16 CNC machining cost reduction techniques summarised by Wiseman Machining Factory

Huiwen Mechanical Parts Processing Factory Summarizes 16 CNC Machining Cost Reduction Techniques

See The Common Situations Of CNC Machining: Cumbersome Clamping, Accumulated Waste, Long Processing Time.

As An Engineer, What Do You Think? I Have Been Obsessed With Cost Reduction Design For Too Long, So When I See This Scene, The Picture I Think Of Is: ▲How Much Money Will This Cost!

Each Piece Of Waste Material Is Bought With Money, The High-Speed Rotating Tool Rotates In Circles, Which Means The Expenditure Of Money. Yes! Among The Many Parts Processing Technologies, CNC Processing Should Be One Of The Most Expensive Processes. This Article Will Introduce 16 Cost-Reducing Design Techniques For CNC Processing.

Cost Drivers For CNC Machining In Machining Parts Factories :

1) Processing Time

The Longer The Machining Time, The Higher The CNC Cost. Machining Time Is The Main Driver Of CNC Cost.

2) Material Cost

The Cost Of Blank Material Is An Important Part Of CNC Cost. Material Cost Can Be Reduced By Optimizing The Design To Use Standardized Blanks As Much As Possible Reduce Waste.

3) Installation Time

When The Batch Size Is Small, The Preparation Of The Geometric Model The Planning Of The Machining Process Seriously Affect The CNC Cost. This Part Of The Cost Is A Fixed Cost, Which Can Be Amortized By Large-Scale Production.

4) Other Design Factors

When CNC Part Design Has Special Requirements (Such As Close Tolerance Requirements Thin-Wall Design), Special Tools, More Precise Quality Control, Lower Processing Speeds, More Complex Processing Steps Are Required, Which Will Seriously Affect CNC Costs.

Once We Understand The CNC Cost Drivers, We Can Take Corresponding Cost-Cutting Design Measures To Reduce CNC Costs.

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Cost-Saving Design #1: Rounding Of Internal Vertical Right Angles

All CNC Tools Have A Cylindrical Shape. When Processing A Slot, A Fillet With The Same Size As The Outer Shape Will Be Generated At The Connection Between The Vertical Surfaces Of The Slot. 

If The Radius Of The Vertical Surface Connection Of The Groove Body Is Too Small During Product Design, A Small Tool Will Be Needed, Which Means Increasing The Processing Time Because The Processing Efficiency Of A Small Tool Is As Good As That Of A Large Tool - This Will Lead To An Increase In Processing Time Cost.

To Reduce Costs:

+ The Radius Should Be At Least 1/3 Of The Tank Depth, The Larger The Better;

+ All Fillets Have The Same Size; This Allows The Same Tool To Be Used For The Entire Process;

+ Design A Very Small Fillet (0.5mm 1mm) At The Root Of The Slot, Do Fillet It.

+ The Ideal Fillet Size Should Be Slightly Larger Than The Radius Of The Tool, Which Will Reduce The Load On The Tool During Processing Thus Reduce The Processing Cost. For Example, If The Depth Of The Slot Is 12mm The Fillet Is Designed To Be 5mm Larger, A Tool With A Diameter Of 8mm (Radius Of 4mm) Can Be Used During Processing To Ensure Processing Efficiency. Huiwen Zhizao Is A Machining Factory With More Than Ten Years Of CNC Processing Experience . It Has A Full Range Of Equipment, CNC Lathe/Milling/Grinding/Drilling/Processing. Partners With Parts Processing Needs Are Welcome To Call Us For Quotes.

+ If The Rounding Is Allowed Due To Design Requirements, For Example, It Needs To Be Matched With Another Square Part, In Order To Avoid The Small Fillet, The Following Design Can Be Made:

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Cost Reduction Design #2--Reducing The Tank Depth

Slot Machining Greatly Affects Part Cost Because A Large Amount Of Material Needs To Be Removed, Which Significantly Increases Machining Time.

The Processing Depth Of CNC Tools Is Limited To A Certain Extent. The Best Processing Performance Is When The Groove Depth Is 2 To 3 Times The Diameter Of The Tool. For Example, A Milling Cutter With A Diameter Of 12mm Can Process A Groove With A Maximum Safe Depth Of 25mm.

Of Course, It Is Possible For The Machine Shop To Process Deeper Grooves, Up To A Maximum Of 4 Times The Tool Diameter, But This Will Increase Costs, Especially When Using Multi-Axis CNC Machines.

