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Problem with DRO's memory or with mine?

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Bill Phinn02/01/2021 20:45:26
601 forum posts
87 photos

I've got a factory-fitted two axis DRO on my Warco WM18, the type that comes with the SDS6 user manual. I've been doing a bit of milling over the last few days, having not had much chance to do any lately.

I seem to recall that in the past I could switch off power to the DRO [whilst keeping the rocker switch on the back of the DRO display in the "on" position] and, if I had moved the table during the power-off time, when I powered back on the DRO would indicate the new position accurately [i.e. work like the battery powered Z-axis DRO I fitted myself at a later date]. Am I imagining this?

I ask because what is happening at the moment is that when I power off the DRO whilst x and y are both set to zero, say, when I power back on having moved the table a little during the off time in one or both axes, the DRO somewhat unhelpfully still displays zero. This makes repeat work with vice stops somewhat inconvenient because on powering on after some down time I have to edge-find all over again if I've inadvertently moved the table during the down time.

Page 13 of the manual talks about a sleep switch that sounds tantalizingly like it might alllow me to overcome this problem [i.e. get the DRO to function like a digital caliper or my battery-powered Z-axis DRO] but it's not in very intelligible English, and in spite of following the instructions [mainly concerned with the HA button] it has not helped.

However, as I say, I may just be mis-remembering how my factory-fitted DRO works.

Martin Connelly02/01/2021 21:01:53
1931 forum posts
207 photos

You don't say how old the unit is. It is possible there is a small backup battery that needs replacing.

Martin C

Bill Phinn02/01/2021 21:05:15
601 forum posts
87 photos
Posted by Martin Connelly on 02/01/2021 21:01:53:

You don't say how old the unit is. It is possible there is a small backup battery that needs replacing.

Martin C

It's 10 months old, Martin. Where would this back-up battery be if there is one? My manual doesn't seem to mention such a thing.

Michael Briggs02/01/2021 21:37:49
217 forum posts
12 photos

Hello Bill, I have a SDS6 on my lathe. The display counts pulses from the scales when they move while it is powered up and stores the position when power is turned off. It can’t measure if or how far it has moved without power applied.

Edited By Michael Briggs on 02/01/2021 21:41:44

Nick Hughes02/01/2021 21:43:19
256 forum posts
143 photos

According to my manual, the Sleep function is only available on the 3 Axis version.

GordonH02/01/2021 22:46:46
18 forum posts
3 photos

In my version of the SDS6 manual, there's an ambiguous reference to the 3 axis display in the Sleep function heading.

On my 2 axis display, pressing the HA button puts the display to sleep, while the unit remains switched on and continues to calculate x and y axis positions. Pressing HA again turns on the display.

I think that the section heading may be intended to say that the sleep function is not available on the 3 axis display but cannot confirm if this is so.


Clive Foster02/01/2021 22:53:43
2880 forum posts
104 photos


Unless the DRO uses scales encoded for absolute position outputs it will loose position when moved with the power off.

Common scales and read heads are simple pulse output devices with no absolute position encoding so the DRO has to be turned on to count the pulses and register a move.

Most reasonably modern DRO boxes seem retain the position output when powered off. Usually non volatile memory these days rather than back up battery. My Sino SD 2 system is around 15 years old and still holds the position display so I guess thats non volatile memory, not battery back up. The on-off switch on the back went dicky very early on so, like you, I use the wall switch to power on and off.

My practice is to lock the axes on the Bridgeport before turning off so the position is never lost. I keep Memory 1 permanently set to a base, middle of X and Y axes, zero and usually set back to that before shutting down. Any job specific presets are done using other memeory locations. Wherever I can I like to set up cuts to finish on zero.

The first DRO I used was an old Newall Digipac 5 which forgot everything on power off so disciplined return of all axes to zero before turning off was a very useful habit.


Edited By Clive Foster on 02/01/2021 23:16:13

ian j02/01/2021 22:56:27
306 forum posts
285 photos

According to my manual, the Sleep function is NOT APPLICABLE TO the 3 Axis version.

