Climb and conventional milling secrets that you should know

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When a cutter moves through material it can mill up (conventional milling) or down (climb milling). Many machinists use climb milling for most, if not all, of their CNC projects. Climb milling is known for producing better surface finish than conventional milling and overall does have more advantages than conventional. However, climb is not always the better of the two options and any machinist should know that there are times when conventional is preferable, and when those times are.

Climb and Conventional Milling

Climb and Conventional Milling

Using climb milling, each tooth on your cutting tool makes contact with the material you are working with at a defined point and moves out, cutting thinner parts of the material until it is no longer touching the material. So, the width of the material being cut starts at the maximum length and decreases to zero as the cutter moves. This causes chips to be thrown behind the cutter, making chip removal an easier process while machining. Tool life is also extended because each tooth on the cutter is not rubbing against the material. One of the major downsides of climb milling is that it can potentially produce a lot of backlash. As a result this method should mainly be used on machines that can eliminate large amounts of backlash and it may not always be usable with older CNC machines.
Conventional cuts in the opposite direction of climb. Using conventional milling, the teeth of the cutter will start at zero thickness and work their way up to the maximum thickness that you are cutting. When first making contact with the material your cutter does not even cut the material; it slides across the material surface until enough pressure is built up for the tooth to dig in and begin cutting. This causes the work material to become hard and somewhat deformed and also causes cutters to dull faster than when using climb. The sliding and biting of this cutting process also tends to leave an inadequate surface finish on work materials. On the upside this process does not generate anywhere near as much backlash as climb and is a perfectly sound cutting method on almost any CNC machine. The two methods do not have to be used independently either; climb can be used for rough passes while conventional milling is used for finishing passes.
Climb does have a few distinct advantages over conventional when your machine can manage it. As mentioned before, your tool life will be longer, surface finish will be better and chip removal is much easier. Additionally, you do not need as advanced of a hold-down system. Climb exerts force downwards instead of upwards like conventional milling. You can also use higher rake angles while climb milling, saving you a little money on the amount of power needed. Just do not forget about the excessive backlash when looking at all of the positives of climb milling.
When using climb milling, deflection can causes some problems with surface finish. Climb cutting causes tools to deflect, deforming the surface finish of projects and leaving you with less than adequate results. If you run into this issue try switching to conventional cutting; that will likely make a big enough difference to correct any issues you are having with maintaining a good surface finish. While conventional cutting can help it will not always fix your problems. If you have tried climb cutting and conventional cutting and are still having issues you can decrease deflection further by reducing the depth of your cuts. Using a small amount of your cutters diameter will make it less likely that you will experience any deflection.

Summary
Article Name
Milling Climb and Conventional
Description
When a cutter moves through material it can mill up (conventional milling) or down (climb milling). Many machinists use climb milling for most, if not all, of their CNC projects. Climb milling is known for producing better surface finish than conventional milling
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