To Reduce Costs: + The Tank Depth Should Exceed 4 Times The Tank Length.

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Cost-Saving Design #3-Avoid Thin Walls

Unless Otherwise Required, Thin-Wall Design Should Be Avoided Because Thin Walls Are Strong Enough The Processing Cost Is High.

Thin Walls Are Prone To Deformation Even Cracking During Machining. In Order To Avoid This, Mechanical Parts Processing Factories Need To Add More Complex Processing Paths, Which Will Consume More Processing Hours. Thin Walls Are More Prone To Vibration, High-Precision Machining Of Thin Walls Is A Big Challenge.

To Reduce Costs, Machining Parts Factories:

+ For Metal Parts , The Wall Thickness Should Be At Least 0.8mm, The Thicker The Better.

+ For Plastic Parts, The Wall Thickness Should Be At Least 1.5mm, The Thicker The Better.

+ The Minimum Thickness Of Metal Parts Can Be 0.5mm, The Minimum Thickness Of Plastic Parts Can Be 1mm, But This Is Recommended;

When Designing Holes (Including Through Holes Screw Holes) Slots On The Edge Of A Part, Thin Walls Often Occur You Need To Make Sure To Follow The Above Design Guidelines.

▲Avoid Thin Walls To Shorten Processing Time

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Cost Reduction Design #4 - Reduce Thread Depth

Unnecessary Thread Depth Will Increase The CNC Processing Cost Of Mechanical Parts Processing Factories Because Special Tools Are Required. Huiwen Zhizao Is A Machining Factory With More Than Ten Years Of CNC Processing Experience. It Has A Full Range Of Equipment, CNC Lathe/Milling/Grinding/Drilling/Processing, Which Can Effectively Save Costs For Customers. Partners With Parts Processing Needs Are Welcome To Call Us For Quotes.

Remember: Excessive Thread Depth (More Than 3 Times The Hole Diameter) Does Increase The Strength Of The Connection.

To Reduce Costs:

+ The Thread Depth Can Be Up To 3 Times The Screw Hole Diameter.

+ For Blind Hole Tapping, It Is Best For The Machine Shop To Add At Least 1/2 Hole Thread Diameter Extra Length At The Root Of The Hole.

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Cost Reduction Design #5 - Designing Holes With Standard Sizes

Using A Standard Drill, Holes Can Be Processed Quickly Accurately; For Non-Standard Holes, Using An End Mill Will Increase Costs.

In Addition, The Depth Of The Hole Should Exceed 4 Times Its Diameter. Deep Holes (Up To 10 Times The Diameter) Can Be Processed, But This Will Dramatically Increase The Cost Because Of The Difficulty Of Processing.

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Cost-Saving Design #6: Avoid Tight Tolerance Requirements

Close Tolerance Requirements Increase Costs Because They Require Complex Machining Operations, Increase Machining Time, Require More Inspections.

When Defining Part Size Tolerances, You Must Take It Seriously Avoid Marking Tolerances On Any Dimensions. Tolerances Should Be Marked Only When Necessary, Precision Tolerances Should Be Marked Only When Absolutely Necessary.

If Tolerances Are Defined In The Part Drawing, The Part Will Be Machined To Standard Tolerances (± 0.2mm Looser), Which Is Sufficient For Most Non-Critical Dimensions Can Significantly Reduce Machining Costs.

For Internal Features, Precise Tolerances Are More Difficult To Guarantee. For Example, When Machining Holes Slots That Intersect Internally, It Is Easy For Small Defects Such As Burrs To Appear On The Edges Due To Stress Deformation.

These Features Require Inspection Deburring Processes, Which Can Only Be Done Manually, Which Is Labor-Intensive, Time-Consuming, Therefore Costly.

To Reduce Costs:

+ Define Close Tolerances Only As A Last Resort.

+ All Dimensions Are Dimensioned The Same Datum.

+ Remember: The Decimal Points In The Tolerance Are Important, It Defines The Degree Of Precision What Kind Of Measuring Tool Needs To Be Used. For Example, Two Decimal Points Can Be Measured With A Vernier Caliper, Three Decimal Points Can Be Measured With A Micrometer A CMM. To Reduce Costs, Try To Avoid Adding Unnecessary Decimal Points.

