Today’s topic is mainly for CNC router programmers but can be used in metal applications as well. Here is the scenario, you need to finish profile some ⅜ wide slots and your running into issues with the lead-in/out not having enough room for cutter compensation. What options can you use to finish the slot profile and have enough room to turn on and off cutter compensation?
What is cutter compensation?
As you program your 2D part profiles, your tool will need to be offset. Half the tool size needs to be offset from your part geometry in order to machine the part geometry to size. BobCAD’s profile feature has compensation options built in and there are multiple ways you can use these settings.
Here are the default settings for compensation of 2D Profiles.
System compensation is when BobCAD applies the offset for your tool. The software will look at your entered tool size and offset for half of it automatically. All of the math to offset for the cutter is done for you.
Machine Compensation vs System Compensation
With the default settings of system compensation, there aren’t any adjustment factors for the “tool offset” at the controller. This means if the tool size isn’t spot on, the size of your cut parts could be out of tolerance.
This is why many shops will choose to use G41/G42, also known as machine compensation. Using this option allows operators to make adjustments to the size of the tool at the control.
Machine Compensation Rules
There are some rules for using G41/G42. These rules vary slightly based on what machine and what controller you are using. The rules we are referring to are the lead-in move and where compensation is turned on.
For most machines, they require a line arc move in order to turn cutter compensation on. The line arc move needs to be greater than the radius of the tool you are using, giving the machine “room” to turn G4 /G42 on.
In today’s example, we will be utilizing machine compensation. Due to its rules, we instantly run into a problem. We are cutting a ⅜ wide slot with a ¼ end mill. It requires a line arc move with a minimum of a .125 radius lead-in/out in order to turn G41/G42 on. We don’t have enough room!
As you can see in this cutaway view of the backplot toolpath, we do not have enough room for the required lead-in/out to turn on and off cutter compensation. The required lead in/out results in the tool running into the part geometry. How do we get around this?
Like many topics and workflow for CAD-CAM programming, there multiple approaches to solve this problem. We are going to keep it simple and use our entry options.
Typically for a profile finish pass, we would use Plunge as our entry option. Today we are going to mix it up and use the ramp option, but not like you think…
We are going to turn the ramp option on and change the angle of approach to 90.
This simple solution will result in the lead-in/out to be above the part.
Now that lead-in/out is above the part, we no longer are restricted to the width of the slot, leaving room on the lead-in and out. It’s as simple as that!
If you are interested in seeing what BobCAD-CAM software can do to maximize your shop’s productivity & bottom line, download a copy and try it out today.
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BobCAD-CAM has provided CAD-CAM CNC Software products to the global manufacturing industry for over 30 years. BobCAD-CAM software can be found to increase CNC productivity for many applications in aerospace, automotive, production manufacturing, mold making, general machining, woodworking as well as the medical manufacturing industry, consumer products, musical instruments, custom fabrication, defense industry and many others due to the products ability to automatically generate NC programming code for such a wide variety of CNC controllers. BobCAD-CAM software is also found in educational institutions throughout the world as well as independent hobby home use. Products include machining technology for 2, 3, 4 & 5 Axis CNC Milling, Routing, Waterjet, Plasma and Laser machines as well as 2 Axis CNC Lathe. BobCAD-CAM is modular allowing shops to start off at a reduced technology level and add technology as it is needed including an add-on, BobART, for artistic machining. Unique technology includes adaptive high-speed machining multiaxis milling and routing which is a first in the world of CAD-CAM software. BobCAD-CAM also provides a variety of quality training products that include regional and online training classes or private sessions tailored to specific applications. Professional certification and multi-tiered support solutions are available. Contact BobCAD-CAM directly for more information at 877-262-2231 or 727-442-3554.