Design for Manufacturing (DFM): Reducing Cost in Design, Not at the Machine

Design for Manufacturing (DFM) is an engineering discipline that reduces the number of operations, labor and material loss by considering the geometry and production method of a part together at the design stage. Let's state the concrete result from the beginning in this case study: A clamping part produced from AISI 304 stainless steel with lathe + milling + leveling chain, with approximately 30 minutes of labor per part, was redesigned while preserving its functional dimensions exactly; Laser cutting + short leveling flow was started from ready-made pipe profiles and production time decreased from minutes to seconds..

The part was already working; it wasn't causing any problems on the field. The problem was the cost of making it. Below, we explain step by step how this decision was made, what questions were asked, and where the same approach could work on your parts..

What is DFM, How is it Different from Classical Design??#

DFM does not match design to production; aligns design with the realities of production. Concept, With Boothroyd Dewhurst's DFMA methodology It has become systematic: the determining part of the part cost — material, number of operations, machine hours, operator dependency — is locked in with the geometry while it is still on the design table. The production engineer can only make limited improvements in the field; The real profit is made or lost when it is decided how the part will be produced.

The fundamental question of DFM is: is this geometry really necessary to fulfill this function, or is it just drawn that way out of habit??

Why Was the Part on the Field Expensive??#

The part in question had a cylindrical clamping function and was produced with a classical machining flow.:

The first improvement that came to mind was to speed up production: CNC lathe and live tooling could actually reduce cycle time. However, this moved the cost from one item to another — machine hours, fixtures, investment and operator dependency came into play. Faster machining was still machining.

Original Question: Why Is This Part Being Processed??#

DFM, with design for assembly (DFA) Taken together, a critical point became apparent: manufacturing the part by machining was not a functional necessity. The cylindrical form was not essential for the squeezing function, but was dictated by the first chosen production method..

Once this was realized, the design goal changed. The aim was not to process better, but to eliminate the need for processing. The geometry and production method were redefined while preserving the clamping function and functional dimensions; The output question was not "how do we machine this part faster" but "how do we achieve this function without a machining operation".

Solution: Production in a Single Operation#

In the redefined design, the part was produced from ready-made AISI 304 pipe profile supplied from stock:

• Pipe profile was cut with laser profile cutting in a single operation and in quantities.
• After a short leveling, the part was ready for use..
• The dimensions ensuring the function were preserved exactly; The only thing that changed was the method of achieving those measurements.

The correct starting material and a single cutting operation were used instead of a geometry shaped by machining chips.

What Was the Result??#

• Production time reduced from minutes to seconds.
• Turning and milling operations are completely disabled.
• Raw material loss in machining has been minimized.
• The margin of error due to operator and connection is eliminated.
• The process became suitable for mass production.

The gain came not from speeding up a single operation, but from eliminating an entire chain of operations. The cost fell on the design decision, not on the machine.

For Which Parts This Approach Works??#

Parts that receive the highest return from DFM inspection generally have this profile:

• Parts that are produced repeatedly and require multiple operations,
• Parts whose geometry comes not from function, but from the habit of "it has always been produced this way",
• Parts whose workmanship depends on operator skill and whose cycle time varies.

It is also necessary to know its limits: DFM does not reduce each part to a single operation. Areas requiring tight tolerances and precision seating surfaces may require machining; In order to realize the profit, it is necessary to verify that the functional dimensions can be achieved by the cutting method. The correct question is not "how do we remove processing" but "what operations can be removed without breaking functionality". The wasteful side of this look 7 wastes (muda) in our article, On the tolerance side In our article on GD&T we are considering.

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Do you have a repetitive, expensive or operator-dependent part in production? At Takt, we re-evaluate your existing parts with a DFM/DFA perspective without disrupting their functions, and reduce the number of operations and costs at the design stage.. Contact / Request a design review.

Resources#

• Boothroyd Dewhurst — Design for Manufacture and Assembly (DFMA) methodology