3D Printing FAQ

 3D Printing, formally known as Additive Manufacturing (AM), is a process of creating three-dimensional objects from a digital file. unlike subtractive manufacturing (CNC) which removes material, 3D printing builds parts layer by layer. This process enables the creation of complex geometries, internal lattices, and organic shapes that are impossible or too costly to produce with traditional machining or injection molding. It is defined by ASTM F2792 standards.

At Boona Prototypes, we categorize our industrial AM services into three primary technologies:

• SLA (Stereolithography): Uses a UV laser to cure liquid resin into hardened plastic. Best for high surface finish and fine details.

• SLS (Selective Laser Sintering): Uses a high-power laser to fuse small particles of polymer powder (typically Nylon). Best for functional parts with complex geometries and no support structures.

• SLM/DMLS (Selective Laser Melting): Uses a high-energy laser to fully melt metal powder (e.g., Aluminum, Titanium) into solid metal parts. Best for aerospace and medical applications requiring high strength.

The choice depends on the application:

• Surface Finish: SLA provides a smooth, injection-mold-like surface (Ra < 1μm), ideal for visual prototypes and master patterns. SLS has a grainy, sandy texture (Ra ~5-10μm).

• Strength & Durability: SLS parts (Nylon PA12) are mechanically stronger and more temperature resistant, suitable for functional testing and snap-fits. SLA resins can be brittle and sensitive to UV light over time.

• Support Structures: SLA requires support structures that must be removed. SLS is self-supporting (supported by unsintered powder), allowing for complex interlocking parts.

We offer a wide range of engineering-grade materials:

• SLA Resins: ABS-like (tough), PC-like (clear/transparent), PP-like (flexible), and High-Temp Resins (heat deflection up to 250°C).

• SLS Powders: Nylon 12 (PA12), Glass-filled Nylon (PA12-GF) for stiffness, and TPU for rubber-like elasticity.

• Metal Powders (SLM): Stainless Steel (316L), Aluminum (AlSi10Mg), Titanium (Ti6Al4V), and Maraging Steel.

Tolerances in additive manufacturing are influenced by material shrinkage and laser spot size.

• SLA: Typically ±0.1 mm (or ±0.15% of the dimension, whichever is greater).

• SLS: Typically ±0.3 mm (or ±0.3% of the dimension).

• Metal (SLM): Typically ±0.1 mm – 0.2 mm.

• Note: For critical features (e.g., bearing bores), we recommend leaving machining stock and finishing with CNC machining (Hybrid Manufacturing) to achieve IT7 precision.

Yes. DMLS/SLM technology produces fully dense metal parts (>99.5% density). The mechanical properties (tensile strength, yield strength) are comparable to, and sometimes exceed, those of cast metal. However, parts may exhibit slight anisotropy (different strength in the Z-axis) compared to wrought or CNC-machined metal, which is isotropic. Post-processing like heat treatment (HIP) is often used to relieve internal stresses.

The industry standard format is STL (Standard Triangle Language) or OBJ.

• Requirement: The file must be a “watertight” mesh (manifold), meaning there are no holes in the surface and all normals point outward.

• Resolution: Export STL files with a chord height/deviation of roughly 0.01mm to 0.05mm. Files that are too coarse will show visible polygons; files that are too fine (hundreds of MBs) may crash slicing software. We also accept STEP/STP files, which we can convert for you.

• SLA (Large Format): Up to 800 x 600 x 400 mm.

• SLS: Up to 350 x 350 x 400 mm.

• Splitting: For parts larger than the build volume, we can section the digital model, print the pieces separately, and bond them together using industrial adhesives. After sanding and painting, the seam is virtually invisible.

Raw 3D printed parts often require finishing:

• Standard: Support removal and sandblasting (to remove powder/residue).

• Aesthetic: Primer painting, color matching (Pantone/RAL), and clear coating (for transparent SLA parts).

• Functional: Vapor Smoothing (for SLS to seal the surface), Thread Inserts (heat staking), and Electroplating.

• Choose 3D Printing when: You need low quantities (1-50 units), the geometry is highly complex (e.g., internal channels), or lead time is critical (24-48 hours).

• Choose CNC Machining when: You need high quantities (>50), specific material properties (true metal/plastic alloys), tight tolerances (<0.05mm), or excellent surface finish without painting.

MJF is HP advanced powder-bed technology. Like SLS, it prints Nylon (PA12), but it uses a fusing agent instead of a laser.

• Advantage: MJF is faster for batch production and produces parts with higher isotropic strength (stronger in the Z-axis) compared to SLS.

