Stop Losing Money on Machine Downtime
Your production line stopped. The conveyor belt is not moving. The packaging machine is stuck. You check the motor, and it is fine. The problem is the gearbox. It is broken, stripped, or leaking oil. You need a replacement fast. But new parts from the factory cost a fortune and take weeks to arrive. You look for used parts, but you are scared. Will it work? Is it damaged inside? Will it break again in a month?We understand this stress. You need a part that works right out of the box. You need a part that is built to last. You need the Mitsubishi K9020B Gear Reducer. This is not a cheap copy. This is a genuine Mitsubishi Electric product imported directly from Japan. It is a heavy-duty planetary gear reducer designed for 400W AC servo motors. We have tested it. It runs smooth. It is quiet. It holds the load. It is the exact 1:20 ratio you need to get your machine running at the perfect speed. Do not gamble with cheap Chinese alternatives. Get the real Japanese quality that your machine was built for.
What Exactly is the Mitsubishi K9020B?
This is a planetary gear reducer. “Planetary” means it has a special internal design with sun gears and planet gears. This design makes it very strong and very precise. The model number is K9020B. The “K” stands for the series. The “90” relates to the frame size. The “20” is the most important part—it tells you the ratio.This specific unit has a 1:20 ratio. If your servo motor spins at 3000 RPM, this gearbox slows it down to 150 RPM. But it does not just slow it down. It multiplies the power (torque). Your motor becomes 20 times stronger. This is why it is perfect for 400W servo motors. It takes the high speed of the motor and turns it into raw pulling power.It is a used item, but do not let that scare you. In Japan, machines are maintained perfectly. This unit came from a factory where they changed it out for an upgrade, not because it broke. It is clean, the grease is good, and the gears are not worn out. It is ready to work hard for you.
Technical Specifications You Need to Know
You need to make sure this fits your machine. Here are the exact numbers. Compare these to your old gearbox or your motor manual.
Model and Ratio Details
- Brand: Mitsubishi Electric (One of the best in the world for automation).
- Model Number: K9020B (Also known as K9020).
- Type: Planetary Gear Reducer / Servo Reducer.
- Gear Ratio: 1:20 (Sometimes written as 20:1).
- Compatible Motor Power: 200W to 400W (0.2kW to 0.4kW). This is the sweet spot. It works great with 400W motors like the HC-KFS series.
- Input Speed: Max 3000 RPM (Standard for AC servos).
- Output Speed: 150 RPM (at 50Hz) or 180 RPM (at 60Hz).
Physical Dimensions and Mounting
- Total Length: 165mm.
- Width and Height: 99mm x 99mm. It is a compact square shape, easy to fit in tight spaces.
- Input Shaft: 14mm diameter. This connects to your servo motor shaft.
- Output Shaft: 32mm diameter. This connects to your machine roller or arm.
- Input Flange: 50mm. This bolts to the face of the servo motor.
- Output Flange: 95mm. This bolts to the driven equipment.
- Weight: Approx 3.9 kg (including the motor usually, the gearbox alone is lighter, around 1.5-2kg).
- Origin: Japan.
Where Can You Use This Gear Reducer?
This is not just a spare part. It is a solution for many types of machines. Because it has a 1:20 ratio and high torque, it is used where you need to move heavy things slowly and precisely.
Conveyor Belts and Rollers
If you have a small conveyor belt moving boxes, this is perfect. The 1:20 ratio gives the belt enough power to move heavy packages without slipping. The 32mm output shaft fits standard conveyor rollers easily.
Packaging Machines
In wrapping machines or labeling machines, you need precision. You do not want the label to stick on crooked. The Mitsubishi K9020B ensures the movement is exact. It handles the tension of the packaging film perfectly.
CNC Machines and Lathes
For the Z-axis or X-axis feed on smaller CNC machines, this gearbox provides the torque needed to cut through metal without losing steps. It is rigid and does not flex under pressure.
Robotic Arms
If you are building a small pick-and-place robot, this reducer goes on the wrist or elbow joint. It allows the small 400W motor to lift a decent weight. It is much better than a direct drive because it protects the motor from shock loads.
Printing and Textile Equipment
Any machine that needs to pull paper, fabric, or wire at a constant tension needs this. The planetary design runs very smoothly, so it does not jerk the material.
Why Buy This Used Unit from Us?
