In any manufacturing environment, intralogistics play a critical role in ensuring efficient operations. Nowadays, everything needs to happen faster because cycle times – or the time we have to complete each part of the production process – are getting shorter. Milk runs and tugger trains are fundamental to improving how materials flow from storage to assembly lines. In this guide, I’ll explain how introducing location intelligence helps maximize the use of tugger trains and reduces manual work for route planning and maintenance. I’ll cover:
What are milk runs and tugger trains?
Historically, milk runs involved having a milk float pick up bottles of milk from a dairy and going house-to-house to deliver it, while picking up empty bottles. The main motivation was the short shelf life of milk, which made it impossible to stockpile in times before widespread refrigeration and pasteurization. That’s why they would often deliver other perishables too, such as butter, cheese, and eggs. Unsurprisingly, as more people got refrigerators at home, as well as easier access to local grocery stores, the traditional milk run fell out of favor.
Traditional milk delivery using a float. Source: winteringham.info
In the context of lean manufacturing, milk runs follow a similar principle. In these environments, a single vehicle – typically a tugger train – makes multiple stops to pick up and deliver materials within a plant or warehousing facility or even between buildings. The goal is to consolidate the shipments into a single, more efficient route that keeps lead times and takt times to a minimum.
Milk runs in manufacturing are best-suited for mass-produced goods, such as identical parts and components, even if they’re used for different product variants or production lines. They’re not ideal for assembly lines that need lots of customized items. Nonetheless, kitting, an inventory management technique, can enhance the effectiveness of milk runs by packaging and shipping related parts and materials in a single delivery.
Source: www.still.de
Milk runs at a glance:
- Milk runs replenish consumed materials on a regular schedule, thus they’re only used for products where there’s a constant need to supply the same materials repeatedly.
- They have a fixed route with a fixed number of stops along the line where the milk run removes empty boxes and provides new ones filled with new materials.
- They run on a fixed schedule to replenish only materials that’s been consumed, with a typical route time being anywhere from 10 to 25 minutes.
This is a milk run route with seven stop locations serving three assembly lines.
What are the benefits of milk runs?
Milk runs very much follow the lean manufacturing philosophy which, in turn, relies on the pull principle. This dictates that work should only ever be pulled when there’s a demand for it, thus preventing overproduction and reducing waste.
Let me highlight some of the key benefits of this approach:
- Enhanced management: Excessive inventory ties up working capital, resulting in extra storage and obsolescence costs. By standardizing materials handling, milk runs mark a shift from random requests (“hey we need more material”) to a cyclical, repeatable process.
- Maximizing vehicle use: Underutilized vehicles result in higher fuel and maintenance costs. By consolidating multiple shipments in a single route, including pickup and drop-off, tugger trains aren’t left running empty.
- Improved worker productivity: When workers lack the materials they need to continue production, they end up wasting time. By supporting a just-in-time approach, milk runs ensure they have everything they need when they need it, and not before.
- Avoiding excess production: If more materials are being produced and delivered than necessary, costs rise and waste increases. Properly configured milk runs incorporating kanban pull systems prevent this from happening while also supporting quality control.
- Building an agile supply chain: Modern supply chains need to be able to accommodate constant shifts in demand. Combined with location intelligence and modern project management systems, milk runs may be easily adjusted to consumption rates.
- Reduced inventory and space usage: Arbitrarily transporting of materials tends to lead to shortfalls in inventory or overproduction resulting in excessive use of storage space. Smarter milk runs prevent that with pull-based systems rather than push-based ones.
Despite the clear benefits, implementing milk runs isn’t without its challenges. It requires the strict commitment to all relevant production stages, since a single delay can bring the entire production process to a halt. Fortunately, indoor location intelligence can mitigate that risk by making it easier to track, analyze, and iteratively improve your intralogistics operations.
What are real-time location systems?
Tugger trains rely on static routes and schedules intended to meet the demands of cycle time. However, peaks in demand can lead to material shortages or excesses. This results in delays or may require additional trains. Sometimes, to mitigate these risks, managers may add extra capacity, resulting in reduced cost efficiency. Unfortunately, this results in inefficiency during periods of decreased demand, not to mention higher operational and storage costs. Anticipating and adapting to long-term changes in intralogistics requirements is important for preventing this problems, although it requires continuous evaluation and updates to routes and schedules – much like with fixed routes in public transport.
Real-time location systems (RTLS) aim to tackle these challenges by providing the tracking data and insight needed to continuously optimize milk run logistics. This involves tracking and planning tugger routes according to geolocation information. However, without the real-time data needed to make those decisions, factors like traffic congestion, route interactions, and precise loading/unloading times are compromised. This leads to frequent intralogistics delays, production line downtime, and increased operational costs.
