Cynic-al Posted March 22, 2012 Share Posted March 22, 2012 I know a lot of you are into machining so thought I would give it a shot here. We bought a Colchester 2000 lathe at work a few years ago from a tool room auction for about £500 just for if we need to knock parts up quick. It came with a DRO which I didn't really bother with as we didn't have them when I was at college but i started prodding at buttons as I figured it would be a handy thing to have, especially as the scales on the handles are kind of worn. Problem is it doesn't read right. It seems to be consistant just inaccurate. With a 100mm slip gauge it reads around 75mm in X and Y. I managed to find a manual but it's not the easiest thing to read. Anyone got any advice for calibrating? Or guidance for the correct use. I'm not bothered about all the features it has so long as i can zero it then get an accurate reading. Manual http://www.mitutoyo....tion+Manual.pdf box Cheers Quote Link to comment Share on other sites More sharing options...
zoltan Posted March 22, 2012 Share Posted March 22, 2012 Just quickly scanning that cumbersome manual, is there tool compensation still in its memory? Quote Link to comment Share on other sites More sharing options...
Cynic-al Posted March 22, 2012 Author Share Posted March 22, 2012 ...goes to manual to read that section... Quote Link to comment Share on other sites More sharing options...
zoltan Posted March 22, 2012 Share Posted March 22, 2012 Has the lathe got tracks fitted on both the X and Y axes? Hard to see otherwise why there would be a necessity to scale the figures Quote Link to comment Share on other sites More sharing options...
Cynic-al Posted March 22, 2012 Author Share Posted March 22, 2012 I can't see how to clear the memory but I don't think it can be that, from reading the book all it can really do is alter the zero point depending what size tool you tell it you have, it can't compensate on length as it doesn't know which side of the tool i'm going to be cutting on? Surely if I touch the tool on the chuck, zero the display, move it in the x until I can get a 100mm slip gauge in the display should still say 100mm? Plus its only a 2-axis display, a lot of the functions seem to be intended for 3-axis units for millers? Quote Link to comment Share on other sites More sharing options...
LandyManLuke Posted March 22, 2012 Share Posted March 22, 2012 On my old Heidenhain DRO, you can change it to read pulses/mm/inches, is it possible yours is showing encoder pulses (75000 maybe?) over 100mm? If the manual doesn't talk about scaling the pulse input, in terms of mm per pulse etc, is it possible that the scales/DRO aren't a matched pair? As it's reading short, is it possible that the tracks are dirty? does it stop counting at any particular point on the scale? is the error linear - do you half the error if you only do a 50mm move? Quote Link to comment Share on other sites More sharing options...
simonr Posted March 22, 2012 Share Posted March 22, 2012 On the back panel there should be two switches - mode & scale. I would try each of the combinations of these to see if it makes a difference. increments. Page 36 is missing from the manual. The first part of page 37 talks about a dip switch on the head amplifier (the bit that converts the signal from the slide encoder to something the DRO can understand). I would guess at this being the adjustment for how much slide movement coresponds to one mm or inch. It might be worth trying changing the setting of ths switch one switch at a time to see if this adjusts the scaling between the slide and DRO. It is possible that either the DRO or the encoders were changed at some point - and not set appropriately to one another. If this doesn't work - post the message on the CNCZone forum - there are some clever people on there! Si Quote Link to comment Share on other sites More sharing options...
Cynic-al Posted March 22, 2012 Author Share Posted March 22, 2012 Plotted points up and down with the verniers and it was the same both ways within the tolerance I could measure with the vernier. I fiddled with the switches on the back, doesn't seem to have the dip switches, neither fixed it. Its converting correctly when you select mm and inches so I don't think its showing pulses. However I must apologise to zoltan, I spent a bit of time fiddling and found if i pressed the red star it brought up a number '384', change that to zero and enter it and hey presto, it seems to have done it! According to the manual thats the expansion compensation factor? Did a basic test with the verniers and it seemed to be about right but i will check it with the slip gauges later. Thanks all Quote Link to comment Share on other sites More sharing options...
simonr Posted March 23, 2012 Share Posted March 23, 2012 Well done! A DRO is a fantastic thing to have - much better than numbers on wheels as it is not affected by the backlash in the slides. I would never go back to a machine without them - and it was the DRO's that persuaded me that upgrading to CNC made sense! Si Quote Link to comment Share on other sites More sharing options...
Cynic-al Posted March 23, 2012 Author Share Posted March 23, 2012 I'm trying to get work to buy a CNC miller or machining centre, I've just got to find a way to make it an essential item for an R&D project... Quote Link to comment Share on other sites More sharing options...
CwazyWabbit Posted March 23, 2012 Share Posted March 23, 2012 I'm trying to get work to buy a CNC miller or machining centre, I've just got to find a way to make it an essential item for an R&D project... They won't care if it is essential or not, they'll want you to play a bit of buzzword bingo with them and say how much costs will be reduced. For R&D you should be able to make a good case fairly easily..... rapid repeatable prototyping.... reducing delays..... fail fast thus avoiding expensive mistakes at external machine shops..... You get the idea, I'm sure you can think of a million specific examples for your work area. Just remember they normally care little about the technical side as they don't really understand it and care far more about reducing costs and speeding up workflows, so if you want new toys learn to play their games. Of course I'm probably already preaching to the converted here Quote Link to comment Share on other sites More sharing options...
Cynic-al Posted March 23, 2012 Author Share Posted March 23, 2012 Got to be careful how much I promise, only want it for Land Rover parts, Don't want to be stuck to it 9-5 Quote Link to comment Share on other sites More sharing options...
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