infill doesn't go fast

hi everybody,
I need to stress my Kossel, to evidence a problem it often does : sometime, likely after much working, a layer 'slides' a bit, the work goes on, and then (or not) it 'slides' again in opposite verse and the solid return regular; almost everytime the defect is very little, but it exists; so, I have to 'stress' my Kossel to investigate about he real cause, I had several thoughtes :
- a4988 chips too much warming? ( I used a fan to cool them, but I remove it now to evidence the defect, if it is the cause)
- I didn't set any type of acceleration, and I don't know in this case how acceleration is managed; anyhow, I left the default value in firmware (MAX 9000)
- too much current in a4988 ? I set it to 1.8 A (the chips has thir little dissipator mounted on), using Wantai motors , requiring up to 2.5 A for coil

to 'stress' the printer, I created a 'stress_profile', to increase the speed for creating the defect much possible as possible, here is the 'stress_profile' :

# generated by Slic3r 1.2.4 on Fri Jan 16 08:13:25 2015
avoid_crossing_perimeters = 1
bottom_solid_layers = 3
bridge_acceleration = 0
bridge_flow_ratio = 1
bridge_speed = 100
brim_width = 0
complete_objects = 0
default_acceleration = 0
dont_support_bridges = 1
external_fill_pattern = rectilinear
external_perimeter_extrusion_width = 0
external_perimeter_speed = 70%
external_perimeters_first = 0
extra_perimeters = 1
extruder_clearance_height = 20
extruder_clearance_radius = 20
extrusion_width = 0
fill_angle = 45
fill_density = 15%
fill_pattern = rectilinear
first_layer_acceleration = 0
first_layer_extrusion_width = 200%
first_layer_height = 100%
first_layer_speed = 70%
gap_fill_speed = 20
gcode_comments = 0
infill_acceleration = 0
infill_every_layers = 1
infill_extruder = 1
infill_extrusion_width = 0
infill_first = 0
infill_only_where_needed = 0
infill_speed = 200
interface_shells = 0
layer_height = 0.3
min_skirt_length = 0
notes =
only_retract_when_crossing_perimeters = 1
ooze_prevention = 0
output_filename_format = [input_filename_base].gcode
overhangs = 1
perimeter_acceleration = 0
perimeter_extruder = 1
perimeter_extrusion_width = 150%
perimeter_speed = 200
perimeters = 2
post_process =
raft_layers = 0
resolution = 0
seam_position = random
skirt_distance = 10
skirt_height = 1
skirts = 8
small_perimeter_speed = 70%
solid_infill_below_area = 70
solid_infill_every_layers = 10
solid_infill_extruder = 1
solid_infill_extrusion_width = 0
solid_infill_speed = 100%
spiral_vase = 0
standby_temperature_delta = -5
support_material = 0
support_material_angle = 0
support_material_enforce_layers = 0
support_material_extruder = 1
support_material_extrusion_width = 0
support_material_interface_extruder = 1
support_material_interface_layers = 3
support_material_interface_spacing = 0
support_material_interface_speed = 100%
support_material_pattern = pillars
support_material_spacing = 2.5
support_material_speed = 150t
support_material_threshold = 0
thin_walls = 1
threads = 2
top_infill_extrusion_width = 200%
top_solid_infill_speed = 70%
top_solid_layers = 3
travel_speed = 200
xy_size_compensation = 0


I set infill to 200 mm/sec, and solid infill too (100%); I set three horizontal shells at bottom and top, but, while the first three layer goes fast, since fourth layer, it goes down, doesn't proceed to same speed as I expect; I don't know what are missing or where I'm confuse

any help appreciated

regards

How large of an object are you printing? Depending on your cooling settings, slic3r will slow things down if the layer takes too little time to print. This usually shows itself when you get to the sparse infill layers. The cooling settings let you specify a minimum layer time. If the time is less than that, slic3r will slow down the speed in an attempt to make the layer last that amount of time.

many thanks, I solved changing that parameter...