Why Tool Clamping Force is Important?
Do you ever want to drive a car with the wheels’ nuts loosen or broken? Definitely, it is a BIG NO!
Similarly, do you ever want to run a machine with its machine tool spindle that has broken disc springs in it? I bet it is a NO too. Being in the precision industry, we know that how much quality is important to us and our customers. Broken disc springs will undoubtedly affect the tool holding condition on the spindle. This in return will cause an increase in tool runout, chattering marks, and poor surface finishing during precision machining, and directly rejects all the machined parts. Other than that, this can cause issues like:
- The inability of releasing/clamping tool holder during the tool change
- Loosen the tool holder which may drop off during the cutting process
The picture below demonstrates a set of spindle drawbar, which is found in all machining centres as a mechanism of tool clamping unit. In this blog, we are going to look further at the functions and its benefits to CNC machine users.
What Clamping Force Values are Acceptable?
The drawbar force varies by spindle manufacturer but is typically about 900kgs for a 40-taper spindle and about 1800kgs for a 50-taper spindle. The drawbar force in an HSK spindle may be more than twice as much as an SK/BT taper of similar size.
What causes Clamping Force to Reduce?
A typical machine tool spindle drawbar may have 100 or more numbers of disc springs and it is designed to last for at least 1 million cycles. This may sound like a substantial number but consider this: – a typical machine that runs for 20 hours a day, 300 days a year and performs an average of 2-3 tool changes every minute, can reach the critical 1 million number, in less than 1 year. Over time, the contact surfaces of the springs will begin to wear due to fatigue, corrosion, or overload. However, springs will not break all at once. Initially, only one spring might break without a significant impact on the tool holding force. Soon, others will also break since they have to do the work of the initially broken spring(s), and the clamping force will gradually decrease.
Spintec’s Solution for Customers!
It is particularly important for machining centres users to get their spindles checked for tool clamping force on a regular basis which we recommend for a monthly cycle. HOW?
In Spintec, we had helped many of our customers to check on their drawbar clamping force using our portable clamping force measuring device. Our complimentary service* has helped many customers to detect any failures in the clamping system earlier so that action can be taken before the clamping system fails. After the check, we will advise the customer on how they can take care of their drawbar if no major damage is found. Otherwise, we will help the customer to repair the entire drawbar set at a reasonable price.
Need help? Drop your queries below or contact us for a cost-free consultation with our well-experienced engineers!
*Service available within Singapore only.
