Tutorials/Mob grinder

Mob grinders are the last part of a mob farm and are used to kill mobs in massive amounts while also collecting all dropped items at a convenient location. They are a mechanism and can be considered a special type of trap.

Mob grinders are sometimes specific to a certain size of mob. Tall mobs usually refer to tall hostile mobs, namely skeletons, zombies, and creepers, but can also refer to cows, sheep and zombie pigmen. Small/short mobs are only 1 block tall and are spiders, pigs, wolves, chickens and ocelots.

Squid and Ghasts have unique behavior, spawning conditions, and/or size making them difficult to grind. Therefore, they are often omitted when someone says 'all mobs'.

Mob grinders will not produce Music Discs or rare drops as the mob deaths do not meet the conditions for dropping those items.

Common Styles
The following are the most common styles of mob grinders. They are efficient and relatively small.

Lava Retrieval Traps


Lava tends to destroy drops, but this can be avoided by suspending the end of a lava stream on a ladder or forcing mobs to the termination point of a lava stream. Ladders and signs are considered solid blocks by liquids but empty blocks by mobs or players. Also consider using water to drown mobs to ensure that no drops will be lost. You may use a simple 8X8 area with a mob spawner leading to a water drop that mobs can push each other into, making so the drops come out when mobs spawn, and makes lag a nonoccurrence.

The canals from the mob farm send mobs into this final water channel. The mobs are forced into the chest high lava blade. The same water that drags the mobs into the lava also pushed the drops into a collection point. Combine with a final perpendicular-flow water current to deliver all items to a single tile, on which a wooden pressure plate may be placed and attached to redstone torches to indicate the availability of items. As of the second Pre-release of 1.9, Endermen do not pick up Stone or Cobblestone, so you do not have to worry about them ruining your system of spawning the mobs.

Piston Smasher Trap
This trap consists of a piston which pushes a mob under a sticky piston. The sticky piston simultaneously pushes a block on the mobs head to suffocate it. This setup is connected to a repeater to allow new mobs to enter the smashing area. Water can be used to transport items from the smashing area to a collection point. The trap damages about one heart per second. This setup only works for tall mobs, but the 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.

Timing is very 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 set up, 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 you 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 for at least 48 repeaters.

Another downside to piston smashers is the inability to handle spiders. You would need another way to sort out spiders (such as a cactus choke).

Drowning
Drowning grinders work by sending mobs into a small area without an air pocket. Items drop in water and can be easily collected from below. This video tutorial shows step by step how to attach a simple drowning trap to a vertical mob elevator. This type of trap is advantageous because of the impossibility of losing items to lava/cacti as well as the possibility for compact designs.

DJ and Riggaz's Spider Falling Grinder
To make a spider spawner grinder, the fall chamber will need to be at least 2x2. A video tutorial on this is available here So to make this:
 * Firstly put water under your spawner on one side so that it will all flow into one direction.
 * Where the water ends, dig a 2x2 shaft at least 20 deep (best to do more for insurance as they sometimes grab the wall and reduce damage)
 * At the bottom of this chamber make a little room with a ladder or stairs to the surface or your base, etc. (Down here is where you will collect your drops from)
 * Remove all lighting from near the spawner and make it completely dark, but light the bottom chamber to prevent anything spawning in your collection area.
 * Note that it would be smart to dig under the spawner and look for any cave systems, light them up so nothing spawns, this will increase your overall yield.

1x1 Fall Chamber
This is a good method of killing mobs and getting their drops. How to set up:


 * Dig a 1x1 hole down 20 blocks (minimum).
 * Connect the bottom to some stairs leading to your house. (You will go down here to get the drops.)
 * On the top, make a piston disappearing floor using a sticky piston and a NOT gate. See the section Tutorials/Piston Uses for more information on this.
 * Connect the this. floor to a lever in your house.
 * Build fences all around the hole and connect to your mob farm.

You are done!

How to operate:
 * Wait for the mob to stand on the floor.
 * Pull the lever.
 * Pull the lever back, then go down the stairs.
 * Get the drops, and repeat.

Note: This will not work with chickens, ghasts, or blazes due to their flying ability. This will also not work for spiders as they need a 2x2 minimum to fall and often grab onto the edges of walls and reduce fall damage. Make sure you can see the grinder from the lever, so you know when to pull the lever. You can make more holes and make this bigger. Just repeat the process.

Another tactic is to place water on a higher area so it is flowing. Put your hole at the end of the water. I recommend doing this in a large row, and inside a completely dark building so mobs will spawn even in daytime. You will need a separate shaft connected to it in order to retrieve the dropped supplies. This is advantageous because it will work by itself 24/7 and is fairly simple to build. Once completed, all you have to do is look for stuff on occasion. You do not have to watch and wait for a mob to walk into place, and this works with any mob, also except ones that can fly.

Uncommon
The following grinders can be effective in the right situation but are less common due to size, inconvenience, or other disadvantage.