+ Precision Tolerance Requirements Can Be Avoided Through Optimized Product Design, Such As Shortening The Dimensional Chain Using Positioning Features. For Details, Please Refer To Chapter 7 Of The Book "Product Guide For Manufacturing Assembly".

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Cost-Saving Design #7--Reduce The Number Of Clamping Times

Reduce The Number Of Times Parts Are Clamped As Much As Possible, Preferably Only Once.

For Example, A Part With Blind Holes On Both Sides Requires Two Clampings. After One Side Is Processed, It Must Be Rotated Re-Clamped Before The Other Side Can Be Processed.

Rotating Repositioning The Part Increases Machining Costs, Since Clamping Is Usually Done Manually. In Addition, For Complex Part Structures, Custom Clamping Fixtures Are Required, Further Increasing Costs. Especially Complex Part Structures May Require Multi-Axis CNC Machines, Which Further Increase Costs Because Multi-Axis CNC Machines Have High Hourly Rates.

You Can Consider Dividing The Complex Part Structure Into Multiple Parts For CNC Machining, Then Fastening Them Together Through Threads Welding.

To Reduce Costs:

+ Design Parts To Be Clamped Only Once.

+ If It Is Possible, Divide The Complex Parts Into Multiple Parts Fasten Them Into One Piece Through Subsequent Processes. The Shenzhen Huiwen Intelligent Manufacturing Technology Co., Ltd. Team Was Established In 2010 Is Located On The 1st Floor Of Building F3, Tianyou Maker Industrial Park, Lixinhu, Fuyong, Bao'an District, Shenzhen. It Has Long Been Committed To The Processing Of High-Precision, High-Difficulty, Easy-To-Deform Metal Plastic Parts , Small Medium-Volume Production Manufacturing Of Light Alloy Composite Materials (Such As Aluminum Alloy, Carbon Fiber, Etc.),  Robot Parts Procurement Customization Services.

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Cost Reduction Design #8 - Avoid Small Features With Large Aspect Ratios

During CNC Machining In A Machined Parts Factory, Some Small Features With A Large Aspect Ratio Are Prone To Vibration, Making Them Difficult To Machine Accurately.

To Avoid This, These Small Features Should Be Connected To Some Thicker Walls Supported By Some Ribs.

To Reduce Costs:

+ Avoid Designing Features With An Aspect Ratio Greater Than 4.

+ Small Features Are Connected To Thicker Walls Ribs Are Added For Support.

-9-

Cost Reduction Design #9--Remove Text Symbols Part Surfaces

Text Symbols On The Surface Of The Part Will Significantly Increase CNC Costs Because Additional Machining Steps Processing Time Are Required.

Text Symbols Can Be Added To CNC Parts Using Some Surface Treatment Techniques, Such As Silk Screen Printing Painting, Which Is A More Cost-Effective Method.

To Reduce Costs:

+ Remove All Text Symbols The Surface Of Parts;

+ If Text Symbols Are Necessary, Choose Recessed Rather Than Raised, As The Latter Requires More Material Removal.

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Cost Reduction Design #10--Consider The Processability Of Materials

The Processing Properties Of A Material Refer To The Ease With Which The Material Can Be Processed.

The Better The Machining Process Of The Mechanical Parts Processing Factory, The Easier It Is To CNC Machine The Parts The Lower The Cost.

The Processability Of A Material Depends On Its Physical Properties. Generally Speaking, The Softer More Ductile The Material, The Easier It Is To Process.

For Example, Brass C360 Has The Highest Processability Can Be Processed At High Speeds; Aluminum Alloys (Aluminum 6061 7075) Can Also Be Easily Processed.

The Processing Technology Of Steel Is Very Low. Compared With Aluminum Alloy, Steel Requires More Than 2 Times The Processing Time. Of Course, The Processing Technology Of Different Steels Is Different. The Processing Technology Index Of Stainless Steel 304 Is 45%, While The Index Of Stainless Steel 303 Is 78%, The Latter Is Easier To Process.

The Processing Performance Of Plastic Materials Depends On Their Stiffness Thermal Properties. During CNC Processing, Plastic Materials Can Easily Melt Deform At High Temperatures.

POM Is The Easiest Material To CNC Process, Followed By ABS; PEEK Nylon Are Common Engineering Plastic Materials That Are Difficult To Process.

To Reduce Costs:

+ Whenever Possible, Choose Materials With Good Processing Properties.

