Conditional statements (IF-THEN) in CNC Programming - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to check if the spindle speed is greater than 1000.

CNC Programming

IF SPINDLE_SPEED [1] 1000 THEN
  M03 ; Start spindle
ENDIF

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

A<

B>

C=

D<=

Attempts:

3 left

💡 Hint

Common Mistakes

Using '<' instead of '>' causes the spindle to start at lower speeds.

Using '=' checks for exact speed, not greater than.

The condition checks if SPINDLE_SPEED is greater than 1000, so the correct operator is '>'.

2fill in blank

medium

Complete the code to stop the coolant if the temperature is less than 50.

CNC Programming

IF TEMPERATURE [1] 50 THEN
  M09 ; Stop coolant
ENDIF

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

A>=

B>

C<=

D<

Attempts:

3 left

💡 Hint

Common Mistakes

Using '>=' would stop coolant at higher temperatures.

Using '<=' includes 50, but the instruction says less than 50.

The coolant stops when temperature is less than 50, so the operator is '<'.

3fill in blank

hard

Fix the error in the code to check if tool number equals 5.

CNC Programming

IF TOOL_NUMBER [1] 5 THEN
  M06 ; Change tool
ENDIF

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

A=

B==

C!=

D>

Attempts:

3 left

💡 Hint

Common Mistakes

Using '==' causes syntax errors in CNC IF statements.

Using '!=' checks for inequality, which is not the goal here.

In CNC programming, '=' is used for equality check in IF statements, not '=='.

4fill in blank

hard

Fill both blanks to check if feed rate is less than or equal to 200 and stop feed if true.

CNC Programming

IF FEED_RATE [1] 200 [2] THEN
  M05 ; Stop feed
ENDIF

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

A<=

B>

CTHEN

D=

Attempts:

3 left

💡 Hint

Common Mistakes

Using '>' instead of '<=' reverses the condition.

Forgetting 'THEN' causes syntax errors.

The condition uses '<=' to check if feed rate is less or equal to 200, followed by THEN to start the block.

5fill in blank

hard

Fill all three blanks to create a condition that checks if the axis position is greater than 100 and stops the machine.

CNC Programming

IF AXIS_POSITION [1] 100 [2] 
  [3] ; Stop machine
ENDIF

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

A<

B>

CM00

DTHEN

Attempts:

3 left

💡 Hint

Common Mistakes

Using '<' reverses the condition.

Omitting 'THEN' causes syntax errors.

Using wrong stop command causes unexpected behavior.

The condition uses '>' to check if position is greater than 100, 'THEN' to start the block, and 'M00' to stop the machine.

Practice

1. What does an IF-THEN statement do in CNC programming?

easy

A. It repeats a set of commands multiple times.

B. It stops the machine immediately.

C. It defines the speed of the machine.

D. It makes the program choose actions based on conditions.

Solution

1. Step 1: Understand the purpose of IF-THEN

   IF-THEN checks a condition and runs commands only if the condition is true.

2. Step 2: Compare with other options

   Repeating commands is done by loops, speed is set by other commands, and stopping is a different command.

3. Final Answer:

   It makes the program choose actions based on conditions. -> Option D

4. Quick Check:

   IF-THEN controls flow based on conditions [OK]

Hint: IF-THEN means "if this, then do that" [OK]

Common Mistakes:

• Confusing IF-THEN with loops
• Thinking IF-THEN sets machine speed
• Assuming IF-THEN stops the machine

2. Which of the following is the correct syntax for an IF statement in CNC programming?

easy

A. WHEN condition DO
commands
END

B. IF (condition) {
commands
}

C. IF [condition] THEN
commands
ENDIF

D. if condition:
commands

Solution

1. Step 1: Identify CNC IF syntax

   CNC uses IF [condition] THEN ... ENDIF structure.

2. Step 2: Check other options

   Options B and C use programming languages like C or Python syntax, A is not standard CNC syntax.

3. Final Answer:

   IF [condition] THEN commands ENDIF -> Option C

4. Quick Check:

   CNC IF syntax uses THEN and ENDIF [OK]

Hint: Look for THEN and ENDIF keywords in CNC IF syntax [OK]

Common Mistakes:

• Using parentheses or braces like other languages
• Omitting THEN or ENDIF keywords
• Confusing IF with WHEN or DO

3. What will be the output of this CNC code snippet?

IF #100 GT 50 THEN
  #101 = 1
ELSE
  #101 = 0
ENDIF
PRINT #101

Assuming variable #100 is 60.

medium

A. 0

B. 1

C. Syntax Error

D. No output

Solution

1. Step 1: Evaluate the condition #100 GT 50

   #100 is 60, which is greater than 50, so condition is true.

2. Step 2: Determine the assigned value to #101

   Since condition is true, #101 is set to 1, then printed.

3. Final Answer:

   1 -> Option B

4. Quick Check:

   60 > 50 is true, so #101 = 1 [OK]

Hint: Check condition truth to find which branch runs [OK]

Common Mistakes:

• Confusing GT (greater than) with LT (less than)
• Ignoring ELSE branch
• Assuming syntax error due to ELSE

4. Identify the error in this CNC IF statement:

IF #200 EQ 10
  G01 X100 Y100
ENDIF

medium

A. Missing THEN keyword after condition

B. Incorrect variable name #200

C. Missing ENDIF keyword

D. G01 command is invalid inside IF

Solution

1. Step 1: Check IF statement syntax

   CNC IF requires THEN after the condition, missing here.

2. Step 2: Verify other parts

   Variable name is valid, ENDIF is present, G01 is valid command inside IF.

3. Final Answer:

   Missing THEN keyword after condition -> Option A

4. Quick Check:

   IF must have THEN before commands [OK]

Hint: IF condition must be followed by THEN [OK]

Common Mistakes:

• Forgetting THEN after IF condition
• Thinking ENDIF is missing
• Assuming commands can't be inside IF

5. You want the CNC machine to move to X=50 only if the tool number (#1) is 3 or higher. Which IF statement correctly does this?

hard

A. IF #1 GE 3 THEN
G01 X50
ENDIF

B. IF #1 GT 3 THEN
G01 X50
ENDIF

C. IF #1 LE 3 THEN
G01 X50
ENDIF

D. IF #1 EQ 3 THEN
G01 X50
ENDIF

Solution

1. Step 1: Understand the condition "3 or higher"

   This means #1 is greater than or equal to 3 (GE 3).

2. Step 2: Check each option's condition

   IF #1 GE 3 THEN G01 X50 ENDIF uses GE (greater or equal), B uses GT (greater than) which excludes 3, C uses LE (less or equal), D uses EQ (equal only).

3. Final Answer:

   IF #1 GE 3 THEN G01 X50 ENDIF -> Option A

4. Quick Check:

   GE means "3 or higher" [OK]

Hint: Use GE for "greater or equal" conditions [OK]

Common Mistakes:

• Using GT excludes the value 3
• Using LE or EQ does not cover all values 3 or higher
• Confusing GE with GT