DIY magnetic DRO

[ChrisBParticipant @chrisb35596]

Posted by Beaker on 12/07/2019 19:32:23:

I just wanted to bump this thread back up. Chris B: This is really interesting stuff, please keep us updated. I'll definitely be doing this if you're successful. Thanks for blazing the trail!

Hi Beaker, thanks. I did progress a bit further with these DROs.

I received the TouchDRO adapters from Yuriy some time ago. I downloaded the TouchDRO app on a tablet and connected via bluetooth to the adapters – it's very neat and clear and has lots of functions.

Next I hooked up the read heads to the adaptors to check if they actually work – moment of truth!

I did a temporary set up as I have not attached the read heads and magnetic tape to the lathe and mill yet, so I just slid the read head over the tape by hand on a table, surprise surprise it worked!!

I had a small hiccup as I found that one of the adapters had a defective input channel so I contacted Yuriy and did troubleshooting together. He confirmed that part of the board was defective so he sent me another one – thumbs up for his aftersales.

Next step is installing the tape and read heads on the lathe and mill and calibrate the scales, but I'm holding off for now. It's unbearingly hot in the workshop and I can't concentrate in this heat – I desperately need an airconditioner!

[ChrisBParticipant @chrisb35596]

Being too hot to work in the shop I retreated to my study (thank God for the ac!) trying to figure out how to connect the read heads to the TouchDRO adapter.

I have a question regarding this connector (9 pin type). The circuit board came with these female ports – they look like a LCD/monitor type connector (don't know the name). Now I need to connect the read head cable to these ports. All cables with this type of connection I've seen (like data cables) are molded to the plug.

Does anyone know what connector I would need, or is it a case of buying some 9 pin data cables, cut the plugs off and solder them to the read head cable?

Chris

[Mike PooleParticipant @mikepoole82104]

Search fo D sub or D subminiature, widely available from electronic suppliers.

Mike

[ChrisBParticipant @chrisb35596]

Hi Mike, thanks for pointing me to the right direction. Something like these links should work I guess.

**LINK**

**LINK**

[Mike PooleParticipant @mikepoole82104]

Yes Chris that is what you need.

Mike

[ChrisBParticipant @chrisb35596]

Hi Mike thanks. I got the connectors yesterday (backshells out of stock arrgh!) and soldered all the connections – tedious job as the wires are so thin! Anyway, I hooked up the readheads and checked them one by one, and after sorting out a couple of crosswired connections, got them all working. Next step mount the heads and tape on the machines and figure out how the DRO app works!

[Clive FosterParticipant @clivefoster55965]

Nice work Chris.

Soldering and sleeving is indeed tedious.

For future reference crimp type push in connectors are much easier and, if you make a mistake, sorting out is a simple matter of pushing the connector out and popping it back in the right hole. Shells cost little more and crimp tools are, probably, a bit too expensive. Pro ones like mine are far too much! But frustration saved is well worth it if you are doing a few.

I got my tool set years ago from RS components when I had to do about 8 of the big ones. Not cheap but well worth it. I imagine E-Bay et al can offer much better deals now. I imagine crimp contacts could be gently squeezed and soldered rather than properly crimped or you can get solder bucket types. The insertion and extraction tools are cheap, about £5 for the combined tool from RS. Its the crimper that costs.

Clive

[ChrisBParticipant @chrisb35596]

Thanks Clive. I would much prefer the crimp option rather than solder. One of the adapters I received was with crimp type pins, so much easier to remove and install pins. But for a one off project like this investing in tooling I would have no further use for would not be worthwhile. But for sure if I were making a lot of these that would be the way to go.

I now need to build an enclosure for the adapters as exposed electronics and swarf are not the best of friends. Not sure how to go about it, two options pop into my mind: fabricate a box from sheet metal, or mill a case from a block of plastic…the latter is more within my capability as I do not have a sheet metal bender.

[ChrisBParticipant @chrisb35596]

I'm in the process of installing the DROs to the mill and lathe now. The plan is to stick the magnetic tape (supplied with double sided tape) directly to the machines and then fabricate the brackerty for the read heads. Started with the brackets for the mill first and that's almost sorted – I just need to install and align everything to the table and column.

The lathe on the other hand is a problem – my plan for the Z axis is to install the tape directly to the bed shown in red in the picture below. The read head I'll install under the carriage – should be protected from unwanted hits etc and excessive swarf and oil.

The X axis however id proving to be a bit of a headache. Preferably I would like to install the magnetic tape directly to the cross slide aft face (tailstock side) but the gib screws are getting in the way. Most X axis installations I've seen seem to extend quite a bit back onto the tailstock area and I would like to avoid that if at all possible.

Would it be a good alternative to install the tape and head on the forward (chuck) side?

Ps the lathe is a WM280, I would like to know how owners of this type or similar lathes got around the installation of the X axis readout

Edited By ChrisB on 25/07/2019 19:19:46

[JasonBModerator @jasonb]

on my 280 have thought about putting the strip on the underside of the cross slide offset slightly above the lead screw, there looks to be just about enough room to also get the read head (small emsi) in beside the screw or maybe a small extension out the back so the strip can be longer and you get more room for the head.

