The Multi-Stage Polishing and Grinding Process
UNIK's precision grinding process is implemented in multiple stages following initial CNC milling, each designed to progressively refine the cavity surface to exacting tolerances.
The process follows a systematic sequence:
Rough grinding: Removes initial machining marks left by the milling process and establishes the baseline geometry.
Fine polishing: Utilises high-speed tools to achieve a uniform surface finish across all cavities.
Mirror finishing: Delivers a near-mirror surface with roughness values of Ra ≤ 0.4μm or better, preventing micro-adhesion and air entrapment.
Rust-proof coating: Applies a protective layer to safeguard the finished surface.
This staged approach ensures progressive refinement rather than aggressive material removal that could compromise dimensional accuracy.
How Grinding Ensures Cavity-to-Cavity Consistency
The precision grinding process directly addresses the three critical factors that determine block dimensional consistency:
1. Eliminating Dimensional Variation
Without precision grinding, conventional moulds-particularly cast or fabricated versions-can develop dimensional drift between cavities, with variations exceeding ±0.5mm. In a multi-cavity mould, this means blocks from different cavities may not stack or interlock properly.
UNIK's grinding process maintains each cavity to a single-cavity dimensional tolerance of ±0.1mm, verified using a large-scale Coordinate Measuring Machine (CMM) that can measure down to ±0.01mm. This ensures that a block produced in cavity one is effectively indistinguishable from a block produced in cavity four.
2. Maintaining Uniform Wall Thickness in Hollow Blocks
For hollow block production, precision grinding is especially critical. The core pins that form hollow cavities must be precisely positioned relative to the cavity walls. In UNIK moulds, core pin positions are machined in the same CNC setup as the cavity itself, with alignment maintained to ±0.05mm.
After precision grinding, this alignment is preserved across all cavities. The result is consistent wall thickness across every hollow block produced-typically within 0.1mm variation, which directly improves compressive strength and reduces material waste.
3. Achieving Superior Surface Finish
A polished cavity surface is essential for consistent demoulding. When surface roughness is uneven, concrete can adhere to rougher sections, causing sticking and uneven release. This can deform the block edges or mark the surface during ejection.
UNIK's grinding process achieves a surface finish of Ra 1.6 or better, with some applications reaching Ra 0.8μm or even Ra 0.4μm. This mirror-level finish not only ensures clean, effortless demoulding but also contributes to a uniform gloss and colour across all blocks.
Quality Verification: The Final Assurance
Precision grinding is only half the equation. UNIK verifies the results through a rigorous multi-stage quality control process:
In-process dimensional checks: Digital callipers and bore gauges verify critical dimensions after each major machining step.
CMM verification: The Coordinate Measuring Machine scans up to 25 dimensional points per cavity, including core pin alignment and cavity wall parallelism.
Final inspection: Hardness testing confirms surface hardness of HRC 58–62, cavity height tolerance of ±0.5mm, presser foot clearance of 0.2–0.4mm, and overall board flatness of ≤0.5mm.
Test block production: Upon request, a test block is produced to verify real-world dimensional accuracy.
Practical Benefits for Block Producers
For manufacturers, the consistent dimensions achieved through precision grinding translate directly to operational advantages:
Reduced reject rates: Dimensionally consistent blocks mean fewer rejects due to size variation, reducing waste and rework costs. Many UNIK clients report fewer rejects after switching to CNC-polished moulds.
Faster installation: Consistently sized blocks lay flat with uniform joints, significantly accelerating on-site construction speed.
Lower mortar usage: Uniform block dimensions mean thinner, more consistent mortar joints-reducing material consumption and improving structural integrity.
Extended mould life: The combination of precision grinding and heat treatment extends mould lifespan to 80,000–100,000 cycles, maintaining dimensional accuracy throughout.
Conclusion
Precision grinding is not merely a finishing step in mould manufacturing-it is the engineering discipline that transforms a collection of machined cavities into a consistent, reliable, high-performing production tool. By combining CNC-machined solid steel, multi-stage polishing, and CMM-verified quality control, UNIK ensures that every cavity in a multi-cavity mould delivers identical blocks-run after run, shift after shift.
About Fujian Unik Mould Technology Co., Ltd.
Founded in 2010 and headquartered in Quanzhou, Fujian Province, UNIK specialises in the design and manufacture of high-quality brick machines and precision concrete moulds. The company's ISO 9001:2015, CE, and SGS certifications underscore its commitment to international quality standards. UNIK exports to 28 countries across Southeast Asia, the Middle East, Africa, and beyond.
For more information:
Website: www.unikmould.com
Location: Quanzhou, Fujian Province, China