ADJUSTING THE FORAGE HARVESTER FOR CORN
SILAGE PARTICLE SIZE
Ronald T. Schuler, Professor
Extension Agricultural Engineer
Biological Systems Engineering Department
University of Wisconsin-Madison
Team Forage
Corn Silage Particle Size-Factors
 Machine Adjustment
Feed roll and cutterhead
Crop processor
 Crop maturity
 Storage
 Animal
Forage Harvester
• Functions:
 Gather the crop
 Size the crop, primarily length of forage particles
 Deliver crop to transport unit
Typical Configuration
• Crop Unit
 Hay head or row crop
• Feed rolls
 Compressing material
for cutting
 Determining TLC
• Cutterhead
 Chopping material
• Crop Processor
 Crop damage
• Blower
Typical Configuration of Pull Type Harvester
Processor
Feed rolls
Cutterhead
Auger
Feedrolls
• Typically two sets
 Larger, front set for feeding
 Smaller, rear set to meter material into the
cutterhead
• Bottom rolls are fixed
 Can contain metal detectors
• Top rolls float
 Spring pressure to grip material
Feed rolls
• controls the rate of
feeding into
cutterhead
• compresses mat of
material so it is easier
to cut
Theoretical Length of Cut
• Definition - feed roll travel per knife
• Recommendations
 Dependent on
• Animals
• Feed handling equipment
• Crops
 Corn silage - 3/8 in.(no crop processor)
 Corn silage - 3/4 in.(crop processor)
Theoretical Length of Cut
• Adjusting theoretical length of cut
 Feed roll speed
 Number of knives
 Cutterhead speed
• Not practical
Actual Length of Cut
• Longer than the TLC
• Windrowed crops longer than row crops
 Alfalfa feeds in a tangled mat of material
 Corn stalks feed mostly straight
Crop Processor
Blower
Crop Processor
Cutterhead
Feed rolls
Crop Processing
• Used only for whole plant corn silage
• Kernels are difficult to digest
 Contain starch and energy
• Damaging the kernel shell allows the rumen
bacteria to digest the starch
• Breakup cob pieces (avoid hockey pucks)
Crop Processing
• In the past, very short lengths of cut were
used to damage more kernels
 Recutter screens also used
• Increased power requirements drastically
• Shortened fiber length too much
Crop Processor Characteristics




1 – 15 mm (1/16 to 5/8”)-clearance range
5 – 25% speed difference
Speed 2500 – 4000 RPM
3 – 6 grooves per inch
Crop Processing
A properly adjusted kernel processor
 Damages more than 90% of the kernels
 Pulverize cob pieces
• Minimizes waste in the feed bunk
 Allows for longer length of cut
• Longer fiber
• Less power consumption
Crop Processor Pulleys
Crop Processor
Clearance Adjustment
Crop Processing System
Cutterhead
Processing Rolls
Differential
speed
between rolls
Kernel Damage
100
96
100
88
90
Kernels 80
Damaged,
70
%
67
58
60
50
3/8" TLC 3/4" TLC
Unprocessed
0.04"
0.12"
0.20"
Processed - Roll Spacing
(3/4" TLC)
Kernels damaged with respect to
TLC and processing
100
80
Kernels 60
Damaged,
40
%
0.08
0.16
None
20
0
0.750
0.500
0.375
Theoretical Length of Cut, in.
Particle Size with respect to TLC and
processing
0.6
0.5
0.4
Particle Size,
0.3
in
0.08
0.16
None
0.2
0.1
0
0.750
0.500
0.375
Theoretical Length of Cut, in.
Crop Processor - Tips for Success
• Increase the theoretical length of cut (TLC) to
¾”
 Processor will reduce overall particle size further
• Set roll gap between 0.08” and 0.12” (2-3
mm)
 Will result in 100% cob breakage and 90-100%
kernel damage
Don’t crop processors take A LOT
of extra horsepower??
Not if set up properly!
• Power consumption for
 3/4” TLC and a processor set to 0.20” (2.70 Hp-hr/ton)
is only slightly higher than
 3/8” TLC with no processor
(2.69 Hp-hr/ton)
Power Consumption
3
2.5
2.99
2.69
2.76
2.70
2.14
2
Energy, hp1.5
hrs/ton
1
0.5
0
3/8" TLC 3/4" TLC
Unprocessed
0.04"
0.12"
0.20"
Processed - Roll Spacing
Roll Wear
 PTFH - Rolls Wear At Center
 SPFH - Rolls Wear At Edges
 Helical Knives - Uneven Wear
 As Teeth Wear:
•
Capacity Is Reduced
•
Plugging More Likely
•
Processing More Difficult
Dealing with Worn Rolls
 Replacement ~ $1,500 per Roll
 Re-Grooving ~ 1/3 to 1/2 Cost of New
 Re-Grooving Considerations:

Won’t Last As Long As Original

Can Only Be Done Once

Tolerances Not As Good
WHAT TO LOOK FOR
IN A CROP PROCESSOR
 Roll Diameter
 Tooth Pitch
 Ease of Checking and Adjusting Roll Clearance
 Ease of Unplugging
 Ease of Switching Between Corn silage and Haylage
Machine Power Consumption
 Gathering and feeding
• 20% of total
 Cutterhead and processor
• 40 – 50% of total
 Blowing into wagon / truck
• 30 – 40% of total
Reducing Power Loss




Maintain sharp knives
Keep close knife to shearbar clearance
Properly adjust processor
Keep blower band clearance small
Concluding Remarks
 No Processor-TLC=0.375 in.
 Processor-TLC = 0.75 in and
roll clearance= 0.8 to 0.12 in.
Questions
QUESTIONS