DRO Origin Setting

[Peter Cook 6Participant @petercook6]

In a moment of weakness – or frustration having got fed up of counting turns, I have invested in a DRO kit for the mill. Head end has come, but I am still waiting for the scales and have not yet fitted it.

The head end is a Sino SDS3MS 3 axis unit and the scales glass. Having spent some time reading the manual, I still have what may be a simple (and stupid?) question. Do glass scales have some form of absolute origin which can be used to set the zero point of the co-ordinate system, or is it all relative?

I am happy with the idea of setting the zero point from a physical datum (corner of the vice or job) and using that as the base, and also the ability to save multiple datum points (centre of the rotary table for example). But how do you accurately return to those positions after powering down the system.

The manual refers to mechanical origin finding but that is with magnetic scales in the section for segmented compensation. There is nothing about finding the origin on power up for glass scales. I can find nothing online about  zero finding on power up.

Do I need to physically re-find the base datum each time the system is powered up, be VERY careful not to move the table with the system switched off, or not switch the power off at night?

What do others do to retain position across multiple workshop sessions?

[Anonymous]

On my professional (Newall) DRO there is no absolute zero; it’s not really a useful feature, although the system does have absolute co-ordinates and relative co-ordinates referenced to whatever zero point was set in absolute co-ordinates.

I always set a zero at a point on the work, normally corresponding to the reference point for dimensions on the drawing. Relative zeros can then be set as needed.

My DRO is based on steel balls in a carbon tube so if the table is moved less one ball diameter while powered off it retains the set zero in absolute terms to within a couple of tenths. But if I really need to retain a reading overnight I normally just leave the DRO powered up.

Andrew

 

[JasonBModerator @jasonb]

On the odd occasion where I may not get a job complete on the same day I may leave the unit switched on overnight.

I have also locked the table and switched off the DRO making sure to turn it on again before moving the table some days later.

But most of the time the part is not really on the machine long enough to need worry, I just set my zero depending on the job be it two faces, back of the vice or most commonly ctr of a part. Mine is a Sino with glass scales.

[davidr8Participant @davidr8]

I have a DRO on my mill and it’s a complete game changer.
There is no need to find the origin because during the course of working you will zero the axis many times over.If you leave a project over night you can leave the DRO on and come back the next day and resume working.

The same applies to magnetic scales.

[NealebParticipant @nealeb]

My glass scale DRO as fitted by Warco has a reference point somewhere in the middle of travel on each axis. By hitting the right buttons, then moving each axis in turn, it picks up the reference point so can “remember” position when switched off. Useful if you have a machining session long enough to need a break halfway through! On the other hand, my lathe has magnetic scales and no reference point, although it does seem to remember the last position when switched off (as long as you don’t touch anything).

Just as important – when you first set up the DRO, make sure you get the XY directions correct. New users can get a bit confused about plus and minus directions and it gets a lot worse later if it’s not right from day 1.

[John HinkleyParticipant @johnhinkley26699]

I always set the DRO on my mill to a known datum from the drawings, as many above have done.  If I was in the position of having to carry over a job to the next day as often happened, to save having to leave the DRO switched on overnight, I would finish a specific cut, then reset the machine to the datum 0,0,0, table positions and then switch off, noting, if necessary, any Z-axis displacement from zero, knowing that whatever happened in the interim, or however long the interval, when switched back on, it would always be at that datum, without having to worry about whether the axes had moved.  That worked for me, and I didn’t have to worry if I couldn’t get back in the workshop the following day.

John

 

[Nigel BennettParticipant @nigelbennett69913]

I just use zero datums (data??) to suit the job – like Jason, it’s very often in the centre of the component. I’ll switch to another datum if moving from the vice to the rotary table, and then I can switch back and forth until I move one or other.

One thing I do if I’m leaving a job mid-process is to lock all the table locks, switch off the DRO and plonk a piece of cardboard in a prominent position, generally leaning against the spindle. Written in large red letters is the one word “SET” so that (hopefully) I won’t absent-mindedly twiddle things before turning the DRO back on again.

On my unit (supplied by Machine-DRO a while ago) it never seems to forget where it was when it is switched back on again. I assume there must be a small battery in it to stop it forgetting – but how long they last if so is another question.

[Michael GilliganParticipant @michaelgilligan61133]

If the job is complex, or you need to be obsessive about it … have a look at this:

https://youtu.be/Np497YjpJao?feature=shared

The tooling-ball [ickey ball] dates back to before DROs, but the fundamental concept remains useful, and rather brilliant.

MichaelG.

[Dave HalfordParticipant @davehalford22513]

Most modern displays have memory which retains the positions upon switch off.

If the both scales that you ordered have reference marks and the display can use them then it is possible to recover a previous position if someone has moved the handles with the DRO powered off. This is done by traversing the read head over a mark on the scale. The display remembers where the reference mark should be in relation to the last position and the difference between them is how far extra -ve or +ve the read head needs to move to re-acquire the lost point.

The ref obviously has to be set up first before you start a job.

And it’s also just as easy 9 times out of 10 to re-acquire the start yourself anyway unless you’re chasing half a thou.