Cactus Choke
This mob grinder is for killing off spiders, sorting out spider-size/spider-jump/spider-climbing related issues. This is a simple design, relying on the spider's 2x2 size and jumping ability. 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 (make sure the cactus is out of the water so it doesn't destroy the drops).

Alternate Cactus Choke
Similar to the above cactus choke, but more efficient and items won't get stuck behind the sand block. At the end of a stream, there is a small gap with a stream and a cactus behind that. This allows cacti to kill spiders without having them climbing to get to the cactus. This can also sort mobs from spiders similar to the above cactus choke if done right.

Fall Damage Mob Killer
Space permitting, fall damage can be used to dispatch mobs. This style of mob grinders doesn't work for chickens since they glide rather than fall. Spiders should be sorted out before they are dropped as they can climb the inside of the drop-tube and potentially clog it. Mobs must drop from at least 23 blocks to receive fatal damage. Use a water column full of source blocks to float mobs up at least 28 blocks. At the top of this column of water, have another stream push the mobs into an empty tube (the drop-tube). This tube helps prevent skeletons from firing arrows at you while they fall. If desired, a control lever can be built that will collect mobs at the top. This can either toggle a door or piston, both designed to artificially clog the machine until released.

Here is a how-to on a simple but effective Fall Damage Mob Trap/Grinder.

1. Construct a 20x20 platform of any solid block 28 blocks high above the ground.

2. Make walls surrounding platform six blocks high.

3. Inside the walls, make four water channels coming from the middle of each four walls to the center. This should create a 2x2 square of dry block in the middle. Cut out that square, that will be the hole the mobs fall through.

4. Make the channels 2 blocks high so mobs can't jump out of them.

5. Make four platforms between the four corners that the water channels create that are flush with the top of the water channels. (this will be the area that the mobs spawn on)

6. Make a roof over the whole thing. You should be able to walk around inside your spawner with a space 3 blocks high. A second layer of ceiling blocks can be added to prevent Endermen from spawning.

7. Remove any torches to make it dark inside.

Fall Damage Experience Grinder
When a skeleton, zombie, or creeper (Which have 10 hearts of health) drops 23 blocks it will leave it with one half-heart of health left. Endermen have 20 hearts, so at 42 blocks, they will have 1/2 of a heart, and spiders have 8 hearts, so they need to fall 18 blocks. A canal can then carry them to a hole in the wall, where the player can reach in and punch them to gain both experience and the drops. This works best when you make this in a dungeon.Firstly, make water flow to a 1x2 hole in the dungeon. Then,have water source blocks alternate with signs to the desired drop height. At this point have water flow to its end and then mine down to the place where the mobs hit. It is best to leave them with half a heart, because mobs do not disappear over time, but pickups do. Then mine a pathway to your house. Then go back to the fall point and place a block so that only the mobs' legs are showing so that they cannot hurt you. Then you have a working mob trap.

Sunlight Death Chamber
Zombies and Skeletons burn in sunlight which can be an effective way of dealing damage and separating creepers. This can also be done with monster spawners, a tutorial is available here. A sunlight death chamber is simply a room with a glass or hollow ceiling. This is a very simple mob grinder to make but has several downsides:
 * Daytime. Only the sun can burn these mobs, making this useless at night and when overcast.
 * Unblocked. No blocks can be directly above the trap (with the exception of glass).
 * Dry. Water extinguishes fire and since the mobs burn, no water can be present in the chamber. This can be simplified by having a valve which can be shut off during the day.
 * Limited Selection. This only works for Skeletons and Zombies. (As of 1.0 this no longer works for Endermen).

Mob arena
Strictly speaking, this is not a mob grinder but does have a similar outcome and is a way of using the mobs spawned from a mob farm. The mobs are collected in chambers and slowly released into the 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.

Video explanation and showing the concept at work: Youtube

Egg Spawner Grinder or "Mob Vending Machine"
With the addition of the mob spawner eggs in Minecraft 1.1, it is possible to create an egg spawner based grinder. Very useful for getting mob based items such as bone and rotten meat in adventure maps, but useless in survival because it requires spawn eggs.

You put an egg over a block which have a sign or a ladder blocking the water in the upper layer to flood down and at the same time pushing mobs up, then they go through a corridor and falls in a 1x3x5 corridor covered in the upper block with air, midblocks with cobweb (or air) and in the down block with water and with a dispenser that shoots fire arrows with a clock mechanism. It is possible to shoot the eggs with a dispenser creating a "mob item vending machine".

You only need to be careful with one thing: NEVER put creepers with other mobs in the machine because if they start to fight inside the water canal the creeper could blow up and destroy part of the machine causing lava to flow outside of the machine in 90% of the cases killing you. It is secure to put creepers alone in the machine even if you put 64 or more creepers in so they don't blow up. and the overhang in the egg placing area prevent creepers and other mobs to attack you one time that the water push the mobs up in the moment that they spawn.

To automate the entire mechanism, place a dispenser in the egg placing area, stock it with eggs, and connect it with redstone to a button. Connect a lever to a clock mechanism to shoot the arrows. From here, it's just a matter of pressing a button to spawn a mob, and then using the lever to launch arrows at it.