You might ask, “Why not buy a new one?” The answer is simple: Price and Availability. A brand new Mitsubishi gearbox can cost $800 or more and have a 12-week lead time. We have this one in stock. We ship it fast. And it costs a fraction of the new price.But why buy this specific used unit?
- Japanese Quality: It was made in Japan. The steel is high grade. The bearings are NSK or Koyo brand. It is not a generic rebrand.
- Tested: We do not just list it and hope. We plugged it into a test rig with a 400W servo motor. It ran for 2 hours. No noise. No overheating. No oil leaks.
- Clean: It looks good. The paint is not chipped. The shaft has no rust. It will look great on your machine.
- Direct Import: We cut out the middlemen. You get the part directly from the import source.
We know the fear of buying used industrial parts. That is why we describe them honestly. If there is a scratch, we show it. If it makes a noise, we say it. This one is quiet. It is a workhorse.
Installation and Maintenance Tips
Installing this is easy if you know the basics, but you must do it right to avoid damage.
Step 1: Alignment is Key
When you bolt the gearbox to the motor, make sure the shafts line up perfectly. Even a tiny misalignment will destroy the bearings inside the gearbox in a few days. Use a dial indicator if you have one. If not, make sure the coupling fits tight.
Step 2: The Coupling
Use a flexible coupling (like a bellows coupling or Oldham coupling) between the motor shaft (14mm) and the gearbox input. This absorbs vibration. Do not connect them rigidly.
Step 3: Lubrication
This unit comes with grease already inside. You do not need to add oil immediately. Planetary gearboxes are sealed. However, if you run it for 2000 hours, check the oil level. Use Mitsubishi recommended grease (usually lithium-based). Do not mix different types of grease.
Step 4: Break-in Period
Even though it is used, treat the first 24 hours as a break-in. Do not run it at 100% full load immediately. Run it at 50% load for a few hours. This lets the gears seat properly. Listen for any clicking or grinding. If it is quiet, you are good to go.
Common Problems This Part Solves
- Motor Overheating: If your motor gets too hot, it might be working too hard because the gear ratio is wrong or the gearbox is jammed. This K9020B fixes the ratio issue.
- Positioning Errors: If your machine misses the target position by a millimeter, the gearbox might have “backlash” (slop). Mitsubishi K9020 series has very low backlash (less than 1 arc-minute). It fixes precision issues.
- Loud Whining Noise: A worn-out gearbox sounds like a jet engine. This unit is silent. It will make your factory floor quieter.
- Shaft Stripping: Cheap gearboxes have soft metal shafts. The keyway shears off. The Mitsubishi shaft is hardened steel. It will not strip.
Frequently Asked Questions
Q: Will this fit my HC-KFS23G1 motor?A: Yes. The K9020B is the standard reducer for the HC-KFS series 400W motors. The flange bolts match perfectly.Q: Is the output shaft keyed?A: Yes, it usually comes with a standard keyway. If you need a specific key size, let us know, but the standard metric key is included.Q: What is the maximum torque?A: For a 400W motor at 1:20 ratio, the output torque is roughly 11 Nm to 14 Nm depending on the service factor. This is enough to move a 100kg load on a conveyor easily.Q: Do you ship to the USA/UK/Australia?A: Yes. We ship worldwide via DHL or FedEx. Because it is a small, heavy item, shipping is fast and affordable.Q: What is the warranty?A: We offer a 30-day functional warranty. If it arrives dead on arrival (DOA), we replace it or refund you. We trust the quality of Japanese engineering.
Don’t Wait Until Your Machine Breaks Completely
You are reading this because you have a problem. Maybe your gearbox is leaking oil right now. Maybe it is making a grinding noise. Maybe you are looking for a spare to keep on the shelf “just in case.”Smart factory managers keep critical spares in stock. They know that waiting for a shipment from Japan takes too long. They know that buying a cheap generic gearbox is a false economy.This Mitsubishi K9020B is the middle ground. It is OEM quality at a used price. It is the safest bet for your production line. We have limited stock. These do not sit on the shelf for long because they are such a good value.If you need a 1:20 ratio for your 400W servo, this is the one. Do not settle for less. Get the part that was built to last 20 years.Click “Send Inquiry” now. Tell us your motor model or your required ratio. We will confirm the stock and give you the best price including shipping to your door. Let’s get your machine running again.