What Is Direct Part Marking?
Direct part marking (DPM) is a process to permanently mark parts with product information including serial numbers, part numbers, date codes, and barcodes.
This is done to allow the tracking of parts through the full life cycle.
The interpretation of ‘permanent’ often depends on the context the part is used. In the aerospace industry an aircraft part may be in service for over 30 years.
Within telecom and computer industries the life cycle may only last a few years.
Direct part marking (DPM) is often used by automotive, aerospace, and electronic manufacturers to facilitate a reliable identification of their parts.
This can assist in data logging for safety, warranty issues and satisfy regulatory requirements.
Also, the United States Department of Defense demands a physical mark on tangible assets in conjunction with the Item Unique Identification.
What Are Types of Different Direct Part Marking Methods?
#1. Laser Marking.
In simplest terms, laser marking is a permanent process that uses a beam of concentrated light to create a lasting mark on a surface.
Typically performed with a fiber, pulsed, continuous wave, green, or UV laser machine, laser marking encompasses a wide variety of applications.
Laser marking can be automated and processed at high speeds, while leaving permanent traceability marks on a range of materials, including steel, titanium, aluminum, copper, ceramic, plastic, glass, wood, paper, and cardboard.
Parts and products can be marked with text (including serial numbers and part numbers); machine-readable data (such as barcodes, Unique ID codes, and 2D Data Matrix codes); or graphics.
Laser Etching
Laser etching is the fastest laser process and is the one we recommend for most marking applications.
It etches a raised mark by melting the micro-surface of the material. It can be used to trace most metal parts, including steel, aluminum, anodized aluminum, lead, magnesium, and zinc.
Laser Engraving
Laser engraving is the ideal process to track parts subjected to high abrasion levels. It engraves machine-readable codes deep into the material through laser ablation.
Deep Laser Engraving
Deep engraving is used to engrave codes, logos, and characters that must meet specific depth and aesthetic requirements.
Typical applications include deep logo engraving, stamping plate engraving, and mold insert engraving.
Laser Annealing
Laser annealing is a special process used to track parts that must preserve their corrosion resistance, such the ones made of stainless steel or that are chrome plated.
The laser beam heats the surface of the material until it creates a chemical reaction under the surface, leaving a well-defined laser mark.
#2. Dot Peening.
Dot peen marking technology allows manufacturers to automate the direct part marking process, ensuring 100% reliable part traceability.
Dot peen marking systems give you the ability to place high quality marks on your products consistently and quickly, allowing you to be more productive.
The Dot peen process is considered a “low-stress” marking method because the mark is generated via material displacement rather than material removal.
The carbide stylus strikes the material surface to produce the mark via a series of cold-formed stamped dots.
Compared to Laser Marking Systems, Dot Peen does not induce thermal shock to the part surface since the material is cold-stamped rather than super-heated to produce the mark.
Dot Peen systems are commonly used by manufacturers in the aerospace and oil & gas industries where low-stress marking is required, such as tubular and flow control products that are exposed to extreme pressure differential in the oilfield.
Dot Peen marking is viable for material hardness up to 63 HRC. Typically, when a part hardness is greater than 63 HRC, laser marking systems are recommended.
#3. Ink Jet Printing.
Depending on who you talk to, inkjet printing may or may not be classified as a direct part marking method.
Although it creates markings by propelling ink directly on the part, the resulting ink layer is not permanent.
Ink markings can be erased or severely damaged as a result of abrasion. Ink can also partially clog the nozzle, requiring more maintenance and diminishing the quality of the codes over time.
#4. Scribing marking.
Scribing industrial engravers use a carbide or diamond tip to create a continuous, clean, and aesthetic marking.
The tip glides over and scratches the part leaving a permanent, deep and clearly legible mark.
Scribing is a part identification solution dedicated to metal: it can be used on a wide variety of metal parts such as aluminum, brass, and copper, as well as hard materials such as steel and stainless steel.
Scribing part marking systems also offer another important advantage: by remaining in continuous contact with the parts, the part identification process is much quieter than dot peen, which strikes the parts.
Scribing is therefore recommended for materials that resonate, such as sheet metal and hollow parts.
#5. Indenting.
Indenting is a method of direct part marking where information is permanently indented, or stamped, into the material.
Achieved by using character stamps or a dot peen pin, the code or message is made by applying force to the material being marked to form a permanent mark.
#6. Embossing marking.
Embossing is a tried and true marking process used for marking metal tags and nameplates. The process utilizes a male and female die set to press a raised design into a metal substrate.
For each design, a custom embossing die set must be produced. This can then be used in an industrial press to churn out a large quantity of tags.
A custom die leaves a permanent mark that will last for decades. These raised characters provide long distant readability as well as extreme durability.
Note that incorporating multiple designs can get extremely costly.
#7. Debossing marking.
Debossing and embossing are incredibly similar as far as marking processes go. Both processes create their designs using a male/female die set.
The biggest differences are the direction which the design is imprinted, as well as how the tags are used.
The actual process for marking a debossed design is very similar to the embossing process. The custom made die set produces an indented design in the metal material.
While embossing creates characters that are raised upwards, debossing imprints the design downwards. In other words, the reverse side of the tag will have the raised impressions.
A quick way to tell the difference between embossing and debossing is to look at the back of the marked nameplate.
