How Often Should You Change the Blades on a Robotic Mower?

The blades on the robotic mower have a limited service life, as they wear out over time. But how often should you change the blades?

The blades of the robotic mower should be changed about every 1 – 3 months. Unfortunately, it is not possible to give more detailed information on this, as the precise service life of the blades of each robotic mower depends on a number of factors. Changing the blades regularly is important for the cutting pattern and the health of the lawn.

Why Would You Change Blades?

The blades of your lawn robot will wear out over time. The result is that the grass is no longer being cut properly, but is rather plucked. This not only affects the cut of your lawn, but also damages it, which can worsen the health of your lawn in the long run.

The condition of the blades not only determines the cutting pattern, but also influences the volume at which your robotic mower operates. Blunt blades lead to louder mowing noises. At the same time, particularly high-quality blades can make the mower creep silently like a lynx- or close to it, at least.

And as if that wasn’t enough reason to change the blades more often, sharp blades also ensure that the robotic mower uses less energy. Not only does this reduce electricity costs, but the mower also has to return to the charging station less often. It also protects the battery in the long term, as each battery can only cope with a limited number of charging cycles. 

Advantages

Typical Service Life of Robotic Mower Blades

It is very difficult to predict how long the blades will last. According to most manufacturers you should change the blades about every 1 – 3 months. With the large, star-shaped individual cutting blades (I call them “star blades” from here on) you only need to change them once a season. There are a number of factors that influence the life of the blades. These factors can be different for every lawn.

The size of the lawn, the nature of the soil, the type of grass, surrounding objects such as branches, fallen fruit, or pine cones, the season and weather conditions, as well as the nature of the blades themselves all influence the life of the blades. Factors that influence the life of the blades:

• The size of the lawn
• The nature of the soil
• The grass variety
• Objects that get into the mower
• Season and weather conditions
• Characteristics of the blades

The Lawn Area and the Season Influence the Life Span

A larger lawn area requires a longer operating time, which leads to faster wear on the blades. The nature of the soil and the type of grass determine the speed of growth of the lawn and the amount of resistance it gives the mower. A more robust lawn is a good thing, but wears out the mowing blades a little faster.

Of course, no stones, yard tools, dog toys, or the like should be left lying around on your lawn, as they can damage the blades of the robotic mower or even the engine, just like a normal lawnmower.

Among the things that can wear out the blades are branches, twigs, large amounts of leaves, fallen fruit, or pine cones. These should also be regularly removed from the yard.

The lawn grows at different speeds depending on the season. In spring, it can grow relatively quickly if the right temperatures and sufficient rainfall are available. In midsummer, when it is dry and hot, the lawn grows more slowly, and the lawn can be mowed less often.

Some robotic mowers with weather timers are able to calculate independently how fast the lawn is growing at the moment and therefore go out to mow more or less often. As a consequence, the blades also wear out more slowly or faster, depending on the mowing frequency.

Depending on the Design of the Blades, the Service Life Varies

Ultimately, the condition of the blades also determines wear and tear. First of all, a distinction must be made between blade discs and star blades. Blade discs are turntables with 3 small, movable, mounted blades, which are often used, for example, in Husqvarna and McCulloch robotic mowers and should be replaced every 1 – 3 months.

The individual cutting blades, are large, star-shaped blades that are used in Robomow robotic mowers, for example. They only need to be replaced once per season, but they are also a bit more expensive than the small blades of the blade discs.

In addition, the quality and material are important factors that influence the service life of the blades. The blades supplied with most robotic mowers last for approximately 60 to 80 hours, although here too there can be large differences due to the factors mentioned above.

When you buy new blades, you can choose especially high-quality stainless steel blades with titanium coating, which last much longer. However, it is not possible to give exact details about this.

How Can the Durability of the Blades Be Increased?

Removing Objects from the Mowing Area

You only have to pay attention to a few things to increase the durability of the blades significantly. Essentially, it is important that you take care that no foreign bodies get into the mower deck.

You should not only remove stones, yard tools and toys from the lawn. Fallen fruit, twigs, branches and pine cones can also dull the blades and shorten their lifespan.

Likewise, you should not allow too many large piles of leaves to pile up in your yard. These can also cause the blades to dull more quickly and also cause the robotic mower to use more energy while mowing. 

You should remove the following items:

• Stones
• Garden tools
• Toys
• Fallen fruit or walnuts
• Branches and twigs
• Excessive foliage
• Tennis balls or baseballs

Shortening the Mowing Time

Another way to extend the life of the blades is to avoid unnecessary mowing. Firstly, you need to take into account the weather conditions and thus the speed at which the lawn grows. Then, the routes that the robotic mowers drive can be optimized, which protects the blades and saves energy at the same time. 

