Learn how to handle heat and thermal expansion when CNC machining steel. Find out how to choose the right tool, optimize the feed and speed, use coolant, measure, control, and follow best practices.

Machine condition is most important when attempting any high precision operation. Knowing that your ballscrews, linear guides, box ways are all in good condition with proper lubrication can avoid the variable least noted. The machine condition along with spindle health will add to vibration and chip loads not calculated. Premature tool wear in a production environment is caused by this factor alone. As you ran xx amount of parts per tool and under same conditions now run less, then this is a time to look at the machine. Working with application engineers in cutting tools we have identified machine problems and with a proper intervention have kept that tool running as intended. Preventive Maintenance and periodical evaluation is key .

How do you handle heat and thermal expansion when CNC machining steel?

Heat and thermal expansion are two common challenges when CNC machining steel. Steel is a material that can generate a lot of heat due to its high cutting resistance and low thermal conductivity. It can also expand and contract with temperature changes, affecting the accuracy and quality of the machined parts. In this article, you will learn some tips and tricks on how to handle heat and thermal expansion when CNC machining steel.

1 Choose the right tool

The first step to handle heat and thermal expansion is to choose the right tool for the job. You want to use a tool that has a high hardness, wear resistance, and heat resistance, such as a carbide or a coated tool. You also want to use a tool that has a suitable geometry, such as a positive rake angle, a small nose radius, and a large helix angle, to reduce the cutting force and heat generation. Additionally, you want to use a tool that has a good chip evacuation, such as a flute or a groove, to prevent chip recutting and heat accumulation.

Add your perspective

Manny P.

TECH CNC VP of Business Development 🔧
Report contribution
When drilling holes the point angle will determine % of tool contact to your work piece. In case of a 165 degree angle much more engagement is made increasing load. Thus a 118 degree angle point will reduce it. Knowing your materials and composition will help you best choose tool design needed. This works same as choosing a 30 degree flute helix for softer materials such as aluminum . Chip breakers on point and flutes are a popular choice to make smaller chips while avoiding the "stringy" buildup that will drastically reduce the life of your tool and require added machine tending. The function of cutting tool geometry is a widely overlooked necessity to optimize any machining operation.

Like

Load more contributions

2 Optimize the feed and speed

The second step to handle heat and thermal expansion is to optimize the feed and speed for the machining operation. You want to find the optimal balance between the material removal rate and the heat dissipation rate. If the feed and speed are too low, you will create more friction and heat, and increase the risk of tool wear and thermal expansion. If the feed and speed are too high, you will create more impact and vibration, and increase the risk of tool breakage and thermal shock. A general rule of thumb is to use a high feed and a low speed for roughing, and a low feed and a high speed for finishing.

Add your perspective

Manny P.

TECH CNC VP of Business Development 🔧
Report contribution
Machine condition is most important when attempting any high precision operation. Knowing that your ballscrews, linear guides, box ways are all in good condition with proper lubrication can avoid the variable least noted. The machine condition along with spindle health will add to vibration and chip loads not calculated. Premature tool wear in a production environment is caused by this factor alone. As you ran xx amount of parts per tool and under same conditions now run less, then this is a time to look at the machine. Working with application engineers in cutting tools we have identified machine problems and with a proper intervention have kept that tool running as intended. Preventive Maintenance and periodical evaluation is key .

Like
Nikhil Antani, P. Eng
(edited)
Report contribution
A higher feed rate generates a thicker chip which in turn helps in carrying the heat away from the cutting zone. A high cutting speed increases the temperature at the cutting edge which will influence the thermal expansion of the workpiece. Using adequate coolant is the solution. Use coolant through insert holders that will direct the coolant at the cutting zone.

Like

3 Use coolant or lubricant

The third step to handle heat and thermal expansion is to use coolant or lubricant during the machining process. Coolant or lubricant can help reduce the friction and heat between the tool and the workpiece, and improve the surface finish and dimensional accuracy of the machined parts. You can choose between different types of coolant or lubricant, such as water-based, oil-based, or synthetic, depending on the material, tool, and machining conditions. You also need to consider the delivery method, such as flood, mist, or minimum quantity lubrication, depending on the chip formation, tool life, and environmental impact.

Add your perspective

Manny P.

TECH CNC VP of Business Development 🔧
Report contribution
High pressure coolant systems used on through spindle ready machines can give you a double edged sword effect. Rotary unions allow for coolant to pass through the TSC system and 1 : Evacuate chips quickly and 2 : Keep temperatures at bay. Many systems for all applications exist . Lathe , Swiss turn, Machining centers can all be piped with an external system to improve your process and at most times make cost in time and tooling efficient.

Like

4 Measure and compensate

The fourth step to handle heat and thermal expansion is to measure and compensate for the thermal effects on the machined parts. You want to use a reliable and accurate measuring device, such as a micrometer, a caliper, or a CMM, to check the dimensions and tolerances of the machined parts. You also want to use a consistent and stable temperature environment, such as a climate-controlled room, to minimize the temperature variations and fluctuations. Additionally, you want to use a compensation method, such as a software algorithm, a thermal sensor, or a correction factor, to adjust the machining parameters and compensate for the thermal expansion or contraction.

Add your perspective

Sean Grow

Former Machinist | 5-axis machining | Journeyman CNC Toolmaker | Aerospace and Defense
Report contribution
Most machines will have some form of chilling system for the multiple axis and spindle of the machine. Temperatures must be maintained between 68-72 degrees F. This temperature range is the same that is used for calibrating and certifying measuring equipment. Ultimately the effects thermal expansion will have in your shop will be determined by the tolerances that need to be held.

Like

5 Control the cutting environment

The fifth step to handle heat and thermal expansion is to control the cutting environment and prevent external factors from affecting the machining process. You want to avoid direct sunlight, drafts, or other heat sources that can cause uneven heating or cooling of the workpiece and the tool. You also want to avoid dust, moisture, or corrosion that can damage the workpiece and the tool. Furthermore, you want to avoid shocks, vibrations, or noises that can disturb the machining accuracy and quality.

Add your perspective

Load more contributions

6 Follow the best practices

The sixth and final step to handle heat and thermal expansion is to follow the best practices and tips from experienced CNC machinists. You want to use a proper clamping method, such as a vise, a fixture, or a chuck, to secure the workpiece and prevent movement or deformation. You also want to use a proper alignment method, such as a dial indicator, a probe, or a laser, to ensure the workpiece and the tool are in the correct position and orientation. Moreover, you want to use a proper maintenance method, such as cleaning, lubricating, or replacing, to keep the workpiece and the tool in good condition.

Add your perspective

How do you handle heat and thermal expansion when CNC machining steel?

1

2

3

4

5

6

1 Choose the right tool

2 Optimize the feed and speed

3 Use coolant or lubricant

4 Measure and compensate

5 Control the cutting environment

6 Follow the best practices

Computer Numerical Control (CNC)

Rate this article

Thanks for your feedback

More articles on Computer Numerical Control (CNC)

More relevant reading