How to Optimize Your Jaw Crusher’s Closed Side Setting (CSS)

Do you want more tons per hour. Every mine boss wants that. The secret is often hidden in a small gap. This gap is the Closed Side Setting (CSS). It controls your profit; Many people ignore it. This guide helps you fix it. We use data from real mines. We explain it simply. You can reduce wear and tear. You can save energy too? Let us look at how SBM helps you.

• What is the Closed Side Setting (CSS)?

  First we must define the terms. The jaw crusher has two plates. One moves and one is fixed. The rock gets crushed between them. The moving jaw goes back and forth. This is the stroke.

  CSS Definition: The CSS is the smallest distance between the plates. It is measured at the bottom of the crushing chamber. You measure it during the crushing cycle. It happens when the jaw is closest to the fixed plate.

  Why it matters:

  • It sets the product size.
  • It impacts the energy use.
  • It affects the liner wear.

  There is also the OSS. This is the Open Side Setting. It is the largest gap. It happens when the jaw pulls back. The relationship is simple. OSS equals CSS plus the throw. The throw is the distance the jaw moves.



• The Core Working Principle and Tech Specs

  You need to know your machine. A jaw crusher uses compressive force. The motor spins a flywheel. The flywheel moves an eccentric shaft. This moves the pitman. The pitman holds the moving jaw die.

  Key Parameters to Watch:

  • Nipping Angle: This is the angle between jaws. It should be 18 to 22 degrees. If it is too big the rock pops out. If it is too small you lose capacity.
  • Reduction Ratio: This is the feed size divided by product size. A standard ratio is 4:1 or 6:1. Don’t push it too hard.
  • Motor Power: This drives the crushing. SBM matches power to the rock hardness.
  • Rotational Speed (RPM): This is how fast the flywheel spins. Usually 200 to 300 RPM.

  Reference data from Minerals Engineering journal shows facts. A correct CSS reduces recirculation load by 15%. This saves electricity. It also stops the secondary crusher from choking. You must balance the CSS with the feed size.

• Does Your Crusher Have These Symptoms?

  Is your crusher sick. Look for these signs. They mean your CSS is wrong.

  • High Power Spikes: The amp meter jumps around. This means the chamber is packed. The CSS is too tight.
  • Flaky Product: The rocks look flat. This is bad for concrete. It happens if the reduction ratio is too high.
  • Liner Wear: The bottom of the jaw wears out fast. This is “toe” wear. It costs money.

  The Solution: You must adjust the setting. Do not guess; Use a gauge. Measure the gap. Check the manual.

• Step-by-Step: How to Adjust the CSS

  There are three main ways to do this. It depends on your machine age. It depends on the model too.

  1. Shim Adjustment

  This is the old way. You use steel plates. They are called shims. You put them behind the toggle block.

  • Stop the machine. Lock it out. Safety first.
  • Loosen the bolts. Pull back the wedge.
  • Add or remove shims. More shims means a smaller CSS.
  • Why use this: It is cheap. It is simple mechanics.

  2. Wedge Adjustment

  This is faster. It uses two wedges. A screw moves them.

  
  • Turn the screw. It pushes the wedge.
  • The jaw moves forward. The gap closes.
  • Why use this: It is easier than lifting heavy shims.

  3. Hydraulic Adjustment

  This is the best way. SBM uses this often. It uses oil pressure.

  • Push a button. The cylinders move the jaw.
  • It is instant. You can do it while running sometimes.
  • Why use this: It saves downtime. It is safer for workers.

• Data Table: CSS Impact on Output Gradation

  Data is king. Look at this table. It shows a test with Granite. The rock hardness was 150 MPa. See how CSS changes the product.

  Effect of CSS on Product Size Distribution

  CSS Setting (mm)	% Passing 75mm	% Passing 50mm	Energy (kWh/t)
  75 mm	85%	55%	1.45
  100 mm	65%	40%	1.10
  125 mm	50%	30%	0.95

  Analysis: A tighter CSS (75mm) makes finer rock. But energy goes up. A loose CSS (125mm) saves power. But the rock is big. You must choose the balance.

• Case Study 1: Granite Mine in Peru

  Project Background:

  A client in Peru had a problem. They process hard granite. The altitude is 4000 meters. The air is thin. Cooling is hard.

