View Full Version : CNC night light for my girls
02-15-2009, 04:49 PM
Mostly just showing it off, but I do have a question too. The finish pass was with a .25" ball end mill, 10% stepover, and the engraving still has ridges reminiscent of a fingerprint. Am I doing something wrong, or is this just the best it gets off the mill and maybe needs manual sanding? Anyhow, I think it came out pretty good. The rotozip for a spindle machined the whole thing in less than 30 minutes. With the old air die grinder spindle I had to take suck light cuts that it was the better part of 3 hours to do the same engraving.
Here are the pictures:
02-15-2009, 05:23 PM
looks cool jason
02-15-2009, 07:33 PM
Really nice job!
Is that lexan? What software do you use?
02-15-2009, 09:12 PM
It is just .25" acrylic. I buy all the drops of .25" from the local hardware stores glass counter. I get most of the pieces for under $.50 each, no idea of pedigree as to cast or extruded. The only thing I know for sure is it is acrylic. It doesn't machine the nicest, but it does okay with windex or even straight compressed air for coolant.
The software is artcam, I have a buddy who has it and let me do the design and save the code to my flash drive.
Anybody have any input on the finish? The ridges from the "offset spiral" toolpath?
02-15-2009, 11:12 PM
WOW that does look nice. I bet your girls love it.
What are you using for light?
02-15-2009, 11:42 PM
The lights are six 3mm "pink" leds. I ask my 2 year old (the oldest) what color she wanted it, and she said pink. I ordered 50 from china. There are 2 parallel pairs of 3 in series on a 9 volt wall wart, so I got away with no current limiting resistors or other junk to squeeze into the picture frame. The led's are just hot glued in their holes, 3 on top, and three on bottom.
My oldest loved it when I put it in durring the afternoon, but screamed for 5 minutes at bed time about wanting me to shut it off. LOL, she just did not want to go to bed...
Later gents. Gotta hit the hay.
02-18-2009, 12:50 AM
Jason, thats pretty cool, can you say hellllo Christmas presents? (I'm borrowing your idea, I'll give it back when I'm done).
On the finish, your stepover is pretty large. You have a cad system, so you can easily draw out your cusp height. Which with a quick draw is .00063. Doesn't sound like much, but its quite visible.
What you are doing is basically what the mold guys are doing and there is a reason some of their finish passes will run for days. There is also a reason that the mold guys pay some big huge massive sums of money for their machines. Accuracy and rigidity. If one pass is off 4 tenths(Z) from the last one, your cusp height can increase 60%, that can be very visible.
Try knocking your stepover way back. Maybe try backing your feedrate off a bit to limit the following error.
You can think of your stepover when 3D contouring like your feed rate on a finish pass on a lathe, except that you have about 4000 other things that are working against you also.
The machine itself just may not be capable of giving you a "mirror" finish. Just keep playing with it, and remember that 3D contouring with a nice finish is not a fast process. A few weeks ago I had to make a metal spinning die, and didn't have the tools to do the undercuts on the lathe, so I finished it off with a .25 ball mill on one of the mills. Ran from .002 to .005 stepover depending on the angle and I still hit it with sandpaper and a scotch pad, especially in the flat areas where the mill is cutting on the end. This was on an 11k lb machine that is tweaked in pretty damn good, so just keep playing with it to get the best results you can.
02-18-2009, 02:33 PM
Thanks Bob, for that advise! Yesterday I did a Alienware logo and 3d alien head for a guy I work with (Alienware is a high end gamer PC brand). I did the 3d passes with .01" stepover instead of .025" and it is much, much better. It still has some small ridges in but no where near as bad. It is unlikely I will even need to sand it. While machining, I could easily see through the part where with the first teddy bear it always looked cloudy. All in all, it worked out good with the bear, as it makes it look like fur when it is lit. Once I get the alien head wired and lit I will shoot some pictures of that.
02-18-2009, 10:23 PM
Here is the alien head all lit up. I couldn't get a good pic with the leds off. The white background in this one is to reflective. You can see that the contours came out a lot better though. Still not perfect, but really pretty good for a rotozip...