3D Printing Guidelines for Each Process - GKN Additive (Forecast 3D)

The following are our 3D printing guidelines for process specific dimensional variation and manufacturing capabilities. If your project has unique requirements, we will work with you to ensure that goals are met within the limitations of our technologies' and capabilities of our processes and craftsmen. Any drawings, prints, tolerances, or other requirements must be presented in writing at time of quotation.

SLA & SLS Patterns:

General guidelines for SL Pattern creation:

SL Pattern standard dimensional variation is typically within .005" for the first inch and .003" per inch thereafter
Line width for embossed graphics should be at least .016" wide by .016" tall
Line width for recessed graphics should be at least .012" wide by .012" deep
Features in a vertical build plane should be at least .020" wide
Features in a horizontal build plane should be at least .010" wide
Overall wall thickness for of a part should be at least .030"
Wall thickness for tongue and groove applications should be at least .020"
Gear teeth, blade edges or similar geometry should be thickened at the ends to .010"; the laser will stop building geometry small than the beam's width of .0099"
Hollow walls or sections in CAD data will be filled with liquid and supports / powder for SLS patterns
Please note that walls thinner than 0.040" and features smaller than 0.035" may not fully resolve in the LS process. Due to the thermal nature of the LS process, surfaces may experience overgrowth of 0.003-0.005" per surface. Diameters may experience overgrowth of approx. 0.020" These process specific tolerances should be accounted for in mating parts

Hi-Resolution SLA Patterns:

SL Pattern standard dimensional variation is typically within +/-.005" for the first inch and +/-.002" for every inch thereafter
Line width for embossed graphics should be at least .010" wide by .010" tall
Line width for recessed graphics should be at least .008" wide by .008" deep
Features in a vertical build plane should be at least .015" wide
Features in a horizontal build plane should be at least .010" wide
Overall wall thickness for of a part should be at least .020"
Wall thickness for tongue and groove applications should be at least .015"
Hollow walls or sections will fill with liquid and supports if represented in CAD data
Gear teeth, blade edges or similar geometry should be thickened at the ends to .008"; the laser will stop building geometry small than the beam's width of .0079"

PolyJET Patterns:

PolyJET patterns standard dimensional variation is typically within +/- .005” first inch and +/- .001” for every inch thereafter
Layer Resolution: High Quality: 16 Microns, Normal: 30 Microns (single material only), Digital Mode: 30 Microns (multiple materials)
Standard Surface Finishes: PolyJet can be print in two distinct surface finishes; Glossy and Matte. Glossy: Builds without support on upwards facing surfaces. Any overhanging and downward facing surface(s) will have support underneath. Matte: Builds a layer of support surrounding the entire part
Maximum single part size if built in Glossy: 19.3 x 15.4 x 7.9 inches
All PolyJet parts are printed with a solid support structure that is removable. Any hollow walls or sections will be filled with support material if not addressed early
Parts cannot have “overlapping” CAD data shells
VeroClear: This material is not printed “clear” directly off of the machine. The green state of this material is translucent. Optically clear surfaces can be achieved by hand finishing; post-printing. Small features and/or geometry may not be able to be finished and become optically clear. Recommended printing mode is Normal with a Matte finish as this aids in preventing yellowing from excess UV exposure
Guaranteed Minimum Resolution for Wall Thicknesses: Rigid materials: .020" Flexible Materials: .030" Digital ABS: .040"
Actual wall thickness that can be achieved may be thinner or thicker than the “printed minimum” thicknesses. All parts are geometry dependent and may be fragile in finishing / post-processing

FDM Patterns:

GKN Additive (Forecast 3D) uses only FORTUS FDM machines for model creation.The Fortus line of Stratasys FDM machines produce parts with far better tolerances and properties compared to the older Stratasys product lines. We can therefore prescribe the following dimensional guidelines:

Fortus FDM standard dimensional variation is typically within: +/- a single build layer thickness for the first inch and +/- .002” for every inch thereafter
Layer Resolution:0.005” (all ABS blends and PC) small frame Fortus equipment only, 0.007” (all ABS and PC blends; Nylon 12), 0.010” (all materials), 0.013” (all materials except PPSF), 0.020” (ASA and ULTEM 1010 only) large frame Fortus equipment only
Sparse Mode: Large parts can be printed in sparse mode which is a honeycomb like structure. This saves material and print time without being detrimental to the strength of the part
Maximum single part size must fit in a 36 x 24 x 36 inch volumetric cube. Parts can be made in multiple pieces and can be solvent bonded for thermoplastics that are conducive to solvents
Support material is water soluble with the exception of ULTEM and PPSF. Any hollow walls or sections will be filled with support material if not addressed early
Standard Surface Finish – Plastic with visible layer lines. Parts can be sanded and smoothed to remove layer lines depending on the geometry
Minimum Wall Thicknesses: ABS, ASA & PC blends as well as Nylon 12 is .030", ULTEM is .040”, ASA and ULTEM 1010 are .060” when utilizing .020” build resolution
Actual wall thickness that can be achieved may be thinner or thicker than the “printed minimum” thicknesses. All parts are geometry dependent and may be fragile in finishing / post-processing

