As a trainer and consultant in lean manufacturing. I stumbled upon the 7 types of wastes – TIMWOOD. This kindled my curiosity to consider the different sorts of waste inside a typical Injection Molding process and classify them in to these 7 kinds of waste.
Naturally, Injection Molding is really a complex procedure that involves coordination among various departments. There’s great potential for reducing waste in the Molding Process.
1. “T” for Transportation – The unnecessary movement of people or parts between processes.
e.g.
- Moving molds from storage to the press and vice versa
- The movement of resin from warehouse to the press
- The movement of tools and auxiliary device
- The unnecessary movement of finished goods or semi-finished goods before they are shipped
Address transportation issues by
- If possible, placing the process nearby, using material that shifts from tactics to process without significant delays
- Expansion of production route
- Acquiring multiple storage locations
- Not creating extended or complicated material handling system
2. “I” for Inventory – Holding unnecessary material or parts when not needed
e.g.
- Extra resin inventory – Stocking more resin than necessary
- Surplus parts inventory – Producing parts more than necessary
- Extra machine spare/expendable items/tools
To avoid getting over stock, you can
- Adjust the development process to achieve smooth flow
- Work with a small batch size
- Adhere to the first-in-first-out principle of stagnant material.
- Reduce switching time
3. “M” for Motion – Unnecessary Motion that contributes no value
e.g.
- Opening and closing the security gates for removing parts from the mold/tool without using sprue robots
- Manual de-gating and extra secondary operation
- Reaching too far over for handling parts
- Walking around for searching tools
Reducing motion waste by
- Improving workstation layouts to avoid excessive walking or bending
- Organizing techniques to allow parts to transfer easily from one hand to another
- Redesigning work layout to reduce change in direction of material
- Reduction of batch size
4. “W” for Waiting – People or parts that wait for a work cycle to be completed
e.g.
- Waiting for Machine – Barrel heating, mold heating/cooling, hot runner manifold, machine failure, machine maintenance
- Waiting for Material – Preheating
- Waiting for Men – Paper making for quality inspection/approval, missing schedule
- Waiting for Mold – Tool repairing, tool adjustments under out-of-tolerance conditions
The key to eliminating waiting waste is
- Procedures
- Following checklists for activities where available
- Keeping the work area to specified standard
5. “O” for Over-processing – Using equipments that are not necessary for the work
e.g.
- Making parts which are of tighter tolerance than is needed by Customer
- Over rejecting/over inspecting parts beyond customer needs
- Using bigger press/greater tonnage press that is needed for that mold
- Produce parts with more cycle time
- Running multi-cavity tool with cavities off leading to more cycle time/part produced
Reduce over-processing by:
- Standardizing best approaches for workers to follow along with
- Setting obvious specifications and quality acceptance standards
6. “O” for Over-production – Generating parts than precisely what it takes
e.g.
- Producing more parts than customers need
- Making more parts in anticipation of more orders
- Making many parts due to schedule problems
- Running a mold when only one part is required from multiple cavities
Avoid over-production by:
- Dealing with smaller sized batch sizes
- Making more reliable processes
- Creating stable schedules
- Balancing cells or departments
- Using accurate forecast information which reflects the particular demand
7. “D” for Defects – Rework, Scrap, Incorrect documentation
e.g.
- Making wrong parts – wrong specifications/color/wrong Rev
- Wrong set up – secondary operations
- Parts with missing documents/documents with errors
- Packaging parts with incorrect/wrong box labels
- Mixing two various parts while shipping
To reduce the regularity of defects, attempt to
- Institute sufficient training to enhance workers’ skills
- Improve processes
- Source capable suppliers
- Reduce operator error
- Lower the surplus stock
- Improve transportation plans
There’s also another kind of waste – Skills wastage which is recognized as the eighth kind of waste
e.g.
- Allowing untrained/under-trained Labor or Operator to function specialized equipment
- Insufficient specialized training sources for that molding operations personnel
- Underutilizing human sources for doing rudimentary tasks
Identifying these kinds of wastes and classifying them in to the 7/8 kinds of waste could be useful in creating a Lean Molding Shop. As more shops around the world adjust to Lean culture, this exercise could be interesting for that Injection Molding Business.
