How can precision parts machining ensure accuracy?

The Machining Accuracy Of Precision Parts Refers To The Degree To Which The Actual Geometric Parameters (Size, Shape Position) Of The Parts After Machining Are Consistent With The Ideal Geometric Parameters Specified In The Drawings. The Higher The Degree Of Consistency, The Higher The Machining Accuracy. In Machining, Due To The Influence Of Various Factors, It Is Actually Impossible To Make Every Geometric Parameter Of The Part Completely Consistent With The Ideal Geometric Parameters, There Will Always Be Some Deviations. This Deviation Is The Machining Error.

To Ensure The Accuracy Of Parts, We Need To Ensure The Following Aspects:

(1) Trial Cutting Method

That Is, First Try To Cut Out A Very Small Part Of The Machining Surface, Measure The Size Obtained By The Trial Cut, Appropriately Adjust The Position Of The Tool Cutting Edge Relative To The Workpiece According To The Machining Requirements, Then Try Cutting, Then Measure. After Two Three Trial Cuts Measurements, When The Machined Size Meets The Requirements, Cut The Entire Surface To Be Machined.

The Trial Cutting Method Is To Repeat The Process Of "Trial Cutting-Measurement-Adjustment-Retrial Cutting" Until The Required Dimensional Accuracy Is Achieved. For Example, The Trial Boring Of The Box Hole System.

The Trial Cutting Method May Achieve Very High Accuracy, It Does Require Complex Equipment, But This Method Is Time-Consuming (Requiring Multiple Adjustments, Trial Cutting, Measurement, Calculation), Inefficient, Dependent On The Worker's Technical Level The Accuracy Of The Measuring Instrument. The Quality Is Unstable, So It Is Only Used For Single-Piece Small-Batch Production.

As A Type Of Trial Cutting Method, Matching Is A Method Of Processing Another Workpiece That Matches The Processed Workpiece, Combining Two ( More) Workpieces Together For Processing. The Requirements For The Final Processed Size In Matching Are Based On The Matching Requirements With The Processed Workpiece.

(2) Adjustment Method

Use Samples Standard Parts To Adjust The Accurate Relative Positions Of Machine Tools, Fixtures, Tools Workpieces In Advance To Ensure The Dimensional Accuracy Of The Workpieces. Because The Dimensions Are Adjusted In Place In Advance, There Is No Need For Trial Cutting During Processing. The Dimensions Are Automatically Obtained Remain Unchanged During The Processing Of A Batch Of Parts. This Is The Adjustment Method. For Example, When Using A Milling Machine Fixture, The Position Of The Tool Is Determined By The Tool Setting Block. The Essence Of The Adjustment Method Is To Use The Fixed-Range Device Tool Setting Device On The Machine Tool The Pre-Adjusted Tool Holder To Make The Tool Reach A Certain Position Accuracy Relative To The Machine Tool Fixture, Then Process A Batch Of Workpieces.

Feeding The Tool According To The Scale On The Machine Tool Then Cutting Is Also A Kind Of Adjustment Method. This Method Requires First Determining The Scale On The Scale By Trial Cutting. In Mass Production, Fixed-Range Blocks, Samples, Templates Other Tool Adjustment Devices Are Often Used.

The Adjustment Method Has Better Machining Accuracy Stability Than The Trial Cutting Method, Has Higher Productivity, Does Require High Machine Tool Operators, But Has High Requirements For Machine Tool Adjusters. It Is Often Used In Batch Production Mass Production.

(3) Fixed Size Method

The Method Of Using The Corresponding Size Of The Tool To Ensure The Size Of The Processed Part Of The Workpiece Is Called The Fixed Size Method. It Uses Standard Size Tools For Processing, The Size Of The Processed Surface Is Determined By The Tool Size. That Is, Using Tools With Certain Dimensional Accuracy (Such As Reamer, Reamer, Drill, Etc.) To Ensure The Accuracy Of The Processed Part Of The Workpiece (Such As Hole).

The Sizing Method Is Easy To Operate, Has High Productivity, Relatively Stable Processing Accuracy, Is Almost Independent Of The Worker's Technical Level. It Has High Productivity Is Widely Used In Various Types Of Production, Such As Drilling Reaming.

(4) Active Measurement Method

During The Machining Process, The Machining Dimensions Are Measured While Machining, After Comparing The Measured Results With The Dimensions Required By The Design, The Machine Tool Is Either Allowed To Continue Working Stopped. This Is The Active Measurement Method.

At Present, The Values In Active Measurement Can Be Displayed Digitally. Active Measurement Method Adds The Measuring Device To The Process System (I.E. The Unity Of Machine Tools, Tools, Fixtures Workpieces) Becomes Its Fifth Factor.

Active Measurement Method Has Stable Quality High Productivity, Is The Development Direction.

(5) Automatic Control Method

This Method Is Composed Of Measuring Device, Feeding Device Control System, Etc. It Combines The Measuring, Feeding Device Control System Into An Automatic Processing System, The Processing Process Is Completed Automatically By The System.

A Series Of Tasks Such As Dimension Measurement, Tool Compensation Adjustment, Cutting Processing, Machine Tool Parking Are Automatically Completed To Automatically Achieve The Required Dimensional Accuracy. For Example, When Processing On A CNC Machine Tool, The Parts Are Controlled By Various Instructions Of The Program To Control The Processing Sequence Processing Accuracy.

There Are Two Specific Methods Of Automatic Control:

① Automatic Measurement Means That The Machine Tool Is Equipped With A Device That Automatically Measures The Size Of The Workpiece. When The Workpiece Reaches The Required Size, The Measuring Device Will Issue A Command To Automatically Retract The Tool Stop Working.

② Digital Control Means That The Machine Tool Has A Servo Motor, A Ball Screw Nut Pair A Complete Set Of Digital Control Devices To Control The Precise Movement Of The Tool Holder Worktable. The Acquisition Of Dimensions (Movement Of The Tool Holder Worktable) Is Automatically Controlled By A Pre-Compiled Program Through A Computer Digital Control Device.

The Initial Automatic Control Method Was Completed By Active Measurement Mechanical Hydraulic Control Systems. At Present, It Is Widely Used To Control The Program According To The Processing Requirements, The Program-Controlled Machine Tools That Work By Issuing Instructions The Control System, The Digital Control Machine Tools That Work By Issuing Digital Information Instructions The Control System, The Adaptive Control Machine Tools That Can Adapt To The Changes In Processing Conditions During The Processing, Automatically Adjust The Processing Amount, Optimize The Processing Process According To The Specified Conditions For Automatic Control Processing.

Automatic Control Processing Has Stable Quality, High Productivity, Good Processing Flexibility, Can Adapt To Multi-Variety Production. It Is The Current Development Direction Of Mechanical Manufacturing The Basis Of Computer-Aided Manufacturing (CAM).