Just been to the workshop (BRR) and tried my 2 axis DRO on the milling machine

The DRO must be in INC mode, pressing HA puts it to sleep mode and the displays go blank as if powered down but still tracks any axis movements which are displayed when HA is pressed again. But if the DRO is switched off either by the rear switch or wall socket any axis movement is not stored.


Gordon and Clive replied as I was typing !!


Edited By ian j on 02/01/2021 23:00:54

Edited By ian j on 02/01/2021 23:01:44

Bill Phinn03/01/2021 02:31:41
601 forum posts
87 photos

Many thanks to everyone for your helpful replies; they've cleared things up considerably, and helped me to see firstly that it was my own memory that was at fault, and secondly that I can at least get the DRO to keep a record of table movements whilst having a blank screen even though I have to compromise by keeping the power on. If I'm not prepared to compromise and do want the power off, I can always follow Clive's advice and apply table locks between sessions.

If I could guarantee I'd be able to finish batch work in one session or at least one day, it's likely my "problem" would never have appeared to be a problem, but circumstances tend to call me away without much warning at the moment, often without the possibility of going back any time soon.

I see the critical bit I misinterpreted in the manual's instructions on page 13 was "In not ALE [my underlining] working state, if there [sic] a need of Sleep Switch Off, key HA, the digital display box will turn off the display."

Thanks to your help, and Ian's input specifically here, I see I should have interpreted "in not ALE working state" as "in the INC working state or one of the 200 other modes where you can establish separate reference readings". I'm almost certain what the Chinese will have said for "in not ALE working state"; if I'm right, the instruction would have been both idiomatic [where the English isn't] and much more readily intelligible.

A remaining puzzle is that I don't see any reference in my manual to the sleep mode working only on a 2 axis or 3 axis display as the case may be. No doubt there are many different versions of the SDS6 manual and probably as many subtly different versions of the actual DROs the manuals relate to.

Edited By Bill Phinn on 03/01/2021 02:34:43

Martin Connelly03/01/2021 09:06:20
1931 forum posts
207 photos

Reading this makes me wonder if there is a need for some sort of homing system on manual machines. This is easy to implement on CNC and something similar could be considered for manual use. If you have a roller microswitch mounted on the machine, a small battery and an LED it would be easy to have a repeatable absolute zero position. Move the axis to the point where the microswitch is actuated and the light comes on then slowly back off until the light goes out. Set absolute zero on your DRO axis. Essentially what CNC does. This zero point does not need to be at the extreme travel of an axis, just somewhere convenient, you could pick the centre of travel. If you used a dowel in a reamed hole to operate the microswitch you could have a number of holes to fit the dowel and use a convenient one for the set up you have for the work in progress. Once you move to a suitable datum point on your workpiece note the absolute axis values, record them for that setup, then use incremental modes for the work. This would also cater for the unfortunate event of a power cut.

Martin C

Clive Foster03/01/2021 09:45:54
2880 forum posts
104 photos


Its probably good practice to get into the habit of locking the axes whenever you leave the machine. I've made a few oopsies on coming back to a machine and diving straight in without properly thinking through where I'd got to.


I considered the microswitch zero indicator idea but got into the habit of reserving one memory location for zero and locking the axes as a temporary measure until I got round to doing the switch. Never seemed worth the effort for what would, to me, have been small gains. I already have a couple of lifetimes worth of stuff on the"nice to do" list anyway.

I reckon you are overthinking the multiple zero thing. KISS is important when it comes to references. In practice you'd probably do better to use the DRO memory set-up to directly input offsets.

Taking the switch idea and running with it what I want is a DRO with a control output pulse when an axis counts down to zero. Hook that up to a relay in the feed drive(s) and instant bed stop functions with as many positions as you have memories. Or even the main drive on a lathe to give repeatable feed and threading stops. Especially if you add an electronic brake or use the power down feature on a VFD. Maybe something under one turn of the spindle variation with most machines.


