In-Cycle Probing: The Secret to Simplifying Part Setup and Reducing Scrap

Fusion 360 facilitates the implementation of probing, enabling the efficient manufacturing of consistent parts.

Autodesk has sponsored this post.

(Image courtesy of Conturo Prototyping.)

(Image courtesy of Conturo Prototyping.)

The pressure is on for manufacturers to cut costs and increase profit margins, while consistently producing higher quality parts. Equipment use is expected to be maximized, with every squandered minute on machine tools translating to excessive losses for the company. Material waste must also be curtailed in this new era of sustainable manufacturing.

In-cycle probing may be a viable solution for addressing all these needs.

As the name suggests, in-cycle probing involves inspecting the geometrical characteristics of a CNC machined part with a probe to identify problems before the part goes all the way through its machining process—and ultimately becoming scrap should a problem be found. By discovering issues while machining is ongoing, operators have the opportunity to react quickly and potentially salvage parts, saving valuable time and money.

“In some cases, the part is not retrievable and you’re better off stopping,” said Philip Hewitt, product manager at Autodesk. “Or you may be able to adapt for position if there is enough stock—depending on your critical tolerances. If you don’t measure, it’s all a bit of a gamble.”

“Normally, you don’t inspect a part until the end of the cycle,” added Richard Stubley, senior technical consultant at Autodesk. “You could actually have a scrap part in the first 10 percent of the machining cycle. You’re then going to spend 90 percent of that cycle making scrap parts. That’s waste in every way you look at it.”

There are many applications for companies to adopt in-cycle probing in their machining operations. On a foundational level, machine tool measurements can help manufacturers verify that their machines are running to spec. During machining, probing can assess part setting and fixturing. Product quality can be ensured without removing parts from machine tools for checks, only to be faced with the complicated process of resetting the parts.

Setting up parts manually requires extremely skilled personnel and/or expensive fixturing systems. Probing allows operators to quickly and accurately measure the precise position of loaded stock material, and to bring all cutting paths to that location. Automating setup leads to the benefits of repeatability in not only quality but also in time, since the process is not left to machinists of varying skill levels. Furthermore, probing can help assess at the very start of a process whether a good part can be achieved from the stock—before the milling tool even touches the material.

During cutting operations, tool wear is an important variable that is constantly changing. The in-cycle probing of features additionally helps operators zone in on where tool wear is occurring.

When it comes to the machined part itself, fixture slippage could take place—or the part could move or distort due to temperature variation. With parts increasingly being made lighter, there is a higher chance of them becoming susceptible to the effects of temperature.

“It could also be stress relief,” said Clinton Perry, Autodesk product marketing manager. “If you’re machining a near-net forging, as you get under the skin of that forging, you release a lot of stresses within that workpiece. Having in-cycle probing built into the manufacturing process allows you to monitor the dimensional precision of your part and how the component is moving dynamically during your machining process.”

Although machine tools frequently come fitted with probes—and can even be retrofitted—in-cycle probing is surprisingly underutilized in industry.

“The probe may just be a glorified doorstop,” quipped Perry.

The problem often arises due to the fear factor where operators are intimidated by the idea of shop floor programming. While most tools are used alongside CAM software, probes are perceived as a throwback where machinists are expected to know long lists of specific codes and formats.

“For example, you would need to know P9810—a protective positioning move,” suggested Stubley. “No one wants to know that. You want to be able to go onto a CAM system, program a block of material, and set it up using a mouse and keyboard.”

This is where Fusion 360 comes in. Integrating probes graphically through the accessible CAM software allows for probing cycles to be programmed within the same system, in the right sequence, using the same types of programming methods, and outputting with the same post processor. With one program comprising all operations needed for the manufacturing process, the usage of probes becomes simplified.

Probing with Fusion 360

Fusion 360 has an integrated design and manufacturing capability, forgoing the need to cobble together several types of software for a workflow. With design, manufacturing, probing and quality control all occurring within a single interface, data no longer has to be exported out of one package to another (for instance, if a designer chose to modify a feature)—massively circumventing the chances of error. There is the further ability to input measurements from tools such as calipers, micrometers and height gauges, which can coalesce together into one results file.