MJF Patterns:

Dimensional Accuracy of +/-.012 up to 3.937 inches and +/-.003 for every inch above that value
Minimum hole Diameter .021” [.5mm]
Minimum shaft diameter .021” [.5mm]
Minimum clearance between features .021” [.5mm]
Minimum slit between walls .021” [.5mm]
It is recommended for any text or numbering to have at least .039” [1mm] of depth or height
The minimum gap that is recommended in a lattice structure to ensure that all material can be removed is .039” [1mm]
The minimum wall thickness on the XY plane is .012” [.3mm] and for the Z plane .020” [.5mm]
It is recommended if you have mating parts to have gaps of at least .024” [.6mm] +/- .012” [.3mm] between the interface areas that should fit together, in order to ensure correct assembly
Minimum spacing on assembly parts that are printed together should have a minimum clearance between parts of .020” [.5mm]

DMLS / SLM Patterns:

.005" for the first inch, with an additional .002" per inch thereafter
Specific tolerances per geometries can be held with specific orientation and post machining as considerations when planning build. For discussion with your Project Engineer during quote process
Minimum Feature Size is 150 microns
Features that are tall and thin are best oriented in the Z (build) axis, especially when self-supporting
Threads can be modeled in part and build best in a vertical orientation. All standard threads will be chased by a tap or die prior to shipping
Leave a minimum distance of .010” between part features
Angles > than 30 degrees result in self-supporting geometry
Utilize filets and chamfers in corners and features
Implement features to reduce volume
Critical tolerances can be achieved through in house post machining
Post processed finishing standards are the same as billet machined parts, including heat treatment, HIP treatment, electro polishing, and extrude honing, among others

CNC Patterns:

Sharp internal corners may not be machinable and minimum corner radius relief could be required. Actual radius will be governed by depth of cut
Tolerances tighter than +/-0.005”, bi-lateral profile 0.015”, and true-position 0.014” dia., will be attempted on a best effort basis. Results will vary based on geometry-specific conditions and are not guaranteed

ProCast/Hybrid RTV:

Standard for Hybrid and ProCAST RTV parts is typically within:

ProCAST RTV	Hybrid RTV
+/- .007" first inch plus .003" per inch thereafter.....	+/- .007" first inch plus .002" per inch thereafter.....

Production mold tuning, machined inserts and secondary machining may be used to achieve much tighter tolerances in many cases. Please ask your Project Manager for more details
Bosses requiring threaded inserts should allow for minimum .040" outside the insert, consult manufacturer's website. We stock PEM and Dodge inserts
Overmolding or co-molding should be discussed at the onset of a project for an understanding of the additional requirements
Polished surfaces and geometry requiring machined mold inserts require extra time and cost if not quoted as such
Dimensions intersecting the parting line may see an additional +/- .015" of dimensional variation
Parts with wall thicknesses under .040" or over .187" may exceed standard tolerances due to warping and excessive shrinkage respectively
Foreign resins or resins with a high shrink rate may also interfere with standard tolerances

When using our Additive and Short-run manufacturing technologies, customers often supply drawings with tolerances and notes intended for typical, high volume manufacturing methodologies; these are used by us in a ‘for reference only’ capacity. Customer must request specific tolerance requirements in writing - receipt of drawings is not to be construed as acceptance. Please note that secondary machining can be used to achieve tighter tolerances than Additive and RTV based manufacturing methods typically allow.

Inspection Levels

Parts that are manufactured through any of our Additive Manufacturing, secondary services or CNC departments all go through one of our Quality Assurance inspection plans. Here are the details of each plan:

Standard Inspection Plan- Prototype

Part is visually inspected for missing features, warp, material, and finish specified
Dimensional inspections per part are not performed
Drawings/prints used for feature reference only, customer-supplied CAD file is the primary reference, if conflicting
All deviations of significance are reported to the appropriate internal department for purposes of continuous improvement
Any deviations believed to impact customer specifications will be sent to customer for review and buy-off

Customer Specified Inspection Plan

This inspection process is driven primarily by customer needs. All inspections points and tolerances required must be presented before final quotation
Part is visually inspected to CAD data / engineering prints / supplied master pattern with any non-conformities recorded
If requested, Forecast inspects dimensions specified by client via drawing or email to mutually agreed upon tolerances
If requested, Forecast inspects parts using fit check parts, go/no go gauges, pressure testing devices or other clients specified procedures
If requested, Part is measured in X,Y and Z extents (or where appropriate) and dimensions are held to a mutually agreed upon general tolerance
Color will be checked if color matching is required
Any out of spec parts will be rejected internally or communicated to customer for review through MRB and potential customer buy off

Visual Inspection Plan

Part is visually inspected to CAD data / Engineering prints / supplied Master pattern with any non-conformities recorded
No dimensional inspections are performed
Drawings are not referenced, not supplied
Color will be checked if color match performed
Any deviations believed to impact customer satisfaction will be sent to customer for review and customer buy-off

AS 9102 Inspection Plan

Project inspected to AS 9102 standards

*last updated August 18, 2021

STANDARD GUIDELINES