Tony Pratt 103/01/2021 10:07:34
1752 forum posts
8 photos

Just lock the axes when finished for the day or leave the DRO on.


mgnbuk03/01/2021 12:22:02
1051 forum posts
69 photos

Reading this makes me wonder if there is a need for some sort of homing system on manual machines.

Many DROs have this facuility as a standard feature, usually described as "Ref" or similar.

To use this function, the scales must have an accessible reference mark ( the "Z" channel on the scale output). By "accessible" I mean that the scale has been mounted in such a way that the fixed reference mark can be traversed over by the read head. The position of the fixed reference mark (or marks) depends on the manufacturer and / or the model of scale - Heidenhain scales,as an example, can have one fixed mark in mid travel, a fixed mark 10mm from each end of travel, a single mark whose position is variable in 50mm increments depending on the position of an internal plate, or "distance coded" markes on a pre-determined variable spacing that requires software to determine where on the scale the read head currently is when two adjacent marks are traveresed, dependant on type of scale..

To make use of the reference facility, the DRO counters have to be "referenced" before setting the workpiece datum. When th "Ref" key is pressed, all readouts go to zero & the axes are traveresed in turn towards the reference mark on the scales - the counters don't start to count until the reference mark is traversed. There is usually some indication (an Led, for example) that the counter has been referenced.

Following referencing, a workpiece datum is set as usual. When it is required to pick up the same workpiece datum after a power down, the "Ref" procedure is redone after power on - the numbers that come on the counters after traversing the reference marks are relative to the datum that was previously set.

It isn't just high end industrial DROs that have this facility, the M-DRO basic units I fitted at work have it & I'm pretty certain the the "Jingce" unit currently langusihing on the bench & destined for my FB2 clone does as well.


Nigel B.

Nick Hughes03/01/2021 15:43:14
256 forum posts
143 photos

Just to back up my previous post, here's the relevant section heading, from my manual:-

sino sleep function.jpg

I've just tested this (to make sure I wasn't mistaken) on my 3 Axis display and the HA Sleep function does work.

This section also has  "In not ALE working state", so to use sleep, the unit must be in INC ( the HA button is disabled in ALE), as suggested in a previous post.

Edited By Nick Hughes on 03/01/2021 15:54:06

Bill Phinn11/03/2021 17:48:02
601 forum posts
87 photos
Posted by mgnbuk on 03/01/2021 12:22:02:

Reading this makes me wonder if there is a need for some sort of homing system on manual machines.

Many DROs have this facuility as a standard feature, usually described as "Ref" or similar.

Nigel B.

Apologies for my necro-reply to this, Nigel; I've only just got round to giving it due attention.

I looked at a video corroborating what you say.

A problem I have is that, contrary to your and the video's description, there is no "ref" key on my DRO [see pic].

I'd hoped my manual might clarify what to do instead, but it doesn't really. On p.11 ["Methods of finding mechanical origin"] it says:

"Move the raster ruler to the position which is initially set up as the mechanical origin [not sure what this position is], and then enter into the select page of Segmented compensation. Choose Find_ZE and press ENT to the interface for choosing compensation method, press ENT the interior of digit display meter handles automatically. At this time finish finding the mechanical origin and quit the absolute co-ordinate system automatically."

It goes on, in a similarly cryptic style, with more instructions than I can quote here at the moment.

In order to try and get to the "Find_ZE" point indicated on p.11, I previously tried following the instructions on page 8 relating to "segmented error compensation":

1). "Move the raster ruler to the smallest end of the co-ordinate [not sure what is meant by that] and enter into ALE right-angle co-ordinate system.
2). Press X> M/1 enter into the input function of multi-segment compensation of x-axis.
3) Set the segment compensation
1). Find_ZE..."

The problem was that "Find_ZE" is not what came up on the display at this point, so I was unable to comply with the instruction on page 11 "Choose Find_ZE" , which I'd hoped might have allowed me to arrive, via an alternative route, at the outcome suggested by you and the video.

