the mystery of the wonky corners

[stirling]

4 clues... you said...

see how its rounded the edges of two of the corners but not of the other two?

only thing ive changed today is... .... and ive increased the acceleration on X

looking at both the photos X is vertical... Y is horizontal

if I put G61 at the beginning all is fine....


What you're seeing is the classic behaviour when in G64 with unequal accel on X and Y. If your accel was equal but "poor" you'd get 4 rounded corners. If equal but "good" you'd get 4 sharper corners. If you'd increased your accel on Y instead of X it would be the other two corners that rounded. The rounded corners will switch to the other 2 if you reverse cut direction. etc. etc.

[Jonathan]

Yes, just what I was thinking...I'm expecting that if we get the configuration file it will show that the acceleration on one of X and Y is lower than the other. Perhaps a typing error was made and the acceleration has actually been reduced significantly (decimal point in the wrong place) since it would have to be very low to make the large difference we're seeing here.

[Danielroyal25]

Hi Matt,
what did you do in the end to overcome this problem? my machine was doing this the other day on a simple rectangular profile with rounded corners. It was only happening on the 2 opposite corners. will check if the settings are the same for x and y, but if they are identical how did you resolve it?

[JAZZCNC]

Hi Matt,
what did you do in the end to overcome this problem? my machine was doing this the other day on a simple rectangular profile with rounded corners. It was only happening on the 2 opposite corners. will check if the settings are the same for x and y, but if they are identical how did you resolve it?

Dan if it's jurking just in the corners then chases are your running G61 Exact stop mode. Your better running in G64 constant velocity (CV) mode.
If your using Mach standard 1024 screen set then you can tell by the LED light just to the right of the Reset button and next to Dwell LED. It will be lit green when in G64 CV mode and off when in exact stop.

To test this type G64 into MDI before running the G-code again. First check the G-code for G61, it will be somewhere near the top of the code and delete if there. You could always put the G64 command in the G-code file but I wouldn't.

Better place to do this is the initialzation string in the General Config so when Mach starts up it's always in G64 mode. There is actually a setting in Gen config for this as well so check that but having both doesn't hurt.

[kingcreaky]

Dan. These lot will correct me when im inevitably wrong, but ensure you velocity and acceleration values are the same for both X and Y axis

make sure your acceleration is not too slow

that always sort it for me. Im not too sure of the technicalities of why. There is a code you can inject... like 'G60' or something you append to your gcode file before opening with mach. but it makes the machine stop at every change of direction. but I managed to sort it with the explanation as above.

Matt