Chipper Discharge Options: Top, Bottom, or Rear?
Most sawmill operators are familiar with top discharge and bottom discharge chippers. Each has its place—and each comes with trade-offs that tend to show up over time.
But there’s a third option that doesn’t get talked about nearly as much: rear discharge. In the right situation, it can solve problems that both of the other designs create.
Top Discharge Chippers
Top discharge chippers are popular largely because of how easy they are to install. They can often sit directly on an existing slab. Fan blades mounted to the chipper disc convey chips upward through a chute on top of the hood. From there, chips move through piping—typically a 90-degree elbow—and into a cyclone, a chip van, or even directly onto a pile.
Advantages:
- Quick installation
- No conveyors required
- Flexible chip handling (cyclone, van, or pile)
Disadvantages:
- Wear over time in:
- Belly liner
- Hood
- Pipe and elbows
- Cyclone (if used)
- Higher maintenance as the system ages
Top discharge systems work well up front—but they tend to tell on themselves after a few years of operation.
Bottom Discharge Chippers
Bottom discharge chippers take a simpler, more mechanical approach. Chips fall directly beneath the machine onto a conveyor.
Advantages:
- No belly liner wear
- Minimal hood wear
- No pipes, elbows, or cyclones
- Generally lower long-term maintenance
Disadvantages:
- Requires a conveyor underneath
- Installation can be challenging:
- Chipper must be elevated, or
- Foundation must allow space for a conveyor below
- Difficult to retrofit if not planned in advance
Bottom discharge is often the better long-term solution—but only if your layout can accommodate it.
Rear Discharge Chippers
Both top and bottom discharge chippers share one common issue: heavy wear on the rear wall, where chips strike immediately after cutting.
Rear discharge eliminates that problem entirely.
Instead of a rear impact wall, the chipper is open at that point, with a rectangular chute integrated into the housing. Chips exit horizontally out the back and drop into a conveyor positioned just behind the machine.
Advantages:
- Eliminates rear wall wear
- No fan blades, piping, or cyclone
- Can often be mounted on an existing slab
- Clean, direct chip flow to conveyor
Considerations:
- Conveyor must be positioned slightly below chipper base level
- Discharge chute must be designed to contain high-velocity chips
- Loading/discharge area typically needs to be enclosed
A Practical “Best of Both” Option
Rear discharge chippers combine several of the best features of the other two designs:
- Like top discharge: can often be installed on an existing slab
- Like bottom discharge: avoids complex air systems and related wear
- Unlike both: eliminates rear wall impact wear entirely
If your layout allows for a conveyor behind the chipper, rear discharge can be a true win-win solution.
Final Thought
Too often, discharge style is treated as a secondary detail. In reality, it has a major impact on:
- Installation cost
- Maintenance over time
- Wear patterns
- Overall system layout
Choosing the right discharge configuration isn’t just about the chipper—it’s about how the entire system works together.
See an Example of Rear Discharge in Practice
We currently have a rear discharge chipper available. If you’d like to see how this design is implemented in a real machine: