Rest machining for remaining material in CNC Programming - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to start rest machining with the correct tool call.

CNC Programming

T[1] M06 ; Tool change command

Drag options to blanks, or click blank then click option'

A01

B04

C03

D02

Attempts:

3 left

💡 Hint

Common Mistakes

Using the wrong tool number for rest machining.

Forgetting the M06 command after the tool number.

Tool 02 is commonly used for rest machining to remove remaining material after roughing.

2fill in blank

medium

Complete the code to set the spindle speed for rest machining.

CNC Programming

S[1] M03 ; Set spindle speed and start spindle clockwise

Drag options to blanks, or click blank then click option'

A3000

B1500

C4500

D6000

Attempts:

3 left

💡 Hint

Common Mistakes

Setting spindle speed too high or too low for the tool and material.

Omitting the M03 command to start the spindle.

A spindle speed of 3000 RPM is typical for rest machining to balance speed and finish quality.

3fill in blank

hard

Fix the error in the rest machining feed rate command.

CNC Programming

F[1] ; Set feed rate for rest machining

Drag options to blanks, or click blank then click option'

A200

B100

C300

D400

Attempts:

3 left

💡 Hint

Common Mistakes

Using feed rates that are too high causing tool breakage.

Using feed rates that are too low causing inefficient machining.

A feed rate of 200 mm/min is appropriate for rest machining to ensure smooth cutting without tool overload.

4fill in blank

hard

Fill both blanks to complete the rest machining loop and tool path command.

CNC Programming

G[1] X[2] Y50 ; Rest machining linear move

Drag options to blanks, or click blank then click option'

A01

B00

C100

D150

Attempts:

3 left

💡 Hint

Common Mistakes

Using G01 for rapid moves which slows the program.

Using invalid coordinate values.

G00 is the rapid positioning command, and X100 moves the tool to X=100 for rest machining.

5fill in blank

hard

Fill all three blanks to complete the rest machining conditional check and loop.

CNC Programming

IF [#[1] [2] [3]] GOTO 100

Drag options to blanks, or click blank then click option'

A500

B>

C0

D<

Attempts:

3 left

💡 Hint

Common Mistakes

Using incorrect variable numbers.

Using wrong comparison operators.

Omitting the GOTO command.

The condition checks if variable #500 is greater than 0 to continue rest machining by jumping to line 100.

Practice

1. What is the main purpose of rest machining in CNC programming?

easy

A. To remove leftover material after rough machining

B. To perform the initial rough cut on the raw material

C. To polish the surface after finishing

D. To drill holes in the workpiece

Solution

1. Step 1: Understand rest machining concept

   Rest machining focuses on removing leftover material that rough machining did not clear.

2. Step 2: Differentiate from other machining steps

   Rough machining removes bulk material; rest machining cleans remaining parts for better finish.

3. Final Answer:

   To remove leftover material after rough machining -> Option A

4. Quick Check:

   Rest machining = leftover removal [OK]

Hint: Rest machining targets leftover material after rough cuts [OK]

Common Mistakes:

• Confusing rest machining with rough machining
• Thinking rest machining is for polishing
• Assuming rest machining drills holes

2. Which of the following is the correct way to specify a block range for rest machining in a CNC program?

easy

A. G71 P100 Q200 U-0.5 W-0.3

B. G71 P100 Q200 U0.5 W0.3

C. G71 U0.5 W0.3 P100 Q200

D. G71 P200 Q100 U0.5 W0.3

Solution

1. Step 1: Identify correct block range order

   In G71, P is the start block number, Q is the end block number; P must be less than Q.

2. Step 2: Check allowance values

   U and W specify allowances and must be positive for rest machining.

3. Final Answer:

   G71 P100 Q200 U0.5 W0.3 -> Option B

4. Quick Check:

   Start block < end block and positive allowances [OK]

Hint: Start block P < end block Q; allowances positive [OK]

Common Mistakes:

• Swapping P and Q values
• Using negative allowance values
• Placing parameters in wrong order

3. Given the following CNC code snippet for rest machining:

G71 P150 Q180 U0.2 W0.1
N150 G01 X50 Z-20
N160 G01 X55 Z-25
N170 G01 X60 Z-30
N180 G01 X65 Z-35

Which blocks will be used for rest machining?

medium

A. Blocks N150 to N180

B. Blocks N100 to N150

C. Blocks N160 to N170

D. Blocks N180 to N200

Solution

1. Step 1: Identify block range from G71 command

   G71 specifies P150 and Q180, meaning blocks from N150 to N180 are selected.

2. Step 2: Confirm blocks exist in code

   Blocks N150, N160, N170, and N180 are present and will be used.

3. Final Answer:

   Blocks N150 to N180 -> Option A

4. Quick Check:

   Block range P150-Q180 matches blocks used [OK]

Hint: Use blocks between P and Q numbers inclusive [OK]

Common Mistakes:

• Choosing blocks outside P-Q range
• Selecting only middle blocks
• Ignoring block numbers in code

4. Identify the error in this rest machining code snippet:

G71 P200 Q180 U0.3 W0.2
N180 G01 X40 Z-15
N190 G01 X45 Z-20
N200 G01 X50 Z-25

medium

A. G71 command is missing

B. Allowance values U and W are negative

C. Block numbers are missing

D. Start block P is greater than end block Q

Solution

1. Step 1: Check block range order in G71

   P=200 and Q=180 means start block is after end block, which is invalid.

2. Step 2: Verify allowance values and blocks

   U and W are positive; blocks N180, N190, N200 exist, so no error there.

3. Final Answer:

   Start block P is greater than end block Q -> Option D

4. Quick Check:

   Start block must be less than end block [OK]

Hint: Ensure P < Q in block range for rest machining [OK]

Common Mistakes:

• Reversing P and Q values
• Assuming negative allowances are allowed
• Ignoring block numbering order

5. You have a rough machining program that leaves a small amount of material on the surface. To optimize the finishing process using rest machining, which approach is best?

hard

A. Skip rest machining and do a full finish pass over the whole part

B. Apply rest machining over the entire rough machining block range with large allowances

C. Use rest machining with block range covering only leftover areas and small allowances

D. Use rest machining without specifying block ranges or allowances

Solution

1. Step 1: Understand rest machining goal

   Rest machining targets only leftover material to save time and improve finish.

2. Step 2: Choose block range and allowances carefully

   Select block range that covers leftover areas only and use small allowances to avoid overcutting.

3. Final Answer:

   Use rest machining with block range covering only leftover areas and small allowances -> Option C

4. Quick Check:

   Target leftover with precise range and allowances [OK]

Hint: Focus rest machining on leftover areas with tight allowances [OK]

Common Mistakes:

• Using large allowances causing excess cutting
• Applying rest machining to entire rough range wasting time
• Not specifying block ranges causing full part machining