An interior fit-out contractor in Kobe, Japan is working on architectural metalwork with 3 m flat oval stainless tube, 60 x 20 mm, and the buyer's own inspector is rejecting the brightness under raking light rather than by roughness number. SurfacePolish supplies finishing machines, media and compounds across borders and runs a free sample trial on cut sections shipped to Xiamen. This brief is written for a buyer in Kobe working on architectural metalwork; it describes equipment, media and a scoped sample review, not a local polishing service.
Will the finish be judged by a roughness number, by a physical reference panel, or by both, and who views the parts before they are accepted?
Which faces of each profile are actually seen when installed, from what distance and under what light, and which faces can be finished to a coarser standard without it showing?
How much of the incoming mill seam, joint weld or transit scratch must be removed, and what minimum wall thickness has to remain after that removal?
An elevation is normally assembled from lengths made and finished at different times, so the lot definition matters as much as the finish itself. Decide how parts are grouped into finishing lots: by profile, by wall thickness, by alloy heat, by incoming mill finish, or by the date the material arrived. Then decide how lot identity is preserved through finishing, fabrication and despatch, because a length that cannot be traced back to a lot cannot be compared with another length in a dispute. Where an order will be produced over several weeks, keep an unprocessed reference length from the first delivery in store, and keep a finished reference panel from the first accepted lot. Both are needed before anyone can argue about whether a later length matches.
Inside whichever machine is chosen, the fixture or the load arrangement decides whether thin sections survive. A thin-wall rectangular profile will flatten under its own weight in a deep bed, and two loose lengths finished together will nibble each other along the contact line. Practical measures are cradles that follow the profile, dividers or compartments that keep parts apart, end caps or plugs for open tube ends, and clip-on carriers that present the visible face to the media evenly. The fixture also fixes the finish: a part that rotates freely receives an inconsistent texture, while a part held at a controlled orientation receives a directional one. Build the fixture around the longest and thinnest part in the order, not the average one.
| Machine route | Where it fits | What it will not do |
|---|---|---|
| Magnetic finishing machine | Small precise parts and localised areas that are difficult to reach with loose media in a conventional chamber. | Size and mass limits keep it away from architectural lengths and large diameter profiles. |
| Centrifugal barrel finishing machine | High-speed finishing of small precise parts, including where a bright appearance is required on a compact geometry. | Chamber geometry and high contact forces rule it out for long, thin-wall or easily marked sections. |
| Dry polishing machine and dryer | Post-wet drying and dry luster work, particularly where a hollow section must come out clean and dry inside. | Dry routes cut less than wet media, and dust control and media separation need planning. |
| Barrel finishing machine, rotary barrel tumbling | Gentle, precise batch processing of small parts, finials, sleeves and short connector pieces. | Part length and part-on-part contact restrict it to short fittings rather than long architectural runs. |
Media must be small enough to reach the root of a seam or into the concave corner of a rectangular profile, and large enough not to lodge in the bore, in a drilled fixing hole or in a slotted channel. On small sections those two conditions conflict, and the resolution is usually to plug or cap the openings rather than to compromise the media. Where the visible face has a shallow cove, a smaller media class gives better access but wears faster and produces a shorter texture pitch. Where the profile is open, a larger class cuts more evenly and separates more easily. Decide the size against the tightest feature that must be finished and the smallest opening that must stay clear, and state both in the trial request.
| Media | Best fit | Watch out for |
|---|---|---|
| Grinding media, alumina-based | Higher material removal where a mill seam, a joint weld or a deep transit scratch has to be cut back before refining. | Aggressive on thin wall, can over-round edges and change cross-section geometry, and needs tight depth control. |
| Ceramic media, spheres and balls | General deburring and edge work on cut ends, brackets and small fittings in the same order as the long runs. | Produces overlapping crater-like marks that work against a linear brushed appearance and can peen a thin wall. |
| Dry media, walnut shell and corn cob | Dry polishing and support for post-wet drying, particularly where a hollow section must not stay wet or carry residue inside. | Low cutting power, and dust generation and media separation need managing in the surrounding area. |
| Plastic media, cylindrical | Light surface refinement on thin rectangular sections where holding the shape matters more than cutting power. | Little cut power, and the size class changes quickly as the media wears, which shifts the texture pitch over a run. |
A surface can measure inside a roughness band and still fail visually. Orange peel, a mottled texture with a pitch of a few millimetres, appears when the surface is over-worked with a coarse medium or worked with too much pressure on a soft or thin section. Hazing is the diffuse, milky appearance that follows a fine but non-uniform cut. Both are geometry effects rather than amplitude effects, so a profilometer reading across them may be entirely acceptable while a reflection test shows a broken image. This is why an architectural finish cannot be accepted on a roughness number alone, and why a visual standard viewed under defined light at a defined distance has to sit beside the numeric one. Ra and appearance answer different questions.
