Rapid moves really slow when doing 4th axis work

[Brute440]

I am working on a project in a Mazak VCN with a 4th axis and need some advice on the rapid movements from one shape to the next. I am pocketing a series of circles .100 deep. 4 of them across the and 4 of them evenly spaced around a cylinder. When the tool rapids out of the pocket (.100 above) it does a G0 and rapids in the X to the next shape just fine. But, Once it rapids out of the 3rd shape the rapid CRAWLS (roughly 300 degrees per minute) when it does an X and an A movement together. If I do a rapid in just the A it will rapid quickly (where I want it) and It will also rapid in the X,Y, & Z just fine. When I try to rapid both the X and A at the same time it will crawl. I don't have a copy of the program here and won't be near the machine again until Monday. What gets me, is when I do a G30 to bring the table up to the door it rapids all the axis just like it is supposed to.

 

What is the easiest way to get around this reduced rapid? I am thinking that it is a parameter in the machine but... I am not sure where or what it would be. Can I break up the rapid movements in MasterCAM? Has anyone ever ran in to something like this?

[Guest]

Do you have a z2g you can share?

 

I am thinking right off the top of my head this is a post issue.......that move "should" happen in G0

[Brute440]

I forgot to bring my flash drive home so, I won't be able to get near the machine until Monday morning.

 

I do know that it does a rapid like this when I have the issue.

 

G0 z.1

X5.0 A180.

G1 z-.050 F30.

 

Of course I am just pulling those numbers out of my head but, I believe that is the format it is using. I usually turn the rapid feed rate down at the machine while I am dry running it. So, I know it is doing a rapid when it rolls the X and A because I crank the rapid feedrate up to 100% and watch it crawl to the next shape. Then I slow the rapid back down to dry run it.

 

The very first test part I did I ran in to this issue but, since it was just a test I went through the program and changed all the rapid XA movements to G1 with a feedrate of 1500.

 

G0 z.1

G1 X5.0 A180. F1500.

G1 z-.050 F30.

 

That fixed the issue but, I can't figure out how to get MASTERCAM to do that and

.. That is kind of why I think it is a parameter in the machine.

[GPC_CNC]

Mazaks interpolate their rapids so that both axis arrive at the same time. This happens a lot on our 5th axis where the rotaries are much slower than the X/Y/Z axis. The rotaries are the slowest so the main axis rapid at a much slower rate, but it's still the fastest combined movement rather than moving the A/C and then X/Y/Z. Which would be slower even though it's visually faster for independent axis.

 

Is this more or less what you're observing?

[Brute440]

Not necessarily, but I understand what you are saying. I worked on a part last week where I had to cut a series of grooves around a cylinder. Strictly rotating the A axis while stepping the Z down and the X back and forth. I kept the Z down in the part and was able to cut north of 70ipm... According to the feedrate I programmed in MASTERCAM using axis substition. The A feed rate for the diameter of the part I was working on translated to roughly 1700 deg. Per minute (according to the readout on the console).

 

I can get the A to do G1 movements with a feedrate of F2000 and when I do a G0 Axxx it will rapid at 3000 deg. Per minute. Atleast according to the readout on the screen. The main axis (x,y, and z) all rapid normally. But, when I combine the X and A on a rapid move the feedrate slows down to a crawl of 300 accoridng to the screen on the mazak. This kills my cycle time. If instead of,

 

G0 Z.1 (rapids out of the part)

X5.0 A180. (Rapid to the next pocket-this is where it crawls at 300)

G1 Z-.05 F30.

 

If I plug in a G1 and a feedrate of F1500. Or F2000 after it rapids up out of the part it will move much much faster.

 

G0 Z.1 (rapids out of the part)

G1 X5.0 A180. F1500. (This will move faster than the G0)

G1 Z-.05 F30.

 

Which doing that for a test part wasnt a problem but, when I have more than a few rapid movements it becomes counter productive.

 

I tried to change all the rapid movements to linear movements at their maximum feedrates in MASTERCAM. But, when I set the max linear feedrate at 150.0 and the rotational feedrate at 3000.0 the machine would move the X from one pocket to the next at 150 IPM. Which is fine but, when it would move the X and the A from one packet to the next... It would do it at 150. Which is unfortunately even slower than the G0.

 

Is there a way I can break the rapid movements up to where they will not move simultaneously?

 

G0 Z.1

X5.0

A180.

G1 Z-.050 F30

[Brute440]

Sorry, apparently posted the same message twice