  • Equipment: SBM PE-900×1200 Jaw Crusher.
  • Problem: The jaw plates broke every 2 months. The CSS was set to 60mm. This was too tight for the feed size.
  • The Symptoms: The crusher stalled often. The toggle plate broke twice.

  The SBM Solution:

  We analyzed the “work index”. The rock was very hard. We opened the CSS to 90mm. We installed a curved jaw plate. This changed the nipping angle.

  The Results:

  • Wear Life: Plates now last 4 months.
  • Capacity: Throughput went from 180 tph to 220 tph.
  • Client Quote: “SBM fixed our bottleneck. The maintenance team sleeps better now.”

  Why it worked: Opening the CSS lowered the pressure. The curved plate gripped the rock better. This prevented slipping.



• Why is my Output Size inconsistent?

  This is a common question. Operators hate this. One day the rock is small. The next day it is big.

  The Cause: Liner wear is the culprit. As you crush rock; steel wears away. The CSS gets bigger every day. You might not see it.

  The Fix: Measure the gap daily. Adjust the CSS weekly. Do not wait for it to look bad. SBM machines have easy adjusters for this reason.

• Case Study 2: Limestone Quarry in Indonesia

  Project Background:

  This was a cement plant. Limestone is soft but sticky. It rains a lot there.

  • Equipment: SBM C-Series Hydraulic Jaw.
  • Problem: Wet material packed the chamber. The “pancaking” effect happened. The CSS was 80mm. The crusher would trip on overload.

  The SBM Solution:

  We used a hydraulic CSS system. It has an auto-clear function. If pressure spikes; the jaw opens. It clears the mud. Then it resets.

  The Results:

  • Downtime: Reduced by 8 hours per week.
  • Energy: Saved 12% on electricity bill.
  • Client Quote: “The auto-reset is magic. We do not dig out rocks by hand anymore.”

  Why it worked: The hydraulic system reacts fast. It prevents packing. It protects the motor from burning.

• How do I calculate the best CSS?

  Do not guess. Use math. It is simple math.

  The Rule of Thumb:

  The CSS should be slightly smaller than the required product size. But; it must allow for “bulking”.

  Formula: Expected Top Size = CSS x 1.4 (for standard rock). If your CSS is 100mm, your top size is about 140mm. Some flat rocks will slip through.

  Check the Secondary Crusher:

  Look at the next machine. Is it a Cone Crusher? What is its feed opening? The Jaw CSS must make rocks small enough for the Cone. If the Cone takes 150mm; set Jaw CSS to 100mm.

• Installation and Maintenance Tips

  A good machine needs love. Treat it well. It will make money.

  Installation:

  • Foundation: Concrete must be heavy. It absorbs vibration.
  • Leveling: The frame must be flat. Use a laser level.
  • Feed: Use a vibrating feeder. It spreads the rock. Do not dump directly.

  Maintenance Checklist:

  • Daily: Check CSS. Check oil temp. Listen for knocks.
  • Weekly: Grease the toggle seat. Tighten wedge bolts.
  • Monthly: Check liner profile. Flip liners if needed.

  Why do this: Loose bolts break castings. Uneven feed wears plates wrong. Good feed extends life.



• Is a smaller CSS always better?

  No. Definitely not. This is a myth.

  The Risk: If CSS is too small; the rock cannot exit. It stays in the chamber. It gets crushed again and again. This is “over-crushing”.

  The Consequence:

  • You make dust (fines). Dust is waste.
  • You create heat.
  • You stress the shaft. It might crack.

  The Lesson: Crush only as much as needed. Let the secondary crusher do its job.

• Investment and ROI: The Bottom Line

  We won’t list every dollar. Every site is different. But the logic is the same.

  The Cost of Bad CSS:

  • Wasted Energy: 10% to 20%.
  • Wasted Liners: 30% faster wear.
  • Lost Production: 100 tons per day?

  The Gain with SBM:

  Our crushers allow fast adjustment. You keep the CSS optimal. If you save 15 minutes a day; that is 90 hours a year. That is 10,000 tons of extra rock. The machine pays for itself.

• Summary and Final Thoughts

  Optimizing CSS is not hard. It requires discipline. It requires the right machine. You understand the physics now.

  Recap:

  • Measure it often.
  • Understand the nipping angle.
  • Match it to your secondary crusher.
  • Use SBM hydraulics for safety.

  Mining is tough business. Your equipment should be tough too. SBM provides the tools. You provide the drive. Together we build efficiency. Check your CSS today. Your profit margin depends on it.