Unmatched CNC Feed Speed & RPM. Why is it a major problem?

To ensure the tool works at its best, matching feed speeds and RPM on your CNC machine is one of the first things you must look for.

When they're incorrectly matched it can lead to tool breakage, premature bluntening, burning & bad edge fnishes. Matched speeds result in a higher quality cut, better surface finish, longer tool life and reduces the risk of unexpected downtime.

When cutting, there is an enormous amount of heat created, and only 2 places for that heat to go - into your tool or out to the chip. By matching the feed speed & RPM, the cutting tool engages the workpiece properly, maintains a consistent chip load, and achieves the desired surface finish.

A BREAKDOWN OF EACH OF THE BASIC FACTORS AT PLAY IN THIS

1. What is Feed Rate?

Feed rate refers to the distance the cutting tool travels during one minute, really the velocity at which the cutter is advanced against the workpiece. It can generally be thought of as how fast the machine moves the router bit through the material when cutting. The feed rate is typically measured in units per minute (i.e., metres per minute).

The suggested feed speed for a given project will vary depending on the material you are cutting, the material of the cutter itself, and several other factors.

Feed speed has a massive impact on the outcome of your work, and is directly related to:
• Safety
• Productivity
• Surface finish
• Part quality

Feed speed can also contribute to the wear on your CNC machine components over time.

2. What is Slew Speed?

Slew speed, also known as traverse speed, refers to the speed at which the machine moves when above the material traveling between cuts. In most scenarios, the slew speed is set as high as possible to help reduce cycle times and improve efficiency.

3. What is Plunge Speed?

Plunge speed is the speed at which the router bit is driven down (or plunged) into the material when starting a cut. The ideal plunge speed will vary depending on the bit used and the material being cut, but it is always important not to plunge too quickly as this can damage the tip of the cutter.

4. What is Spindle RPM?

Spindle rpm or spindle speed is the rate at which the spindle revolves while cutting. This should also be set to a value appropriate for the tool being used and the material being cut. It is sometimes possible to cut at a faster feed rate by increasing the spindle rpm.

If you cut at too low of a feed rate or with too high of a spindle rpm, there is a risk of overheating the router bit and burning or melting the workpiece.

5. Feed Rate Optimisation

Feed rate optimisation is important to maximising the efficiency and quality of a cut. It can also help preserve the long-term condition and performance of your CNC machine.

Consider a project where the cutter is engaged in the material accelerating at 10 metres per minute along a linear path. When it comes to a 90-degree corner, the cutter must decelerate to a dead stop precisely at the corner point, change directions, and accelerate back up to 10 metres per minute to continue cutting. This rapid deceleration results in increased torque loads on the machine.

Think of the cutter like a car. If you were driving 100 kph approaching a 90-degree turn, it would be smart, even safer to slow down ahead of time. This is where feed speed optimisation comes in.

WHAT HAPPENS IF FEED SPEED & RPM AREN’T MATCHED UP?

No matter what material you are cutting (MDF, plywood, particle board, plastics, aluminium, bamboo, FR materials, …), if the feed speed is too slow and the RPM is too high, the cutting tool can cause excessive heat and wear, which can damage the tool and the workpiece. This can result in a poor-quality cut, an uneven surface finish and sometimes, tool breakage.

Watch the video to find out more.

AVOID A RISKY OUTCOME

It is critical to have feed speeds and RPM matched up. However, it is equally important to note the ideal feed speed and RPM will differ based on the material being cut, cutting tool being used, and the specific machining operation being carried out.

Since each machine, material, and application is unique, it is recommended that you experiment with your machine to achieve the best outcome for your application.

As experts in the field, we have assisted numerous businesses in preventing potential failures and breakdowns. Here are some tips and answers to the common burning question "what if...?".

• increased tool wear and elevated heat generation
• greater risk of tool breakage due to excessive forces & clogging
• adverse impact on surface finish and overall machining efficiency

• inadequate material removal, leading to incomplete cuts, chattering
• diminished tool life due to accelerated wear
• great risk of tool breakage due to excessive forces on the tool

c. Incorrect Plunge Speed

• too slow will mean excessive heat build up at the point of entry causing the end of the tool to blunten very quickly
• too fast creates huge cutting pressure on the tool tips which often leads to tools breaking or the plunge points breaking off

CALCULATE YOUR FEED & SPEED

It's important to remember the manufacturers' guidelines and suggestions for the cutting tool and material being used. However, to ensure the best possible results, we recommend experimenting with your machine following the instructions.

How do you calculate speed and feed? Use our Feed Speed Calculator.

1. visit our TECHNICAL HUB
2. fill in the product code and push enter (this will automatically fill the diameter and number of flutes)
3. select the material you are cutting
4. select the best RPM for your application
5. feed speed result will display in the "Recommended Speed in Meters Per Minute" area

DO YOU HAVE MORE QUESTIONS?

Feel free to contact us at 0800 488 647 or sales@tungstenandtool.co.nz for more information on matching feed speed and RPM.