Why Scheduling Always Feels Broken—And How to Fix It

Let’s be honest: most custom part manufacturers hate their scheduling systems.

It’s often hard to trust them because they’re frequently inaccurate, and it’s frustrating to work with something that’s always wrong. But here’s the thing—those issues aren’t necessarily the fault of the scheduling software.

The real problem starts earlier in the process, with estimating. Let’s break down a few reasons why that happens:

Using Cycle Times as a Pricing Lever (Rather Than a Cost Driver)

Estimators use cycle time to calculate costs. This sounds straightforward in theory, but it’s often flawed in practice. Too frequently, an estimator starts with a reasonable cycle time but then tweaks it until they see a part price they think the customer will accept.

Here’s where it gets even worse: once that unrealistic cycle time is locked into the quote, you’re stuck. You win the job, but the shop floor can’t hit the runtime you modeled and often doesn’t update it after the parts are programmed or run. Now you’re seeing variances pile up in your operations, your margins take a hit, and your P&L starts showing red flags.

Ignoring the Full Cycle Time

Another common pitfall is focusing solely on spindle-on time. That’s just one part of the equation. The full cycle includes:

• Opening the machine door.
• Loading and fixturing the part.
• Running the program.
• Removing the part, cleaning it, measuring it, and preparing for the next one.

When estimators ignore these steps, they underestimate how long the job will take. That underestimate ripples downstream, creating unrealistic schedules.

Not Factoring in Efficiency

Efficiency ratings exist to account for the reality of shop floor operations. Machines don’t run at 100% capacity 100% of the time.

For example, a job might have an efficiency rating of 80%, meaning 20% of the time is lost to things like:

• Operator breaks.
• Material handling delays.
• Miscellaneous downtime.

If you estimate a job at 100 hours but don’t apply an efficiency factor, your schedule will be off. In this case, the actual time required would be 125 hours (100 hours ÷ 80%).

Understanding your true efficiency isn’t just a nice-to-have—it’s essential. If you don’t calculate efficiency accurately, your schedule won’t reflect reality, and you’ll end up scrambling to adjust on the fly.

Neglecting Yield

Yield is another critical factor that’s often overlooked in the estimating process. It’s not just about how many parts you plan to produce—it’s about how many you actually need to account for.

If you need 100 finished parts but don’t account for scrap, you’re setting yourself up for trouble. Let’s say your yield is 95%—your estimate should include the time to produce 106 parts to ensure you hit the target.

The Downstream Impact of Unrealistic Estimates

When estimates are wrong, the consequences go beyond just scheduling headaches. They create a domino effect: Unrealistic cycle times lead to underperforming operations. Variances pile up when the shop floor can’t hit the estimated targets. Margins shrink as inefficiencies increase.

Predicting accurate cycle times, especially for complex machined parts, is always complicated and a bit unpredictable. The type and availability of raw materials (near net shape or rectilinear from bar or plate), how operators choose to fixture a part, how programmers choose to program a part, what machining center is used, or how different tools impact material removal rate can all create deviances between predicted runtimes and actual runtimes. An estimator’s job is to put forward a reasonable assumption that the team on the floor can realistically execute.

Give Your Team a Head Start

With so much that is unpredictable in accounting for accurate runtimes, estimators can help their teams at least get off to a solid start by implementing a few best practices:

1. Stop adjusting cycle times to manipulate prices. If you need to adjust prices to make the cost palatable for the customer, consider adjusting pricing variables or rates (e.g. how much of a markup you apply to raw materials, outside operations, or purchased components).
2. Account for the full cycle—not just spindle-on time.
3. Apply realistic efficiency ratings. Don’t assume machines run non-stop.
4. Dial in your yield. Plan for scrap, setup, and any other factors affecting the number of parts you need.

Why does it matter?

Small mistakes in estimating can have a big impact on your margins and your ability to deliver on time. Being late lowers your supplier rating with your customers, which is key to getting more work from them. By focusing on better estimating practices, you’ll create schedules that are more accurate, more reliable, and much easier to trust. It’s a simple shift that can save you a lot of headaches—and help you keep your margins intact.