G85 boring cycle in CNC Programming - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to start a G85 boring cycle at X10 Y5 Z-20.

CNC Programming

G85 X[1] Y5 Z-20 R1 F100;

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

A5

B20

C10

D15

Attempts:

3 left

💡 Hint

Common Mistakes

Using Y coordinate value instead of X.

Using Z coordinate value instead of X.

The X coordinate for the boring cycle start point is 10, so you fill in 10.

2fill in blank

medium

Complete the code to set the feed rate to 150 mm/min in a G85 boring cycle.

CNC Programming

G85 X10 Y5 Z-20 R1 F[1];

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

A150

B200

C50

D100

Attempts:

3 left

💡 Hint

Common Mistakes

Using the R value instead of F.

Confusing feed rate with spindle speed.

The feed rate (F) should be 150 mm/min as specified.

3fill in blank

hard

Fix the error in the G85 boring cycle code by completing the missing retract plane value.

CNC Programming

G85 X10 Y5 Z-20 R[1] F150;

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

A5

B20

C0

D1

Attempts:

3 left

💡 Hint

Common Mistakes

Using the Z depth value for R.

Using zero which may cause crashes.

The retract plane (R) is usually a small positive value like 1 mm above the part to safely retract.

4fill in blank

hard

Fill both blanks to complete the G85 boring cycle with correct spindle speed and coolant on.

CNC Programming

G85 X10 Y5 Z-20 R1 F150 S[1] M[2];

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

A1200

B1000

C3

D8

Attempts:

3 left

💡 Hint

Common Mistakes

Confusing M codes for spindle direction instead of coolant.

Using wrong spindle speed values.

S is spindle speed, here 1000 RPM. M8 turns coolant on (flood coolant) in many CNC controls.

5fill in blank

hard

Fill all three blanks to create a dictionary comprehension that maps hole diameters to feed rates for boring.

CNC Programming

feed_rates = { [3].[1]: [3].[2] for [3] in holes if [3].[2] > 0 }

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

Adiameter

Bfeed_rate

Dhole

Attempts:

3 left

💡 Hint

Common Mistakes

Mixing up keys and values in the dictionary.

Using wrong variable names in the loop.

This comprehension maps each hole's diameter to its feed rate if feed rate is positive.

Practice

1. What is the primary purpose of the G85 command in CNC programming?

easy

A. To perform rapid positioning without cutting

B. To drill a hole with peck drilling cycles

C. To perform a boring cycle without dwell for smooth hole finishing

D. To execute a tapping cycle for threads

Solution

1. Step 1: Understand the function of G85 and compare with other cycles

   G85 is a boring cycle used to create holes smoothly without dwell time, unlike other cycles that may pause. Drilling uses G81 or peck drilling uses G83; tapping uses G84. G85 is specifically for boring without dwell.

2. Final Answer:

   To perform a boring cycle without dwell for smooth hole finishing -> Option C

3. Quick Check:

   G85 = boring cycle without dwell [OK]

Hint: G85 = boring without pause, not drilling or tapping [OK]

Common Mistakes:

• Confusing G85 with drilling cycles like G81 or G83
• Thinking G85 includes dwell time
• Mixing G85 with tapping cycles

2. Which of the following is the correct syntax for a G85 boring cycle command?

easy

A. G85 X20.0 Y10.0 Z-15.0 R5.0 F100

B. G85 X20.0 Y10.0 Z-15.0 R5.0 S100

C. G85 X20.0 Y10.0 Z-15.0 F100 D5.0

D. G85 X20.0 Y10.0 Z-15.0 R5.0 T100

Solution

1. Step 1: Identify required parameters in G85 and check each option

   G85 requires X, Y, Z for position, R for retract height, and F for feed rate. G85 X20.0 Y10.0 Z-15.0 R5.0 F100 uses X, Y, Z, R, and F correctly. Others use incorrect parameters like S, D, or T which are not valid here.

2. Final Answer:

   G85 X20.0 Y10.0 Z-15.0 R5.0 F100 -> Option A

3. Quick Check:

   Correct G85 syntax includes R and F [OK]

Hint: Look for R (retract) and F (feed) parameters in G85 [OK]

Common Mistakes:

• Using S or T instead of F for feed rate
• Omitting retract height R parameter
• Confusing feed rate with spindle speed

3. What will be the tool movement sequence for the command G85 X30 Y20 Z-10 R2 F80?

medium

A. Feed directly to Z-10, dwell, then rapid retract to R2

B. Rapid to retract height 2, feed to Z-10, then rapid retract

C. Rapid to Z-10, dwell, then feed to retract height 2

D. Feed to retract height 2, rapid to Z-10, then feed retract

Solution

1. Step 1: Understand G85 movement sequence and match to options

   G85 moves rapidly to retract height (R2), then feeds down to final depth (Z-10) without dwell, then retracts rapidly. Rapid to retract height 2, feed to Z-10, then rapid retract matches this. Others mention dwell or wrong order.

2. Final Answer:

   Rapid to retract height 2, feed to Z-10, then rapid retract -> Option B

3. Quick Check:

   G85 = rapid to R, feed to Z, rapid retract [OK]

Hint: G85 always rapid to R, feed to Z, then rapid retract [OK]

Common Mistakes:

• Assuming dwell occurs in G85
• Mixing feed and rapid moves order
• Confusing retract height with final depth

4. Identify the error in this G85 command: G85 X25 Y15 Z-12 F120

medium

A. Missing retract height parameter R

B. Incorrect feed rate parameter F

C. Z value should be positive

D. X and Y coordinates cannot be used together

Solution

1. Step 1: Check required parameters for G85 and analyze given command

   G85 requires retract height R to define safe rapid retract position. The command lacks R parameter, which is mandatory. Feed rate F and coordinates are correct; Z can be negative for depth.

2. Final Answer:

   Missing retract height parameter R -> Option A

3. Quick Check:

   G85 needs R parameter [OK]

Hint: Always include R for retract height in G85 [OK]

Common Mistakes:

• Omitting retract height R
• Thinking Z must be positive
• Believing X and Y cannot be combined

5. You want to bore a hole 20 mm deep with a retract height of 3 mm and feed rate of 90 mm/min using G85. Which command correctly achieves this if the hole center is at X50 Y40?

hard

A. G85 X50 Y40 Z-20 F90

B. G85 X50 Y40 Z20 R3 F90

C. G85 X50 Y40 Z-20 R30 F90

D. G85 X50 Y40 Z-20 R3 F90

Solution

1. Step 1: Set correct depth and retract height, then verify feed rate and coordinates

   Depth is negative for downward movement, so Z-20 is correct. Retract height R3 means rapid retract to 3 mm above surface. Feed rate F90 is correct. X50 Y40 sets hole center. G85 X50 Y40 Z-20 R3 F90 has all correct parameters.

2. Final Answer:

   G85 X50 Y40 Z-20 R3 F90 -> Option D

3. Quick Check:

   Negative Z for depth, R for retract, F for feed [OK]

Hint: Depth is negative Z, retract R positive, feed F set [OK]

Common Mistakes:

• Using positive Z for depth
• Setting retract height too large
• Omitting retract height R