Is the double sided tape solvent proof? I would worry about paraffin or WD40 dripping onto the Z strip

[ChrisBParticipant @chrisb35596]

Posted by JasonB on 25/07/2019 20:26:05:

on my 280 have thought about putting the strip on the underside of the cross slide offset slightly above the lead screw, there looks to be just about enough room to also get the read head (small emsi) in beside the screw or maybe a small extension out the back so the strip can be longer and you get more room for the head.

Excellent idea Jason thanks! Would have never thought of that.

I think that might just work, will have a look tomorrow morning and see if things fit in. The read head is very small it's 25mm long by 18mm high (might be smaller than the emsi ones) so it might squeeze in.

As for the Z axis, the adhesive tape looks like its quite resistant to chemicals…according to the RLS website FAQs regarding the tape. **LINK**

[old martParticipant @oldmart]

Isn't the tape for the lathe in a rather vulnerable position? Could it go at the rear of the bed underneath the overhanging part? Just below the saddle clamps.

Edited By old mart on 25/07/2019 22:05:22

[Mike PooleParticipant @mikepoole82104]

Posted by Clive Foster on 17/07/2019 10:53:44:

Nice work Chris.

Soldering and sleeving is indeed tedious.

For future reference crimp type push in connectors are much easier and, if you make a mistake, sorting out is a simple matter of pushing the connector out and popping it back in the right hole. Shells cost little more and crimp tools are, probably, a bit too expensive. Pro ones like mine are far too much! But frustration saved is well worth it if you are doing a few.

I got my tool set years ago from RS components when I had to do about 8 of the big ones. Not cheap but well worth it. I imagine E-Bay et al can offer much better deals now. I imagine crimp contacts could be gently squeezed and soldered rather than properly crimped or you can get solder bucket types. The insertion and extraction tools are cheap, about £5 for the combined tool from RS. Its the crimper that costs.

Clive

You are dead right about crimping Clive but a bit of preparation can make the solder bucket version much less painful, many years ago I made a heavy block with tapped holes for various d-sub plugs, I then tin all the holes and ends of the wires after a light twist to stop any stray strands. A quick touch with a fine point iron and a nice bright secure joint with no bridging to adjacent pins should be achieved. Getting the cable cores the right length will help, too short makes life difficult and too long will leave a lot of cable to try and stuff in the shell. I don’t usually sleeve but I try to minimise any bare cable and not use cable that is too big. It’s always worked for me.

Mike

[ChrisBParticipant @chrisb35596]

Posted by JasonB on 25/07/2019 20:26:05:

on my 280 have thought about putting the strip on the underside of the cross slide offset slightly above the lead screw, there looks to be just about enough room to also get the read head (small emsi) in beside the screw or maybe a small extension out the back so the strip can be longer and you get more room for the head.

Took the cross slide off this morning to see if the read head would fit next to the lead screw. Unfortunately there's not enough space, my read head is 7mm wide and the space between the lead screw and slot in carriage is about 5.5 – 6.0mm.

There seems to be just enough space above the lead screw however, so if I mounted the read head directly to the under side of cross slide directly above the lead screw, and then installed the magnetic tape to the side of the slot in the carriage, it might just work. Will take a some pictures as it's difficult to explain with words sometimes!

Posted by old mart on 25/07/2019 22:04:04:

Isn't the tape for the lathe in a rather vulnerable position? Could it go at the rear of the bed underneath the overhanging part? Just below the saddle clamps.

Edited By old mart on 25/07/2019 22:05:22

The casting below the saddle clamp is not ideal to directly tape the magnetic strip – it's a bit uneven and the read head would not ride constantly above it. Where I plan to place it, the read head will be out of harm's way under the carriage. True the tape is exposed but I can't see it getting damaged in that area. The tailstock will mostly live there and there will be enough clearance – so I think it should be fine.

[ChrisBParticipant @chrisb35596]

Photos as promised:

 

As can be seen in this photo of the carriage, there is not enough space for my read head to fit in next to the leadscrew, (7mm wide head)

 

However I can install the magnetic tape to the side of the slot in the carriage where the cross slide lead screw lives. ( note: the tape is the other way round holding on as it's a magnet – still not 100% committed so did not install it permanently yet)

 

The read head just fits in the space above the lead screw between the carriage and cross slide. I can install the read head in the position shown in the photo below. The head will need to be secured to the bottom of the cross slide and the head cable fixed securely out of the way of the lead screw.

 

I think this might just be possible, but I would like to know what's your opinion, especially Jason's (since he came out with the original idea!)

Edited By ChrisB on 26/07/2019 13:34:59

[JasonBModerator @jasonb]

I think where you show the head in the last photo will clash with the nut when the cross slide is wound fully towards the operator.