Using technology based on ultrawideband (UWB) technology, RTLS systems provide ultra-high reliable indoor tracking to an accuracy within 10 centimeters. That way, you can monitor the movement of all your milk runs and tugger trains and collect data on their performance to gain real-time conveyance visibility. Factor in data analytics and visualized insights, and operators can make informed decisions, identify areas for improvement, and the why behind them.
Why do you need location intelligence for milk runs?
Location intelligence transforms milk runs into dynamic, data-driven operations. By integrating advanced tracking systems, manufacturers gain visibility and insight into every component of their intralogistics strategy. This enables precise adjustments in real-time to maintain a continuous components supply for manufacturing lines under all conditions.
Let me elaborate on the key advantages of milk run tracking:
- Reduce line stops and downtime: Location-tracking technology gives production and logistics managers insights into factors like traffic congestion, bottlenecks, and delays in the flow of materials. This way, they can take proactive measures to improve route efficiency.
- Maximize transportation usage: By real-time location data and automating routine decision making, production managers can ensure they’re using precisely the right number of tugger trains and routes to meet demand. This helps you get maximum use from your entire tugger train fleet.
- Reducing manual work: Optimal route-planning can be time-consuming, especially in large factories like automotive plants. However, automated tracking and reporting can greatly reduce the time it takes to identify and design the most efficient routes.
Quantitative benefits
- Reduce line stops: Prevent tugger train delays that decrease production capacity
- Increase driver productivity: Have drivers complete more routes during a single shift
- Reduce manual work: Free up time spent on manual compliance and route monitoring
- Train new associates faster: Speed up onboarding processes with simplified training
Qualitative benefits
- Route optimization: Achieve shorter travel distances for tugger trains, reducing energy consumption and charging management
- Real–time feedback loops: Provide immediate updates to associates and team leaders via Andon screens as to whether routes are on track or delayed
- Increased efficiency for team leads: Reduce the time spent on manual time studies or process compliance assessments to improve worker experience and productivity
- Performance comparisons: Compare performance metrics between the lowest and highest performers in your fleet to identify areas for improvement
- Enhanced safety and process compliance: Improve safety and adherence to protocols by consistently applying compliance measures
Four ways to use location intelligence for milk runs
Location intelligence gives manufacturers a complete view of every facet of their intralogistics operations by identifying any deviations from the plan and allowing them to take corrective actions proactively. Below are the metrics and processes I recommend for tracking milk runs with the help of location intelligence software:
1. Measuring tugger train performance
One of the most basic but important metrics to track is run time and stop time. By reporting how much time a given tugger train spends in motion versus moving, you can get a high-level overview of performance.
A detailed route report showing the required and actual number of routes completed per hour, along with an overview of the reasons reported for delays.
2. Route planning and analysis
A route analysis report shows whether routes have been completed, with tugger trains going through all designated stop locations. The report should also show whether or not the routes were completed within the expected timeframe and in a defined sequence.
This is an example of a route map that includes stop locations. Tugger trains should stop at exact locations, while the trajectory visualizes deviations from the expected route.
A sample route analysis report showing route start time, duration, and whether or not the route was successfully completed and materials were delivered on time
Milk run route reports incorporating location intelligence can also help team leaders plan and optimize routes by identifying reasons for delays. For example, if there were fewer completed routes per hour or shift than expected, the report will inform you of such. Furthermore, weekly reports can provide a more comprehensive view, allowing you to identify trends and recurring issues with ease.
3. Optimization of materials transport
By integrating real-time location data and collecting it over time, line managers can continually improve their routes. This involves identifying the shortest possible travel distances and balancing the utilization of tugger train fleet via parametric modelling. For instance, you might merge routes to reduce the inefficient transport of given lines, move different parts between routes, or evaluate your options for implementing one- or two-way milk run routes.
Every bar graph above depicts a single tugger train and its utilization breakdown. The goal of parametric modelling optimalization is to find the ideal balance of logistics tasks among the trains and, when possible, reduce their number.
4. Real-time route tracking and navigation
Andon screens are visual displays and alerting systems that enhance communication and visibility on production floors. For operators, they can inform where they should travel and which tasks (i.e. loading, unloading, or both) are required at a given stop. For managers, andon displays can provide real-time visibility and alerting across the entire fleet.
By assisting in route optimization, location intelligence plays a central role in transforming the habits of tugger train operators. With dynamic navigational assistance and real-time updates, operators can adapt quickly to new and more efficient routes without having to go through any retraining.
Operator Andon is reporting the current situation in real time.
Getting started with smarter milk runs
I hope the tips and benefits of incorporating location intelligence in milk runs I’ve highlighted in this guide will help in your journey towards developing a leaner manufacturing environment. To recap, let’s emphasize the overarching benefits of smarter milk runs:
- Minimized line stops and downtime,
- Real-time conveyance visibility,
- Efficient resource utilization and data driven fleet balancing,
- Reduced operating costs.
