WeTeamUp Terms: “Air Blast”

Air-Blast-Cover

[ er blast ]

 

What’s “Air Blast”?

An air blast is a device that delivers a stream of high-pressure air to the tip of the milling tool while it is cutting. They are widely employed in both industrial and dental grade CNC machines. The purpose of an air blast is to remove debris from the milling tool while it is cutting. It’s very important to move debris away from the tool because it prevents re-cutting of material. A properly set up air blast is essential for efficient milling all dry dental materials.

 

Interesting Details about “Air Blast”

  • Why is it important?

Milling inherently creates waste debris and it needs to be removed effectively. As a milling tool cuts and creates this waste, it is possible for the waste to stay in the cutting area. If this happens, the material will be re-cut. Re-cutting material creates extra heat, abrasion, and load on the tool. The use of an air blast assures that this effect is minimized.

  • Improper setup can cause problems:

Issues with air blasts are a leading cause of pre-mature chipping and/or tool failure. If your air is not aimed or pressurized correctly, it won’t work. Your milling machine will still operate, but the extra heat and abrasion is hard on the tool. Without air, the tool is essentially scrubbing its way through the material. This can reduce the life of your tooling and cause non-ideal milling results. If you’re getting margin chipping or your tools aren’t lasting, make sure to check that your air is at the correct pressure and properly aimed.

  • They affect milling temperature.

To a minor degree, air blasts also serve to regulate the temperature of the milling tool as it is working. The cool, dry air removes heat directly from the tool through contact, and indirectly removes heat by evacuating waste material effectively.

  • The source matters:

The compressed air you feed your milling machine needs to be very clean and dry. Untreated compressed air contains moisture, oils, and particulates. These contaminates can cause adverse effects if they contact your restorations and can also contribute to pre-mature spindle wear. If your air is wet, it can cause certain materials to cake on the milling tool – which also reduces tool life. The investment in good air filtration and drying is certainly well worth it.

 

Thanks for reading! We hope this break down of the term “Air Blast” has been of value. Stay tuned next week for another post like this!

 

 Check out the growing list of WeTeamUp Terms posts HERE

 

WeTeamUp Terms: “Yttria”

 

Yttria-Cover-image

What is “Yttria”?

[ih-tree-uh]

Yttria, otherwise known as Yttrium Oxide (Y2O3) is an additive used in all dental grade zirconia material. It is used to stabilize the zirconia during sintering.  As your zirconia restoration is sintered, it experiences a crystalline phase change. As the zirconia undergoes this phase change, it is inherently unstable. Without the addition of yttria, the zirconia we use would not have the properties needed for dental crowns.

Interesting Details about “Yttria”

 

  • Pure, unstabilized zirconia undergoes a phase transition from monoclinic (below 1170 °C) to tetragonal (between 1170 °C and 2370 °C) then to cubic (above 2370 °C). The use of a stabilization agent like yttria enables control of this crystalline growth. By changing the amount of yttria, we can control the strength and toughness of the final material.
  • The use of yttria in dental zirconia essentially “locks-in” the desired microstructure during sintering, thus allowing the correct crystalline phases in the material to develop. The stabilized zirconia has a much wider processing window, which allows multiple sintering temperatures and a reduction of the material’s sensitivity to variations in sintering process.
  • The concentration of yttria directly effects the strength and translucency characteristics of the zirconia material. Generally, the more yttria that is in the mix the more material will enter the cubic phase – resulting in more translucency and less flexural strength. This is why more translucent materials tend to be weaker.
  • “Zirconia” is a slang term. In the dental lab industry, when someone says “zirconia” it’s shoptalk for “Yttria Stabilized Zirconia”, or “YSZ”.

Thanks for reading! We hope this break down of the term “Yttria” has been of value. Stay tuned next week for another post like this!

 

 Check out the growing list of WeTeamUp Terms posts HERE

 

 

 

WeTeamUp Terms: “Collet”

Collet-and-tool

What’s a “Collet”?

[kol-it] – Noun

The collet is the mechanism that holds the milling tool in the spindle during operation. It transmits the spindle’s power into the tool while keeping it precisely centered under milling loads. In dental milling machines, the collet opens and closes to allow for tool a changes during milling.  A properly functioning collet is essential to trouble free dental milling.

Interesting Details about Collets:

  • Collets require regular care.

A dirty or worn collet doesn’t work correctly. Make sure you’re aware of the proper maintenance recommendations for your milling machine’s collet. It’s common for them to be neglected. Sometimes the pressure of production makes it easy to forget to care for your machine’s collet. Keeping your collet clean, inspected, and in overall good health will help you avoid common milling issues like chipping and premature tool wear.

  • Collets wear out.

The life expectancy on a collet will vary from machine to machine, but they all eventually wear. A worn collet will suffer from reduced clamping force and will fail to hold the tool perfectly centered. A poorly performing collet will increase the amount of tool runout you have. Typically worn collets will be accompanied by heavy tool wear and lots of margin chipping.

  • Sub-par tools can reduce collet life.

Tools and collets must be precisely matched dimensionally. Lower quality tools can be under or oversized. Any inaccuracy in the roundness of the tool will be translated to the collet and cause excess wear. Keep this in mind when you’re calculating the cost of your tooling options.

