Challenges for Dental Milling Machines

Challenges for Dental Milling Machines:

 How to maintain the machining accuracy of the milling machine?

Since the bite and appearance of teeth greatly affect our daily lives, milling machines are required to have high machining accuracy.
However, the accuracy of the milling machine itself is not enough for precision processing.
Two essential prerequisites for maintaining machining accuracy are accurate "originating the tool/home positioning," and "workpiece positioning".

What is originating or homing the tool?

It refers to determining the starting point of tool machining.
Milling machines use ultra-fine tools with a diameter of 1mm or less to process hard materials, which causes wear. Machining with unexpected wear or chipping on the tool can lead directly to machining defects due to dimensional deviations in the finished product. Especially when machining continuously, it is necessary to check each time.

What is workpiece positioning?

The workpiece must be held firmly so that it will not move during machining.
If a disc is machined with a loose fixture, even with high accuracy of equipment, an error* will occur in the dimensions of the finished product, resulting in defective machining. This becomes especially important in unattended operation with a disc changer not monitored by a person.

*Example of dimensional errors

Drilling holes in the wrong position

Drilling a hole that is larger than the dimension.

Drilling a disc at the wrong angle

To prevent the above risks, the tool or disc must be machined while accurately determining its position using a sensor.

Issue 2. Milling Machine Too Small to Attach a Sensor?

There is a problem of not having enough space for sensor mounting.
Many dental milling machines are small (desktop size) but designed to accommodate more milling bars, so sensor mounting space is limited. So, a compact sensor that can be mounted in a limited space is required.

Issue 3. Sensor Damaged or Malfunctions Due to Chips or Liquids

If a sensor is damaged, the equipment cannot be used until it is restored, so the sensor must also be durable.
Especially, the inside of a milling machine, whether dry or wet, is an adverse environment where fine chips and liquids scatter, and sensors with weak protection structures are at high risk of penetration into the main body and damage. Non-contact laser sensors and proximity sensors are not suitable for installation due to the high risk of failure caused by flying debris.

To maintain the machining accuracy of a milling machine, one must take into account several key factors:

Accurate Tool Setup and Alignment: Ensuring that the tools are properly installed and aligned is crucial for maintaining precision. Improper alignment can lead to tool wear and ultimately affect the quality of the finished product. Regular inspections and alignments are essential to ensure consistent machining accuracy.

Fine-tuning Machining Parameters: The machining parameters, such as spindle speed, feed rate, and depth of cut, must be carefully adjusted based on the material being processed and the desired accuracy. Optimizing these parameters can significantly improve machining accuracy and reduce the likelihood of errors.

Regular Preventive Maintenance: Preventive maintenance is key to ensuring the long-term accuracy of the milling machine. This includes lubricating moving parts, checking and tightening bolts, and replacing worn-out components as needed. Regular cleaning of the machine, especially the areas where chips and dust accumulate, is also essential to maintain its performance.

Effective Cooling and Lubrication: The milling process generates a lot of heat, which can affect the accuracy of the machine if not properly managed. Effective cooling systems and lubrication of critical parts are vital to ensure that the machine operates at optimal temperatures and with minimal wear.