This document is intended to assist customers with their software, specifically reducing your machining time while maintaining cut quality. In this tutorial we will be examining a 3-D modeled part that I have created in a different CAD software and imported into aspire. If you only have Vcarve Pro the ideas will translate to 2-D machining as well, but it’s easier to illustrate on a three dimensional model. **Material is not assumed, please alter for your machine and material**
First I will demonstrate how incorrect feed rates and stepover can increase tooling time and/or decrease cut quality. I’ll begin by applying a roughing tool path to the material boundary, with an offset of a ½’’. This offset makes sure that my 3D roughing tool path goes over the entire model, making sure not to leave any area un cut. You will be able to see the tool path in blue, and where it starts and stops. *Note this part does not necessarily need a roughing tool path due to its material thickness and size, but I added it in for demonstration purposes.
Trial 1: Machining Quickly In the tool settings I have made the step over very large, and the feed rate quite fast. As you can imagine running the machine faster will decrease the time is takes to produce a finished part. I have also done the same thing with the finishing pass, using a ⅛’’ ball nose bit. The results are as follows:
If I were to keep these settings and run my part I would find that yes i’ve completed the job in record time, but I have also produced unacceptable finish quality. A proper finishing pass, depending on the material will need a stepover of <25%. Trial 2: Machining Slowly In our second trial we will be taking things a little slower, with the feed rates, and step overs dramatically reduced. I will only be showing the tool info from now on, because the other settings have been kept constant.
In this 3-D roughing toolpath I have decided to make the stepover 20% and the feed rate 50 in/min, half of the trial one. This will dramatically increase the tooling time of the part. I have also reduced the finishing pass to a 6% step over at a mere 20 in/min. As you can see in the results this has made the tooling time much larger and is extremely inefficient at almost 4 hours compared to the 9 minutes of trial one.
Trial 3: Finding the balanced medium It will take time and practice to efficiently reduce your average machining time. Finding the proper feed rates and stepover will depend on the material, bit, part, and feedback from previous attempts. To illustrate this I will provide a balanced feed rate/ stepover to obtain a finished edge quality and reduced machining time.
In this roughing pass I’ve increased the step over to 80% of the bit, which is a little high. Since the roughing pass isn’t doing much on the part it will still provide an excellent tooling time as well as cut quality. For the finishing pass I’ve made the step over 21% which may be a little high, but depending on the material you may be able to get away with it. The results prove to be slightly over trial one but drastically under trial two’s tooling time.
By playing with the feed rates and stepover of your tool paths you can drastically reduce your tooling time. This is important in any manufacturing application, but remember to not sacrifice cut quality for tooling time. As I mentioned in the beginning these values hold true to 2D tool paths as well.