[Arbo]

That sounds cool. I wouldn't think LEDs at the bottom would provide the right lighting for it.

You know of any picture examples around here of that sort of thing done?

Would be cool if they have tool and feed speeds as well.

[CarveOne]

That sounds cool. I wouldn't think LEDs at the bottom would provide the right lighting for it.

You know of any picture examples around here of that sort of thing done?

Would be cool if they have tool and feed speeds as well.

I ran across an LED hobbyist forum where they were carving 2.5D portrait images into the back side of PlexiGlas and then drilling some holes in the edges of the PlexiGlas to insert the LEDs. The LEDs can be on all sides of the PlexiGlas. There was a circuit board available to drive the LEDs, which could be white or colored and the board could change the colors in a linear shifting of colors. The carved image lights up while the rest of the Plexiglas stays clear. The light reflects off of the cut surfaces.

I can't find the link now. Bummer. I wanted to do some of that in the near future.

CarveOne

[Arbo]

I've seen a few boxes made with LEDs. I'll have to fiddle with it when I get better at these things.

Did another one, up to 25 ipm, down on router rpm. Much better outcome. I think a bit faster cut will really hit the mark.

[CarveOne]

Looking good.

CarveOne

[Arbo]

I decided I didn't like how I had my work top set up, so I started re-thinking it.

I now have 5/16 steel plates that ride in the tslot slots, between each leg of the base.

I can attach worktop to them, it will gain me about 1/2 of Z, and be more stable, as the steel isn't going anywhere, thus the work top isn't going anywhere. I figure I'll cut MDF to size and attach it in there.

Now to figure out how to attach it. I'm thinking drill the steel and tap it, and sink a bolt down into the mdf from the top. Just don't like the idea of tapping a lot of holes again.

[Arbo]

Another mod-in-works....

Using some mylar, I'm going to cover the x carriages, which will extend to wipe the rail as it goes. Need some small angle to screw down and keep pressure on the part that goes to the rail. And of course it will go all he way to the y beam to prevent stuff from getting down in between the wipers.

[ger21]

You might want to consider using thin brass instead of the mylar. We have a vertical panel saw at work that uses brass "scrapers" to keep dust out from under the bearings. Better yet would be oil soaked felt wipers.

[Arbo]

I figured the oil stuff would just attract dust and make it worse.

The brass won't wear the steel?

[ger21]

No, the brass is softer than steel. The brass will slowly wear over time.
Yes, the oil will attract dust, but the trick is to have the felt wrap completely around the bearing, and wipe the rail on both sides of the bearings. That keeps the bearing running on an oiled surface, which will extend the life of the system. The felt wipes away the dust and keeps it from getting between the rail and bearing.

The brass (or mylar) is much easier and should work fine, though.

[juzwuz]

Hi! Did you use Cut3D to generate the toolpaths for the glider tail? What size bit and step size did you use? I was messing around with Cut3D and a glider fuselage mold (negative) but I couldn't get a nice smooth perimeter in the Cut3D preview picture. In general, when you are cutting a mold, do you want to use small ball bits and small stepsizes or maybe big bits and small stepsizes?

Been cutting some positive glider tails out of MDF to test things. Here is one a friend did the other day, then soaked in epoxy. Another layer of epoxy and finishing sand and it will be good for him to make molds with.

[Arbo]

Unfortunately I can't answer your questions as to what bits and stepovers one should use, as I'm just figuring this stuff out myself. All trial and error so far... I've asked a few people that have done it on other forums, but the only information I've received so far (on that subject) has been crickets chirping...

The tail part tool paths were generated by a friend (who's tail it is) in RhinoCAM. He got the crisp lines with a pencil trace (I believe that's what it was called), after the roughing and finishing passes.

I have found, so far, if you are using a ball nose for a finishing pass, and want it smooth, you are looking at setting the step size to 10 percent or less, and of course that rapidly increases machining time.

[Arbo]

Drilled/tapped the steel, and then pocketed the surface MDF to fit the bolt and shoulder washer and set them lower than the tslot. Only got a couple pieces on today.

[CarveOne]

That sounds cool. I wouldn't think LEDs at the bottom would provide the right lighting for it.

You know of any picture examples around here of that sort of thing done?

Would be cool if they have tool and feed speeds as well.

I found a few samples this morning on the Zone. The Phoenix is near what an engraved portrait would look like. Look at post #1 in this thread. The LEDs can be placed all around or just on the sides, top, bottom, etc. Different combinations of color LEDs will allow for more effects if a circuit board is designed to cycle the colors at different speeds. etc.

CarveOne

[Arbo]

Very cool, thanks for the link.

[Arbo]

Question on cutting MDF. Was using a 1/4 end mill to rough out some pieces, I think at 100 ipm. .2 inch depth per cut. I got a lot of bits where the MDF chipped up and tore away (see picture).

The piece in the picture should be full height and about 1/4" wide, but with each pass it ripped off bits of it. Is it due to cutting to fast, or too deep, or something else?

Thanks...

[ger21]

Not necessarily in order:

Dull tool.
Depth of Cut.
Limitation of MDF.

Thin strips of MDF are very weak, and can easily break apart. A bit that is not razor sharp will put more force on the MDF causing it to break. A downcut spiral can help, as it's not trying to pull the MDF up. Although the side force can still break it if it high enough. I wouldn't slow the cut, but more shallower passes can also help.

Are you using an endmill for metal, or a router bit?

[juzwuz]

Just curious what the spindle rpm was? Perhaps it was too slow for your feed rate? You might want to play around with the feed rate and spindle speed on some mdf to see if you can get a good cut.

[Arbo]

An end mill as bought from American Carbide. Was brand new, so I wouldn't think it dull. And I'll have to check when I go out there next, but I believe it's a down cut.

It seems I've read in general you shouldn't go deeper than half the bit diameter, but of course I did, so that could be it.

Spindle RPM was at it's top setting, which is like 26400.

I guess I'll make some thin test pieces to try tomorrow, need to cut a new dust boot for the bristles I bought as well... My makeshift xray film 'bristles' don't stop mdf dust very well.

[ger21]

Wow, American Carbide has some god prices, I'll have to try them. I'd recommend the DC-4120. I don't think you are using a downcut. If you were, the top edge of the cut should be clean and sharp, not fuzzy like your seeing.

With wood, you can easily cut the tool diameter deep and even deeper. 1/4" depth per pass should be no problem. At work I've routinely cut 3/4" MDF in 2 passes with a 1/4" bit. And I've heard of people cutting 3/4" in one pass at up to 1000 ipm with a 1/4" bit on large commercial machines.

As for your rpm's, they are way too high. I've been cutting MDF at 125ipm and 10,000-12,000 rpm. My machine has a little flex, so I limit my depth of cut to around 1/8", and haven't tried deeper cuts yet.

If you need to keep a small island like that, I'd recommend making shallower cuts, perhaps as shallow as .05 per pass, to keep them from tearing away. And again, try the DC-4120 or DC-4121, I think you'll get better results, but you'd still need to make multiple passes, as you're running into a limitation of the MDF. Teo full depth cuts with a 1/4" of material between them will probably tear that material out a good percentage of the time.

As a test, cut a small 1/4" strip from a sheet of MDF, and see how easy it breaks apart in your hands. For certain applications, MDF is a great material. For others, not so much.

You

[Arbo]

I'll do some test cuts today. And I ordered a couple of the down cut bits.

Just emptied my dust collection bag for the first time. I think I let it get a bit too full. Live and learn.