Possibilities for shortening the mowing time:

1. Moderate mowing instead of running the robotic mower around the clock
2. Manual adjustment of the mowing times to the season (mow less often in dry periods)
3. Weather timer for automatic adaptation to weather conditions
4. Calendar function to optimize the mowing cycles
5. GPS-supported navigation
6. LogiCut function (mowing with a set system instead of randomly)

1. Moderate Mowing

Excessive mowing should be avoided. The robotic mower does not have to drive around your lawn every day for 16 hours. In most cases it is sufficient to program your robotic mower to mow about every one or two days. In midsummer, however, the robot can also mow less often when it rains less, as the lawn grows more slowly.

2. Weather Timer

Some robotic mowers have various technical aids to help avoid unnecessary mowing. A weather timer on the robotic mower, for example, is not designed to drive the robotic mower into the garage when it rains, but can determine how fast the lawn is currently growing by measuring the resistance on the rotor of the blades. If the resistance is greater, the lawn seems to have grown faster since the last mowing. If it is smaller, the speed of growth has decreased. Accordingly, the lawn robot then goes out to mow either more or less often.

3. Calendar Function

With some robotic mowers a very similar feature is available, called calendar function. Here, the lawn size, the mowed area per battery runtime, and the necessary charging times are used to calculate the optimal mowing cycles.

4. GPS-supported Navigation

There are some robotic mowers that have GPS-supported navigation. During the first few weeks, the robotic mower collects GPS data about the lawn and then creates a digital map of the yard. It uses this map to optimize the mowing routes and avoid unnecessary overlapping mowing of the same area. This feature is especially useful for more complex yards. You can read more in this detailed article about GPS.

How Do You Change the Blades?

The procedure for replacing the blades differs here, depending on whether you have a blade disc or a star blade. I’ll offer here a brief explanation, so that you can determine which type of turntable your robotic mower is.

A blade disc consists of a turntable with 3 or sometimes 5 swiveling, mounted, very small blades, which are pressed outwards by centrifugal force during mowing.

The star blade consists of a large, star-shaped blade. Larger robotic mowers can also have several star blades.

There are two different types of mowing units: mowers with a star blade, and mowers with a blade disc. There are also robotic mowers with several star blades. These pictures can help you to see what kind of model you have.

Changing Blades on a Blade Disc

Changing the blades on robotic mowers with blade discs is relatively simple. The only tool you need is a screwdriver.

Required tools

• Screwdriver

If additional tools are required, these are included in the accessories of the lawn robot.

The following instructions explain how you can replace the blades on blade discs in just a few steps. It is best to use protective gloves to avoid injury.

1. Make sure that the robotic mower is switched off (main switch to OFF)
2. Use protective gloves
3. Turn the robotic mower over on its back
4. Remove the three screws holding the blades in place with a screwdriver
5. Remove the blades
6. Attach and tighten the new blades and new screws (Careful, the blades are very sharp!)
7. Make sure that the blades can move freely, this reduces wear

In this short video you can see again the changing of blades on a blade disc using the example of a Husqvarna robotic mower.

Changing a Star Blade

Blade replacement on a star blade is even easier than on a blade disc. You do not need any tools for this. However, there are special grippers that make it easier to change the blades. Perhaps one of these pliers was included with your robotic mower. You should also wear protective gloves to avoid possible injuries.

With these few steps you can replace the blade on robotic mowers with a star blade.

1. Make sure that the robotic mower is switched off ( main switch to OFF)
2. Use protective gloves
3. Turn the robotic mower over on its back
4. The star blade has two pressure flaps which you have to press together in the middle to be able to remove the star blade (Caution: blades are very sharp!)
5. You can simply press the new star blade onto the lugs until it locks into place

This short video shows the replacement of the star blade using the example of a Robomow robotic mower.

Can the Blades Also Be Sharpened?

You can also sharpen the blades of the robotic mower so that you can continue using them. But is that the best option in your case?

If you have no experience in blade sharpening and do not have a particularly great passion for craftsmanship, I would advise against sharpening them. By sharpening you can get very good and sharp blades, but this requires some experience and time. If you want to save time when you buy a robotic mower, you should not do the sharpening.

Nor can you necessarily claim to save a lot of money. After all, you have to look at all the grinding tools. Among other things, you need different Japanese grindstones to get the right sharpness. If you have also adopted the motto “time is money”, sharpening the blades is not worth it.

On the other hand, if you enjoy grinding and handicraft activities in general and you have grinding tools at home anyway, then just give it a try. In any case, a very good Japanese sanding tool is required to achieve acceptable results.

Conclusion

Regular replacement of the blades is worthwhile. This will give you a better cutting pattern and a healthier lawn. How often you should replace the blades depends on many factors, as well as your personal demands on the yard. However, for robotic mowers with blade discs it is generally advisable to change the blades every 1 – 3 months. For lawn robots with a star-shaped star blade, you only need to replace the blades once per season.