Today we would like to share the boundary machining methodology I tried recently. In one of my recent project on Aluminum machining, I have nested four parts. My intention was to create four different parts from a single stock. It includes the rough cavity cut and finish fixed contour cut.

I have used #8 counter sunk screw to hold the part and used a 1/8″ dowel pin to avoid rotation of part. 1/8″ Ball nose cutter was used for entire machining.

I normally prefer to use a single cutter for complete machining which eliminates the need of “Z” point reset.

Instead of machining the unnecessary stock material, I have created a rough boundary against each part which is slightly greater than the tool diameter. I wanted to separate the remaining stock in block form itself instead of machining it into chips.

I have taken care to use the transfer plane as clearance plane instead of previous plane at each level of cut. Well, it all worked well except for one problem. There was a chunk of island remained after the boundary cut which was separated from parts. I have not cleared the bottom surface of material so that this island can fall down.

Hence, it remained inside the pocket hindering the tool movement in successive cuts. Luckily I was watching the machine that time, slowed down the cutting speed and carefully removed the island. It was almost breaking the cutter.

So, here is the lesson I learnt. It is a very good practice to do the boundary machining with clearance plane transfer (don’t forget this to avoid cutter fouling with in process work piece). You have to make sure the solid scrap material will fall down automatically after its separation from the blank stock.

This method can save up to 30 to 40% of overall machining time.

Hope you found this article useful.

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Nesting the parts while machining using CAM

While working on a recent CAM project using CAD model, we found few interesting techniques. In the first job, we requested the operator to use a 1/4″ Ball nose cutter of 1″ long. We were expecting there could be some tool flexing because for the first cavity profile cut. But he used almost 1 1/2″ long cutter. Finally, once the machining is done there is a clear cut draft left on the part which is almost 3 degrees. Also, there was not enough overpass of ball nose at the bottom of the part leaving a radius there. It was not too bad other than doing some manual cleanup of the part after machining.

In our second batch of CAM, we nested four parts as shown on image from two separate CAD models. So, we have to make a single pre-machining block to make two separate parts of quantity two each. Also, we tried to machine only up to 4 mm around the part using 1/4″ cutter. This saved us almost 50% of machining time as we eliminated machining unneeded stock. Also, we ensured the cutter overhang is only 22mm just more than nose overpass. This didn’t cause any tool flex and squeak.

Nesting the Parts example

 

Another interesting thing is after doing the rough cut with 1/4″ cutter, we lost the datums where we set original zero. So, for finish cut we have not changed X and Y coordinates. But, asked the operator to reset Z with respect part top surface which was intentionally left unmachined before. This helped us in quickly running the finish cut using 1/8″ cutter without much time on reference point set.

Hope you found this article useful. Please share your comments below.