Tutorials/Mob grinder

Mob grinders are the final part of a mob farm, the mob killing mechanism. Mob grinders can be used to kill many mobs while simultaneously collecting all dropped items at a convenient location.

Most mob grinders are specific to certain categories of mobs. Some grinders only work with tall mobs such as skeletons, zombies, and creepers, but don't work with shorter mobs such as spiders, pigs, and wolves. Other grinders work with both tall and short mobs, but don't work with mobs which are immune to fire damage.

Most of these mob grinders do not produce music discs or other rare drops as the mob deaths do not meet certain conditions. It is possible that these grinders can be built in a particular way which would make it easy to fulfill these conditions, however.

Common grinders
The following are some of the most common styles of mob grinders.

Fall damage grinder
Fall damage is one of the simplest and quickest methods of mob grinding. This method is often done in combination with a mob farm where the mobs are forced into water streams and can easily be dropped from a lethal height. Some mobs, such as those which can fly, are immune to fall damage. Notably, these include blazes and iron golems. Most common mobs, however, can be killed with a 24 block drop.

Arguably the most important aspect of a fall damage grinder is the drop height. Different mobs need to be dropped different distances in order to kill them. Some mobs such as zombies and skeletons can occasionally spawn with Feather Falling boots or armor which may change the required distance. Because of this, it is often better to make the drop further than necessary.

When using a fall damage grinder, it is often desirable to kill the mobs manually in order to obtain experience and other exclusive drops. By dropping the mobs slightly lower than the minimum death height, it possible to make most mobs end up with health points, the ideal number before you deal the finishing blow. Note that $$ it is not possible to bring zombies to half a heart, even with a combination of falling and suffocation, because zombies have natural armor points. If you wish to use your fist rather than a tool to kill the mobs, a strength beacon may provide the extra damage necessary to kill zombies and mobs with armor in a single hit.

Spiders can be tricky to deal with as they can grab the walls and reduce fall damage. To kill spiders, a minimum of a 2&times;2 pit is necessary. You may want to dig the pit deeper than the required 19 blocks in case a spider does brush the wall at some point in its descent.

Tips:
 * Bubble columns are useful when getting the mobs up high enough to drop.
 * If dropping the mobs to kill later, make an opening showing just their feet so they can't attack you.
 * Witches and endermen must be killed immediately or the witch will heal and the enderman teleport.
 * Magma blocks may be useful to kill Feather Falling survivors.

Magma blocks
Magma blocks are a simple method of mob grinding. When mobs walk on a magma blocks, they are dealt damage every second. This means an unarmored skeleton will die in about 20 seconds. To avoid being damaged while building, you should obtain Frost Walker boots, drink a Fire Resistance potion, or just crouch.

Although magma blocks do not destroy items, collecting the items can be a little tricky. There are generally two options for item collection: Use water streams to wash items off the magma blocks or use hopper minecarts. Water streams have the downside of negating any fall damage and potentially causing the mobs to bob up and down, taking damage only some of the time. Running hopper minecarts on rails underneath the magma can solve both of these problems but is more expensive.

Not all mobs can be easily killed by magma blocks. Nether mobs, such as wither skeletons and blazes are not affected by fire damage, so magma blocks are not useful as a nether grinder. Magma blocks are also ineffective against witches as they drink fire resistance potions negating damage. Spiders can also be tricky as they may climb walls and cause issues.

Lava grinders
While lava is good at dealing damage, it also tends to destroy items. The loss of items can be avoided by suspending the lava on a sign and pushing the mobs into it. When a mob dies, its items then fall below the lava and into the hopper. This type of grinder is often called a "lava blade."

Instead of pushing mobs into the lava, it is also possible to douse them using a dispenser. During the short period of time in the lava, the mobs catch fire and are weakened until a player can easily kill them with one or two hits.

Trident killer
When a player thrown trident kills a mob, the game makes the mob drop experience and exclusive loot even if the player threw the trident hours ago.

Trident killers are a completely automatic method of killing mobs and making them drop experience and other player exclusive loot. They work by throwing a trident onto a piston and using the piston to push the trident into mobs. Although the player may have thrown the trident a long time ago, the game still thinks the player is attacking the mob. As a result, the mobs killed by the trident count as a player kill and the loot drops accordingly. When playing with multiplayer, whoever threw the trident must be on the server in order for this to work.

Tridents killers never despawn and they decrease in durability only when they are thrown. Because the trident is thrown only once, it does not run out of durability. In addition, if you hold a Looting sword while using a trident killer, the effects of the enchantment are applied to all the mobs killed by your tridents.

Many Bedrock mob farms are much worse than their Java counterparts and thus need to be supplemented with the looting enchantment. However, since Bedrock Edition does not have the sweep attack it can be difficult to kill large quantities of mobs manually with a sword. Trident solve this problem, providing both looting and a way to kill many mobs easily.

Below are a couple of videos demonstrating some basic trident killers:

Trident killers use glitches, and in bedrock 1.16, these don't work.

