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Mazak QTN 200 MS Rapids to z limit


Sep 20, 2022

My Mazak QTN200 MS lathe rapids to the soft limit away from the main spindle instead of selecting the second tool and continuing on with the mazitrol program.

I am learning how to use my Mazak QTN200 MS lathe with 640 T control and have machined the first few simple test parts using up to four tools for one part without any problems.
However I ran a simple program yesterday which uses an OD turning tool and threading tool. When I hit cycle start the first tool runs through the program correctly however instead of selecting the second tool in the program the turret rapids on the z axis to the soft limit away from the main spindle. If there is only one tool in the program it still rapids on the z axis to the soft limit away from the main spindle once the program is finished rather than rapiding to the home position. If the tool selected before I hit cycle start is not the correct tool for the first sequence instead of selecting the correct tool and running the program it rapids to the soft limit on the z axis as previously mentioned without running the program at all.

I have tried a few different programs some which were previously working fine and some that were created to fault find and I have the same issue with all the programs I try.

I havn’t made any changes that I can think of that could have caused this. I did recently change the chuck barrier position parameter but programs seem to be running okay after making this change.

All of the programs I have looked at stored on the lathe that were created by the previous owner have manual program sequences ( MNP) at the beginning of the programs. Maybe the lathe has had this fault for a while (although I used it for a while without this problem) and the previous owners worked around it with a MNP. I’ll see if I can run a MNP.

If anyone can provide any help that would be appreciated. Thanks
QTN 200 MS is a sub spindle lathe with tools facing both directions and Mazatrol will allow you to have many tools assigned in the same position, 3A, 3B, 3C, 3D, etc. some front working, some back working and defined in Mazatrol. TOOL BARRIER looks at all of them and if you have some tool defined as a 78" boring bar the Z axis may want to clear that distance. That tool may not exist, or may be in your desk drawer. But if defined in the TOOL FILE Mazatrol will think it is there. So check for ghost tools and tool measurements with a screwy Z dimension. Or tools on one side of the turret and defined and measured on the other side.
My 2 cents and worth at least twice that.
I have tools defined like that on both of my 640T lathes and nothing runs without hitting BARRIER CANCLE. All production programs so we walk through first part and run it for a few days in BAR LOOP until bins get filled. Newer Smooth control will not run with BARRIER CANCLE. Found another way to lie to it.
G'day Scruffy. Thank you very much for putting the time in to try and help me out. All the programs I have tried so far have tools without a letter (e.g tool 1,2,3 etc and not 1a,1b,1c etc) and the ones I created before the issue started were working correctly but now they aren't. I tried running a program with barrier cancel selected (at very low rapid speed so I don't smash anything) but it went to the z soft limit after running the first tool (correctly) the same as before. With my limited knowledge it looks like its getting confused when it comes time to change to a different tool because it will run the first tool correctly (machine the part correctly) with the first tool as long as the first tool in the program is all ready selected before hitting cycle start (the turret does not need to rotate to bring up the correct tool). If the first tool is not selected before hitting cycle start it will just go straight to the soft limit on z axis after hitting cycle start without rotating to the correct tool. I will play around with it a bit more just to make sure I havn't missed something though. That is very handy to know about the potential for barrier dramas with the sub spindle. I'm sure I'll face that issue sooner or later if not now.
I just had a thought. One thing that indicates that it may not just be a turret rotating issue in auto operation is the fact that it rapids to the z soft limit after correctly running the first tool (if the first tool is selected before hitting cycle start) even if there is only one tool in the program. So in other words in that case it will rapid to the z limit even though there is no requirement for the turret to change to another tool in the program. So in that instance its the finish of the program that appears to trigger the rapid to the z limit but in all the other cases it appears to be the tool change while the program is running that triggers the rapid to the z limit.
Did you do like scruffy887 suggested? To me it sounds exactly what he is trying to get you to look at. When it does a tool change, it looks at the longest tool and goes back far enough to clear the turret. Read his post again.
G'day Scruffy and Camhead. I played around with the lathe a bit more and found that you are both correct. Thank you both very much for taking the time to help me. Hopefully I can do the same for someone one day. What actually happened is I re set my threading tool (which was performing okay) using the tool eye just to get a feel for how much the tool eye reading changes without taking the tool out. After working out the position of the cutting tip on the z axis (subtracting the distance from cutting tip to the edge that contacts the tool eye sensor) I entered the position in the tool set section. I forgot to add a minus symbol so it was entered as a positive number. I should have followed your advice straight up Scruffy rather than going on about it. Thanks again to you both.