First metal part!

[mcphill]

I made my first part in metal today! It is an aluminum piece to replace a headlight adjuster in a friends Wagoneer. Apparently you can't get that part any more, can only scrounge them out of wrecks. Hope to make a few hundred of them as there seems there is a market...

Did my CAM in BobCAD. Had a few mistakes, and it took me over 3 hours to make one part, but in the end it proves the steps are OK. The first part has "issues", though is likely useable. I lost my 0,0,0 a couple times due to stupid mistakes on the machine (learning is HARD!)

Anyway, no pix right now, but will update the thread with some tomorrow. Getting some late dinner now!

[mcphill]

Uploading some videos of each step of the operation here:

Wagoneer Parts album | mcphill | Fotki.com, photo and video sharing made easy.

This was my first part. It has quite a few issues... 3 of the next 5 I made look great. One came out of the vise as I was machining and got banged up (but still usable), and one has a thin "foot", must have had a chip under it in the vise. Also usable, but not perfect... Will post more of those parts later. Off to a Beer Bash!

[mcphill]

So, some details on this part. Designed in SolidWorks. CAM made in BobCAD. All major cuts were done with a 0.5" cheap Chinese HSS end mill, with depth of cut at 0.125" or less (even cut depths calculated in BobCAD), stepover up to 0.25", rpm 4000, 40 ipm cut and 10 imp z (these speeds calculated with GWizard). Roughing passes left 0.010" for a final finish pass (GREATLY improved surface finish that way). Center drill and drill speeds calculated in BobCAD using defaults for Aluminum.

[slowtwitch]

LOOKS GOOD !!! for the first part. I just cut my first piece also. Nothing as complicated as yours, just a rectangle (6.5" x 13.75) out of .750 6061....lol

I'm still a beginner with this G-code stuff

pete

[DSpeck]

I watched your videos, and saw some things to comment on.

If you are using 1/2" or larger tools, you'll get a quieter cut if you go to 4-flute cutters. Keep the same speeds and feeds, just use twice as many flutes on the tool.

When you are drilling the spotting holes for the blind and through holes, you would get better results if you used a 90 degree spotting drill. If you make the depth of cut such that the spotted hole ends up slightly larger than the drill diameter, you will have a nice 45 degree chamfer and an accurately located hole. I could hear the long drill make noise each time it entered the hole, which says that it is not entering straight. That might mean the drill has a bit of runout, or that the drill tip was a little off-center when it started the hole. Drilling also would go better if you used the flood coolant with it - the coolant gets right to the bottom of the hole on the upstroke with the bit out of the way.

You might also have a look at your G-code, as I could hear the spindle change speed between roughing and finishing passes (slowing down, then speeding up again). It doesn't really need to do that, and that puts more of a load on the spindle. This may just require a setting change in BobCAD (I've never used that package, so I'm not sure).

Just some observations from watching the videos. I hope they help in making your parts easier or better in future endeavours. For a first part, it looks fine.

[SWATH]

He may have been stopping the spindle between RPM changes because as some have reported the Mikini may not register an accurate spindle speed after a speed change unless an M5 command is issued first. Just a guess. I too also noticed the runout on the drill, you can kind of see it when the drill first starts to spin.

However the most amazing thing to me is that the spindle works and sounds great! I'm jealous.

[ROCKYMTN]

Nice part !

My parents had a Wagoneer when growing up so I have found memories of that jeep.

[mcphill]

Thanks for the comments. I had not heard of using a 4-flute on larger tools, but what you are saying makes sense. I also read you can use a depth of cut of up to 1/2 the tool diameter and use the same feedrate, so I could have done some of the cuts 2.5 times deaper (and therefore faster for the whole part!).

On the drills, the situation is even worse than you think I did the center drilling on each part (which was no where near deep enough, but I was too lazy to go back and make them deeper), then put each part back in to the vise (one at a time) to drill through each, then back in a third time to do the third drill size. Totally NOT the "right" way to do things, but it worked for what I needed. If I end up making these parts "for real", I will set up a fixture to machine 4-5 parts at a time with known proper spacing, and not make them one at a time (or I will hire it out to a real shop!). I do plan to use the machines for prototypes prior to sending the "real work" out for higher volumes of things I design. As for the drill "scraping" each time it enters and exits the hole, you can certainly see in the video that the drill bit has a ton of runout too - it was one of a cheap set from Harbor Freight - something like $15 for a full number set, so I can't complain. I couldn't use flood coolant as the chuck I have is too long to let my coolant lines reach down and around. I need to extend the lines some but I keep forgetting to buy some more of the segmented tubing....

The spindle slows and speeds up again because BobCAD thinks there is a tool change and is stopping to change the tool. It won't let me specify a rough and finish pass in one step using the same tool, and I am too lazy to do it in two steps. I just used the keystroke to initiate the cycle again. I should just delete the toolchange line and it would run straight through (I have each tool in a different Gcode file already, and I was using the same tool to rough and finish).

Anyway, thanks again for the tips. I have done some manual milling before, but that was really my first real part in metal on a CNC - and it worked!