Preventing Unscheduled Mold Stops

by Steve Johnson, president
MoldTrax Maintenance Solutions
Table 1. A sample mold stop reason report showing only the top 20 x-stops, sorted by total cost

Every molder’s goal is the same: to efficiently produce quality parts on time, regardless of the type of product molded. “Efficiently” was added to this mantra after the crash of 2007. In talking with thousands of employees from hundreds of molding companies all over the globe, one thing is certain – Unscheduled Mold Stops are the single most prevalent and costly reason for not achieving that goal.

It has been proven and written about time and again by maintenance managers, economists and financial administrators of manufacturing companies: Unscheduled Mold Stops cost companies five times as much to correct as Scheduled Stops.

Why are they so expensive to deal with? Consider all that happens when a press door is opened mid-run or when the press “red lights” and stops.

Press is stopped (door opened, red light, power failure):

1. Data about the stop date, stop time, who stopped it, etc., must be entered (usually manually) in the log book or noted in the work order system.

2. The issue must be determined: What exactly is the problem?

  • Part quality issue (flash, burn, non-fill, etc.)
  • Mold function issue (water leak, runner hanging up, broken tooling, etc.)
  • Press issue (press preventative maintenance, oil leak, material problem, etc.)

3. Once the issue is known, a preliminary decision must be made concerning how long the mold can sit idle while determining a corrective action plan.

  • Do the hot runner manifold and nozzles need to be dialed back?
  • Does the nozzle need to be retracted?
  • Does the barrel need to be purged?
  • Does the water need to be shut off?

Now we are ready to troubleshoot the issue:

4. Once the root cause is determined (if it can be determined):

  • How much time will it take to repair the issue?
  • Do we have the tooling to repair the issue?
  • Do we have the people to repair the issue?
  • Does the mold need to be pulled and sent to the tool room?
  • Do we need to do a lockout/tagout?

Pull the mold (if repairs cannot be made in the press):

5.Find a fork truck, alert necessary personnel and pull the mold.

Complete the corrective actions (in or out of the press)

6.Perform the corrective action (hopefully the repair technician does not run into any unforeseen issues).

Reset the mold

7.When the mold is ready, reset it per the mold set instructions/procedures.

Restart the mold

8.After the mold is set, perform start-up procedures and shoot the mold.

Corrective Action Verification

9.After the mold is restarted, run for the necessary time for the process to stabilize.

10.Verify the part now meets Q/A specs or that the mold is functioning properly.

Wow. Now we can finally get back to back to business of making money – instead of spending it. As you can see, Unscheduled Mold Stops can require time for critical decision making and may involve as many as five different departments (process, mold setters/pullers, quality control, production and the tool room) to get the mold back up and running. If this unforeseen maintenance cost is not in the piece part price, guess who is footing the bill.

In a firefighting maintenance culture, companies are at the mercy of the mold. Those practicing this expensive and archaic shop strategy do not set x-stop reduction goals, but instead depend on scheduled PMs to prevent unscheduled stops. This is just not enough in today’s landscape, with molders looking for any edge to get better production from their molds. Molds get heated, cooled, smashed, yanked open, pounded on and put away wet. No amount of PM (mostly just scheduled cleanings) is guaranteed to prevent molds from breaking down or wearing out tooling prematurely.

So, What Do We Do?

A question we always ask those who attend our managers course is “Do you know what your #1 Unscheduled Mold Stop reason was for last year?” Too many times, the answer is no. If the #1 reason isn’t known, then you can be sure a Top 10 list doesn’t exist either. Think about how crazy that is! We don’t make money in the business unless our molds are in the press running, yet we don’t know the #1 reason that doesn’t happen. Given the cost and potential harm to customer relationships, it is highly advantageous to not only develop the necessary data tools/skills to track Unscheduled Mold Stops, but to target them for extra attention when the molds make their way to a bench. Remember, nothing will get fixed unless the repair technician is made aware of the issue.

Here are five steps we should take to prevent – or greatly reduce – the number of Unscheduled Mold Stops.

1. Create standard terms for mold stops. There are only two categories of Mold Stop Reasons: Scheduled or Unscheduled. Companies can have dozens of reasons for stoppages, but none of them can be addressed unless a common set of terms is established. As an example, we use the term “x-stops” instead of Unscheduled Mold Stops when training attendees to develop and use standard terms when documenting mold performance and maintenance history.

Any Unscheduled Mold Stop should be listed with an X in front (thus x-stops) to make sorting quick if using an Excel spreadsheet or other electronic work order system. Do not make the list of mold stop reasons too granular, as it will be too long. In the world of drop downs, more than 50 items in a list will cause users to tire of reading and pick inaccurately. Do not include mold-specific defects, such as Flash on Parting Line, Long Gate, Flash on Seal, etc. These issues and other specific defects should be tracked under a specific mold number and tracked separately. The mold stop reason list should be constructed as a high-level view, using more generic terms to keep the list shorter. For instance, a mold might be stopped for “X-Flash Issues” with the specific flash term (Flash on Valve Gate) noted on a defect list for that mold.

2. Track (measure/count) them. X-stops should be continually monitored and counted over a specific time frame, such as quarterly or annually. They should be sortable by frequency, corrective action costs (tooling and labor) and/or high visibility (critical customer) to determine which of these is most important to your business model and future goals. It is not uncommon for custom molders and proprietary molders to have vastly different requirements – and thus, worries. It may be more important to target critical customer molds for improved mold performance or part quality issues than focus on the x-stops that require many labor hours to repair.

3. Post the target list. Once the top targets are determined, post the list on the molding floor and in the tool room. These employees need to know so that they can have their antenna up when any of the target x-stops strike again. Better information is gathered and employees are more engaged when brought into the loop early to become part of the efficiency improvement game plan. Molding operators and production floor personnel who are around the molds all day pick up on small details such as squeaks, clunks, bangs, sticky runners and other things that can be great clues for the repair technician. Also, everyone likes a game plan where an actual cost savings – the score – can be calculated and kudos delivered.

4. Troubleshoot the x-stop. Using your maintenance history, repair technicians should scour past work orders and maintenance history looking for patterns and trends that point to root causes by comparing specific molds. These issues could include the following:

  • Specific mold tooling configuration
  • Run date and time during which the mold suffered the x-stop
  • Press the mold was running in when the x-stop occurred
  • Which process technician started and stopped the mold relative to the x-stop
  • PM dates during the time frame the x-stop occurred
  • Past corrective actions for the specific x-stops (including what tooling and work was required)
  • Number of cycles the mold was running between the corrective action and the next x-stop

5. Perform the corrective action. Once the troubleshooting (soft skills) has been accurately accomplished, the hard skills of your technicians now take over. Skills such as precision measuring, fitting, stoning, polishing, grinding and fabricating are critical for corrective action success. After all corrective actions have been made and the documentation (again using standard corrective action terms) is complete, the mold can be returned to production.

X-stops not only cost companies thousands – and sometimes millions – of dollars per year, they are a source of major stress within companies. Unscheduled stops disrupt scheduling with presses, parts and people; sustain the firefighting culture; stifle skill growth as data analysis is not a priority; and takes time away from more proactive work. Don’t let x-stops reduce your profits; instead, control them.

To see how much x-stops are costing your company, go to and fill out the Unscheduled Mold Stop Calculator.

Steve Johnson is president of MoldTrax Maintenance Solutions, the only mold maintenance program created specifically for tracking the performance, maintenance efficiency and repair costs of a variety of molds and dies. To learn more, call 419.281.0790 or visit