Traceability: The Why and How of Using Date Stamps in Molds

When consumers purchase or use products made with plastic parts, they probably never look for, nor care about, the various date-stamp marks molded onto them. They have no interest in who designed the parts, who built the molds, who molded the parts, or where and how the parts were assembled to create the finished product. They just want that product to do what it’s supposed to do.

But what if the product fails? What happens if a component within the product — be it an automobile, a plane, an appliance or a medical device — does not function as intended and something goes wrong?

Identifying the problem becomes paramount to the manufacturing supply chain, and those date markings offer critical clues about the origin of the product and its components. A single date stamp — or a group of them — can reveal the year, month, day, shift and batch in which the part was manufactured, speeding up the process of uncovering what went wrong and when. It is all about traceability.

Date Stamps Provide Multiple Benefits

While the possibility of personal injury and property damage due to malfunctioning products is a compelling reason for using date stamps on almost every plastic product or component, it’s not the only reason manufacturers use them.

For long-running tools, molders purchase date stamps annually, replacing at least the center arrow plug with the new year engraved on it. This enables more accurate record-keeping and shipping schedules in the warehouse and on the manufacturing floor. Down the supply chain, date marks help personnel know which batch of components or parts should ship and be used first.

In automotive, electronics or packaging, where designs change more frequently, date stamps reduce waste by offering a reliable guideline for manufacturers to know which parts should be used first, discarded or reground.

When products are made using biodegradable materials, they can have a more limited lifespan. Date stamps can be invaluable for managing product inventories more efficiently while also optimizing overall product quality. Examples include biodegradable medical products, food packaging or plates, cups and utensils, as well as biodegradable planters. With sustainability trending across industries, more and more products are being made at least in part with environmentally friendly materials, and date stamps will continue to play a critical role in tracking their use and utility.

Finished products like child car seats are also dated for consumer safety purposes and traceability due to recalls or failure. By law, they are labeled with their manufacturing dates (via date stamps) to tell consumers what the recommended life cycle is for use. Most are made from polypropylene (PP), a commonly used plastic material valued for its durability and melting point of about 320°F. That sounds quite heat tolerant, and it is, but constant exposure to high heat over time, combined with wear and tear, can make it vulnerable to failure. The Centers for Disease Control and Prevention (CDC) confirms that the interiors of automobiles can reach triple-digit temperatures after only 20 minutes on an 80°F day. For this reason, car seats are tested by manufacturers to determine a realistic safe usage timeline for families to follow, and in the event of a recall, date-stamp marks provide essential tracking data for the OEM and its supply chain.

In industries like automotive, electronics or product packaging where designs change more frequently to meet market demands and trends, date stamps reduce waste by offering a reliable guideline for manufacturers to know which parts should be used first, discarded or reground for later use. As a result, these processes become more cost-effective and efficient.

Engineering changes, which can happen for any reason and at any point in a product’s life cycle, also require date-stamp adjustments or replacements, indicating the effective date of the changes. As with design changes, molding managers, inventory supervisors and assembly workers can use the updated markings to manage products more efficiently.

Legal and Regulatory Compliance

Manufacturers operate under various regulatory requirements based on laws enacted by federal, state and, sometimes, local governing agencies. Some industries, like automotive and medical, are regulated more than others, but in all cases, compliance is a must.

A low-cost insurance policy for molders and OEMs, date stamps can play an essential role in protecting an enterprise from legal actions and penalties due to product failures or recalls. With due diligence in managing date-stamp markings and good record-keeping, traceability via date-insert markings expedites the investigative process, pinpoints the problem and, hopefully, resolves it. In turn, this traceability enables companies to determine how far back in production a recalled part was used and quantify what the fallout in lost time, material and profits will be.

Date-Stamp Considerations

While mold manufacturers typically install date stamps in molds they build as part of a job’s requirements, it is the molder or the OEM customer who specifies the type or style of dater to fit their traceability needs.

Over the years, wider ranges of date-stamp products have become available. Most daters are included as part of the moldmaker’s bill of materials and purchased together with other components for new molds. Otherwise, molders and OEM maintenance technicians place yearly orders to restock daters for existing molds.

It’s recommended that, whenever possible, date-stamp changeovers should be coordinated with scheduled preventive maintenance to save time.

All date stamps are made from stainless steel for its corrosion resistance, durability and heat tolerance, and are offered in diameters ranging from 3-20 mm, the smallest of which are known as micro daters. The most commonly used sizes range between 6-12 mm, according to mold designers who emphasize the importance of markings being legible without magnification. Plus, they’re easier to update using a flat-head screwdriver, which fits into and rotates the arrow engraved on the center plug of the date-stamp assembly. For very small or micro-sized parts, such as those for medical products, dates are commonly laser etched or distributed in dated packaging.

