knocking sound coming from printer after etch line.  

knocking sound coming from printer after etch line.

I start to print and i heare a sound knocking from printer.

When this sounds come i see this code from octaprint.

Send: N87429 G1 X121.355 Y129.732 E19.75907*91
Recv: ok
Send: N87430 G1 X121.259 Y129.718 E19.76271*95
Recv: ok
Send: N87431 G1 X121.252 Y129.716 E19.76299*93
Recv: ok
Send: N87432 G1 X120.252 Y129.544 E19.80079*95
Recv: ok
Send: N87433 G1 X119.257 Y129.329 E19.83853*95
Recv: ok
Send: N87434 G1 X118.377 Y129.102 E19.87236*92
Recv: ok
Send: N87435 G92 E0.0*84
Recv: ok
Send: N87436 G1 F9600.000*81
Recv: ok
Send: N87437 G1 X118.106 Y129.027 E19.81402*90
Recv: ok
Send: N87438 G1 E19.07236 F2100.00000*32
Recv: ok
Send: N87439 G92 E0*70
Recv: ok
Send: N87440 G1 Z9.943 F12000.000*63
Recv: ok
Send: N87441 G1 X118.202 Y128.662*38
Recv: ok
Send: N87442 G1 Z9.593*119
Recv: ok
Send: N87443 G1 E0.80000 F2100.00000*28
Recv: ok
Send: N87444 M204 S800*101
Recv: ok
Send: N87445 G1 F3687.467*85
Recv: ok
Send: N87446 G1 X117.428 Y128.428 E0.83333*111