Particles insertion

Hi every one....!
i am trying to simulate a mixer that contain glass beads with impeller in the middle.I am a new user of LIGGGHTS, i don't know how to make geometries for this setup.I means which components to be made in CAD?? which CAD software is to be used ???currently i made a vessel and impeller in PRO E and saved in STL format.when i use this then vessel geometry does'nt import nd i get problem with this.
Also plz tell me how i can insert particles in order i means i want first add large particles then small one and then wanna to mix .plzzzzzzz any one is there to help me

atom_style granular
atom_modify map array
boundary f f f
newton off
communicate single vel yes

units si

region cyl cylinder z 0. 0. 0.09 0. 0.33 units box
create_box 2 cyl
group cyl1 region cyl
group rest subtract all cyl1
delete_atoms group rest

neighbor 0.003 bin
neigh_modify delay 0

#Material properties required for new pair styles
fix m1 all property/global youngsModulus peratomtype 72.e9 72.e9
fix m2 all property/global poissonsRatio peratomtype 0.25 0.25
fix m3 all property/global coefficientRestitution peratomtypepair 2 0.5 0.5 0.5 0.5
fix m4 all property/global coefficientFriction peratomtypepair 2 0.4 0.3 0.3 0.5
fix m5 all property/global coefficientRollingFriction peratomtypepair 2 0.1 0.1 0.1 0.1

#New pair style
pair_style gran model hertz tangential history #Hertzian without cohesion
pair_coeff * *

# physical characteristics of the particles:
fix pts1 all particletemplate/sphere 30492 atom_type 1 density constant 2456 radius constant 0.002
fix pdd1 all particledistribution/discrete 63243 1 pts1 1.

fix pts2 all particletemplate/sphere 30492 atom_type 2 density constant 2456 radius constant 0.003
fix pdd2 all particledistribution/discrete 45324 1 pts2 1.

# Import mesh from cad:
fix zwalls1 all wall/gran model hertz tangential history primitive type 1 zplane 0.0
fix zwalls2 all wall/gran model hertz tangential history primitive type 1 zplane 0.32
fix cylwalls all wall/gran model hertz tangential history primitive type 1 zcylinder 0.08 0. 0.

fix cad2 all mesh/surface file meshes/impeller.stl type 2 curvature 1e-5
fix mixer all wall/gran model hertz tangential history mesh n_meshes 1 meshes cad2

# Integrator
fix integrate all nve/sphere
# Gravity
fix grav all gravity 9.81 vector 0.0 0.0 -1.0

# Timestep
timestep 0.00005

# area where the particles are introduced from is set:
group nve_group region cyl
region factory1 cylinder z 0. 0. 0.08 0. 0.32 units box

#set region factory1 property/atom Color <2.0>
# Thermo settings
thermo_style custom step atoms ke cpu
thermo 1000
thermo_style one
thermo_modify norm no #lost ignore
compute_modify thermo_temp dynamic yes

### Execution and further settings
# Particle insertion – large particles
fix ins1 nve_group insert/pack seed 30000 distributiontemplate pdd1 verbose yes &
insert_every 1000 overlapcheck yes all_in yes vel constant 0.0 0.0 -1.0 &
volumefraction_region 0.15 region factory1 ntry_mc 10000

run 2000 upto

# Particle insertion – small particles

fix ins2 nve_group insert/pack seed 30000 distributiontemplate pdd2 verbose yes &
insert_every 1000 overlapcheck yes all_in yes vel constant 0.0 0.0 -1.0 &
volumefraction_region 0.15 region factory1 ntry_mc 10000
run 2000 upto
# Thermo settings
thermo_style custom step atoms ke cpu
thermo 1000
thermo_modify norm no #lost ignore
compute_modify thermo_temp dynamic yes

run 2000 upto

# Make a dump of particles and the stl file
#dump dmp all custom 2000 post/dump*.mixer id type x y z vx vy vz &
radius mass f_color

dump dmp all custom 2000 post/dump*.mixer id type type x y z ix iy iz vx vy vz &
fx fy fz omegax omegay omegaz radius
dump dumpstl all mesh/stl 2000 post/dump*.stl

# Rotate central shaft
fix movecad2 all move/mesh mesh cad2 rotate origin 0. 0. 0. axis 0. 0. 1. period 0.5

# Run 5 seconds
run 10000
unfix movecad2
run 2000