Additionally, date stamps can be purchased with raised or recessed numerals. The choice may depend on aesthetics or part function, as raised numerals could interfere with mating parts in an assembly. All date stamps are designed so that the center plug, featuring the current year and an arrow that points to the date, month or other important detail, stays flush within the body assembly.

A ‘Necessary Evil’

Updating a date stamp requires simply turning the center arrow to point at the correct date, but some manufacturers view date stamps as a “necessary evil” because as much as their benefits outweigh any challenges, problems can occur if changes aren’t properly managed. For example, daily changes of dates, batches and even shifts are not uncommon in the automotive industry, and production managers must ensure that employees who are running molds keep up with date-stamp changes to meet both manufacturing regulations and customer requirements.

For many, date-stamp changes are a part of the training process in molding facilities. If there is frequent employee turnover at a molding facility, it’s a good idea for the company to make date-stamp inspection a part of every shift’s startup checklist.

In addition, ordering date stamps or center plugs for active molds and coordinating timely changeovers can be costly in man hours and production downtime, especially in a facility that runs hundreds of molds each year. It’s recommended that, whenever possible, changeovers should be coordinated with scheduled preventive maintenance intervals to save time.

If the wrong type of date stamp is selected for the wrong molding application, some issues can arise. For example, in a high-heat molding application, the spring holding the arrow plug in place tends to break down over time, causing the arrow to rotate out of alignment and mismark the part during production.

Similarly, if the plastic material is glass- or mineral-filled, the molding pressure may cause the arrow to rotate in the direction of the material flow. In addition, low-viscosity, flashing materials can seep down into the date-stamp’s pocket, causing the dater to move or making it difficult to remove or adjust it. Even worse, off-gassing can gum up or jam the date stamp, increasing the likelihood that a technician, while using a screwdriver to remove or reset it, could slip and damage the mold cavity, resulting in expensive repairs and downtime.

Engineering changes also require date-stamp adjustments or replacements, indicating the effective date of the changes that were made.

Some suppliers offer locking-style daters to keep them properly aligned. Nevertheless, regular inspection of parts is recommended to catch any discrepancies early and avoid material waste or downtime. It’s also advisable to remove date stamps and center plugs to clean them when performing maintenance on molds, as this will help prevent issues like these from occurring.

Common Dater Varieties

The following are a few of the more commonly used date-stamp products:

• Standard date stamps: Standard date stamps are the most widely used and include those marked to indicate work shift, month, day or year. They can be used together in any combination or individually. Standard blank inserts have the arrow insert and can be customized to reflect any desired markings for product tracking. According to some designers, shift daters are rarely used, but if they are specified by the customer, it’s likely for high-volume packaging products. Day daters are most commonly used in the automotive industry for more granular tracking in the case of recalls or rejections, as well as for inventory purposes.
• Center inserts/plugs: Center inserts typically comprise versions including compact height daters for molds with limited space; remains flush (RF) daters that stay flush within the dater assembly, including when the plug is being rotated to a new designation; and standard style plugs with the arrow or arrow-and-year options.
• Double date stamps: These date stamps indicate both month and year of production in one assembly, eliminating the need for multiple machined holes. These are widely used across industries for their convenient assembly of dating capability. There are daters available that offer users the ability to indicate the year in the center plug (with the arrow) while customizing the outer rings to show the month and either the day or week within that month. One sees usage of more detailed daters in the automotive, military and aerospace industries where a shared part is designed to be used for various product models over several years.
• Blanks: In the early days before date stamps were prefabricated and sold ready to use, toolmakers engraved the ends of core pins or ejector pins with desired date marks to track part fabrication. Today, blank date rings and plugs are available in a variety of sizes and styles so users can customize them.

Depending on the supplier, there are many other date-stamp products available, including those to address very specific molding needs and applications. Most supplier websites offer helpful selection guides to simplify the decision-making process. For best results, consult with a date-stamp supplier who can assist with choosing the right dater configuration for any application.

ABOUT THE AUTHORS: Mark Casey is a seasoned plastics industry professional whose career began as a mold maker and mold design engineer. Over the years, he has expanded his expertise to encompass mold engineering, component engineering, operations, plant management, ownership, and sales and marketing. Currently serving as the outside sales representative for PCS Company in the Southeastern U.S., Mark leverages his comprehensive industry knowledge to drive business development and enhance customer operations. Contact: 800-521-0546; mcasey@pcs-company.com.

Kelly Beauchamp brings more than 30 years of experience to her role as a product manager at PCS Company. Her career in the plastic injection industry is rooted in strategic product development and a keen eye for market trends. She plays a pivotal role in driving the company’s product initiatives. As a graduate of the University of Phoenix, she combines her academic background with practical industry insights to deliver solutions that meet and exceed client expectations. Contact: 800-521-0546; kbeauchamp@pcs-company.com.