Any help would be greatly appreciated.

dro display.jpg

Nigel Graham 211/03/2021 22:45:26
1767 forum posts
22 photos

Normally. I return the table to the (0.0,0) reading, but if it's easy to re-enter the co-ordinates if the unit usually retains them but has forgotten them, write those down - and lock the table - before switching off.

Generally I finish a session at the end of a particular set of operations, so returning to the origin sets things easily for the next steps.

I know it should not matter... in theory... but I always advance the table in one direction as if using the hand-wheel dials alone. This is mainly to retain the habit because I don't use the DRO (a Machine-DRO set) for all work; but also my second-hand Myford VMC's long travel has a very odd break point where the handle sometimes suddenly seems to run one turn without doing anything.

Fitting the DRO to a machine not designed for such a system entailed a heck of a lot of involved metalwork, including a piece of 2" X 2" aluminium-angle whose end protrudes by the cross-travel handle. It is ideal for writing notes on in pencil - such as co-ordinates!

mgnbuk12/03/2021 13:45:00
1051 forum posts
69 photos

Hi Bill,

I don't have a Sino SDS6 or access to one, I'm afraid, but I did find this manual online

Page 10 of this manual refers to using the HA key to find the "first absolute zero of the raster ruler as the mechanical origin". I see that your keyboard does have a HA key (Home Axis ? ). The keyboard description describes the HA key as "Function key for sleep", though !

The manual refered to is particularly difficult to understand - so many functions & so many obscure descriptions ! I have found the same manual as above on a couple of sites & also references to the console as having a referencing or "power down memory" feature as standard, so it should "just" be a case of working out how to access it.

M-Dro (Allendale Electronics) used to sell these consoles & make mention of the fact that they supplied them with a "UK written manual". As they show this console to be superceeded in their line-up, you could see if they would send you a copy of their manual ? I have installed a couiple of M-Dro readouts at work (not the SDS6 console, though) and have found M-Dro's technical support to be very helpful.

Nigel B.

ps. Found another version of the manual

Pages 20-22 give a bit more coherent description of referencing, but also suggests there is a "memory" function to retain displays after a power interruption if the axes are not moved while powered down (not sure I would trust it, though ). It also suggests that the HA key may have different functions between  2 or 3 axis counters. This manual has a picture of a consolew ith coloured keys, so may be later / updated version than yours. Might help some though ?

Edited By mgnbuk on 12/03/2021 13:59:23

Dave Halford12/03/2021 16:52:57
1817 forum posts
19 photos

Bill says this "I ask because what is happening at the moment is that when I power off the DRO whilst x and y are both set to zero, say, when I power back on having moved the table a little during the off time in one or both axes, the DRO somewhat unhelpfully still displays zero."

He's not saying the memory is lost, just that it displays what it did before it was turned off.

To do what Bill wants would require a switch to turn off the display, but leave all 3 scales LED lights constantly lit + whatever counting ccts to read the new positions in to memory as the table moves when knocked etc. and powered from an on board battery. I have no idea what all that might draw over, say a week, but is it practical to offer that function?

Bill Phinn12/03/2021 18:55:36
601 forum posts
87 photos

Many thanks for your replies, Nigel G., Nigel B. and Dave.

Nigel B., I've spent some time looking at both the manuals in your links, and also a pdf from Chronos, which covers a different kind of DRO from mine but discusses the use of the REF button for retrieving an origin after power off in some depth [starting at 3.9]. Sadly, none of this has so far assisted me in replicating finding an origin as set out in the short video I linked to in my post of yesterday.

Dave, I'm not sure I've understood your post properly, but the video I linked to ["DRO PROS demos Power Off Memory"] is showing you how to recover a zero that is effectively lost after a power off during which the table was moved; as far as I understand it, no onboard battery or other alternative power source is required to enable a recovery of this kind; you simply access a reference datum point built in to the DRO scale. My inability to access a ref. datum point on my own DRO appears to be where I'm coming unstuck.

Edited By Bill Phinn on 12/03/2021 18:56:47

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