A raw stone block can weigh over ten tonnes and sits outdoors in stacks; slabs stand side by side on edge. Counting stock on paper or with barcodes often means climbing over blocks and pulling slabs out one by one. This article covers how we actually applied RFID in stone plants while building a "stone digital-inventory pilot system" with the Stone & Resource Industry R&D Center (SRDC) in 2023.
Eastern Taiwan (Hualien and Taitung) has around 193 stone companies with annual output of nearly NT$9 billion — the country's most important stone-industry cluster. But stone inventory has problems most industries don't:
Counting blocks and slabs requires reading tags from at least 4 meters away, so staff don't have to walk up to every stone. We therefore chose longer-range UHF RFID tags with a handheld reader: a smartphone plus a tag read/write controller and cradle connected over Bluetooth, with an app on the phone connecting back to the system over Wi-Fi or mobile data.
Blocks can't be drilled and their surfaces are rough. We fixed plastic suction cups to the stone with steel-reinforced putty (a paste that cures hard and resists heat, acids, alkalis and water pressure), then tied the tag to the cup with a thin cable tie. The method passed three practical checks: it holds tightly, it lasts, and on-site staff can do it quickly.
The block tags were developed with help from an RFID tag designer: a plastic-sealed outer casing to withstand wind, sun and rain; a thin metal sheet (such as aluminum foil) on the back to extend the reading range; and the block's barcode on the front. Each block gets two tags with the same barcode, so if one falls off or is damaged, the other serves as backup.
The slab edge tag must be narrower than 2 cm, and the edge is also covered in stone powder and tiny pores. We first apply white glue to the edge to bind the powder and pores, then stick on the tag sandwiched between two plastic sheets. The sheets protect the tag and improve water resistance, and the tag isn't damaged when peeled off. Each slab gets one RFID tag and one barcode, backing each other up.
Blocks become slabs, and slabs become finished products — the items keep changing. Throwing a tag away after one use would get expensive. So we deliberately don't use the tag chip's own ID (TID) as the identifier; the barcode number is the primary ID, written both into the RFID tag and printed on a label.
SRDC coordinated an industry-wide barcode format for stone:
Before the next processing step, the tag is removed, its barcode is read and checked against the inventory record online, and once they match, the barcode data in the tag is cleared and the barcode label removed or painted over — the tag is then ready for reuse. Because the identifier follows the barcode, reusing a tag never duplicates inventory or transaction records.
To locate an item, choose it first; as the reader picks up tag responses, the app estimates distance from the signal strength (signal-to-noise ratio) and guides you with sound volume: the closer you get, the louder it gets. Once found, you can open its digital record and pattern photo the same way.
Field validation showed the pilot system could count and locate both blocks and slabs quickly and accurately.
The system has two parts: web-based data management (organization, member, raw block and slab management) and handheld RFID field operations (counting, locating and intake for blocks and slabs). The web side was built on .NET Core with a MySQL database on IIS; the field side is an Android app connected over the plant's Wi-Fi. The system can also import stone-pattern photos from a company's existing NAS.
After the pilot, we brought RFID into the ERP's storage-location management: 2D/3D site maps combined with ERP location data give dual positioning — "ERP location + handheld sensing". Stock counts update the latest locations at the same time, and RFID automatically detects slabs entering and leaving the warehouse. These features became part of our stone-industry ERP; see our Industry ERP service page.
A few things we learned from this project:
If your plant has trouble counting stock or finding material — stone industry or not — we'd be glad to hear about your situation.