[Peter Cook 6Participant @petercook6]

Thank you for the help and all the ideas. Dave and Nealeb hint that what I was hoping may be possible. I often have the mill set up with a vice at one side of the table and the rotary table at the other.

I was hoping that having indicated the centre of the table and the vice corner, and storing their positions in one of the 200(!) memories I would be able to swap between setup origins easily. However there didn’t seem to be any way to set an absolute zero.

Perhaps there is, both the display and the scales have an “R” signal on pin 9. Once all the bits appear and I get them installed I will experiment a bit. The manual is “less than clear”, and in trawling the internet I haven’t found any material about setting zero on power on – which seemed odd, but it could just be the way I think! I also wondered about the usefulness of having 200 stored locations if you can’t easily reacquire the origin!

[Nigel Graham 2Participant @nigelgraham2]

You normally establish the origin for the task in hand (or vice…), based on e.g. the work-piece’s datum corner, a rotary-table centre, vice’s fixed jaw, angle-plate, etc.

An absolute (0,0,0) on the system itself is not very helpful: if you put it at the extremes of travel you would always be calculating the work and tool positions.

If you put the relative origin in the centre of the work then the readings are plus or minus according to which way you move the table, and that can be useful when matching parts whose outer edges are irregular or do not need co-incide.

In fact I had such a task yesterday, making some press-tools: the hole centres in pairs of plates have to co-incide  and be equi-distant from the front edge (and they do!) but the plates’ lengths were not critical and do differ a bit.

 

My DRO, on a Myford VMC milling-machine, retains its settings after I have switched it off but as a precaution I normally move the table back to (0, 0) before doing so.

[John HaineParticipant @johnhaine32865]

This is a similar issue to whether one “homes” a cnc mill or lathe.  Almost always it suffices just to reference the system to the work in hand.  Rater than spending a lot of time trying to establish an origin for “machine coordinates”, I would recommend acquiring or making edge finders etc to make it easy and quick to set the machine to a datum on the work.

[JasonBModerator @jasonb]

The 200 memories are used for tool settings and I’m not sure they would work to remember a vice and R/T position.

Even if they did you would then have to work out how to relate that to the actual absolute and incremental zeros that are used when actually using the DRO

[Dave HalfordParticipant @davehalford22513]

Peter,

Setting zero is easy, you just press the x or y button without touching the numerical keys which clears the memory or inputs zero depending on how you look at it.

IF your scales have an Ref signal, (which is not the same as having a pin merely designated as ‘R’) the position will be clearly marked on the outside of the scale.

Knowing where the corner of the vice is doesn’t help much unless you are very careful in positioning the work.

Useful in production with a fixture to hold the work in the same place.

[Peter Cook 6Participant @petercook6]

Thanks again for all the advice. Scales arrived today, so the next job is to fit them and then start to climb the learning curve.

Wasn’t quite as silly a question as I originally thought. Much useful advice  garnered.

[Clive FosterParticipant @clivefoster55965]

The Sino SDS 2MS 3 axis DRO system I put on my Bridgeport approaching 20 years ago stores teh last set of numbers in all memories when its turned off. Presumably either rechargeable battery for back up or some form of flash RAM.

I park the table after finishing work with the quill over the middle of the table in both axes, set X and Y to zero and store the values in memory locations 0 or 1 which are actually the same location. Something that can be mildly confusing. With the table locks engaged I know it will still be at zero-zero when I return.

First job after firing up is to switch to another memory location so I can play about with offsets et al without looking zero reference.

Last job before shutting down its to switch to memory location 1 (or 0) and wind the table back to zero-zero and engage the table locks.

Unless I carelessly start working using the 0 (or 1) memory location I always know that my baseline centre of table home position is stored. Its been may be 3 years since I last screwed up the zero setting by not changing mermaids on start up.

For actual job I pick up off the work as appropriate. Generally using a Huffam wiggler to pick up off both sides and the 1/2 function to define the middle. Any subsidiary offsets I store in other memory locations.

I don’t worry about Z as that always has to be picked up off the workpiece whatever you do. I prefer to define tool contact as 0.0000 in whatever memory I’m using and go from there. My Z scale is on the knee with raising teh knee set to give negative numbers so I can directly read the cut as – whatever., Quill stays locked for most jobs except drilling, tapping and similar.

Clive

[Gary WoodingParticipant @garywooding25363]

I’m a bit late on this thread. I have a Newall 3-axis on my mill and an M-DRO 2-axis on my lathe. Both retain their readout settings when switched off.

[Anonymous]

Seems to me that there are two levels of “turn off” – switching of the device at its panel switch and complete removal of power at the wall socket. It seems to me possible that the latter might lose the setting even though the panel switch retains it.

I’m not casting nasturtiums here just musing. I have no evidence that this is so in any instance.

[Nigel Graham 2Participant @nigelgraham2]

That may depend on the particular system. That on my mill does seem to remember settings when I switch it off on the unit, then on the wall socket.

Though with the caveat that since I first return the table to the local (0, 0) I had set, it might be the default anyway.

Not a matter of foundry border-plants: just something you need know for your particular installation.

 

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