  • Check your collet first.

If you’re experiencing milling issues, it’s likely caused by a dirty or used up collet. It’s always less costly to replace a collet than your spindle. It’s good practice to rule out collet issues first when trouble shooting milling issues. In fact, we recommend keeping brand a new one in stock for this purpose. Having the part on hand can help get you out of a bind quickly.

Thanks for reading! We hope this break down of the term “collet” has been of value. Stay tuned next week for another post like this!

 

 

 

 

Top Ten Tool Life Tips

 

When you purchase tools for your mill you want to make sure you get the most out of them. Many labs out there don’t realize how many different things that can impact the life they get from their tools. There are numerous contributing factors to tool longevity. We wanted to identify and explain a few of them.

In no particular order, here is our top ten list:

1. Machine Maintenance

The easiest thing you can do to help your tool life is to be diligent with your machine maintenance. A well-maintained machine is going to subject the tool to the loads that it’s designed to take. Usually, manufacturers have recommended intervals. It’s important to keep up with the scheduled maintenance of the machine if you want to protect your investment. It might be a pain to shut down for a little while, but it’s much better to catch a problem beforehand instead of experiencing a breakdown.

2. Machine Calibration

Calibrating your machine ensures that it carries out commands made by the CAM software in the most precise way possible. A machine that is not calibrated may make erroneous movements. This has a big effect on tool life. It’s comparable to driving a car that has bad alignment. If your alignment is off your tires will wear prematurely. We usually find that labs don’t calibrate enough. Our default recommendation is to do what your manufacturer says to do, but we offer a couple of added layers:

  • If you don’t run your mill much, you still need to calibrate it. The daily temperature variances can affect the calibration of the mill.
  • If you are running the mill in a high production scenario, you want to calibrate more often than the manufacturer recommends.

Properly calibrated machines run better overall and help you get the most life from your tools. You really can’t overdo it.

 3. CAM Software and Milling Strategies.

If you think of your machine system like a nervous system, the software would be the brain. The CAM software deploys the milling strategy to tell the machine how to cut. It has a direct effect on tool wear depending on how aggressive the settings are, and if they are properly matched to the material you are cutting. Typically, when we find an issue with software it’s either out of date or not the right strategy for the material. Every software company out there is constantly tweaking their products to work best. We recommend staying current on your licensing so you can take advantage of the latest improvements.

4. Ambient Temperature

Air temperature can affect tool life because it can affect the calibration of your mill.  If the air temperature changes significantly the mill can change shape due to thermal expansion of its frame. As little as 10 degrees Fahrenheit can have an effect on the calibration of your mill

6. Ambient Humidity

The amount of humidity in your lab can affect your tool life. The higher the humidity, the more material tends to stick to the tool while it mills. Clogged tools run hot and do not efficiently remove material from the cutting area. This increases the load on the tool and reduces the tools service life. It’s always best to keep your mill in a nice, climate-controlled area.

6. Mill cleanliness

Production environments are hard on equipment. Taking care of your mill’s hygiene will help you maintain its peak performance. If the mill is happy and clean, the tool will be too.  In our experience, mills that are kept dirty are usually not maintained and calibrated regularly. Large amounts of material build-up inside your mill will increase the stress on its mechanics and spindle.  This stress will trickle down to the tool, decreasing its life.

7. Material Evacuation: Air and Suction

Removal of powder from the workpiece is critical to the longevity of tooling.  Milling in a pocket full of previously milled material can reduce tool life by 25-40%, depending on how often this condition exists.  Check your airflow and dust collection.  If you are getting milled material buildup adjust airflow accordingly to remove this condition. Most machine manufacturers have a recommended spec for both PSI and CFM; it’s an easy thing to double check.

8. Material Selection

As our digital technology progresses, the variety of materials available is growing. The hardness of the material selected can have a huge effect on the performance of tooling. The harder the material, the shorter your tool life. You can judge hardness of a material by feel. If you’ve cut on multiple brands of zirconia in the green state by hand, you will notice that the feel of each zirconia will differ a bit. The machine notices too. This is something to keep in mind when you are choosing materials to mill in your lab.

9. Spindle Health

The spindle is the lifeblood of your mill. It has a finite life that is rated by the manufacturer – usually in run-time hours. As a spindle ages it will begin to wear out. The spindle bearings become less accurate. This increases the amount of runout (see our article on runout HERE) which can significantly reduce tool life. You can track the health of your spindle by seeing how far into the recommended hours you are. Also, worn spindles will usually tell you they’re worn. If you notice a sharp decline in tool life or an audible pitch change in the way the spindle sounds it might be going out. Make sure to work closely with your machine supplier to keep on top of your spindle health.

10. Collet Health

The collet is a very important part of the tooling recipe. It assures that the tool is held securely and on center to the spindle. It’s good to keep in mind that collets are wear items. They need to be maintained and periodically replaced. If it’s worn, dirty, or not adjusted properly it will not hold the tool right. This can lead to increased runout which will cause the tool to cut unevenly and wear prematurely.  If you notice your mill is chipping margins or wearing tools faster than it usually does, changing your collet is always a good first line of defense.

Conclusion

We hope that this list has given you some insight into the causes of tool wear. This information ought to give you the resource you need to more effectively judge your tooling situation.