(Image courtesy of Autodesk.)

(Image courtesy of Autodesk.)

“Using the same data file, you could even have the NC [numerical control] programs machining the part update automatically once you change the size of a hole or move a hole slightly,” said Perry. “You could automate the associated probing routine that is used to measure those features, so the amount of heavy lifting is greatly reduced for the operator.”

Autodesk had two goals for probing in Fusion 360: making the probe as easy to use as any other tool, and fully utilizing probes for tasks that were not previously considered possible.

“We’ve brought expertise to the table when it comes to complex 5-axis parts, alignment and surface inspection,” said Stubley. “While we do some phenomenal work on the algorithm side with part alignment, the most standout feature for me personally is the accessibility. You don’t have to have a degree in probing. You don’t have to have done it before. You have to understand the basic principles of CAM systems and machine tools, and you can start to use your probe.”

“We have some very sophisticated measurement capability, but we’ve spent a lot of time thinking about the absolute essentials—the most streamlined way to implement probing,” concurred Hewitt.

Fusion 360 has the added benefit of being able to work with more than just prismatic parts.

“It becomes an order of magnitude more difficult to measure the dimensional precision of complex shapes,” said Perry. “With CAM software having the ability to visually display those areas and being easy to use, anybody can look at Fusion 360’s graphical reports and say, ‘That point is good, that point is bad.’”

The software is especially advantageous when automating the setup of near-net shapes, which are becoming increasingly organic in form.

“That would be an example of a part that you couldn’t set by traditional hand means,” stated Hewitt. “There are no straight edges or holes that you can prop up against, so probing is the only way.”

Understandably, controlling near-net input material is only possible if it is quantified accurately.

“Without the ability to measure [near-net shapes] at the start of the process, you would never have any idea where the stock was on the machine, how much stock needed to be removed, or even if you had finished the job properly at the end of your process,” said Perry. “You would be completely in the dark. Using the probe to set up the position of the part simplifies the process and can be carried out electronically using Fusion 360 with very limited skills.”

Getting Started with Probing

The onboarding process with Fusion 360 involves two distinct types of probing. The first one, macro programming, refers to “calling” the predefined cycles that exist on the machine from the probe manufacturer. To avoid users having to program these cycles manually, the necessary values are preset in the NC program through Fusion 360, so that the operator can simply run the NC program to do the probing and milling.

(Source: Autodesk.)

(Image courtesy of Autodesk.)

The second type of probing utilizes an inspect surface toolpath that takes ownership of all the movements and triggering. A specialist post processor goes between the Fusion toolpaths and the NC code executed on the machine. (Check out Autodesk’s listed post processors here.)

The Autodesk team was ready with recommendations for effective probing. Perry advised in-cycle probing with a 5-axis CNC machine for best results when working with high-end applications such as machining castings or near-net forgings. Hewitt suggested measuring a representative selection of features to avoid in-cycle probing beyond its sweet spot. He further cautioned operators not to forget to calibrate the probe at the same speed as its final measuring move during operation. Stubley advocated that while in-cycle probing is important, it would never completely replace the need for coordinate measuring machines (CMMs).

“CMMs are an absolutely independent check on the accuracy of the part because they are in a temperature-controlled environment, unlike the machine tool,” said Stubley. “It is difficult to validate the part entirely on the machine you made it on. If there is a problem with the machine, that could propagate into a problem measuring the part. But when [probing and CMMs] work in tandem, you are checking the part in two different pieces of equipment.”

The problem with relying on CMMs on their own is that when their operators are off their shift, CNC machinists have no way of verifying the quality of what they are producing.

“In-cycle probing on machine tools allows people running the machine tools to take control of their own quality,” declared Stubley.

“The temperature-controlled environment of CMMs is not much use when you are making decisions in the heat of the machining process,” punned Hewitt.

Down the road, in-cycle probing could serve to unleash the potential for lights-out manufacturing. With Fusion 360’s cloud-based system securely providing data to teams on various devices, decision-making can be further enhanced—allowing companies to keep those spindles turning.

To learn more about Autodesk Fusion 360, visit the website.