No discussion of the CNC milling process would be complete without addressing a few tips and tricks on how to get the best surface finish possible. To create truly polished and professional-looking machined parts like you find when you click here, it’s important to utilise the twelve strategies outlined below:
Use the correct feeds and speeds. Never simply guess about which feeds and speeds to use; get a proper feeds and speeds calculator, one which can account for variables like radial chip thinning and ballnose compensation.
Always clear away chips. If chips are allowed to remain, they will scratch work pieces as the cutter moves them around, interfering with the CNC milling process. (This is especially problematic when you graduate to working with harder materials like stainless steel.) It is recommended that you use CNC coolant rather than compressed air to clear away chips.
Remember that roughing and finishing should be done with different tools. Your finish passes should be done with brand new, sharp tools. After these tools have been worn in with use, switch over to using them for roughing work.
Do everything in your power to reduce deflection and chatter. If possible, use a cut optimisation tool to increase the rigidity of your tool and minimise the vibrations which lead to chatter. Note that reducing overhang is often helpful to increasing rigidity. You should also use balanced tooling to keep vibration to a minimum and set your boring bars at an angle rather than parallel.
Use a high-quality facemill. Investing in a more costly facemill can drastically improve the CNC milling process as more expensive facemills usually let you adjust each of their inserts individually. This means that you can compensate for the fact that not all facemail inserts tend to cut at the same depth. (Note that if you are working with aluminium, you should switch to using a PCD flycutter instead as these tools create a peerless finish on aluminium.)
Use a radius with your bullnose or endmill. Using a radius will create a superior finish as compared to the finish left by a flat endmill.
Use sharp inserts and pair them with a greater lead angle and a positive rake.
Roll into and out of your cuts for the smoothest finish possible.
Make sure the tool keeps moving consistently. Any time a tool stops while it is in contact with the workpiece you risk leaving a mark that will seriously mar the finish of the piece, so try to do finishing passes in complete sweeps.
Take the time to tram your mill perfectly. Always re-tram your mill before doing finishing work to ensure the best finish possible.
When working with a lathe, increase your speed in order to reduce edge buildup. Edge buildup is directly destructive to attaining a perfect finish.
Use cutter and toolholder combinations that minimise runout. Runout is when your tool ceases to spin in a true circle, resulting in an uneven and sloppy finish.
No comments yet.