Home Workspace | Making Chips | Pocket NC

Finally, starting to make some chips on the Pocket NC, I decided to get the machine running and make tweaks to the program as went. 

Right away I ran into an issue when I started the machine up, it cut fine the first few passes, but I quickly realized it was cut above the stock in the z-axis. Thankfully it was as easy as inputting the correct b table offset value given in the manual with the machine. After that, I was able to get it running correctly. 

I used the recommended speeds and feeds for cutting aluminum, but had to reduce the rate and chip load some to prevent the metal from overheating. I cut down about a 1/8," and you can notice a slow change on the face of the metal where the heat started to increase and started to become muddled. It also started moving the aluminum rather than cutting it, which you can see at the end came out as strands.

I only had a short amount of time to work on it, but I was able to find some changes I will try out next time. The main one is to lower the roughing stepdown; I think that since it's got so much contact with the material, it's creating more friction and thus heat. I'm going to try the same stepovers and feedrate but reduce the step-downs by half, 1/8" to 1/16".

Machinist Apprentice | Polycarbonate Plates & More Watch Pieces| Day 39

Today I made some thin plates using polycarbonate and some more aluminum watch parts!

These small plates where an interesting but easy part of making. Since it's plastic, I was able to use double-sided tape to hold it down on the fixture plate I used yesterday. Because of the tape, I couldn't use any coolant (which would only get in the way regardless), so I had to skim the surface with a face mill, then wiped down with degreaser on a rag to ensure the adhesion on the tape would stick.

For the programming side of it, I used a 1/2" three flute square endmill to face the top of the 1/8" thick polycarbonate, flipped and cut it again till it was at its final thickness 0.04" (not actual part height, close to). Then I used a 1/8" three flute square endmill to contour each part, leaving five thou axially to remove later, this was done to ensure the adhesive didn't get on the cutter, thus leaving a lousy finish. I had to account for the tape as well, so I measured the thickness with one side of the paper on it, then measured the paper and subtracted it from the total to get my number. From there, it was as easy as cleaning them up with alcohol and a rag, then inspecting each one. Everything was within 0.0002" (two-tenths), which is well within spec. 

From start to finish, the polycarbonate plates took maybe an hour and a half to complete, which was mostly due to trying to find the stock from the scrap piles.

One of the previous projects I worked on a couple of weeks back wanted a few more watch parts made, and so I got to set up the stock and re-run the old program. It took only 30 minutes to set up the machine, cut the aluminum, and mill the first operation out. I did three sets of two and will finish them off tomorrow. 

Home Workspace | Finishing Toolpaths | Pocket NC

Smoothing out some more of the Pocket NC project CAM work, setting all the details in place. My goal is to get this all down on the first try so that I can pretty much-hit start and not have to touch it except to swap tools.

I've also got a public download link (https://a360.co/3hWbbpP) if you're interested in taking a look at some of the toolpaths I'm using to program this part. I should be able to start making chips in the next couple of days, assuming all goes well. I may have my shop work increase, though, so that may throw my timing off. 

I'm also thinking of running this part first in ABS or some other plastic to see how it comes out before doing it in aluminum. Overall I'm pretty pleased with how it's coming along, and I'm pretty confident in the areas I've completed so far. 

I also had some issues originally when trying to post the G-code, where it would fail the .nc code and not allow it to export correctly. I was able to solve this issue by switching the machine type from a v1 to a v2-10 in the post process tab right before exporting the g-code (see picture above).

Machinist Apprentice | Hole Tapping | Day 38

Today I got to work on tapping and threading holes using the Haas minimill and Fusion360.

Unfortunately, I forgot to take pictures at work, so I recreated the drawing in Fusion to use as an example.

The CAM programming end of it was quite easy and only took a minute to setup. I first drilled out the hole using a pecking method (1/3" of the tool diameter) then came in with the tap to thread the hole. How the tapping works is by aligning the spindle rotation (in this case 500 RPM) with the vertical (z) motion of the machine, matching it perfectly to the thread pitch, when it reaches the bottom, it reverses the spindle and comes back out the same way it came in. It's pretty nerve-wracking because if there is any slight thing off, the tap could easily break.

I tried it first with a set of imperial threads, 1/4-20, 10-32, and 4-40, each of which worked fine, though I did snap one of the taps when cutting the 4-40 hole that was due to my random selection of a 4-50 tool in the program. 

Interestingly, when I moved over to equivalent metric holes, 6-1m & 5-0.8m, it was extremely loose when tested with thread gauges. I have no idea why it does that, and nothing in the program is different except the tool size. My boss says he's had similar issues when using metric taps, and the only solution he found was to convert the metric taps to imperial manually, and it seems to work that way. He thinks its due to the conversion and some rounding down or up inside the machine.  

I also got the day off on Friday which is why there wasn't any post then. 

Machinist Apprentice | Finishing up the Stainless Steel Part | Day 37

Today I finished up the steel plate part and got it packaged up.

One area I was kind of nervous about was getting these small tight corners with a few angles meeting all at one spot. The original plan was to come in with a 1/16" square endmill, and adaptive clear out the material, leaving five thou on the walls, then contour it with the same tool. However when I sent the machine running, the endmill snapped right after it touched the material, I am honestly not sure why the chip load on it was well what it could handle, and there were no direct plunges into the content. 

Unfortunately, there weren't any other 1/16" square 4 flute endmills like that long enough to get the whole wall, so I had to revert to using a 1/8" one, this meant I couldn't quite get the corner to how it was drawn but got within ten thou, which is acceptable for this part.

Once getting that corner done, I used a contouring toolpath with a 1/16" ball endmill to finish the chamfer along the edge of the part, using four thou stepovers, which gave an excellent finish. I then took the 1/4" square endmill I used to cut the piece out to finish off the walls of the plate removing the five thou I let behind. Stainless steel makes me very nervous about running anything on, and I quadruple checked each operation I posted. 

I had extra time before the end of my shift so I thoroughly cleaned out the Haas Minimill and typed up a quick checklist reminder for setting up and tearing down at the end of the day.