Mill DRO X/Y axis + and - on readout

I've finally got around to fitting a DRO to my Mill (WM14), its plodded along a bit but is now near final fitting. My slight confusion here is regarding the positive and negative ABS reading when the table is moving in specific directions. The relevant bit of the instruction manual is as such -

Both of the handwheel legends indicate an increasing feed (0 - 2mm) when moved clockwise. With the 2 axis's zeroed at the approximate centre of travel, the display for the X axis seems correct ( positive when handwheel rotated clockwise), but the Y axis confuses me - as increasing the feed as per the handwheel dial (i.e. table going towards the back of the mill) shows as going negative on the DRO display (as per the diagram above). It just seems a bit cockeyed to me.

Is this all correct? Yes, I can easily reverse the scale on the Y axis if necessary - I've no intention of using it for CNC, so in fact does it matter a jot anyway? but after spending so much time and money I would like to get it right, and not find 6 months down the line that I made a rookie mistake which caused issues!

Hope I've explained it clearly, and will really appreciate any thoughts.

All the best, Mike

I’ve never fitted a DRO, so I’m probably talking a load of cobblers, but is it possible the track has been fitted 180 deg out( backwards /. Upside down/ etc)

It makes not one iota, it is just convention. Obviously when used on cnc it makes sense that direction is the same for all machines. Direction is changeable usually with software in the readout.

Mike,

As you say, unless you are using cnc, it is immaterial whether there is a + or - in front of the readout. However, for consistency, I suggest you adopt the accepted convention. That diagram can be a trifle confusing. Imagine the spindle being directly over the X-Y travel intersection. The words 'table travel' are the clue. Thus moving the TABLE to the operator's right - negative X - means any cut will be made to the left or -ve direction. The same applies tothe Y-axis, of course. Similarly for the Z-axis, if the table is raised (or spindle moved down) then that is a negative motion.

I found it took me a long time to get my head around that. You won't be at all surprised to hear I still wind the handles the wrong way on many occasions!

John

Edited By John Hinkley on 21/03/2022 19:33:25

As Howard says, it makes no difference.

Depending on how you work, it can make life easier for you if it is a certain way.

Once you start using the DRO, you will rarely look at the dials again, so it does not need to increase in the way the dials increase. With a DRO, your dials only really need a settable zero mark. If you have to leave a particular setup, you can put the table at (0,0) and zero the dials. The dials will then save you time if there is a power cut.

If you use computer-generated drawings, or calculate co-ordinates using a spreadsheet or other program, it can be useful to have X- and Y- increase in the same way as normal Cartesian coordinate. (so I think that would be the opposite of your diagram - as the table comes towards you and moves to the left, both increase).

In the beginning, or if working very close to the 'zero' lines on your part, it can be helpful to mark these lines on the part, just so you do not confuse the sign (positive or negative.). You will see from your drawing if the feature should be above, below, left or right of the axis and the marked lines give you a visual reference to ensure this is so.

Actually if you are going to use the ARC function of a DRO then you do need to get the direction correct.

Y should increase as handwheel turned clockwise just as it does on the handwheel dial

I have this problem - on my mill the only way to mount the X axis DRO is with the scale moving and the pick-up fixed. Vice versa for Y. I can make the display increment or decrement in the correct sense using the setup page, but the displays for ARC and ARRAY are then reversed - it doesn't really matter, you can ignore the pictorial representation and just step through as normal, but it is slightly annoying if you get distracted and forget which step number you did last.

Swapping the A and B channels in the scale plug will reverse the count.

These systems mostly seem to use 9 pin "D" connectors on the scale cables, so not too bad to get in with a soldering iron - always assuming that the manufacturer didn't use crimped on pins !

Nigel B.

I might look into doing that - though I bet they are crimped!

I do not know if space is an issue, but could you buy a solder bucket plug and socket and make up a short male-to-female lead translating the pins?

though I bet they are crimped!

It is usually possible to remove crimped-on pins / sockets from the connector body by inserting a removal tool (usually a very thin wall tube) to close down the barbs that retain the pin / socket. This makes changing the locations easier than soldering - if you have the correct removal tool !

In the case of a crimped pin D connector, though, I would probably just cut it off & replace with a solder bucket type. A small portable vice to hold the connector for soldering makes life a lot easier fitting these. Not one of my favorite jobs, though.

Nigel B.

Before you dive in with a soldering iron, look for a settings or setup function on the dro display. There may well be an option to reverse direction. It's an obvious requirement if the scale fitting may have either the scale or read head moving. If you make a hardware mod you will probably invalidate any warranty.

There may well be an option to reverse direction.

Indeed there may, but Andy did say " I can make the display increment or decrement in the correct sense using the setup page, but the displays for ARC and ARRAY are then reversed " .

My suggestion to reverse the scale count direction by swapping the A & B channels was based on that comment, which I read as using the counter parameters to set the count direction correctly had introduced other issues.

Nigel B.

I have been giving this a little more thought - always a risky thing to do. I can see no difference in the fundamental question, depending on whether you mount the scales on the front or back of the table for the X-axis. Likewise left-right for the Y-axis. My DRO display certainly has the ability to change polarity.

John

Edited By John Hinkley on 22/03/2022 10:14:59

Thanks for all the very informative comments guys! Although I'm experienced in the mech side of hobby engineering, DRO's are completely new to me so I appreciate the advice - at the end of the day, should it require doing later, these DRO scales are easiiy physically reversible so there should be no need to go to the extent of re-wiring cables / swapping plugs etc.

I haven't delved deep into the user / installation manual yet (looks an awfully detailed job) further than basic guidelines on fitting. I'm pretty confident that buried somewhere in it there will be a parameter to soft adjust the direction reading.

From what I gleen from most of the comments, it doesn't appear to matter too much what polarity shows in the display as I'm only operating it manually, and as long as it's meaningful to me in the context of rotating the feed handles in the correct direction that's all that matters.

As usual, this forum & its members continue to provide a really valuable resource for all levels of user, and we should be proud of it!

Thanks again. All the best

Mike

With my MDRO scales and display, you hold down one of the buttons at switch on to get into the menu, then you can reverse the directions