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Cost Reduction Design #11--Consider The Price Of Raw Materials

Raw Material Billet Price Is Another Key Factor In CNC Cost.

The Table Below Shows The Prices For Common Metal Plastic Raw Material Blanks With A Size Of 150 X 150 X 25 Mm.

Raw Materials

Billet Price (Values Are For Comparison Only)

Aluminum 6061

￥170

Aluminum 7075

￥540

Stainless Steel 304

￥610

Stainless Steel 303

￥1000

Brass C360

￥1006

ABS

￥115

Nylon 6

￥204

POM 

￥180

PEEK

RMB 2000

Aluminum 6061 Is Obviously A Very Cost-Effective Material. Only Is The Billet Price Low, But The Processing Technology Is Also Good, Which Is Very Suitable For Making Prototypes.

Stainless Steel 303 Brass C360 Also Have Good Processing Properties, High Processing Efficiency Short Processing Time, But The Billet Price Is Very High, So It Is Only Suitable For Mass Production. Through The Batch Effect, The High Billet Price Is Balanced By The Short Processing Time.

Plastic Materials Such As ABS, Nylon POM Are Close In Price To Aluminum 6061. However, They Are More Difficult To Machine Therefore More Expensive To CNC. PEEK Is A Very Expensive Material Should Only Be Used When Necessary.

To Reduce Costs:

+ Choose Materials With Low Billet Prices Whenever Possible, Especially When Batch Sizes Are Small.

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Cost Reduction Design #12 - Consider Billet Size

The Size Of The Blank Affects The CNC Cost: In Order To Ensure Dimensional Accuracy, The Material On All Sides Of The Part Must Be Removed By Machining In A Mechanical Parts Processing Factory, Which Will Significantly Increase The Material Cost, Especially When The Batch Is Large.

Generally Speaking, The Size Of The Blank Is At Least 3mm Larger Than The Part. For Example, If The Outer Dimensions Of A Part Are 30X30X30mm, Then A Blank Of 35X35X35mm Can Be Selected; If The Outer Dimensions Are 27X27X27mm, Then A Blank Of 30X30X30mm Can Be Selected, Which Can Save Some Material Costs.

To Reduce Costs:

+ The Blank Size Is Generally At Least 3mm Larger Than The Part Size.

+ You Can Consult The Supplier For Standard Billet Size Specifications Try To Design The Parts Close To The Billet Size Specifications To Reduce Material Waste.

—13—

Cost Reduction Design #13 - Avoid Multiple Surface Treatments

Surface Treatment Can Improve The Appearance Of CNC Parts Increase Their Ability To Withstand Harsh Environments, But It Also Increases Costs

If The CNC Part Requires Multiple Different Surface Finishes, This Can Further Increase Costs Because More Steps Are Required, Such As Some Surfaces Needing To Be Masked.

To Reduce Costs:

+ Remove Surface Treatment.

+ Avoid Multiple Surface Treatments.

—14—

Cost Reduction Design #14 - Mass Production

In CNC Machining, Part Batches Affect Machining Costs Because The Initial Setup Cost Of CNC Machining Is Higher Per Part When Batches Are Smaller. When Batches Are Larger, The Setup Cost Is Lower Per Part.

The Larger The Part Batch, The Lower The CNC Machining Costs In A Mechanical Parts Processing Factory. This Is Even More Obvious When The Part Batch Is Small: Even A Small Increase In Quantity Can Significantly Reduce Costs.

The Part Batch Size Increased 1 To 5, The Part Cost Was Reduced By More Than 50%.

To Reduce Costs:

+ Large-Volume Production Reduces Costs By Allowing One Larger Order To Be Placed Rather Than Multiple, Scattered Orders.

—15—

Cost Reduction Design #15 - Designing Axially Symmetric Parts

Axially Symmetrical Parts Can Be Machined Using A Lathe Milling Machine, With Machine Hour Rates Far Less Than A 3- 5-Axis Machining Center .

To Reduce Costs:

+ Try To Design Axisymmetric Parts.

—16—

Cost Reduction Design #16 - Use Other Processing Technologies Instead Of CNC Processing

As Mentioned At The Beginning Of This Article, CNC Machining Is An Expensive Process.

Therefore, No Matter How You Reduce The Cost, It Will Always Be High.

