Bridgeport/Romi EZ Path 2 SD

[JRN]

Need Help. We have a 1999 Brideport Romi lathe that we are having threading issues with. Below is a link to a video of it. It mainly does it on course threads such as 2 or courser. It does not do it everytime. It will also jump in the middle of a thread. The z axis and spindle encoders are good. Does anyone else have this trouble or know what my problem is. Thanks


YouTube - VIDEO0006.3gp

[bret4]

Explain the problem better. At this point it looks like you are cutting a left hand thread.

It looks like your start point in the threading program is set near the chuck and the end point is set out by the tailstock.

That is all I can tell from what I see so far.

[JRN]

Yes I am cutting left hand threads but it also does it on right hand.

[bret4]

I still do not see what the problem is. Only thing I see is that the spindle is not on when you start the program. I always turn on the spindle before I start a program.

Like I said, you need to explain what's wrong. The video seems to just show the machine cutting course left hand threads.

[JRN]

You dont see it jumping? On these brideports you can rapid up to the part then turn the spindle on or turn the spindle on first. It messes up both ways. That is one good thing about these ez paths is you can make a cut, hit feed hold, stop the spindle in the middle of a program, and check your part if you want to.

[bret4]

I guess you mean that when the cutter is in position then you turn the spindle on and it jumps to the right before it feeds into the part. I was using my ipod to view the video and with the small screen I couldn't really tell if that was the problem.

Anyway, I wonder if it does the same thing if you turn the spindle on before you start the program. My thinking is maybe the program is getting confused because the spindle isn't on when threading should begin. It may be to much for the slow computers in these machines to understand. It could have thought that it was going to start cutting threads and skipped ahead losing the first full thread.

What I do when I want to be careful when threading is over ride the feed rate down to 5%. This slows down the rapids during threading to give you a chance at hitting the E-Stop if the cutter is heading someplace you don't want it to go. I always turn the spindle on before starting the program and have never seen my machines do this. But I have also never had to cut threads beyond 10 tpi.

Try it with the spindle on before you start the program and see if that helps.

[JRN]

It does not matter when the spindle is started. It does it both ways.

[bret4]

I tried cutting a 1.5" x .5"tpi thread on my machine today just to see what it would do. It jumped like yours. I was running the spindle speed at 150rpm. After two passes the machine stopped and gave an error message.

What I did was slow the spindle speed down until the thread cut with out jumping. Ended up running it at 25rpm. I did a little math that I can't say is perfect and came up with the thinking that the spindle speed should be closer to 21 rpm for this type of thread for the machine to keep up properly.

I think the machine can't process the information from the spindle fast enough at higher speeds. It kind of makes sense that it would have to be run at around 20 rpm to cut such a large diameter and course thread.

If you didn't already try slower spindle speeds, give it a try and let me know if it works for you like it did for me.

[Jaguar]

Originally Posted by JRN Need Help. We have a 1999 Brideport Romi lathe that we are having threading issues with. Below is a link to a video of it. It mainly does it on course threads such as 2 or courser. It does not do it everytime. It will also jump in the middle of a thread. The z axis and spindle encoders are good. Does anyone else have this trouble or know what my problem is. Thanks YouTube - VIDEO0006.3gp

You will have a lot of difficulty doing what you are doing because the Path won't pick up the marker pulse on the tach properly without jumping like the video shows. A coarse feed rate and enough rpm will force this to happen. The general rule of thumb is 2 threads out in front is the best start position to synch with the tach. In the case of a left hand thread you will have to run the spindle slow enough so that the thread cycle can make the tool dive in at the start of the left hand thread.

Every CNC lathe has a feedrate limitation in the threading cycle and the EZ Path is no exception. When you have a very coarse feed rate as the videos show it's not unusual to see this sort of jumping. Slow the rpm down and start the spindle before the thread cycle is enabled.

J