Mirror Finishing/Mirror Polishing

We are going to introduce TDC’s Mirror Finishing/Mirror Polishing Services.

What Is Mirror Finishing/Mirror Polishing?

Mirror finishing/Polishing is a processing and finishing method for polishing the surface of a workpiece into a mirror-like surface. It can put a shine on the surfaces of workpieces of metals such as aluminum, iron, stainless steel, titanium or acrylic resins such as plastics. This is one of the processing methods with which our familiar products such as furniture, sundries, electronic devices, and automobile components are produced. Mirror finishing is particularly important in the precision processing and precision component fields.

It serves not only to produce the beauty of the surface but also to provide surface accuracy or impart smoothness to a component. In particular, mirror-finishing stainless steel requires high difficulty because different procedures and abrasive compounds are used for different kinds of stainless steel.

Typically, any one of the following three procedures is applied to mirror finishing.

• Precision Cutting
• Precision Grinding
• Precision Polishing

Mirror Finishing by Precision Cutting

This is mirror finishing where the finishing shape and surface quality of a workpiece are obtained by scraping off excess parts from the workpiece using a cutting tool.

Please check “What is Cutting” for TDC’s precision cutting.

Mirror Finishing by Precision Grinding

This is mirror finishing where the surface of a workpiece is finely scraped off using a grinding machine and a grinding wheel rotating at a high speed.

Please check “What is Grinding” for TDC’s precision grinding.

Mirror Finishing by Precision Polishing

This is mirror finishing where the surface processing is applied to a workpiece by polishing it. 

Main polishing methods that are used in mirror polishing are as follows.

• Lapping
  A product is polished with a lapping machine grinding abrasive compound, which contains abrasive grains, and the product abrade. While double-sided lapping is to polish a product with the product sandwiched between two lapping plates, single-sided lapping is to polish a product with the product placed on a lapping plate. Lapping is often used for mirror finishing or mirror polishing because a plane surface can be obtained with precision.
• Buff polishing
  Buffing is a method in which a polishing tool, which is made of cotton or felt, is rotated at a high speed for polishing. This polishing is mostly performed manually. While it results in beautiful finish, it has some disadvantages such as differences in quality of finish and difficulty in large-lot production.
• Barrel polishing
  This method is performed with workpieces, abrasive stones, an abrasive compound, and water set in a tank-shaped machine and then tumbled. While it is suited for large-lot production, it has a disadvantage that it is impossible to polish individual parts of a product.
• Electropolishing
  It is a method where, while a workpiece to be polished is immersed into an electrolytic polishing solution, applied electricity causes chemical reaction that changes a metal surface. This method allows uniform processing of a surface and also allows polishing of parts not easy to physically polish such as narrow parts and minute parts.

Please check “Polishing Service” for TDC’s precision polishing.

Benefits of Mirror Finishing

Mirror finishing mainly provides the following three benefits.

• Effectiveness in deburring
  Mirror polishing flattens irregularities of a workpiece, thereby increasing its smoothness. For example, mirror-finishing the inner surface of a pipe brings about the benefit of reducing resistance against powder or liquid that flows through the pipe and facilitating its flow.
• Beautifully processed appearance
  Mirror polishing flattens irregularities of a workpiece, thereby increasing its smoothness. For example, mirror-finishing the inner surface of a pipe brings about the benefit of reducing resistance against powder or liquid that flows through the pipe and facilitating its flow.
• Increase in surface smoothness
  Mirror polishing flattens irregularities of a workpiece, thereby increasing its smoothness. For example, mirror-finishing the inner surface of a pipe brings about the benefit of reducing resistance against powder or liquid that flows through the pipe and facilitating its flow.
  

Drawbacks of mirror finishing

One of the drawbacks of mirror finishing is its costliness, in general. Another drawback that should be paid attention to is that a workpiece surface beautifully finished just like a mirror needs to be regularly cared for because fingerprint marks, scratches, or rust can easily be noticed on the surface.

TDC’s Mirror Finishing/Mirror Polishing Services

Small piece processing of copper material

• Size: about 20mm square~ 50mm square
• Thickness: about t0.3~2.0

*Sizes other than the above are also available.

