MJF Design Guideline

Introduction

MJF is one of the most accurate 3D printing technologies for high detail parts production. It can offer full colors and multi-materials with smooth surface finish. This is widely used for realistic prototypes and models, but not used for functional applications in reason of brittle properties.

MJF Process

MJF process are little similar to a ink-jet printer. However, it print thousands of layers to build a solid part. The photo-polymer materials are dispensed to a specific area via the tiny jets. Then the print head with a UV light system will solidify these photo-polymer materials. Once a layer is deposited and cured, the build platform will move down in one layer thickness, and repeat this process.

MJF need support structure in printing process, these support can be removed in post processing. MJF has 2 main advantages than other 3D printing technologies, its process is near homogeneous, and MJF parts are very smooth similar to injection molded parts.

MJF operation has a rapid and line wise process, which encourage it can produce multiple parts in one single line without build speed affection. With correct orientation and optimal placement, MJF can produce parts at higher rate than other 3D printing technology.

MJF Design

We summarize several design guidelines in MJF process.

Print Features

FeaturesDescription
Major support wallMinimum wall thickness is 1mm
Other wallMinimum wall thickness is more than 0.5mm
Pin diameterMinimum pin diameter is 0.5mm
Hole sizeMinimum hole diameter is more than 0.5mm,Orientation should be vertical.
Embossed & engraved detailsMinimum depth of engraving is 0.5mmMinimum height of embossing is 0.5mm
Feature sizeParts details are no lower than 0.25mm
Moving partsHinges and joints should have 0.15-0.2mm clearance in all sides.
TolerancesNormally tolerance in range of ±0.1-0.3mm, depend on different geometry and materials.

Common Design Applications

MJF common design apparitions as following:

ApplicationDescription
Full color modelsHigh accuracy, smooth surface finish and various color options, most popular choice ofr form models or prototypes
Injection mold prototypesExcellent choice for injection molding parts prototypes
EnclosuresCustom enclosures with large range materials and colors
FEA modelsMulti-color in MJF is fit for physical FEA models, MJF can create visible FEA color pattern on samples.

Glossy vs Matte

MJF can produce parts with different surface finishes: glossy or matte. The matte setting will add thin layer of support material on the entire part surface. The glossy setting will add support material only on area with requirement like overhangs, drafts, cavities.

Glossy: The glossy setting can increase strength on thin walls, reduce printing materials usage and crease a smooth and aesthetic surface finish. However, it will also create nonuniform finish and round sharp edges and corners on top surfaces.

Matte: The matte setting will create a uniform finish on whole parts, as well as high accuracy. However, this will also need additional material, additional cleaning time. It will also create a softer surface, which leads to weakness in small and thin features.

Disolvable Support

MJF can print parts in 2 different materials, one for main build material and another for dissolavable support. This means support structure will be removed away easily by desolation way, with correct way, this can result in a surface without any indication shows. This technology has more flexible orientation than other 3D printing technologies, and offer greater design freedom. It can produce very complex and intricate parts with easy posting process.

Multi-Color Printing

MJF is the only 3D printing to produce full, multi-color parts with a full suite of color options. All this can be set in printing setup process. Texture layers such as patter prints and finishes also can be add to parts surface in design process, MJF can provide various surface like brush stokes, wood grain, gradient color.

Multi-Material Printing

MJF has the largest advantage of multiple material print capability. MJF printers can print both rubber and rigid parts on the same tray, in the same part or in the blend, in order to create new material properties in requirement.

MJF Materials

MJF has an extensive kinds of materials, all these materials are photopolymers. We normally divided these materials by application.

MaterialDescriptionApplication
Standard rigidRigid and opaque materials with different color.Polyethylene mimic with brittle property.Vero, VeroBlue,Visijet CRHigh detail prototype without function, very smooth surface finish.
TransparentSimilar properties to standard grid, while can be post processed to 100% transparent.VeroClear, Visijet CRClear prototypes and models.
ABS-likeDigital blend materials with higher temperature and strength, good flexibility.Minimum thickness of 0.85mm.Digital ABSSimulate ABS parts, but more brittle than FDM parts.
Polypropylene-likePloypropylene mimics, excellent for flex and snap feature.RigurSimulate PP parts, but more brittle than injection molded parts.
FlexibleRubber mimics, custom durometer form very flexible to fully rigid.TangoExcellent for testing and design in gasket seals, overmolds, button.
High TemperatureHigh temperature materials as ABS, require thermal post processing to achieve maximum thermal resistanceRGD525Application up to 90℃.
CastableHigh accurate materials with fine details, near 100% burnoutVisiJet M3 ProcastDental, jewelry and custom casting.
Bio-compatibleSpecific materials for sterilization and short term bio-compatibility.MED610Dental & Medical

Process Limitations

Mechanical Properties

MJF parts are less strong than other technologies, the brittle nature of MJF materials is an issue for functional testing. The low resistance temperature is an issue for most testing and functional applications. The lack of elongation in rubber-like materials will lead to issues in application testing. The lack of temperature resistance and strength will limit functional testing and real applications.

Cost

MJF is the most expensive 3D printing method, in reason of the high materials cost. MJF support as a solid mass give rise to a large amount of waste. MJF build materials are very expensive than other 3D printing technologies.

Post Processing

The most common post processing methods for MJF:

Support removal

Sanding

Polishing

Dying

Metal plating