Recoater carriage

1. A recoater carriage assembly for use in an additive manufacturing system, the recoater carriage assembly comprising:

an elongate powder build material spreader to spread powder build material in use;

a recoater carriage to support the spreader; and

a lid to at least partially cover the spreader when the spreader is engaged with the recoater carriage;

wherein the spreader is to engage with, and to disengage from, the recoater carriage by movement of the spreader non-concentrically to a longitudinal axis of the spreader;

wherein the lid is to retain the spreader relative to the recoater carriage when the spreader is engaged with the recoater carriage.

2. The recoater carriage assembly of claim 1 , comprising a retainer to retain the spreader in engagement with the recoater carriage.

3. The recoater carriage assembly of claim 2 , wherein the retainer comprises a resilient element to bias the spreader into engagement with the recoater carriage.

4. The recoater carriage assembly of claim 1 , wherein

the spreader comprises at least one projection,

the recoater carriage comprises at least one recess, and

the at least one projection of the spreader projects into the at least one recess of the carriage when the spreader is engaged with the carriage.

5. The recoater carriage assembly of claim 1 , wherein

the spreader comprises a drive element,

the carriage comprises a drive mechanism, and

the movement of the spreader is to engage the drive element of the spreader with the drive mechanism of the carriage.

6. The recoater carriage assembly of claim 1 , wherein the spreader is a roller.

7. A carriage to carry a recoater roller for use in an additive manufacturing system, the carriage comprising:

a first support and a second support, wherein the first support is spaced in a first direction from the second support, and

a lid to at least partially cover a recoater roller when the recoater roller is engaged with the first support and the second support,

wherein the first support and the second support are to engage with the recoater roller by movement of the recoater roller in a second direction that is different from the first direction,

wherein the lid comprises a retainer to retain the recoater roller relative to at least one of the first support and second support when the recoater roller is engaged with the first support and the second support.

8. The carriage of claim 7 , wherein the first direction is orthogonal to the second direction.

9. The carriage of claim 7 , wherein the first support and the second support are immovable relative to each other.

10. The carriage of claim 7 , wherein at least one of the first support and the second support comprises a channel or slot in the carriage.

11. The carriage of claim 7 , wherein the retainer is resilient to bias the recoater roller towards the first support and second support when the recoater roller is engaged with the first support and the second support.

12. The carriage of claim 7 , wherein the carriage comprises a gear to engage with a gear of the recoater roller when the recoater roller is engaged with the first support and the second support.

13. A method of using a recoater carriage assembly in an additive manufacturing system, the method comprising:

removing a lid that at least partially covers an elongate recoater roller and that retains the elongate recoater roller relative to a recoater carriage when the elongate recoater roller is engaged with the recoater carriage; and

moving the elongate recoater roller in a direction non-concentric to a longitudinal axis of the elongate recoater roller and relative to the recoater carriage to disengage the elongate recoater roller from the recoater carriage.

14. The method of claim 13 , wherein the roller is a first roller;

wherein the method comprises, after the moving, engaging with the recoater carriage a second elongate recoater roller; and

wherein a surface characteristic of the first and second rollers differs between the first and second rollers.