Why not put it right at the back, the screw does not extend the full length so you don't have that in the way or risk catching the wire

What are the 3 dimensions of your head and I'll take a better look at mine later. This is a photo I took a while ago of where it would fit with the mag strip extended out the back by 50mm or so with the extension also serving to protect head and scale from swarf.

[ChrisBParticipant @chrisb35596]

Posted by JasonB on 26/07/2019 14:14:34:

I think where you show the head in the last photo will clash with the nut when the cross slide is wound fully towards the operator.

I think I did not explain myself properly Jason. My intention was to install the head aft of the nut (approx 20mm aft of the grease point) The head would be installed directly to the underside of the cross slide and as the nut is also bolted to the cross slide they should not come into contact. My picture above is probably misleading, as the head should be under the cross slide (but then I don't have X-ray photo capability yet!)

I got your point now Jason, yes at the back in the area you point out in your photo the head should fit nicely I think. It's dimensions are 25mm long, 18mm high, 7mm wide. the tape and foil cover is 1.7mm thick and I need a gap of about 0.3mm. So I'd say the total height of the head and tape should be 20mm.

[Clive FosterParticipant @clivefoster55965]

Watching this with great interest as am looking into a similar "concealed DRO" installation for my Smart & Brown 1024. OK I've a bit more room than you have and things are very much at the handwaving, pre back of the envelope, stage. Thinking in terms of putting the scale on a flat carrier affixed to the underside of the cross slide with the head in the space behind the screw as per Jasons picture. Longitudinal scale will go on an alloy beam sat in the gap between the taper turning attachment and the bed fixed to the slots that also hold the taper turning attachment bracket. Probably extruded L shape alloy with the scale underneath.

Intention is to hang both sensors off a single bracket or, if the shapes don't work, fix the wires to one and run them via an energy chain to the display for better control the angles of dangle when moving.

If you can't get the scale in flat to the slide is there room for an alloy "fin" hanging down beside the lead screw with the scale fixed to that. No real force on it so I guess L shape alloy extrusion with the side trimmed down to 1 mm would do.

If it almost fitted I'd have no compunction about milling a mm or so out for just enough room.

Clive

[JasonBModerator @jasonb]

Posted by ChrisB on 26/07/2019 14:41:33:

I think I did not explain myself properly Jason. My intention was to install the head aft of the nut (approx 20mm aft of the grease point) The head would be installed directly to the underside of the cross slide and as the nut is also bolted to the cross slide they should not come into contact. My picture above is probably misleading, as the head should be under the cross slide (but then I don't have X-ray photo capability yet!)

That looks like a plan, there seems to be about 9mm between the top of the screw and underside of the slide so your head will fit there. Strip may be a bit close on the nut but easy enough to shave a fraction off one side of that if the strip needs a bit more room.

[ChrisBParticipant @chrisb35596]

Thanks for checking Jason. I'll try to do a temporary installation and make sure everything fits, I'm confident it should work out – thanks for the idea.

Will report again when I progress further…got too many projects at hand (DROs, Mill Power feed, Solid tool post, Mill way covers…) but the will to visit the workshop in this heat is fading

Out of curiosity, do you have the dimensions of an emsi read head?

[JasonBModerator @jasonb]

11mm on the side that faces the strip x 14mm x 36mm long

[ChrisBParticipant @chrisb35596]

I see, so the magnetic strip is 10mm wide I guess. I'm using 5mm wide tape which makes the heads I'm using narrower. Hadn't thought of the nut but as you said, it's not a big deal to make it fit. Next week will try to make it a point and install both mill and lathe DROs

Clive if you build your own heads you could possibly design them to be even smaller than the one I have, the electronic circuit for the head is barely 10mm square, so the case need not be much larger.

[Douglas JohnstonParticipant @douglasjohnston98463]

I installed a magnetic scale under the cross slide of my Myford Speed 10 lathe a few years ago (a few pictures in my album ) and it has proved to be very nice and reliable. I covered the magnetic strip with a thin strip of non magnetic copper alloy to protect it and that has worked fine.

The whole scale being under the slide keeps it out of harms way and does not clutter up the right hand side of the carriage. I have the read head stuck out at the back of the carriage with an alloy plate to cover and protect it from swarf. All in all it is more work to install it this way but the benefits are really worthwhile.

Doug

[old martParticipant @oldmart]

I would worry about all the ferrous swarf sticking to the strip all the time, or are you only going to be turning non magnetic metals?

[SillyOldDufferModerator @sillyoldduffer]

Posted by old mart on 27/07/2019 21:57:58:

I would worry about all the ferrous swarf sticking to the strip all the time, or are you only going to be turning non magnetic metals?

That's a thought, but as attracting swarf would severely limit their practicality I guess it's unlikely they are magnetic in the usual sense. No luck here finding a description of them on the web though! Does anyone know how they work?

I suggest the tape isn't permanently magnetic like cassette tape. Instead the head might count transitions as a high-frequency magnetic field generated by the head passes over normally demagnetised iron particles embedded in the tape. Although that's also a magnetic tape, it wouldn't attract iron. But there must be other ways of making a magnetic DRO, induction perhaps? Help!

Dave

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