| Failure mode | Likely cause | How to catch it |
|---|---|---|
| Twist along the length | Differential working of opposite faces, or clamping and stacking that loads the section unevenly. | Rest the length on a reference surface and compare the angular orientation of the two end sections with a square. |
| Flat spot or thinning at a dressed weld | Too much material removed in one place while chasing the weld toe, usually with too coarse a medium or too much pressure. | Measure wall thickness with an ultrasonic gauge across the dressed area, and lay a straightedge over the joint to reveal a flat. |
| Longitudinal scratch running along the part axis | Incoming coil or straightener marks, media or swarf dragged along the surface during the cycle, or a finished length sliding over a bare support between operations. | View the surface under raking light at a low angle along the axis, compare the same station on several parts, and compare against the retained reference panel. |
| Hazy or milky patch with a dull reflection | Uneven cut, worn media in part of the chamber, or weak compound flow at the far end of a long tub. | Compare the near end and the far end of the same length, and check compound concentration and fluid flow at both ends of the chamber. |
Kobe's manufacturing is concentrated in food, transport equipment and general machinery. The city's 2020 Census of Manufacture report counts 1,394 establishments with four or more employees, 67,951 workers and 3,421.1 billion yen of manufactured goods shipments, with value added up 3.3 per cent. It states that food manufacturing and metal products together account for about a quarter of all establishments, and that food, transport equipment and general machinery together account for just over half of employment, with Hyogo ward especially strong in transport equipment and Nishi ward in production machinery and metal products. The city also publishes an economic census and industrial statistics series, and the port has been the city's trade gateway since it opened to foreign trade in 1868.
The nearest part of that base to this brief is machinery: Kobe's 2020 Census of Manufacture report lists general machinery among the three industries making up just over half of manufacturing employment, and records Nishi ward as having high shares of production machinery and metal products.
Kobe's three largest manufacturing employers by industry are food, transport equipment and general machinery, so the surface requirement splits between hygienic, cleanable finishes for food equipment and dimensional, burr-controlled finishes for transport and general machinery parts. General machinery and metal products are concentrated in Nishi ward, where small firms supplying machined components need a finish specification that travels with the drawing rather than a verbal agreement.
A Kobe buyer should separate the two cases before choosing a process: transport and general machinery parts where edge and burr limits govern, and food-equipment parts where cleanability and surface condition govern, because the same media and compound choice will not serve both.
Freight context: Port of Kobe (神戸港), open to foreign trade since 1868, Kobe Airport (神戸空港), opened in 2006. Kobe City records that after the 1995 Hanshin-Awaji earthquake the port's facilities were restored within two years, and that the 2006 opening of Kobe Airport established a combined sea, air and land transport system. Customs clearance in the Kobe area is handled by Kobe Regional Customs, one of Japan Customs' regional offices.
Documentation and technical communication are Japanese-language in practice: JISC states that the documents submitted for JIS certification-body accreditation must be written in Japanese, and drawings, inspection sheets and purchase specifications from Japanese buyers are normally issued in Japanese. Import declarations are filed in triplicate and importers commonly use licensed customs brokers, so the commercial invoice, packing list and origin documents must be complete and consistent with the declared commodity code. As general industry practice in Japan, industrial buyers qualify a supplier on documentation, quality-management evidence and a defined inspection standard before volume orders, and expect a named Japanese-speaking contact for technical and commercial follow-up.
