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Mastercams Pocket Entry Motion settings  may need adjusting when trying to enter small pockets or features.

In the example video, we have a small pocket and we are trying to perform a Ramp Entry Motion into the pocket. By default, the setting in the Pocket Toolpath for what the toolpath will do if the defined entry motion fails, is to Plunge. In other words, a straight Z move into stock. Typically, if we are going through the process of enabling an Entry Motion and making settings for that Entry Motion type, the last thing we want is a Plunge into stock.

The cause of Entry Motion failures is usually that the defined Entry Motion is too big and will void into the selected geometry. The fact Mastercam picks up on this is good, otherwise you'd be dealing with a scrap part. When making the settings that define the motion to use, the ones that are most likely to cause the motion to fail are...

Minimum Length/Radius - Ramp will use Length, Helix will use Radius. This sets the minimum size of the motion. Mastercam will attempt to use the Maximum size set first, if that will not fit Mastercam will keep reducing the size until it does fit. If Mastercam keeps reducing the size up to the defined Minimum, and the motion still does not fit, the entry will fail.

XY Clearance - This dictates how close the Entry Motion can get to the wall of the selected geometry. If you cutter is close in size to the pocket, or the overall motion you are after is close to the size of the pocket, you may need to allow the motion to get closer to the walls. I would suggest not getting closer than the amount of material you have left for the finishing pass of the toolpath. 

Auto Angle/XY Angle - In Ramp, you can define the angle at which the ramp occurs. If you need a specific orientation of this motion than defining it may be necessary. However, allowing Mastercam to choose the angle depending on what fits best may be the better option. Enable Auto Angle whenever possible. 

Lastly, if a plunging motion is really something you need to avoid, you can always switch the behaviorfor when the Entry fails. Change this option from Plunge (this is the default setting) to Skip. With this setting, Mastercam will skip cutting features in which the Entry motion fails. 

If you are interested in more information about Entry Motions in the pocketing toolpath, have a look at this blog posting...

Pocket Entry Position

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