All the particles are inserted in the first step,why??

All the particles are inserted in the first step, but I want to make these particles flow from the inlets step by step. I don't know what the problem is , here is my input commands, pls help me , thx~

Inputs:
"
....
neighbor 0.004 bin
neigh_modify delay 0 one 20000 page 500000
....ere the input

timestep 0.00001
....
#particle insertion
fix ins1 nve_group insert/stream seed 32452867 distributiontemplate pdd1 &
nparticles 6000 massrate 0.1 insert_every 500 overlapcheck yes all_in no &
vel constant 0.852813 -7.1349 -6.95456 insertion_face in1 duration 500
fix ins2 nve_group insert/stream seed 32452867 distributiontemplate pdd1 &
nparticles 6000 massrate 0.1 insert_every 500 overlapcheck yes all_in no &
vel constant 5.7526 4.30601 -6.95456 insertion_face in2 duration 500
fix ins3 nve_group insert/stream seed 32452867 distributiontemplate pdd1 &
nparticles 6000 massrate 0.1 insert_every 500 overlapcheck yes all_in no &
vel constant -6.60541 2.82889 -6.95456 insertion_face in3 duration 500
...
"
liggghts .log:
"
...
Step Atoms KinEng 1 Volume
1 18000 0.028577886 1.9165847e-05 0.012
1000 13323 0.038001604 0.021996774 0.012
2000 8756 0.0038217528 0.0041926017 0.012
3000 7832 0.0016293158 0.0022765678 0.012
4000 7266 0.00094546843 0.0015135769 0.012
5000 6653 0.00061950924 0.0010921445 0.012
...
"