• Finish: MJF parts are naturally gray/black with a smoother surface than the sugary texture of SLS.

• Best For: Functional end-use parts and low-volume manufacturing runs (50-500+ units).

Yes. We use industrial FDM printers for large-scale, robust parts. While FDM has visible layer lines (lower aesthetics than SLA), it allows the use of high-performance thermoplastics like ABS, Polycarbonate (PC), and ULTEM 9085 (Flame retardant). It is the standard for printing large automotive jigs, fixtures, and durable housings up to 1 meter in size.

The price is primarily driven by:

1. Material Volume: The amount of resin or powder used (in cm³).

2. Machine Time: Taller parts take longer to print.

3. Orientation: How the part is positioned affects support usage and time.

• Cost-Saving Tip: Hollowing out your part (with escape holes) is the most effective way to reduce material usage and cost by up to 50%.

• Standard: 2-3 business days for plastic parts (SLA/SLS/MJF).

• Rush Service: 24-hour manufacturing is available for urgent prototypes.

• Metal (DMLS): Typically 5-7 business days, as it requires stress relief and wire cutting from the build plate.

• Global Shipping: We use DHL/FedEx Priority, reaching most countries in 2-4 days.

Yes. For quantities between 100 to 1,000 units, 3D printing (specifically MJF or SLS) is often cheaper and faster than Injection Molding because there is no mold cost and zero lead time for tooling. This is ideal for “Bridge Production” (getting to market while waiting for steel molds) or pilot runs.

To ensure structural integrity and prevent warping:

• SLA/Resin: Minimum 0.6mm (0.8mm is safer).

• SLS/MJF (Nylon): Minimum 0.8mm.

• Metal (DMLS): Minimum 1.0mm.

• FDM: Minimum 1.2mm.

• Note: Large flat surfaces need thicker walls (2mm+) or ribs to avoid buckling.

• Generally No. SLS/MJF parts are porous; SLA parts are solid but can absorb moisture over time.

• Solution: For manifolds, bottles, or waterproof enclosures, we recommend Vapor Smoothing (for Nylon) or applying a High-Gloss Clear Coat / Epoxy Sealer (for SLA) to seal the surface completely.

We can print threads (M4 and above), but plastic threads wear out after a few uses.

• Engineering Recommendation: Design a standard hole and request Brass Heat-Set Inserts. We install these into the printed part, providing robust, reusable metal threads perfect for electronic enclosures.

Standard industrial resins and powders are not food safe.

• Option: We offer specific Biocompatible Resins (like Dental SG) or Medical Grade Nylon PA12 that meet ISO 10993 (skin contact) standards. For food contact, a certified food-safe coating must be applied.

• FDM/SLA: Typically Anisotropic. They are weaker in the Z-axis (where layers bond).

• SLS/MJF: Nearly Isotropic. The fusing process creates parts that are almost equally strong in X, Y, and Z directions, making them superior for functional mechanical clips and gears.

• Stiffness: Glass-Filled Nylon (PA12-GF) via SLS/MJF is incredibly stiff and resistant to deformation.

• Thermal/Chemical: PEEK or ULTEM (via FDM) offers aerospace-grade heat resistance and strength comparable to aluminum.

• Impact: Polycarbonate (PC) or High-Impact ABS-like Resin is best for drop tests.

Yes, using SLA Clear Resin (e.g., Somos WaterShed).

• Process: Raw parts look “frosty” or translucent. To achieve optical clarity (glass-like), you must specify “Mirror Polishing & Clear Coat” finishing, where we hand-sand and coat the part. Ideal for lenses, light pipes, and fluid visualization.

Nylon PA12 (SLS/MJF) is the industry standard for fixtures because it is durable, lightweight, and non-marring (won’t scratch the parts it holds). For larger assembly jigs, FDM ABS/ASA is the cost-effective choice.

Vapor Smoothing is a chemical finishing process for SLS/MJF parts. It melts the outer surface on a microscopic level.

• Result: It transforms the rough, sugary surface into a smooth, semi-gloss finish comparable to injection molding. It also seals the surface, reducing bacterial growth and moisture absorption.

Yes.

• Painting: For SLA parts, we mix automotive-grade paints to match any Pantone or RAL code.

• Dyeing: For SLS/MJF Nylon, we use immersion dyeing (usually Black, Red, Blue). Dye penetrates the surface (0.2mm deep), so it won’t chip or peel off like paint.

We use the “Split & Bond” technique.

1. Our engineers cut your large CAD model into sections with interlocking keys/pegs.

2. We print sections separately.

3. We bond them with industrial adhesives and sand the seams.

4. Outcome: A massive part (like a car bumper) that looks and functions as a single unit.

Yes. Beyond printing, we can install helicoils, threaded inserts, and pins. We can also assemble multi-part prints and bond them, delivering a ready-to-use sub-assembly to your door.

