Autodesk has sponsored this post.
The shop floor can be an unforgiving place. Spend any time there and you’re guaranteed to see something go wrong—a machine crash, a broken tool, a scrapped part. If you’re lucky, it’ll be a waste of time and money. If you’re unlucky, it’ll be a waste of a lot of time and a lot of money.
So how can machinists reduce these errors? One method that’s becoming increasingly accessible is machine simulation. With more sophisticated CAD/CAM tools and more capable hardware to run them, small and medium enterprises have easier access to machine validation. A simulated machine crash is a lot less expensive than a real crash in the shop.
In this article, we’ll take a look at common challenges faced by machine operators and how machine simulation can help solve them.
The 3 Main Machining Challenges
Starting out in a family run machine shop, George Roberts has experienced the pain of unplanned machine downtime. “I remember once a machine colliding with fixturing, which caused days’ worth of lost production as well as on-going issues with machine reliability, so I understand all too well the effect that errors can have on all sides of a business.”
Today, Roberts is the Product Manager at Autodesk responsible for machine simulation and post-processing in Fusion 360. Having cut his teeth machining real parts, Roberts is well aware of the problems facing CAM users. “There are three common challenges that I see customers face,” he explained.
1. Machine Crashes
The most common type of error is a collision, otherwise known as a machine crash. This happens when something gets in the way of the tool that shouldn’t be there. This could potentially damage the tool or the part, wasting hours of work and forcing one or both to be scrapped.
A bad collision could even damage the machine itself, necessitating costly and time-consuming repairs during which the machine is offline. Machine downtime is an even bigger problem these days than it used to be, as COVID-19 has limited the availability of repair technicians.
2. Machine Limits
The second most common challenge, according to Roberts, is the problem of axis travel limits. This happens when the CNC programming doesn’t properly account for machine limits, meaning the job cannot be completed. This problem can sometimes be flagged by a machine before a job starts, forcing users back to the drawing board, but exceeding machine limits sometimes goes undetected until well into the job.
“You could get six hours into programming and then an alarm pops up on your machine and it freezes and says you’ve hit an axis travel limit. Doesn’t give you any more than that,” Roberts said. The frustrated users must then retract the tool and figure out how to reprogram their part.
“Of course, all the time the programmer is investigating a solution, the machine is sat idle—which wastes even more time and money. It’s also putting the programmer under immense pressure, which could increase the risk that more mistakes are made,” Roberts added.
3. Machine Predictability
Finally, Roberts identified the common practice of a slow-and-steady first run as an inefficient time sink. Operators running a job for the first time will often run the machine with the feed rate turned down, nervously monitoring the progress to ensure their part goes as planned.
Once the programming is borne out the first time, subsequent runs can be completed much more quickly and confidently. However, that slow first run can waste a lot of time, especially if a shop is only producing a handful of those parts. If the machine were more predictable before that first job, there would be no need for the time-consuming tentativeness.
Protecting Your Investment With Machine Simulation
The answer to all three of these common challenges is clear to Roberts: machine simulation. If users can accurately simulate the behaviour of their specific machine on a specific job, they can be certain of a successful part before they press cycle start on the machine itself. Simulating the entire CNC machining process in CAM software, like Fusion 360, can help prevent machine crashes, eliminate axis limit errors, and avoid costly downtime.
“If you’re in the world of manufacturing, whether you’re a startup, a small/medium enterprise, or a huge multinational conglomerate, you’ve made a decision to invest hard-earned dollars in acquiring very expensive CNC machinery. You’ve got to find every possible way to make the best use of that machinery to shorten ROI, while also protecting it so that you don’t have any issues that could be detrimental to your business,” advised Clinton Perry, a Product Marketing Manager for Autodesk’s manufacturing solutions.
“Machine simulation allows users to visualize what’s going to happen and inform them of any problems and minimize potential issues along the line,” added Roberts.
If only it were that easy. In a perfect world, a machinist could click “simulate” and instantly visualize the toolpath on any machine, on any part, exactly as it would happen in the real world. In this world, however, there can be a discrepancy between what a user sees on screen and what happens on the machine. If you can’t be confident in your simulation, it won’t solve any of the challenges discussed above.
