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 work only 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. Anyway, the mobs drop experience only if killed by the player, not by automated means.
== Common grinders ==
The following are some of the most common styles of mob grinders.
=== Fall damage grinder ===
Mob	Minimum height to death
 	17 blocks
 	19 blocks
 	23.5 blocks
 	29 blocks
 	43 blocks
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 are immune to fall damage. These include iron golems, chickens, cats, and flying mobs such as blazes.
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. Most common hostile mobs can be killed with a 24-block drop, although witches require 30 blocks. Some mobs such as zombies and skeletons can occasionally spawn with Feather Falling boots or armor that can change the required distance. Because of this, it is often better to make the drop further than necessary.
On the other hand, 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, so you can kill them with one hit. , 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. However, stone swords are cheap and plentiful, and you can also use tools (such as shovels) dropped by the zombies.
Spiders can be tricky to deal with as they can grab the walls and reduce fall damage. To kill spiders, a minimum of a 2×2 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 heals itself and the enderman teleports.
* Magma blocks may be useful to kill Feather Falling survivors.
* Landing on stalagmites amplifies fall damage, reducing the height required for killing mobs or bringing them to minimal health points.
=== 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 dies 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.
=== Wither roses ===
Wither roses can be used in a similar manner to magma blocks and sweet berries to kill mobs. Wither roses placed on top of soul sand allow items to sink into soul sand blocks and be picked up by hoppers directly below, avoiding having to use hopper minecarts to pick up items through full blocks.
Wither roses deal the same damage as magma blocks and sweet berries: 1 heart per second. (Also applies the wither effect)
=== Lava grinders ===
If you have a lava bucket, a lava grinder is often the simplest and most practical grinder, particularly for iron golems or mob farms that are not high up above the ground.
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."
Another variant is a pool of lava that the mob falls into, with the lava being suspended above a space that the drops fall into.
Lava grinders are typically ineffective against baby zombies, because even if they fall through a pool of lava, they often survive, and they can fit in the one-block space under the lava being suspended by the signs. It is a good idea to put a fence between the hopper and your collection room (a fence over a chest does not prevent the chest from opening). Then, if a baby zombie happens to be waiting on the other side, you can easily kill it.
File:LavaBlades.jpg|A 3-tier lava grinder for killing iron golems and smaller mobs, although baby zombies can slip through.
File:Lavatrap-frontview.png|Another lava grinder (front view).
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.
=== Campfire killer ===
A campfire killer has advantages over both a lava grinder (above) and a trident killer (below). A campfire does not destroy items like lava can. A campfire can kill nearly any mobs including baby zombies that would normally fit in a space under lava. While it does not bestow experience on players like a trident killer, a campfire killer is much cheaper and simpler to construct, requiring only water, a sign, a hopper, a chest, a glass block, and a campfire. A campfire requires only wood to make the crafting ingredients. It is an excellent choice for early-game farms.
In the figure on the right, a sign (or a button) is used to stop the water flow. The water pushes the mob onto the campfire. A hopper placed directly underneath a campfire pulls in any items dropped. The hoppers feed into a collection chest. The glass block traps mobs in the campfire space, and glass is useful for viewing the mob being killed. The half-block gap between the glass and the campfire allows for safe manual killing if needed (which gains experience for the player).
Although a campfire damages mobs slowly, it works reasonably well on any mob without fire resistance. Most hostile mobs (creepers, zombie variants, illagers, spiders, etc.) die in less than 10 seconds in a campfire. A campfire kills an iron golem in about 50 seconds. A campfire killer does not work well on witches, because they give themselves potions of Fire Resistance and Healing. A witch can survive indefinitely in a campfire, so if a witch gets stuck in this trap, it should be killed manually.
If you have Soul Sand available, you can make soul campfires instead. These kill twice as fast as regular campfires, and give off less light, which usually makes them a better choice than a normal campfire.
