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cnc machine guide

Keeping tool cool when cutting plastic on a CNC machine


The first and most important task when cutting plastic on a CNC machine is keeping your tool cool. This prevents plastic from sticking to the end mill and wearing away at the material you’re cutting. A heat sink is a method of transferring heat away from your tool quickly.

coolant system on the machine

The coolant system on the machine is a critical component of the operation. It must be functional. The cooling system consists of several components that ensure the machine is running at optimal performance levels. If any part of the cooling system is malfunctioning, it can severely impact the performance of the machine and cause unnecessary wear.

The coolant system on the machine consists of several components. Here are the main ones:

Radiator: This is where water and coolant are stored. It has a cap on it to keep pressure in the system. If this cap breaks or becomes loose, it will greatly decrease the performance of the machine and cause overheating problems as well.

Hoses: These are used to transport liquid from one part of your engine to another. They can become brittle over time and leak if not replaced regularly enough.

Thermostat: This regulates how much heat is allowed into your vehicle by opening or closing a valve inside it when needed. If this part fails, then there will be no way for the coolant to get into your engine block where it needs to go in order to cool down properly during use.

CNC machine

use a lower speed

One of the biggest problems with cutting plastic is that it makes your bit hot enough to melt the material. This can be a real problem if you aren’t careful and in fact, one of the main reasons why people struggle while cutting plastic on CNC machines is due to the high speeds they use.

If you’re not careful, it can cause your bit to overheat and become damaged as well as cause the plastic to warp or melt in an undesirable manner. Cutting at higher speeds doesn’t necessarily mean that you’ll get a better result either, so there’s very little downside to slowing down in order to keep your tool cool.

Use a good quality cutting fluid. This step will only work if you have a machine that is compatible with cutting fluids but if you do then it can be extremely helpful for keeping your tool cool when cutting plastic.

use a higher feed rate

I’m cutting a wide variety of plastics on my CNC mill, and some of them are very gummy. I’ve noticed that when the material is difficult to cut, it can start pulling on the cutter and make it heat up.

Because I’m such a dedicated engineer, I hopped online and did some research. And what I found was surprising: most people aren’t really talking about this problem!

Most of the online advice is pretty generic — “use the right tool for the job” or “use a shallow depth of cut” or “cut dry.”

There are several ways to keep tool cool when cutting plastic on a cnc machine.

1. Use a misting system. A misting system will cool the plastic and flushes out chips as well. The misting system is considered to be one of the best ways of cooling because it does not require the intense use of air compressors from your CNC machinery.

2. Use micro-jet systems that come in different sizes so you can easily adjust them according to your needs. These systems are also easy to install and are flexible enough to be used for a variety of applications. The micro-jet system comes with a coolant reservoir and allows for increased productivity for users by providing more efficient cooling and flushing out chips more effectively and efficiently than other cooling methods available in the market.

3. A different kind of water jet system available is the “Through Spindle” water jet system which sprays coolant right through the spindle at the exact point where you need it most, thereby ensuring efficient cooling while eliminating chips efficiently and quickly, like the micro-jets already mentioned above.

If your tools are not getting hot, they probably are not cutting very well.

While cutting plastic with a CNC machine, as the tool wears, it will become less sharp and less able to remove material. At the same time, it will produce more heat as it cuts. This heat will melt the plastic and make it stick to the tool. Eventually, this padding of plastic will completely cover the tool and stop the cutting process.

The goal is to keep this buildup of plastic on the tool within reasonable limits so that we can maintain cutting speeds while avoiding a catastrophic failure of the tool.

An air blast could be used to keep temperatures down.

Many types of plastic can be machined with a CNC machine but will require a slightly different approach to machining than metals.

Unlike metals, plastic tends to melt and deform when cutting, which requires the cutting speed to be reduced significantly.

This slow speed can cause the tool bit to heat up significantly, leading to the melting of the workpiece if it is not cooled properly.

A water-soluble coolant should be used when machining plastics with a CNC machine, but there are some issues that can occur if the coolant is allowed to dry out or becomes contaminated.

An air blast could be used to keep temperatures down.

Proper tool speed and feed rates will improve your finish and tool life.

Properly setting up tool speeds and feeds will help your cutting operations run smoothly. To increase tool life, use high-speed steel (HSS) end mill with a plastic-cutting geometry. If you must use a carbide end mill, you can dramatically improve tool life by using a coolant-fed cutter.

Considerations for Feeds and Speeds

When designing for plastic machining, remember these basic rules of thumb:

Use high-speed steel (HSS) end mill for general purpose milling.

Use a plastic-cutting geometry; this will have a large rake angle and a flat relief angle.

Use an end mill that has fewer flutes; two or three is best.

Speed should be at least 1,000 surface feet per minute (SFM).

Feed rates should be low if possible because most plastics are gummy and tend to pull chips back into the cut — especially when dry machining.

Use proper technique when cutting plastic on a cnc machine.

1. Keep the job clear of chips, coolant, and oil.

2. Keep the tool razor-sharp

3. Pre-drill holes if possible and always use pilot holes for taps

4. Don’t run too fast

5. Use the right grade of plastic for the job and make sure that it is clean, dry, and scratch-free before starting.

6. Dry cut for thinner materials, wet cut for thicker materials

7. Use chip breaker grooves to prevent the built-up edge from occurring.

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