When mirror-finished products are used for setting conditions, testing, and verification in manufacturing, variations in the finish have a large impact on the results. TDC uses the same process every time, so it is characterized by less variation in finished surface roughness.

Customers who want materials with little variation in surface roughness for the manufacturing of precision parts and experiments requiring severe numerical values are pleased.

End face mirror finishing of elongated mold material

• 　External shape dia. 0.2 x L6mm end face mirror surface processing

In order to prevent the long and narrow mold material from falling over or breaking during processing, we produced a dedicated processing jig in-house that matched the shape.

In addition to long and narrow shapes, it is also possible to create special jigs in-house to process products with angled (tapered) shapes, or when you want to finish without sagging up to the end.

The following pages introduce examples of TDC mirror finishing for each material.

• Mirror-finishing for aluminum
• Mirror Polishing for Stainless Steel/SUS304
• Mirror-finishing for plastic/acrylic resin

Reflectance that can be achieved by mirror surface processing of TDC

The reflectance measurement results for each material that has undergone mirror processing and mirror finishing at TDC are as follows.

• Measuring machine:
• JASCO ultraviolet-visible-near-infrared spectrophotometer V-780
• Measurement condition:
• Incident angle: 5 degrees
• Measurement range: 380-780nm
• Data interval: 1nm
• Number of data: 401

Material	Reflectance
A5052（aluminum alloy）	100.2％
SUS304（stainless steel）	68.9％
C1020（oxygen-free copper）	86.7％

*Measurements are made by measuring the relative specular reflectance against a standard aluminum deposition mirror.

*The standard aluminum deposition mirror is set to 100, and each data is measured.

*The reflectance of the standard aluminum deposition mirror is an average value of 93.69%.

TDC’s unique mirror surface processing technology

Even within the category of “metal”, it is not possible to achieve a mirror-like finish or accuracy if processing is done in exactly the same process. It is necessary to finely change the combination of abrasives and surface plates that are suitable for each material for each process.

At TDC, we have accumulated know-how on the best processing processes for each material. We are also actively working on new materials, and we have a track record of processing materials that are independently developed by manufacturers and materials that are generally not mirror-polished.

In addition to manufacturing and experimentation, we have received many requests from the art field.

The sphere-shaped work that reflects light and images on the wall is mirror-finished to eliminate image distortion while achieving a high degree of sphericity.

In another artist’s work, we used our long metal foil precision polishing technology to polish not only the top and bottom surfaces of a 0.3 mm thick long foil, but also the sides.

This kind of prototype processing will also lead to our technical improvement, so please feel free to contact us.

Processing Equipment for Mirror Polishing

In addition to lapping machines, TDC has a variety of processing machines that enable comprehensive ultra-precision manufacturing.

Machine	Brand	Size	Quantity
Lapping Machine (Single Sided) Mirror Polishing Machine	in-house others	dia.63in-dia.12in (Maximum Size ~ dia.800 mm)	90
Lapping Machine (Single Sided) Mirror Polishing Machine	FLTEC	dia.18in (Maximum Size ~ dia.190 mm)	10
Lapping Machine (Single Sided) Mirror Polishing Machine	FLTEC	dia.18in (Maximum Size ~ dia.190 mm)	2
Lapping Machine (Double Sided)	SPEEDFAM others	5B～16B (Maximum Size ~ dia.300 mm)	19
CMP	ENGIS JAPAN others	dia.18in～dia.36in (Maximum Size ~ dia.305mm）	3

TDC’s Mirror Finishing/Polishing

TDC is capable of polishing a wide variety of materials such as metals, ceramics, crystalline materials, and resins to ultraprecision mirror finish. TDC is also capable of polishing a surface into any shape, whether it be a plane surface, a curved surface, or inner or outer diameter of a cylinder, with the surface roughness (Ra) of 1 nm or less. Furthermore, TDC has its original polishing method that can satisfy other highly precise processing requirements such as 100-nm parallelism, 30-nm flatness, +-100-nm dimensional accuracy, +-3 arcseconds, and 50nm sphericity while satisfying the surface roughness of Ra 1 nm or less.

*Results of surface roughness and surface roughness of each material are introduced on the “What is Surface Roughness” page.

Please feel free to contact us if you have any questions and inquiries.