DESIGN FOR ADDITIVE MANUFACTURING

PARTICULARITIES TO BE CONSIDERED WHEN PREPARING PARTS FOR BEING PRINTED ON AN ULTIMAKER FDM PRINTER

Greta D’AngeloMartí BertranThomas J. Howard

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AGENDA

1. Introduction on FDM and AM

2. Geometrical constraints

3. Support structures

• Avoiding support structures• Working with support structures

4. Hollowed parts and infill

5. Printing text

6. Designing mechanisms

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FUSED DEPOSITION MODELLING

• Additive Manufacturing (AM) technologies build parts by overlapping layers of material

• Extrusion of melted material through a nozzle on a build plate

• Cartesian coordinates

• Tolerance (in vertical direction) is determined by the diameter of the nozzle

• Examples: Stratasys, RepRap, Ultimaker

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1 2 3

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WORKFLOW

Design a part • CAD program

Export to STL• All packages can do

it

Check STL• Netfabb

Slice and generate Gcode• Cura

Upload Gcode to printer• SD card

Start printing!• Ultimaker’s

controller

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MATERIAL PROPERTIES

• Ultimaker uses 3mm PLA filament

• Biodegradable thermoplastic

• Highly anisotropic mechanical properties

• Several colors available

PLA Polymer

Physical property  Specific Gravity [g/cm3] 1,25

Melt Index [g/10min] (190º/2,16kg)

4 - 8

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GEOMETRICAL CONSTRAINTS

Minimum Wall thickness:

• Vertical and tilted walls:

• 2mm and above. Recommended• Horizontal walls:

• 1mm and above is correct

Definition 0,5mm minimum details noticed

Accuracy 0,3% (min +/-0,3mm)

Avoid warping Large horizontal and thick surfaces are likely to warp, skip using them if you can.

Overall maximum dimensions 150*150*150 mm (x*y*z)

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FACING GEOMETRICAL CONSTRAINTS

• Scale parts

• After scaling check that your part meets the geometrical constraints

• Notice that wall thicknesses will be scaled down as well, and may not meet the requirements

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SUPPORT STRUCTURES

• Support structures are features added below part areas where there’s nothing

• They prevent layers to collapse during it’s build up and allow part manufacturability

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AVOIDING SUPPORT STRUCTURES: PART ORIENTATION

• Part orientation is a key factor to achieve a good print

• In many cases we can avoid or at least reduce the amount of supports required

• Resolution is better in the z-axis faces (vertical) than XY (horizontal) stepping

• Mechanical properties are better in the XY plane

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PART ORIENTATION

Staircase effect

Smooth surfaces

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AVOIDING SUPPORT STRUCTURES: SPLITTING PARTS

• Splitting parts is a good way to avoid using supports

• Can be done after exporting the CAD to STL by using Netfabb

• To use in extreme causes because:

• We’ll have to glue all the parts after the print

• Tolerances will not be the same

• We’ll see partition lines in our part

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AVOIDING SUPPORT STRUCTURES: MODIFY OVERHANGING SURFACE

• The printer is able to print overhanging surfaces without support structures from a minimum angle α (>30º)

• We must do the modifications before exporting the STL file

• Small projections from the walls (<1mm) can be printed without problems

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AVOIDING SUPPORT STRUCTURES: MODIFY OVERHANGING SURFACE

• Cura Software shows which surfaces needs support structures (<30º)

Support structures required here

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AVOIDING SUPPORT STRUCTURES: BRIDGES

• The printer is able to print flat surfaces without supports between two walls

• Max distance between walls: 20mm

Bridge

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AVOIDING SUPPORT STRUCTURES: BRIDGES

Bridge

Small holes doesn’t require changes

Modified hole

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WORKING WITH SUPPORT STRUCTURES

• Accessibility: We must be able to remove SS easily

• Scaring: Avoid using them in part characteristic surfaces SS can damage the finishing of these surfaces and also the tolerances

• Avoid using SS below thin walls or slender and fragile parts, they can break easily while removing them

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HOLLOWED PARTS AND INFILL

• Hollow can be achieved when gcode is generated, by changing parameters of Cura

• We can also choose how much infill (%) we want inside the part, by default we use between 30% and 40%

• Design Tip: design always solid parts

Infill

Perimeters

Gcode Cura View

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HOLLOWED PARTS AND INFILL

By reducing the infill:

• Build time decreases

• Used material decreases

• It helps to avoid warping

• Strength doesn’t decreases that much

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PRINTING TEXT

• Text in vertical faces will be more visible and accurate

• If it’s not possible, the text at the bottom of the part (the face that sticks to the building platform), must be engraved.

• In the top face of the part, text can be either engraved/embossed

• It should be at least 0,8mm high and 0,8mm wide to be visible.

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PRINTING TEXT

Horizontal engraved text

Vertical embossed text

Vertical engraved text

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DESIGNING MECHANISMS

Joints clearance:

• Design adjustments with a gap of more than 0,3mm between mobile parts

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DESIGNING MECHANISMS

Part orientation

• Try to print the areas of parts that has to fit each other in the same orientation (different orientations could have different deviations/tolerances)

Integrated nut holders embossed is better than engraved!

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QUESTIONS?