In Today's Rapidly Changing Modern Processing Technology, We Should Consider Using Other Processes To Replace CNC, Rather Than Rigidly Thinking That The Previous Generation Of Products Used CNC Processing, So The New Generation Of Products Must Use CNC Processing.

As Shown In The Figure Below, When The Batch Size Is Small, The Cost Of 3D Printing Is Lower Than CNC Machining; When The Batch Size Is Large, The Molding Process Such As Investment Casting Injection Molding Has A Lower Cost Than CNC Machining.

The Following Table Shows The Process Selection For Different Numbers Of Parts:

Number Of Parts

<10

10~100

100~1000

>1000

Plastic

3D Printing

3D Printing

 (Consider CNC)

CNC

 (Consider Injection Molding)

Injection Molding

Metal

3D Printing  

& CNC

CNC

 (Consider 3D Printing)

CNC

(Consider Investment Casting)

Investment Casting

Die Casting

As The Old Poem Says:

There Is Always Someone Better Out There, The Next Process Will Be Better.

In Many Cases, 3D Printing Is Better Than CNC Machining:

3D Printing Can Process Parts With More Complex Geometries.

3D Printing Can Provide Samples Within 24 Hours.

3D Printing Is Usually Cheaper When The Quantity Is Small.

3D Printing Can Process Materials That Are Difficult To Process With CNC, Such As Super Alloys.

To Reduce Costs:

+ Use Other Processes Instead Of CNC.

Note: The Same Is True For Any Other Manufacturing Fastening Processes, Including Injection Molding, Stamping, Welding Riveting. When Selecting A Process In The Early Stages Of Product Design, Recite The Ancient Poem "There Is Always Better Grass In The World, The Next Process Will Be Better" Many Times In Your Mind, Try Hard To Find It. There Must Be A Better Process, But You Just Don't Know It Now.

"Cost-Oriented Product Design: The Way To Cost Reduction Design" Will Have Three Chapters To Introduce How To Manufacturing Fastening Processes.

Final Words

Cost Reduction Design Is A Very Challenging Task, Domestic Engineers Generally Lack Knowledge In This Area. In My First Few Years Of Actual Product Development Experience, I Basically Did Consider Cost When Designing, I Unilaterally Believed That "Customer First" "Customer First" Were The Engineers' Design Duties To Meet Customer Needs, The Cost Was Left To The Manufacturing Department.

This Is A Misconception Of Product Cost:

1) Product Cost Plays A Very Important Role In Product Development

As Integrated Product Development (IPD) Advocates, Product Development Is An Investment Behavior. If The Product Cost Is Too High It Cannot Bring Profit To The Enterprise, Even Losses, Even If The Customer Is Very Satisfied With The Product, Such Product Development Is A Complete Waste Of Enterprise Financial Resources Human Resources, Does Generate Any Value. In This Way, The Enterprise Will Eventually Be Eliminated.

2) More Than 85% Of Product Costs Are Determined By Product Design, The Remaining 15% Is Determined By Product Manufacturing

If Cost-Oriented Product Design Is Carried Out During Product Design, The Final Production Cost Of The Product Will Inevitably Be Too High. In The Process Of Transforming "Made In China" To "Made In China 2025", Cost-Oriented Product Design Must Be Carried Out.

To Carry Out Cost-Oriented Product Design, Enterprises Engineers Must First Change Their Mindset Improve Their Cost Awareness. One Day, Engineers Will Spend Long Nights Lose Sleep Over Every Detail Of Product Design, For Example:

+ Should The Part Wall Thickness Be 4mm 5mm?

+ Should The Radius Be Designed To Be 0.3mm 0.5mm?

+ Should The Tolerance Of Important Dimensions Be 0.05mm 0.1mm?

It Can Be Said That Engineers Have A Preliminary Awareness Of Costs.

Without Such Cost Awareness, An Engineer Is An Engineer, But Merely A Draftsman Who Can Use Creo, UG Solidworks.

If Engineers Do Make Changes, Do Work Hard To Learn, Only Position Themselves As Draftsmen, They Will Never Achieve A Breakthrough In Their Careers Will Wake Up One Day In The Future To Find That Their Jobs Will Be Replaced By AI.

There Are Also Engineers Who Believe That Cost Is The Business Of The Enterprise, Whether The Enterprise Is Profitable Has Little To Do With Them.

In This Regard, I Can Only Hope That You Will Be Laid Off When The Company Lays Off Employees.