I was recently asked by a potential customer how G-Wizard Calculator could make his small CNC business more efficient. In the last few weeks, I have received correspondence from G-Wizard users that tell the story of how the product has helped them. One wrote and flatly said that G-Wizard had saved his firm nearly $25,000 by reducing the time needed to run a particular job. Another was using G-Wizard to good effect to evaluate trade offs of several different kinds of tooling. In particular, this is a manufacturer of custom indexable tooling that wanted to understand the potential value of corncob roughers on jobs that had very large amounts of chip thinning due to running small stepovers. Still another was from one of the largest manufacturers in the world who was looking to improve feeds and speeds for a turbine housing and had questions about how to evaluate tradeoffs of the various cutting parameters G-Wizard uses to determine feeds and speeds. Each conversation touched on one of the big three areas where G-Wizard can help, which I’d like to go over in a little more detail.
Better Feeds and Speeds Starting Point
The first thing G-Wizard can do to help is to generate better feeds and speeds as a starting point. I get letters all the time from users who say the feeds and speeds generated by G-Wizard were better than what they had been using. This is certainly not always the case, but it isn’t easy to generate good feeds and speeds. G-Wizard considers over 50 variables in its calculations, and we have incorporated a lot of tricks passed along by the tooling manufacturers. “Better” can mean higher material removal rates, better tool life, or better surface finish. Each one needs to be optimized for a slightly different feeds and speeds “Sweet Spot”, and I hear stories of GW helping achieve a better result in each area. Improved tool life or material removal rates are the ones I hear most often from professionals and better tool life and surface finish come across most often from hobbyists who frankly care less about achieving high material removal rates. I get these reports from operators, machinists, and programmers from organizations of all sizes.
Sometimes it’s a result of not having good data to even do a calculation for a particular material that’s in our Materials Database. More often, it is a function of G-Wizard doing a more complete calculation of all the variables involved. Even if you’ve reached the level of sophistication to deal with chip thinning, lead angles on insertable tooling, and ballnose effective diameter, you’re probably still not considering all the variables that matter. For example, have you factored your machine’s spindle power curve into your equations? G-Wizard can do that, and when peak power is achieved somewhere off the theoretical best rpm for the cutter and material, this becomes very important. Another great example is G-Wizard’s ability to consider tool deflection. And, closely related to tool deflection is the question of chatter. For many jobs, chatter is the limiting factor to productivity. If you tame tool deflection, you will minimize chatter. But, if you’re still getting chatter, you can measure the distance between chatter marks and G-Wizard will tell you the optimum spindle speed ranges to minimize the chatter.
Another area I get a lot of correspondence about is micro-milling. The tiny little cutters used are expensive and delicate. And, because of the geometry of such cutters at the scales they operate at, calculation of feeds and speeds for them requires almost completely different assumptions. These cutters almost always run with negative rake, and chip loads are so low relative to the radius of the cutting edge that rubbing is more the norm than the exception. It often takes more than one revolution before a chip is finally pulled up out of the workpiece. G-Wizard has a special set of algorithms that are specifically intended for the micro-milling world that have helped many machinists radically improve their tool life as well as their material removal rates and surface finish when micro-milling.
Help Evaluating Multiple Scenarios
As shops become more sophisticated, the ability to evaluate as many scenarios as possible becomes more important. There are an almost infinite number of ways to manufacture a particular part. There are lots of tradeoffs around something as simple as deciding how many passes to make to cut a deep pocket. Add to that different tooling choices, coatings on tools, indexable versus solid endmills, different entry styles (helix, ramp, plunge), and the combinations become almost infinite. Like a game of chess, it’s impossible to evaluate every combination. But, also like the game of chess, the best machinists have an innate sense for how to narrow down the list of possibilities. They know which scenarios they should consider in order to have covered enough territory to optimize the job. G-Wizard is an indispensable tool for letting you plug in the different values and quickly get back the information you need to consider the scenarios.
For example, the chap I mentioned above was already running small stepover toolpaths that have a lot of chip thinning. He was wondering if the use of a corncob rougher would be able to speed up the process enough to be worth the toolchange and extra cost of the tooling. G-Wizard let him see enough possibility there that it was worth ordering some roughers and giving it a try.
Smart machinists are always on the lookout for something new to try to speed up a job the run on a regular basis. G-Wizard can help you to master even more variables in your search for efficiency.
Database Management for Your Cutting Data
The next step after merely evaluating multiple scenarios is to get very systematic about it. The buzzword in the industry for this is Knowledge Based Machining.