The national standards body is the Japanese Industrial Standards Committee (JISC), which states that JIS covers industrial and mineral products, data, services and management systems under the Industrial Standardization Act. Its technical divisions include mechanical engineering, ferrous materials and metallurgy, nonferrous materials and metallurgy, ceramics, medical equipment and safety appliances, and aircraft and aviation, which are the divisions a finishing or deburring requirement is normally read against. Product certification runs through the JIS Mark Certification Scheme, operated by accredited certification bodies compliant with ISO/IEC 17065; as of March 2019 there were 24 JIS-accredited bodies, three of them outside Japan, with about 8,700 certifications issued, and the scheme explicitly covers foreign manufacturers, processors and exporters.
SurfacePolish supplies from Xiamen, China. The buyer's own destination rules, conformity marking, tariff classification and documentation responsibilities stay with the buyer; confirm them against the authorities named above before ordering.
Grain direction is the most common reason a set of individually acceptable lengths is rejected as an assembly. Where two lengths butt at a joint, their texture direction has to run the same way, and the pitch and brightness have to be close enough that the joint does not read as a line. That is a planning decision made before the lengths are run, not a sorting decision made afterwards: define the grain direction on the drawing, mark the direction on every length, and keep the orientation through fabrication and despatch. Then inspect the lengths laid end to end as they will be installed, under the agreed light, rather than one at a time on a bench. A direction reversal that is obvious in an assembly can be invisible in a single part.
The trial result is only meaningful against a documented starting point. Photograph each sample under fixed lighting with a scale in frame, note the direction of the incoming texture, and take roughness readings at marked stations with the traverse direction recorded. Note the incoming straightness with the sample on a reference surface, the edge condition at cut ends, and any existing weld, scratch or discolouration. Keep one piece unprocessed as the baseline. When the trial parts come back, the comparison is between the returned parts and these records, not against memory. This is also how a buyer distinguishes a change made by the process from a feature that was present in the material when it arrived.
Start with a physical sample: if a short section can be removed without damage, send it, together with the retained reference panel from the original order if one exists. An installed surface has aged, been cleaned and possibly scratched, so a new length will not reproduce it exactly, and the visible difference is usually easier to manage by finishing a group of adjacent lengths than by matching one piece in isolation. A trial reports what the tested settings produced on the sample you sent; deciding how close is close enough remains with your own acceptance process and the people who will look at it daily.
It depends on the order book rather than on the profile alone. A tub suits mixed work and shorter runs, because the set-up changes with the part and the chamber can take several profiles. A dedicated arrangement that carries the length past fixed heads, or moves heads along a stationary length, sets the texture direction by machine axis and holds it better over repeated runs, at the cost of floor space and changeover when the profile or length changes. Bring the profile mix, the typical and maximum lengths and the annual volume into the line-concept discussion; we can scope it, though the choice is yours.
Ra is a two-dimensional amplitude average taken along one traverse, and it says nothing about the pitch of the texture, its direction, or whether the surface reflects light evenly. Two surfaces with the same Ra can look quite different: one can carry a directional brushed grain and the other a mottled, hazy appearance with a broken reflection. That is why an architectural callout normally needs both a numeric limit with its measurement conditions and a physical reference viewed at an agreed distance under agreed light. The number controls the process, and the panel settles the argument.
Use Kobe, Japan as the destination on the enquiry and state whether the deliverable is equipment, media and compound, a representative sample review or a line concept. A destination does not imply local stock, a local service point or a local delivery time.
Kobe buyers reference JIS, maintained by the Japanese Industrial Standards Committee, whose mechanical engineering and ferrous materials divisions cover the city's machinery and transport-equipment output, with the JIS Mark scheme available for third-party product certification. For food-equipment work the additional reference is the customer's hygiene and cleanability requirement, which is specified on the drawing rather than by a general finishing standard.
Sources were retrieved on 2026-09-29 and describe the local industrial and trade context only. They do not evidence any SurfacePolish project, shipment, installation or service in Kobe.
An inspector is rejecting the delivered appearance under raking light even though roughness readings sit inside the stated band.
Send the material, dimensions, approximate weight, batch quantity, the incoming condition and photographs of the difficult features. Mark which features must not be contacted by media and state how the result will be inspected. This form carries source reference PSEO-0857; quote it if you prefer an additional manual reference.
Open the SurfacePolish enquiry form Email a prepared enquiry
No price, lead time, certification or result is promised here. Confirm whether a sample trial is available for the specific part and what the trial can and cannot show.
Page PSEO-0857 · revised 2026-09-29 · cross-border equipment, media and scoped sample review. City context is sourced and cited above.
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