A USA-based product brand needed to evaluate several functional components before committing to volume production. The parts had different assembly structures, surface requirements, threaded areas, press-fit features, and branding details. Instead of moving directly into a large order, the customer decided to compare materials, printing processes, and finishing methods through several rounds of prototype testing.
This project demonstrates why rapid prototyping is not simply about producing a physical model. For functional products, the prototype must also help the customer evaluate fit, strength, surface appearance, assembly methods, and manufacturing cost.
Project Requirements
The customer initially provided several 3D files for functional plastic components. The parts included product covers, capsule-shaped housings, plugs, and smaller connecting components.
The main requirements included:
- Functional nylon materials
- Good mechanical strength
- Accurate assembly dimensions
- Separate printing of multiple components
- Smooth visible surfaces
- Threaded or press-fit assembly features
- Logo application on curved surfaces
- Prototype testing before volume production
The customer wanted to compare MJF and SLS printing technologies as well as PA12 and glass-fiber-reinforced nylon. This allowed the engineering team to evaluate which combination provided the most suitable balance of surface quality, stiffness, strength, and cost.
Comparing MJF and SLS Prototype Options
During the first stage, the customer requested samples in several process and material combinations:
- MJF PA12
- MJF PA-GF
- SLS PA12
- SLS PA-GF
MJF parts normally provide a relatively consistent surface and stable mechanical performance. SLS parts are also suitable for strong functional prototypes, although the untreated surface may feel more textured.
PA12 is widely used for functional components because it offers a practical balance of toughness, flexibility, dimensional stability, and cost. PA-GF contains glass-fiber reinforcement and is more suitable when additional stiffness is required.
Producing samples in different materials gave the customer an opportunity to perform real assembly and durability tests rather than selecting a process based only on technical data.
Correcting Parts That Printed as One Assembly
One of the first issues identified during prototype testing involved a four-part component. Some sample pieces had fused together during printing, making it impossible for the customer to test the intended assembly.
After receiving the feedback, the production method was reviewed. The customer confirmed that the smaller elements should be printed as separate parts rather than as one integrated assembly.
Separating the components improved several aspects of the project:
- Each part could be inspected individually.
- Assembly clearance could be tested more accurately.
- Surface finishing became easier to control.
- Damaged parts could be replaced independently.
- The customer could evaluate the real installation process.
This type of feedback is especially important during prototype production. A part may look correct in a 3D file but still require a different manufacturing arrangement to achieve the intended function.
Reviewing Threaded Inserts and Edge Distance
Another technical issue involved an M3 threaded insert located close to the edge of a small nylon component. The distance between the hole and the outer edge was only approximately 1.1 mm.
Installing a metal insert in such a limited area could cause the surrounding nylon to crack. There was also insufficient material around another feature to securely install an M5 insert.
Instead of installing the inserts without reviewing the risk, the engineering team explained the limitation and requested confirmation from the customer. After testing the samples, the customer decided that the M3 screw could thread directly into the plastic. The M5 connection would use the existing hexagonal recess and a separate nut.
This adjustment removed an unnecessary secondary operation while reducing the possibility of cracking during insert installation.
It also shows the value of an engineering review before production. Following the original drawing without discussing manufacturing risks could have resulted in damaged parts and additional replacement costs.
Improving Visible Surface Quality
The customer also reported that one of the initial SLS samples had visible layer lines. Because the component was an external consumer-facing part, its appearance was important.
Several finishing options were evaluated:
- Vapor smoothing
- Manual sanding
- Spray painting
- Clear coating
- Nylon laminated coating
- Printing without additional finishing
Different finishes were selected for different products.
One housing required sanding, painting, a printed logo, and a protective clear coat. Another cover used a nylon laminated coating to produce a smoother appearance. A smaller plug component used standard vapor smoothing without the more expensive painting operations.
Selecting the finishing process separately for each part prevented the project from becoming unnecessarily expensive. Components that required a premium visible surface received additional finishing, while less visible parts used simpler treatments.
Selecting the Right Logo Process
Applying a logo to a curved surface created another manufacturing challenge. Screen printing was considered, but the curved geometry made it difficult to maintain consistent positioning and appearance.
Pad printing was selected as a more appropriate method for the curved component.
The original estimated logo size was approximately 80 mm by 19 mm. However, this size did not maintain the logo’s correct proportions. The manufacturing team recommended changing the height to approximately 16.5 mm while keeping the width at 80 mm.
The customer approved the adjustment because maintaining the correct logo proportions was more important than following the initial estimated height.
This review prevented a distorted logo from being applied to the completed parts.
Adjusting a Press-Fit Connection
During a later production review, the team identified a dimensional issue involving a cylindrical press-fit component.
The mating bore measured approximately 4.3 mm, while the standard cylindrical part measured approximately 3.9 to 4.0 mm. This difference would not create the tight fit required by the customer. The component could become loose or fall out during use.
The proposed solution was to manufacture the cylindrical part separately and increase its diameter to approximately 4.2 mm. This provided a closer interference fit while still allowing the customer to push the part into position by hand.
The customer confirmed that the diameter could be changed.
This adjustment was made before final production, avoiding a functional assembly problem that might otherwise have been discovered after delivery.
Moving from Samples to Batch Production
After several rounds of testing, surface evaluation, and drawing confirmation, the customer approved the prototypes and moved forward with a production order.
The order included:
- 250 PA12 capsule components with clear coating and logo finishing
- Four sizes of finished cover components
- 200 plug components with vapor smoothing
- Separately produced connecting parts
- Multiple surface treatments based on product function
The quoted production lead time was approximately 25 to 30 working days, depending on the final order quantity and production schedule.
Moving through prototype testing first allowed both sides to confirm material performance, finishing standards, assembly structure, logo appearance, and critical dimensions before producing larger quantities.
Combining Prototype Development with Metal Manufacturing
Many product-development projects contain more than one manufacturing process. A finished product may include printed nylon components together with metal brackets, internal frames, panels, mounting plates, or external enclosures.
For these projects, working with a supplier that can provide both prototype engineering support and sheet metal fabrication services can simplify communication between plastic and metal components.
Engineers can review mounting positions, fastener clearances, press-fit dimensions, enclosure space, and assembly sequences as part of the complete product rather than treating each component independently.
Twenty Years of Manufacturing Experience
Hofeng has approximately twenty years of manufacturing experience and supports overseas customers with prototypes, small production runs, and repeat orders.
Our engineering team can review customer drawings and provide DFM recommendations related to:
- Material selection
- Wall thickness
- Hole size and edge distance
- Assembly clearance
- Threaded inserts
- Press-fit dimensions
- Surface finishing
- Logo application
- Production cost
- Batch manufacturing stability
In this USA customer project, early technical communication helped identify several potential issues before volume production. These included fused components, insufficient material around threaded inserts, visible layer lines, unsuitable logo proportions, and an incorrect press-fit diameter.
Addressing these details during the prototype stage reduced production risk and gave the customer greater confidence when placing the larger order.
If you are developing functional components, equipment covers, brackets, chassis parts, or complete product assemblies, send us your CAD files for a free quotation and engineering review. Our team can support rapid prototype development, low-volume manufacturing, and professional sheet metal fabrication services for international projects.
Contact us : mia@hofengfab.com