Additive manufacturing

1. An additive manufacturing process, comprising:

forming a first layer of powdered build material;

dispensing a coalescing agent on to powdered build material in the first layer in a pattern corresponding to a first object slice;

dispensing a coalescence modifier agent on to powdered build material in the first layer surrounding build material patterned with coalescing agent;

solidifying build material in the first layer patterned with coalescing agent to form the first object slice; then

melting some or all of the first object slice;

after melting some or all of the first object slice, pressing a part into melted first object slice wherein some of the melted first object slice is displaced by the part;

forming a second layer of powdered build material on the first object slice and covering the part;

dispensing a coalescing agent on to powdered build material in the second layer in a pattern corresponding to a second object slice;

dispensing a coalescence modifier agent on to powdered build material in the second layer surrounding build material patterned with coalescing agent; and

solidifying build material in the second layer patterned with coalescing agent to form the second object slice covering the part.

2. The process of claim 1 , wherein the solidifying includes:

exposing build material patterned with coalescing agent to light to melt the patterned build material; and

cooling the melted build material or allowing the melted to build material to cool.

3. The process of claim 1 , wherein the solidifying includes exposing build material patterned with coalescing agent to light to sinter the patterned build material.

4. The process of claim 1 , wherein:

forming a first layer of powdered build material includes forming multiple first layers successively one over another;

dispensing a coalescing agent on to powdered build material in the first layer in a pattern corresponding to a first object slice includes dispensing a coalescing agent on to powdered build material in each of the successive first layers in a pattern corresponding to an object slice;

dispensing a coalescence modifier agent on to powdered build material in the first layer surrounding build material patterned with coalescing agent includes dispensing a coalescence modifier agent on to powdered build material in each of the successive first layers surrounding build material patterned with coalescing agent;

solidifying build material in the first layer patterned with coalescing agent to form the first object slice includes solidifying build material in each of the successive first layers patterned with coalescing agent to form each of multiple first object slices;

melting some or all of the first object slice includes melting some or all of the multiple first object slices; and

pressing a part into melted first object slice includes pressing the part into melted multiple first object slices.

5. A tangible non-transitory processor readable medium having instructions thereon that when executed cause an additive manufacturing machine to:

form a first layer of powdered build material;

dispense a coalescing agent on to powdered build material in the first layer in a pattern corresponding to a first object slice;

dispense a coalescence modifier agent on to powdered build material in the first layer surrounding build material patterned with coalescing agent;

solidify build material in the first layer patterned with coalescing agent to form the first object slice; then

melt some or all of the first object slice;

after melting some or all of the first object slice, press a part into melted first object slice wherein some of the melted first object slice is displaced by the part;

form a second layer of powdered build material on the first object slice and covering the part;

dispense a coalescing agent on to powdered build material in the second layer in a pattern corresponding to a second object slice;

dispense a coalescence modifier agent on to powdered build material in the second layer surrounding build material patterned with coalescing agent; and

solidify build material in the second layer patterned with coalescing agent to form the second object slice covering the part.

6. The medium of claim 5 , wherein the instructions to solidify include instructions to:

expose build material patterned with coalescing agent to light to melt the patterned build material; and

cool the melted build material or allow the melted to build material to cool.

7. The medium of claim 5 , wherein the instructions to solidify include instructions to expose build material patterned with coalescing agent to light to sinter the patterned build material.

8. An additive manufacturing machine controller that includes the processor readable medium of claim 5 .

9. A computer program product that includes the processor readable medium of claim 5 .

10. An additive manufacturing machine, comprising:

a first device to layer powdered build material;

a second device to dispense a coalescing agent on to powdered build material;

a third device to dispense a coalescence modifier agent on to powdered build material;

a light source to apply light energy to build material;

a fourth device to place parts;

a heater; and

a controller to execute instructions to:

cause the first device to form a first layer of powdered build material;

cause the second device to dispense a coalescing agent on to powdered build material in the first layer in a pattern corresponding to a first object slice;

cause the third device to dispense a coalescence modifier agent on to powdered build material in the first layer surrounding build material patterned with coalescing agent;

cause the light source to apply light energy to build material in the first layer patterned with coalescing agent to form the first object slice; then

cause the heater to melt some or all of the first object slice;

after melting some or all of the first object slice, cause the fourth device to press a part into melted first object slice wherein some of the melted first object slice is displaced by the part;

cause the first device to form a second layer of powdered build material on the first object slice and covering the part;

cause the second device to dispense a coalescing agent on to powdered build material in the second layer in a pattern corresponding to a second object slice;

cause the third device to dispense a coalescence modifier agent on to powdered build material in the second layer surrounding build material patterned with coalescing agent; and

cause the light source to apply light energy to build material in the second layer patterned with coalescing agent to form the second object slice covering the part.