Piston grinder


Using pistons, it is possible to push blocks into mobs so that they suffocate. In the shown example design, a piston pushes a mob underneath a sticky piston holding a block. The sticky piston extends at the same time to "smash" the mob and cause it to die from suffocation at points per second. The water used to push the mobs can also be used to wash the items to a hopper for item collection. This setup works only for tall mobs, but the same principle can be used for smaller mobs as well.

The downside to this trap is the slow rates of kills, since each mob needs about 10 seconds of suffocation before it dies. This problem can be fixed by having a row of pistons push together at once, suffocating multiple mobs in every smash. Another downside is the inability to handle spiders. You will need to find another way to sort out spiders, such as a cactus choke.

Timing is important for this trap to work efficiently. For single mob smashes, a loop of at least 30 repeaters set at maximum are needed, giving 12 seconds per loop. With this setup, turn on the loop for a little more than 10 seconds to ensure they die, and have the loop off for the rest, giving 10 second kills and 2 second load times. For a full row of 8 pistons, the load time is approximately 6 seconds, meaning the loop needs to have 40 repeaters giving a 16-second loop. Load time for a stream of 8 blocks long and 2 blocks wide, with pistons on both sides, is about 8 seconds. This amounts to at least 48 repeaters.

Alternative grinders
These grinders are not as commonly used and may be somewhat unusual. They can still be useful in some situations, however.

Mob cramming grinder
It is possible to kill mobs using mob cramming. When too many mobs are crammed in one place (by default 24), they start to take damage. This grinder deals damage per second, quickly killing mobs such as skeletons and zombies after about 2 seconds of exposure. Because this trap deals suffocation damage, it works with all mobs, including those which are immune to fire and lava, such as wither skeletons.

To make the grinder, first dig a 1&times;1 pit at least two block deep so mobs can't jump out. Next, place a rail at the bottom of the pit. If you want to automatically collect items, consider placing the rail on top of a hopper. To kill the mobs, place 24 minecarts on the rail. You may want to make one of the bottom wall blocks of the pit a half slab to allow easy access to the rail when placing the minecarts. Finally, you can use water streams to transport enemies into the grinder from above.

The downside to this trap is the high expense, since it requires 120 iron for just the minecarts. It is also annoying to remove if you need to make a change to the trap. It can also generates a lot of noise from the carts continuously trying to resolve their collision issues. Carrying 24 carts at once also takes up most of your inventory space so it is somewhat inconvenient to transport. However, because this trap is otherwise simple to build and extremely fast, it may be worth the effort.

Cactus choke
This cactus choke kills spiders, solving potential spider size/jump/climbing issues. It is a simple design, relying on the spider's 2×2 size. The grinder stops all spiders at a bottleneck, where the water-conveyor narrows from 2 blocks wide to 1 block. A cactus is placed on the side, on top of a sand block, where spiders will run into it.

Sunlight grinder
It is possible to burn zombies and skeletons with sunlight as an effective way of dealing damage and separating creepers. This can also be done with monster spawners. To build a sunlight grinder, simply make a room with a glass or a hollow ceiling. Although it is easy to build, this grinder has several downsides:
 * It only works during daytime, making the grinder useless at night and when overcast.
 * It requires an area where sky access is possible.
 * It requires the kill chamber to be separated from water.
 * It only works with certain mobs.

Mob arena
Strictly speaking, this is not a mob grinder, but has a similar outcome and is a fun way of using the mobs spawned from a mob farm. The mobs are collected in chambers and can be slowly released into an arena to fight against players.

The concept is simple, 2 tall buildings, with about 15 rooms inside, that have holes at all corners, and water around the sides to push anything that goes to the side into the hole at the corner. Then once the mobs fall down, they are trapped in a simple holding area until a lever is pulled to let pistons open so that the mobs can fall out.

Anvil smasher
It is possible to grind mobs by smashing them with an anvil. To start, the mobs should be contained in a small 1&times;1 chamber with an open ceiling. Next you should have a tall pillar on one wall chamber which you can climb and drop an anvil from. If dropped from a sufficient height, all mobs should be instantly slaughtered. You can then collect the drops with a hopper or just by entering the chamber. You may wish to place a torch or sign at the bottom of the chamber to break the anvil and prevent it from being damaged. It would then be possible to automatically transport the items and anvil back up to the top using some sort of vertical item transportation.

Item collection
You will often want to automatically collect items after the mobs have been grinded. The easiest way to do this is usually to place a hopper at the end of your water flow or wherever your items drop out. A double chest can then be placed under or next to the hopper to contain the items. If there is a large area where the items can land, you may need to use multiple hoppers.

For more complicated designs, you can also use hopper minecarts. Hopper minecarts can pick up items through solid blocks, so you can easily run a rail line underneath the blocks where items rest. Rail lines are often useful as an alternative to many hoppers or in combination with magma rock grinders.

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