How to Optimize Operator Efficiency on Any Shop Floor

Reader Question:

John, what is the average number of CNC machines that one operator can effectively run? We seem to have become complacent with throughput, yet orders are backed up, and I don’t know if it’s a staffing issue or an efficiency issue. I look out on the shop and see more idle equipment than I care to see.

Miller’s Answer:

This is a difficult question to answer with a simple number. Machine to operator ratio for a job shop may be closer to 1:1, while a production shop may be closer to 10:1. The difference between carefully walking a few parts through a process versus aggressively pushing thousands through a process can be stark. Regardless of the number, however, idle equipment is always an uncomfortable feeling, especially expensive idle equipment.

Striking the perfect balance of person to machine is unique to each shop and can depend on the type of work a shop undertakes, the available equipment, staffing levels, scheduling, shop layout, automation and probably a dozen other factors. Therefore, I think the answer to this question is more about efficiency, rather than strictly some magic number. To properly orient this discussion, lets focus on identifying what is holding your shop back from doing more with their time and improving throughput with what you have currently. From there, you can identify staff shortages.

The best way to start is to clearly identify what the machinist’s time is being spent on and how much time those tasks consume. Every job that comes through the shop is going to require a few basic tasks like setup, programming, running the job, quality control and probably some administrative duties. Having this broken down gives a clearer picture of what is hurting your throughput so you can solve the biggest areas first. If the biggest hit is setup time, perhaps invest in workholding solutions that are modular. If it’s tool setup, maybe an offline presetter is the right move. If it’s inspection, maybe it’s time for a CMM.

Also, within each of these tasks you should also be looking for time spent waiting, or time spent traversing the shop. In either case, surround the machinist with what they need by properly scheduling raw material or getting their most important resources closer to the machine. The idle equipment you are referring to may be a symptom of idle operators, not necessarily their individual efficiency once all the pieces are in place.

One mistake I often see is shops confusing a job versus a task, and properly assessing the difficulty of each. It stands to reason that a difficult job, whether due to material, tolerances, geometry or timing, should go to a more experienced machinist to ensure success. However, not every task within that job is necessarily hard. Shops nowadays are rarely filled with a dozen machinists with decades of experience, so our most skilled assets must be utilized correctly. To do so, we must properly identify tasks that are intense and tasks that are simple, and then assign these to the right people.

Intense tasks might be a complex setup or difficult programming, while a simple task could be rudimentary inspection or keeping a machine fed with material. By matching these tasks with the skill level of the employee, both can work more efficiently at those tasks, and they can also be done in parallel. This is where the concept of a setup machinist versus an operator comes into play. The setup machinist is generally more experienced or skilled, and they prepare the job properly before moving on to the next one. Meanwhile, the operator keeps the newly setup machine fed with material and handles simple inspection.

Properly identifying jobs and tasks, and properly assigning them to your team, enables more equipment to run in parallel. The exact same principles can apply to equipment as well, but in slightly different ways. Even though a job might be a perfect fit and more cost effective on one piece of equipment, that doesn’t necessarily mean you should wait to execute it.

A mill can make round parts, and a lathe (under the right configuration) can make square parts. A CAT40 machine can cut the same materials as a CAT50, just slower. A five-axis can do what a three-axis can do, even if it might be excessive. With jobs in the queue, a machine doing work it might not be perfect for is still better than a machine doing no work at all. Be creative in your approach to executing work and open to nontraditional setups. It is much better to be executing jobs and building revenue, even if it’s a little less profitable, than it is to be spending money on idle equipment.

From the question, it sounds like you’re in a leadership role of some type. With leadership comes a responsibility to reflect on yourself and constantly ask what you can do to streamline the shop’s processes.

One consideration may be proper scheduling, and a willingness to be flexible with that schedule. For example, your shop may be too rigid with a “first in, first out” approach. Properly assessing the work on the floor and in the queue is a constant task. If the next job on the schedule is waiting for material, or a specific machine, then you should be taking those opportunities to bring other jobs to the top of the line. This will get idle equipment moving and can get machinists working on those parallel tasks.

I’d be remiss to not mention ERP systems and how powerful they can be in helping with some or all the above recommendations. If you are not already engaged with this, I suggest doing so. If you are already utilizing one, then maybe it’s a good time to revisit your inputs and making sure it’s generating what you expect on the scheduling side.

Whether your idle equipment issues are related to staffing or scheduling, there are many ways to optimize your current situation. Get your people, resources and equipment assigned to the right jobs and the right tasks and get those spindles turning. Good luck!