Absolutely. We work with strict confidentiality.

• We are happy to sign a Non-Disclosure Agreement (NDA) before you upload files.

• Your data is stored on secure, encrypted servers and is only accessible to the engineers directly working on your project. We do not share designs with third parties.

Yes. Upon request, we provide:

• Material Data Sheets (MDS) & Certificates of Analysis (COA).

• Dimensional Inspection Reports (using CMM or Scanners) to verify critical tolerances.

• Heat Treatment Reports for metal parts.

Please upload your 3D files (STEP, STP, or IGES are preferred for accurate analysis; STL is acceptable) to our [Online Quote Form]. Tell us the material, quantity, and finishing requirements. Our engineers will provide a DFM review and price within 2-8 hours.

This is critical for budget planning.

• 1-50 units: 3D Printing is usually the cheapest (Zero tooling cost).

• 50-200 units: CNC Machining becomes competitive, especially for simple metal parts.

• 200-500 units: Vacuum Casting (Silicone Molding) is the ideal bridge for plastic parts.

• 1,000+ units: Injection Molding wins on unit price.

Yes, for specific applications. High-performance polymers like PEEK and ULTEM 9085 (printed via FDM) offer a high strength-to-weight ratio and excellent heat resistance (up to 250°C). They are lighter than aluminum and electrically insulating, ideal for aerospace ducting and automotive under-hood components.

Consistency is the biggest challenge in AM. We solve it by:

• Locked Parameters: We use the exact same machine settings, orientation, and material batch for every run.

• Powder Refresh Rate: For SLS/MJF, we strictly control the ratio of fresh-to-recycled powder (typically 50/50) to ensure consistent mechanical properties.

Vapor Smoothing (chemical polishing) does more than just make SLS/MJF parts shiny.

• Watertightness: It seals the porous surface of Nylon, making it air-tight and water-resistant (IP67 potential).

• Bacteria Resistance: By smoothing out microscopic peaks and valleys, it prevents bacterial growth, making parts suitable for medical and food-contact device skins.

• Strength: It significantly improves elongation at break (flexibility).

Direct tapping in plastic is weak and wears out quickly.

• The Boona Standard: We install Brass Heat-Set Inserts into thermoplastic prints (FDM/SLS/MJF). The melted plastic reflows around the insert’s knurls, providing high pull-out resistance.

• For SLA (Resin): Since resin doesn’t melt (it burns), we use specialized glue-in inserts or Helicoils.

Yes. We can plate SLA and FDM parts with Copper, Nickel, or Chrome.

• Structural Plating: Adds a metal shell (0.1mm+) that increases stiffness.

• EMI/RFI Shielding: Essential for electronic enclosures to block electromagnetic interference.

• Cosmetic: Creates a “cool-to-touch” real metal feel.

Hollowing is the #1 way to reduce cost for resin printing.

• Cost: Resin is expensive. Hollowing removes 60-80% of the material volume.

• Quality: Solid resin blocks generate high heat during curing, which can cause warping.

• Rule: Keep wall thickness at least 2-3mm and always add “Escape Holes” for the uncured resin to drain out.

Stair-stepping is the visible layer lines on curved surfaces.

• Solution 1 (Orientation): We orient the part so critical curved surfaces are printed vertically or at 45 degrees.

• Solution 2 (Resolution): Request “High Resolution” mode (e.g., 0.05mm layer height) for finer steps.

• Solution 3: Choose SLA over FDM for the smoothest natural curves.

Yes. We offer flexible materials:

• SLA Flexible Resin: (Shore 50A-90A) Great for visual prototypes.

• SLS/MJF TPU: (Shore 88A) Highly durable, functional rubber. Good for custom gaskets and bellows.

• Production Note: For batches >100, Vacuum Casting is often more cost-effective.

It depends on the technology.

• Standard SLA Resins: NOT recommended. They will yellow and become brittle under sunlight (UV).

• ASA (FDM) & Nylon (SLS/MJF): Highly recommended. ASA is UV-stable. Nylon PA12 is durable but should be painted black for long-term outdoor exposure.

It depends on the material technology:

• Nylon (PA12): We recycle up to 50-70% of the unsintered powder from previous print jobs, minimizing waste.

• FDM Thermoplastics: Materials like PLA are biodegradable; ABS/PETG are recyclable.

• Resin (SLA): Cured resin is generally non-recyclable thermoset plastic and should be disposed of according to local regulations.