Here’s a secret: it’s possible to exceed manufacturer’s recommended parameters for chip load and surface speed by quite a lot. The trick is to know when and by how much. The only way to do that is through Knowledge Based Programming.
Imagine you’re running the same manufacturing job day in and day out. There are thousands and thousands of parts to be made, and this is going to go on indefinitely. So, you start doing some experiments. Each run, you up the feedrate a little bit with your feedrate override. The first time you crank things up maybe 10-15%. Low and behold, nothing breaks, and that makes for a good savings. So you crank it up some more. Perhaps you’re worried so you’re now going up by 5% each time. Eventually, you reach the breaking point, you break a tool, and you hit that big red button to stop the job. You’ve learned a valuable thing–you’ve found the edge of the envelope for your job. So, you put a new tool in the machine and dial back to maybe halfway between the last setting that worked and the setting that broke the tool. You’ve managed to speed things up by 26%, which puts that much more cash right to the bottom line. If you own the business, that’s cash right into your pocket. Now you’re thinking you can do the same thing with spindle speed. It’ll be a little harder to keep track of it, because too much spindle speed shortens tool life versus just breaking the tool suddenly. It’s going to take more record keeping, but you can still get a lot of benefit if you can be organized enough.
This is all great, and it’s exactly how you want to go about optimizing each variable you can until that job is running just as fast as it possibly can. But there are a few problems, and I wonder if you can see them coming?
First, what if you’re making a part that takes hours and hours of machining, and that could be ruined at great cost if you cavalierly break a tool or cause a crash in the course of your experiments? That big hunk of titanium on the mill table represents $15,000 worth of materials cost and machining time and is on it’s way to being a $40,000 part when finished. You may not especially want to be running experiments on it. Maybe Boeing can afford to do that, but you sure can’t.
Or, maybe the part is cheap, but you don’t have thousands and thousands of orders for it. You’re going to run maybe 5 setups worth and then that job is done until they reorder. It may not seem like it’s worth experimenting at all for those quantities. Worse, maybe it’s a quick one off. If you’re a hobbyist, everything is a quick one off.
Do these cases mean you can’t benefit from Knowledge Based Machining? Not at all!
G-Wizard includes a database capability suitable for Knowledge Based Machining. Just set up your cut in G-Wizard and press the button that says “Add to Cut KB”. If you’re running an experiment, enter your increased parameters. The most important part is to be sure to also enter the real world results of the cut. The Cut KB (Cut Knowledge Base) includes a variety of ways for you to characterize how things went. They range from rating the cut with 0 to 5 stars to telling us about the tool wear and chatter. You can add comments and even record the type of coolant and toolholder that was used. The type of cut is also recorded, since it will matter whether your were profiling or pocketing, for example.
The next time you’re researching a cut, set it up in G-Wizard and then press “Search Cut KB”. You’ll get back a list of all the cuts you’ve recorded that are similar. You’ll be able to see very quickly whether you were able to run a similar cut much faster on some prior job. You’ll also see where the edge of the envelope lies if you’ve recorded the cuts that failed for one reason or another. Perhaps tool life was lousy, you broke a tool, or the chatter was fierce. By using a database like this, you’ll build up machining knowledge over time across many jobs that can be leveraged on future jobs. G-Wizard helps keep it all organized and easily searched.
Being able to fall back on a database of cutting knowledge like this is really the ultimate competitive advantage for feeds and speeds. The tooling manufacturers have to provide their recommendations based on the lowest common denominator. But your own shop’s cutting knowledge base will be based on real world scenarios that are tuned to your shops machines, choice of tooling, coolants, CAM software, and the million and one other idiosyncrasies that can make every shop just a little different.
There are a lot of ways G-Wizard Calculator can make your CNC Business more efficient. I’ve touched on three of the biggest. These are the ones I hear about most often from customers. But, there’s a lot more that can be done with it. If nothing else, people tell me it is an indispensable utility to have standing by while programming. They consult it constantly for all kinds of things and we’re continually adding more functions over time to it. We’ve got a large and growing list of some of the biggest names in manufacturing as our customers. We’ve also got a lot of small shops and hobbyists using the software. If you haven’t tried G-Wizard Calculator, give it a shot. There’s a free thirty day trial and all you need is name and email to get started.
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Bob is responsible for the development and implementation of the popular G-Wizard CNC Software. Bob is also the founder of CNCCookbook, the largest CNC-related blog on the Internet.