CNC Series: Weight, where bigger is better.

This is part two of our CNC blog series on CNC router productivity, where will focus on the importance of weight and its place in producing optimum cut quality, increased production, and superior cutter performance.

Choosing the right solution for your shop involves research and understanding which match your production expectations and future goals. First, let’s talk about weight.

CNC Blog Series - Weight

It’s all about choosing the right solution.

Researching CNC routers can be a daunting task for many. There is a wide range of models available, and it takes time to decipher all the differences. However, there are really two main areas where CNC routers differ: features & size when it comes down to it. There are obvious tables or capacity-sized differences when we talk about size, but there are also distinct differences in machine construction. For instance, Anderson manufactures a wide range of CNC routers ranging in weight from 3000 kgs (6600 lbs) to well over 30000 kgs (66000 lbs). So why the wide range in machine weight & models?  It all comes down to matching the right machine with the daily production requirements.

The key factor in cutting speed is not router horsepower or the cutting tool. These both play a role, but the most important consideration is the weight and design of the machine structure.  Omnitech Selexx machines are produced with a cast iron gantry and cast-iron mounting plate known for its vibration-damping properties. As we have learned in our first CNC blog Series (How does cutting speed affect your cutter life?), vibration plays a factor in cut quality, cutting speed, and cutter life.

An accumulation of vibrational energy without adequate dissipation can result in an increasing amplitude of vibration. Excessive vibration will result in rapid cutter wear, poor cut quality, excessive wear on bearings and machine components. Many CNC manufacturers will use aluminum for their backing plate and some for their gantry. One of the reasons is that aluminum is lighter, thus requiring smaller servo drives to move it. However, as illustrated above, it is not ideal for vibration damping. Therefore, utilizing machines with aluminum and other non-damping materials will require reduced cutting speeds to prevent vibration and, in turn, required cut quality. The result is reduced production, greatly increased tooling costs, reduced cut quality, and shorter machine component life. One simple method to identify vibration while cutting with a CNC router is to listen to it simply. The louder the bit is during a cutter operation indicates, the more it is vibrating.

The exceptionally high damping capacity of the heavier cast iron is one of the most valuable qualities of this material. For this reason, it is ideally suited for machine bases, gantries, and supports. The damping capacity of cast iron is considerably greater than that of steel and aluminum, as we can see below:

Relative Damping Capacity
x 104
Gray Iron, Course Flake
Gray Iron, Fine Flake
Ductile Iron
Malleable Iron
Armco Iron
Eutectoid Steel
White Iron
Source: Atlas Foundry Company Inc: Mechanical Properties of Gray Iron – Damping Capacity

Top advantages of cast iron / heavy-duty machine construction.

  • Superior vibration damping
  • Faster cutting speeds
  • Increased tooling life resulting in greatly reduced expenses
  • Increase bearing & component life
  • Precision cut quality

Machine selection is key in matching the right CNC router to your needs. For example, if you are looking for a machine to cut solid wood components utilizing large diameter tooling, there is more potential for vibration. Thus, you need a heavier machine that can handle this job and dampen the vibration. Likewise, if you are looking for maximum cutting speeds while nesting at, say 50 m/min, you need a machine with the weight and structure to handle this day in and day out. Matching the right machine with heavier built construction and heavy-duty servo drives allows you to achieve all the above resulting in a machine with more uptime, greater production, and significant cost saving.

Now that we learned the importance of weight on CNC routing productivity in our CNC Series: Weight, where bigger is better, stay tuned and read our next blog, which discusses CNC productivity’s next point: Vacuum, it’s all in the design.

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