DRO's

Hi Guys

I had a TOWIE moment and lashed out £23 on Ebay (The only way is ....) and have received a used Mitotoyo dail guage model 543-180 IDC. It looked a little battered but the Seller assured me that it was fully working, no jitters or rough spots and recent new battery. Sure enough it does and resolves to 0.00001 in (what!!!). Its a classy piece of kit costing nearly 100quid new (which I would never have afforded. So I am a bit chuffed. I intend to try it out on the cross slide of my Myford and use it as a digital scale (which had excited al lot of comment recently about the difficulties of budget calipers etc.

As the whole gauge is well sealed against outside, it should perform well, I think, worth a gamble

I noticed that there was a 6pin socket for a lead. I ebayed and found the lead would cost more than my gauge, so I don't think I need an external readout

Way to go

Robin

For those interested in fitting magnetic encoders to their lathes / mills (etc), I have just done exactly that to my 3-in-1 machine using the following parts from the following vendors (no links / connections to businesses implied, just a happy customer with the experience of it all working together.)

1um Renishaw / RLS readheads were bought from eBay from America, chap has plenty to offload and is open to offers. Service and knowledge is excellent. **LINK**

Scale and rails can be bought from Allendale, here: **LINK**. I used the 2-part scale support, but the only disadvantage is that the screws to mount it to your table / bed etc are under the middle of the scale, so once the scale is in place it can't be adjusted.

DRO was also bought from Allendale, here: **LINK**. I bought the 3-axis one even though I only intended (thought it possible) to mount X & Y, but now I've worked out a way of doing it I'm going back for more!

Total cost was probably in the region of £300.

Joel

High Joel

sorry to show my ignorance, did follow up the Renshaw link. Looks like the magnetic strip is self adhesive? to stick on an oily mill table? Can't be right, how is it done

These look like serious industrial kit. Is this magnetic strip likely to be affected/corrupted by magnets? such as a DTI

This technology is all new to me, Im afraid Never thought it was possible for a home workshop to have such advanced stuff available at an affordable price

Mind boggling

Cheers

Robin

The first thing I'll say is bear in mind that these bits of kit are designed for a wide range of environments, and in some of them the fact that the scale is stuck to the substrate is actually a good thing from a metrology (accuracy) point of view. I could go into more detail, but in our world the benefits gained from having a scale that stretches as the substrate changes shape due to thermal expansion are by far outweighed by the physical environment. So...>>

I simply mounted the scale in a 2-part support profile (link in previous post). These consist of a bottom part with mounting holes that you screw to your machine and then stick the scale onto, and a top cover, that screws to the bottom part and completely covers the scale protecting it from swarf and coolant and being bashed. The readhead is perfectly capable of reading through the ally top cover with no affect on accuracy (ok, there is a tiny one, but being in the region on nm we can ignore this error source too!). The photo below shows the bottom part mounted, ready for the scale to be stuck to it and the top cover screwed on.

The scale is magnetic and I guess, could get damaged by introducing foreign magnetic fields. However in practice you'd have to be trying pretty hard, i.e. by mounting a mag-base for a DTI right onto it, and even then you'd probably be ok. To give you some idea, I managed to put some scale in the same plastic carrier bag as a replacement motor for my lathe, and had no probs. The actual fields themselves are fairly small and don't radiate much above the surface of the scale so you'd basically have to place a strong magnet right up on the scale itself to damage it - and remember we've now got a cover on it so we've got an extra layer of protection.

You're right, these are serious pieces of kit, and new they cost several hundreds of pounds. But they can be sourced much more cheaply on eBay and I'd much rather have a product designed precisely for this kind of application than one based on dismantled calipers or otherwise. That said, £300 was for me affordable, and for others it may not justify the cost.>>

P.S. Other photos are available in my profile album thingy - called Encoder.

If anyone has any questions I'm more than happy to help - DM me.

I took a photo of the completed axis last night, for comparison to the last photo I put up. Note that the LED is now green, rather than red, showing signal strength & alignment etc are all correct and the encoder is working properly. You can also see how the top cover screws to the backing bar and seals the scale in place, protecting it from swarf & coolant etc.

Smart work CB. Im amazed it works at such a distance from the strip. I thought it would have to be really close, 5 thou say

Robin

Robin,

That was shimmed up using nothing more than a business card - the beauty of these magnetic encoders (compared to the optical ones which are often so finicky that they have to have integral bearings and come as a complete module costing big ££ that they have a really wide range of setup tolerances.

Rideheight (from the scale surface) can be anywhere between 0-1.5mm (compared to an optical which is, say, 0.8mm +/- 100um). Pitch, roll and yaw all have wide tolerances too, so all my holes on the mounting brackets were ovalised to give me maximum play, and the dead-easy-to-use set up LED simply turns green (from red) when everything is aligned.

More info on the readhead itself can be found here: **LINK**, the original manufacturer's page where datasheets and installation guides can be downloaded.

Under normal circumstances I would consider this sort of system to be beyond the budget of the standard home hobbyist, but with a readily available second-hand and v cheap source on eBay it all becomes worthy of serious consideration.

Joel