=== Trident killer ===
Projectiles that can be picked up again by the player after lodging in a block (i.e. arrows and tridents) also have the ability to hit mobs if they are moved after becoming lodged. The total number of hits a projectile can inflict before becoming inert and impossible to retrieve depends on its type and the piercing enchantment: a normal arrow can hit one mob; arrows shot by piercing-enchanted crossbows can hit (enchantment level + 1) mobs; and tridents can hit an infinite number of mobs.The ability of tridents to hit multiple mobs is an intended behavior in Bedrock Edition: see Hits inflicted by moving the projectile after it has been lodged in a block count as hits for the player who launched the projectile, even hours later and/or while the player is no longer nearby. Such hits cause the the mob to drop experience and player-kill loot as long as the player who launched the projectile is loaded somewhere in the world. In addition, the loot dropped is subject to the looting buff if the player holds a looting sword in the main hand at the time the kill occurs.
Trident killers make use of these mechanics to produce a completely automatic method of killing mobs and making them drop experience and other player exclusive loot. They work by throwing a trident into a mechanism that uses a piston to push the trident into mobs and a clock circuit to power the piston on and off.
Trident killers provide a way to get large amounts of player-kill loot and experience from a farm without the need for repetitive clicking and travel between different kill locations. Many Bedrock mob farms are much less productive than their Java counterparts due to differences in the spawning algorithms. Moreover, since Bedrock Edition does not have the sweep attack it can be difficult to kill large quantities of mobs manually with a sword. Players may therefore wish to enhance the effectiveness of their farms by limiting the distance mobs must travel before being killed, and by using the looting enchantment while still killing mobs automatically. Trident killers make this possible. They allow for remote player kills in small, separated modules of a farm, and they allow the player to get the looting buff on those kills. On top of these beneifts, tridents in trident killers never despawn. Tridents decrease in durability only when they are thrown. Because the trident is thrown only once, a trident killer can run indefinitely without needing to be supplemented with additional tridents.
Because tridents cannot be crafted or found in chests, they must be obtained by hunting drowned or by building an aerial drowned farm. Only one trident is needed for a trident killer, even one that is nearly worn-out.
=== 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 must 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.
=== Entity cramming grinder ===
It is possible to kill mobs using entity cramming. When there are more entities sharing a hitbox than the value set in the Entity cramming threshold setting (default 24), if they cannot be pushed apart, 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 1×1 pit at least two blocks deep so mobs cannot jump out. As mobs fall into the hole, their number will eventually accumulate to the point where they pass the cramming threshold and start taking damage. Collect the items with hoppers or hopper minecarts, as with any other grinder. When the farm is turned off and the density of mobs in the hole isn't high enough, they remain stuck in the chamber, but they can be finished off with a sword.
No experience is gained from this farm, aside from killing the leftover mobs manually. However, it is cheap, simple, easy to build, and can kill almost anything. Just don't fall in.
=== 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 run into it. This grinder works well, but the cactus can destroy some of the loot.
=== 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 works only 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 works only 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 1×1 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.
=== Sweet berry bush ===
 Sweet Berry Bushes deal damage to mobs (except foxes) as they move through the bushes. Sweet Berries result in a slow grinder as they deal damage only when the mob moves. Sweet berries can be placed only on top of grass block, dirt, podzol, coarse dirt, or farmland.
=== Floor-suffocation grinder ===
This grinder involves surrounding a 4x4 pit with pistons, one block above the floor of the pit. Have mobs pushed into the pit, and attach the pistons to a loop or a lever so that the pistons quickly go on and off, causing the entities inside the pit to fall into the floor and suffocate. This requires that there is a one-block tall space beneath the floor of the pit, so that the mobs can fall. This kills extremely quickly. 
== Item collection ==
You may want to collect items automatically after the mobs have been killed. Any easty way to do this is 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 multiple hoppers, or manage water flows to move items into a single destination hopper.
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
== Video ==
Category:Modernized tutorial
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