Each issue of The Munro Report will feature one of Munro's Design Principles. Implementation of these principles will help maximize the profitability of your product through its design.

#4 Design Out Handling Problems

Lean Manufacturing Cannot Happen Without Lean Design

Not all products and parts can be assembled right away. Some require an extra step, like screwing. An operator needs to get the part, put the part in its place, then fasten the part to rest of the assembly. Additonally, not all fastening operations can be done by hand like a jar lid. Sometimes a tool will be needed. Throughout the assembly proccess, it is sometimes nescesary to perform non-value added operations such as inspections, moving a part, or causing the operator to move. These extra steps take time, cost money, and create opertunities for poor quality.

In this issue of The Munro Report, we will define common operations required for the assembly of most products. In Munro's Lean Design method, each of these operations recieves a quantified penalty that helps reveal to our customers the Total Accounted Cost of their product. The severity of the penalty is determined by the time it takes to complete each operation and the likley hood of getting it right the first time. It should be your goal to design-out as many of these tasks as possible from the assembly of your design to ensure a profitable, high quality product.

We will address these tasks in two sections; Get - The Part to Operator Interface - and Put - The Part to Part Interface.

Get: The Part to Operator Interface

In this section we are looking at problems an operator will encounter when he tries to remove a part from its shipping container and gets it ready to “PUT” into place. Design your parts so they can be easily removed from bulk storage containers and moved to their position in the assembly.

ONE HANDED PICK UP: The largest dimension for one hand is 18” (1/2 meter), or 10 pounds (41/2 Kilos) or awkward to hold onto.

TWO HANDED PICK UP: If the part is longer than 18” (1/2 meter), or over 10 pounds (41/2 Kilos) or requires two hands to hold onto.

CRANES: should be used if the part is over 42 pounds (19 Kilos).

UNSTABLE PART: Any part that will bend under its own weight or fall apart during handling. Wires, rubber belts, unfastened subassemblies containing loose parts will fall apart if turned over.

PULL APART: Nesting, tangling, hooking together, magnetic
or has design features which requires special packaging or egg crate dunnage.

HANDLE CAREFULLY: Parts easily broken or damaged, painted or plated surfaces or any machined surface.  Any part you will not want shipped in bulk fits this description.

SMALL PART: Parts thinner than .04” (1 mm). Slippery materials or shapes that when dry are hard to pick up. If you are able to pick up more than one part inadvertently due to its size, it is considered "small."

FILTHY PARTS: Oily plates, greased parts, sticky back parts; anything you don’t want to touch.  Remember “You can’t build quality in filth”.

GLOVES: Gloves are a penalty because they reduce tactile sensing and slow operators down.  Gloves are required if parts are hazardous or filthy.

UNWRAP PARTS: Bags, boxes, anything that has to be removed before putting the part in place.  Packaging costs four times, once to buy, once to wrap, once to unwrap, and once for disposal.

HAZARDOUS PARTS OR MATERIALS:  Extremely hot or cold parts, radioactive, touch sensitive, caustic or insidious chemicals (M.E.K.) acid, cadmium, or other heavy metal powder coats or sharp parts are all examples of hazards operators must face.  Don’t be morally bankrupt . . . Get rid of them!

Put: The Part to Part Interface

Now that the operator has the part in his hand, what are the “part to part” problems he faces as he tries to put the product together? Design as many of the following operations out of your products assembly as you can.

COMPLEX MOTIONS: If there is more than one motion to do the job or multiple alignment points or insertion through more than one thickness. 

VISION RESTRICTED: Looking at the spot where the part needs to be is the first thing and operator will do. If an operator has to feel his way in or around the part, or his hand blocks his view of the final location, penalize it!

ACCESS LIMITED: If  an operator has no room for his hands or tools (1” clearance), if he is in a cramped position, bent over, stretching, etc., then access is a problem, penalize it!

OPERATOR DEPENDENT: If the parts don’t self fixture themselves one to another, then penalize the design. A hole to a hole or an edge to an edge is not an alignment feature

HOLD DOWN: Do parts have a feature which holds them in place?  Will they move out of orientation due to future operations?  Remember, one new design and process rule, “Touch the part only once!” Snap fits are preferred over clamps.

ERGONOMIC DANGER: Ergonomics is the study of the man to machine interface. The single biggest avoidable cost to companies is the money paid out to employees who are injured on the job. The average automobile carries as much cost for worker’s compensation as it does for RAW STEEL!

Poka-Yoke: Japanese phrase: “to do without thought” or “it can not be assembled wrong” Make sure to design your parts so they can only be assembled in the correct orientation. If it is possible for a part to leave the station in the wrong orientation, penalize it!

For information on Lean Design®, click here