According to Perry, there’s a spectrum of CAM software tools that ranges between two extremes: entry-level software that represents a machine but doesn’t faithfully simulate it, and high-end verification software that can be expensive to buy, difficult to learn, and result in additional delays in the overall manufacturing process.
“We recognize that between those two extremes, there’s an opportunity for a middle ground,” Perry said. Lying on that ground is Autodesk’s cloud-powered Fusion 360 software, which combines CAD, CAM, and a few other acronyms you can read about in our article Why Fusion is 360.
The Advantage of Integrated Post Processors
Autodesk has been working hard to improve its machine simulation and verification technology. In October 2020 it acquired CAMplete, a Canadian company specializing in machine simulation and post processing. The investment is right in line with Autodesk’s modus operandi, which is summarized in the company’s two-word slogan: Make Anything.
Less marketing-friendly, but more accurate, is Roberts’ version: Make Anything Safely and Efficiently. It’s that last bit that requires accurate machine simulation, and in Roberts’ opinion, the best way to achieve accuracy is with an integrated post processor.
In CNC parlance, a post processor (or “post”) prepares the final, machine-specific programming for a given job. Each and every CNC machine has a slightly different way of handling G-code, the language of numerical control. A post processor takes the toolpath data from a CAM program (specified in a neutral format called cutter location data, or CL Data) and translates it into the appropriate machine-specific G-code.
It is in this translation that discrepancies can arise between machine simulation and reality. There are often two different translations that occur: the CL Data is translated once for the machine simulation, and again for the post processed file to be sent to the actual machine. You’d think that both translations would be identical, but as Roberts explained, that’s not always a safe assumption.
“The simulation in a lot of CAM packages will choose its best guess of how the post processor is going to function,” Roberts said. “It could choose the right solution almost all the time, but there could be one case where it chooses the wrong solution. These discrepancies are what cause problems.”
Fusion 360 avoids these discrepancies by performing just a single translation of CL Data, the post processing, via its extensive library of integrated post processors. It then drives the machine simulation directly from the posted G-code, meaning that what you see is what you get. “There is a serious risk of collision or other unintended outcome if you’re not simulating the actual G-code,” Perry cautioned.
He continued: “Because Fusion 360 provides both CAM programming and simulation in the same interface, users can simulate programs, identify problems quickly, and then make changes to the machining process without having to go through multiple export loops into the verification software. The net effect of utilizing what is essentially a digital twin of your machine is that it is easier and faster to produce collision free NC code, meaning CNC machining can start sooner and businesses can have a higher degree of confidence that there won’t be any costly mistakes.”
Andy Lawniczak, Chief Operating Officer of Fusion 360 customer Conturo Prototyping, attests to this benefit. “Now we can virtually simulate so much… we load [the geometry] into Fusion 360, we pull it up and we can right away start putting it in our machines and see how it’ll fit and how feasible it is… what’s really important about us having these advanced tools is we can be so much more agile.”
Vendor Partnerships and Easier Machine Simulation
The integrated post processors in Fusion 360 come by way of Autodesk’s partnerships with many machine providers, including Haas, Hurco, Mazak, and dozens of others. The complete library of post processors is included for free in Fusion 360, and all of the post processors are user configurable. The CNC suppliers also provide accurate 3D models of their machines, allowing for faithful simulation that incorporates, among other things, correct axis travel limits.
Not only do these machine vendor partnerships help reduce discrepancies in Fusion 360’s machine simulation, but they make it a lot easier for machinists to begin using the CAM software.
“We’re working with the machine tool vendors to provide simulation that already fits to users,” Roberts said. “Which means if you’ve got a Haas UMC 750, you can just go into Fusion 360, choose it from your machine library, and everything’s configured. Your post processor, the machine tool models, everything is ready to go.”
Roberts envisions a not-too-distant future when even this process will seem overly complex.
“We can imagine a time when we can remove the post processor completely without the need for anything upfront for the user to select. Connecting CAM software to a CNC machine should be as easy as connecting a new printer to your laptop. And we’re investigating ways that we can realize that by working in partnership with machine tool partners,” Roberts revealed.
To learn more about Fusion 360’s machine simulation capabilities and more, visit the Fusion 360 product center.