Process Modernization is Scary but Necessary

Reader Question:

Admittedly, we have fallen a bit behind with our machinery; however, we are undergoing a modernization effort to include capital equipment upgrades. Many of our legacy processes will be moving to the new machines. What advice can you offer for things we need to think about to make this as successful as possible?

When evaluating process improvements, it’s important we look at the whole picture — uptime, quality and total cycle time being the most important. Photo Credit: Way of the Mill.

Miller’s Answer:

I’m happy to hear you’re taking the leap to modernize the shop. It’s easy to get in a rut when you have a stable process already making money, but this modernization will open new doors for you and secure the shop for years to come.

Because you mentioned legacy processes, I’m going to work from the assumption that both machines are similar configurations (that is, VMC to VMC, four-axis to four-axis and so on). It goes without saying that an entire platform change would require the proceeding considerations, plus many more.

The first step I would take is to identify where and by how much the new machines differ from the previous ones. By doing this, we can make a strategy around what parts of the legacy process should change — and what could stay the same.

Several questions come to mind when determining these differences. Is the new spindle higher speed? Is it a different taper? Does it have more power and is the power in a different place in the rpm range? Does the machine utilize a different drive system, such as direct-drive rotaries versus gear drive or linear motor versus ball screw? Is the controller capable of handling more code than the previous? By identifying these differences, we can plan to address each one.

Depending on the age of the previous machine, tooling speeds and feeds could be the most drastic change you need to come to grips with. It’s also the one that I see shops struggle the most to adapt to. The new machine is likely lighter duty but faster, so the change to dynamic or high-speed machining (HSM) roughing strategies versus the low and slow approach is a must. The lighter, faster cuts may not be as satisfying as the rumble of the old process, but it’s very likely the final metal-removal rate is competitive, if not better.

Along with the elevated speeds, you should consult with your vendors if your current tooling and supporting cast are up to the task. With more rpm comes more heat, so better coatings and possibly new coolant are needed to fully unlock the machine’s potential.

Finally, don’t expect your brand-new high rpm spindle to perform well with the crusty side lock holders you bought in 2001. The fastest man in the world didn’t set the world record wearing steel-toed work boots. In the same spirit, now is the perfect time to upgrade your holders to appropriate ones that are low runout and high rpm balanced. Press fit collets, hydraulics or heat shrinks come to mind for complementing the machine so it can perform at its best.

Additionally, considering the controller differences is important as we start to reprogram for the new machine. Modern controllers can absorb a lot of code in a hurry. This can yield big benefits when it comes to the dynamic strategies mentioned above, but it also unlocks new potential for 3D surfacing. Features that once required an expensive custom form tool could now be done with a ball nose path. And new work you were afraid to take in can now be done confidently alongside your legacy processes. You should also revisit your CAM system and verify it is up to the task and has the strategies you need to make this machine spin.

We’ve primarily focused on the new machine being lighter and faster than the previous one, as this is the general trend across the machine market. However, your upgrade could be to something more rigid and higher power. If this is the case, consider taking time to dive into machine dynamics, chatter and stability and horsepower calculations. The math and science of any cut can get deep, but a baseline understanding of these topics can ensure that you set up safe yet productive conditions for those aggressive cuts that you never thought were possible.

When evaluating the final process improvements, it’s important we look at the whole picture — uptime, quality and total cycle time being the most important. Uptime and quality are likely to improve simply by virtue of the new, less worn equipment. Cycle time can be tricky if we focus on the wrong things.

For roughing, there is no replacement for horsepower and rigidity, and modern machines tend to lean more towards speed than heft. Therefore, we may take a small loss on the roughing side, but it will be coupled with big wins on the finishing side. In my experience, most processes are only around 20-30% roughing, so a small loss for 25% of the process pales in comparison to big wins for the remaining 75% of the process.

I will caution that I have seen numerous shops expect a “drag and drop” changeover to a new machine only to be greatly underwhelmed with their shiny, new purchase. It takes a careful plan of refinement to reach the expected goals. It’s my hope your entire shop embraces this challenge. Good luck!

Want Miller’s help solving your machining challenges? John Miller, owner of Way of the Mill CNC training and consulting, will use his machining expertise to answer a reader-submitted question in his column each month. Submit your question here!