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General Mach Discussion / Re: Z-Axis Repeatability: Small Changes
« on: November 19, 2012, 08:21:07 PM »
Hello Bobshop, thank you for your reply. I thought I already mentioned this in my post: I am only lifting my "quill" by 1 mm off of my PCB surface. Previously I had this set to 4mm. Reducing the amount of Z-Axis travel did not help my problem, though.
I think your solution implies that I am unable to set the proper distance from the surface. This is not the case. In fact, I get good results when I first start off. It is only after the machine has been running for a while that the problem shows up.
It appears that Mach 3 loses track of the Z-Axis motion after several cycles of up/down motion.
REPOST:
Hello All, I am using MACH 3 to route out my Printed Circuit Boards (PCBs) designs. The main problem that I am encountering is that the Z-Axis looses track of position. My plunge depth is only 0.01 mm, so I cannot tolerate very much error.
For regular DIP or 1st gen surface mount parts, this is not much of a problem. The problem is that I cannot do the latest generation of surface mount footprints without wiping out traces. This is because my "V" bit gets wider as it goes deeper. It goes deeper (hence wider) unintentionally.
The problem occurs for even a small design with just 1 fine pitch part (0.65 mm spacing). Starting off, my vertical repeatability was very good. However, after a couple of hundred lines of code I can tell that the cuts get progressively deeper (can tell by sound). Looking at the Z Axis values, all should be well. However, when I stop the code, and recheck my vertical axis, I see that it has drifted (deeper). It appears that MACH 3 has lost track of a few steps. This problem is not as bad for X and Y axis, but for Z axis, my tolerances are a lot smaller.
I have noticed that the loss of tracking is always unidirectional (not random). Steps are always lost to make the machine cut deeper than intended, never in the opposite direction.
I have read as many post about "Z-Axis Repeatability" as I could find. I have kept my lead screws clean and properly lubricated. I have already decreased my velocity and acceleration to as far down as I could manage. I have also slowed down my feed rate to less than 60 mm/min, my plunge rate is 1 mm/S and my lift bit rate to 750 mm/min. I have also limited the amount of clearance to 1 mm (was 4mm) to decrease the amount of Z-Axis travel. None of the above affected the amount of error I detected (no improvement). I feel that I must be doing something wrong.
I'm not sure how to manage the "backlash", yet. I'm not sure if that is the problem (or one of), but it is something that I have not tried yet.
I would greatly appreciate any advice that anyone can give me.
Thank you, Richard V
I think your solution implies that I am unable to set the proper distance from the surface. This is not the case. In fact, I get good results when I first start off. It is only after the machine has been running for a while that the problem shows up.
It appears that Mach 3 loses track of the Z-Axis motion after several cycles of up/down motion.
REPOST:
Hello All, I am using MACH 3 to route out my Printed Circuit Boards (PCBs) designs. The main problem that I am encountering is that the Z-Axis looses track of position. My plunge depth is only 0.01 mm, so I cannot tolerate very much error.
For regular DIP or 1st gen surface mount parts, this is not much of a problem. The problem is that I cannot do the latest generation of surface mount footprints without wiping out traces. This is because my "V" bit gets wider as it goes deeper. It goes deeper (hence wider) unintentionally.
The problem occurs for even a small design with just 1 fine pitch part (0.65 mm spacing). Starting off, my vertical repeatability was very good. However, after a couple of hundred lines of code I can tell that the cuts get progressively deeper (can tell by sound). Looking at the Z Axis values, all should be well. However, when I stop the code, and recheck my vertical axis, I see that it has drifted (deeper). It appears that MACH 3 has lost track of a few steps. This problem is not as bad for X and Y axis, but for Z axis, my tolerances are a lot smaller.
I have noticed that the loss of tracking is always unidirectional (not random). Steps are always lost to make the machine cut deeper than intended, never in the opposite direction.
I have read as many post about "Z-Axis Repeatability" as I could find. I have kept my lead screws clean and properly lubricated. I have already decreased my velocity and acceleration to as far down as I could manage. I have also slowed down my feed rate to less than 60 mm/min, my plunge rate is 1 mm/S and my lift bit rate to 750 mm/min. I have also limited the amount of clearance to 1 mm (was 4mm) to decrease the amount of Z-Axis travel. None of the above affected the amount of error I detected (no improvement). I feel that I must be doing something wrong.
I'm not sure how to manage the "backlash", yet. I'm not sure if that is the problem (or one of), but it is something that I have not tried yet.
I would greatly appreciate any advice that anyone can give me.
Thank you, Richard V