst taking this photo that I realised it would foul the gib screws:  :facepalm2:



It was an "iterative design" process. Eventually I got there:



The other end was fairly easy. After making a thin steel bracket to attach the sensor to the saddle (M3 tapped hole and bolt) the supplied slide mount was trimmed so that the slide could pass right through it and the table wound hard over to that side to hold the slide and mount in position. The upper mount screw was then removed and its position marked through onto the edge of the table and a hole was drilled and tapped M3 - which also happens to be the same thread as the mount screw. The net result was that I was able to replace the upper mount screw with a longer M3 bolt which, when carefully positioned, would both clamp the mount to the scale AND support it spaced off into the required position as shown below. A locknut and washer on the thread of the bolt then made it all secure:



I then took a piece of the same PVC angle and trimmed it to fit into the small gap between the sensor and the table, with slots to clear mounting bolts. In this case the angle is more than wide enough because this scale isn't spaced off like the Y-axis one:



In that picture you can also see how I've taken another piece of the same angle and trimmed it to make a flanged-strip extension to the x-axis scale  which is in the process of being bonded with PVC cement. All cables have been routed under the covers to keep them out of the way.

And there we have it - three-axis basic digital read-outs with no battery issues and covered scales. I used the x and z axis scales when making that block and it definitely made the job easier, especially in the "iterative" phases where I was above to disengage and re-engage the quill dog and confidently return the tool to the same position. I'll have to leave that PVC cement for 2-3 days to fully harden, but in the mean time I can finish tidying up the display mount with a lick of paint and some labels:



If you look carefully at that photo you'll see one reason why a freee-standing display mount may not be such a good idea. The units are each held to the stand with internal magnets (which give a poor grip on the cast iron of the mill chassis, but an excellent grip on mild steel sheet). But if the displays are anywhere where the ferrous swarf is flying then it sticks to the front of the case where the back of these magnets are just underneath the plastic

 :facepalm:

Anyway - job done. Much learned along the way.

AS
« Last Edit: November 16, 2014, 11:00:26 PM by Allen Smithee »
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Offline Allen Smithee

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Re: Cheap DRO for my Seig X2p
« Reply #27 on: November 16, 2014, 11:09:32 PM »
One thing I learned about these particular DRO units. If for any reason you want to remove the sensor from the scale strip (which I really don't recommend) then it can only go back in from one end (and I can't remember which one it is). Pushing it in from the wrong end bends a brass wiper and requires extensive dismantling to rectify it. During this dismantling a small spring flies out, and I have yet to work out where it came from and how to put it back. Fortunately I had a spare scale...

AS
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Offline Jo

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Re: Cheap DRO for my Seig X2p
« Reply #28 on: November 17, 2014, 07:38:22 AM »
Well done Pete  :ThumbsUp:,

So what is next on your job list  :naughty:

Jo
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Offline Rr12267

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Re: Cheap DRO for my Seig X2p
« Reply #29 on: January 10, 2015, 03:13:47 PM »
Hi Allen,  nice work. Looking to do something very similar to my machine. As for the the display issue, do you know about the android DRO project?  If you have an android phone or tablet it allows you to connect the scales via Bluetooth to your device and renders the scales readings there.

Here is the link to the project page. http://www.yuriystoys.com/p/android-dro.html

Again, nice work.

rr

 

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