If that side is indented then it is likely an embossed design. If the back sports raised markings, it would be considered debossed.
Similarly, it is easy to differentiate debossing from stamping as the backside of a debossed tag will not be flat like it is on a stamped plate.
#8. Coining Marking.
Coining is an economical process whereby the tag or nameplate is indented with a coining die.
This metal die applies very high pressure which leaves behind a deep and permanent mark that cannot be removed.
Coining is used for low-cost applications that require a physical marking, similar to rotary engraving. It is suitable for long-lasting applications in harsh environments.
#9. Abrasive Blasting Marking
Grit Blasting or Abrasive Blasting is the process of pneumatically thrusting a high-pressure stream of fine grit (or another abrasive material such as fine sand, glass beads, or silicon carbide) through a stencil that is placed on the part, thus removing surface contaminants and yielding a crisp mark.
Abrasive blasting is a loose abrasive machining process. The abrasives stream is propelled with compressed air or the centrifugal force against the workpiece surface at high speed.
Sandblasting and shotblasting are two common variants of abrasive blasting. Along with sand, other abrasive materials may be used in the sandblasting process.
Sandblasting and shotblasting processes are quite similar. However, shotblasting is much more aggressive than sandblasting.
Another difference is that centrifugal force is commonly used in shotblasting to propel the abrasives stream, whereas compressed air is employed in sandblasting
#10. Electro-Chemical Etching Marking.
Electrochemical marking and etching are done exclusively on conductive metal surfaces.
A marking head is used to release a weak current to the metal surface through a marking stencil/mask soaked in the electrolyte fluid.
Dark marking and white etching results are achieved by switching between Alternating (AC) and Direct (DC) electric current and through the use of appropriate marking stencils.
Compared to other methods, electrolytic marking/etching is far more flexible and is mostly done with highly portable and affordable equipment.
Electrochemical marking and etching are especially effective on stainless steel surfaces.
Stainless steel is widely used in modern industry due to its anti-corrosion properties and attractive appearance. Machine parts, cutlery, and kitchen appliances are just some of the popular examples.
Electrolytic etching and marking will provide fast and clear results on stainless steel parts and finished products. No surface distortion occurs even on very thin metal plates.
#11. StencilMarking.
Stencilling produces an image or pattern on a surface by applying pigment to a surface through an intermediate object, with designed holes in the intermediate object.
The holes allow the pigment to reach only some parts of the surface creating the design.
The stencil is both the resulting image or pattern and the intermediate object; the context in which stencil is used makes clear which meaning is intended.
In practice, the (object) stencil is usually a thin sheet of material, such as paper, plastic, wood or metal, with letters or a design cut from it, used to produce the letters or design on an underlying surface by applying pigment through the cut-out holes in the material.
Direct Part Marking Method Selection Factors
The marking method depends on a number of different factors:
- Part function: Non-intrusive marking methods are recommended for parts used in safety critical applications like aircraft engines or high pressure and high stress systems.
- Part geometry: It is more difficult to place a Data Matrix on a curved surface than it is on a flat surface.
- Surface: Highly polished metal surfaces should be textured to reduce glare prior to marking. The textured area should extend one symbol width beyond the borders of marking.
- Part Size: When a 2D Symbol is used, the size of the part is not a relevant factor as the available marking area is reduced to below 1/4 inch square.
- Operating environment / age life: It should be controlled, if the used marking method can survive in its intended environment and remain readable for the life cycle of the part.
- Surface roughness / Finish: A rough surface is more challenging for a 2D barcode as the data elements can be recognized appropriately. The surface roughness levels should be limited to 8 micro-inches for dot-peen marking, laser and scribe systems can make a readable mark in rougher surfaces. The laser systems burn a “quiet zone” first and then the 2D code. The scribe method provides a high resolution 2D mark that makes the part readily readable in most cast surfaces.
- Surface thickness: Surface thickness must be taken into account when applying intrusive markings to prevent deformation or excessive weakening of the part. In most applications the marking depth should not exceed 1/10 the thickness of the part.
Materials That Can Be Marked
Wide range of materials can be marked, including metals, plastics, composites, rubber, woods, and foams. Some of our most popular materials include:
- Steel, including hot and cold rolled, annealed, hardened, blue tempered, zinc galvanized, and pickled and oiled steel
- Stainless steel, include spring tempered, brushed, hardened, and annealed varieties
- Copper, including annealed copper
- Bronze and brass, including bearing bronze and spring silicon bronze
- Aluminum, including pre-anodized aluminum
- Titanium, including Grade 2 and Grade 5
- Nickel, including annealed nickel
- Plastics, including ABS, acrylic, acetal, HDPE, nylon, polycarbonate, polypropylene, PETG, PTFE, and UHMW-PE
- Composites such as carbon fiber and Garolite
- Rubber and gasketing materials, including nitrile, cork-nitrile blend, paper fiber-nitrile blend, EPDM, and silicone rubber, as well as PTFE
- Wood, including cherry, poplar, and red oak hardwoods as well as birch, hardboard, plywood, and MDF
- Foam, including EVA, polyurethane, silicone, flame retardant, and high temperature varieties
In addition to marking, most of these materials can have other finishing options applied such as bead blasting, anodizing (both type II and III), powder filming, chem filming, painting, and other custom finishes.