FlyingIsFun
Junior Member
With access to an Epilog Fusion 28 x 40 inch laser engraver, I built/flew my first kit, the FT Explorer from the down loadable plans last week. The design is great, and I added a feature to the plan which made it a bit easier to build.
The suggestion that I have, is to add a "kiss cut" to anywhere the plans call for cutting out that 45 degree foam edge with a razor (found on any movable surface), so that you have a guide for your razor cut from just above the paper fold, to the kiss cut. The video for the FT Explorer build said to make that cut deep, to allow for flaperon use, a kiss cut on the foam parallel to the bend, to mark where that would be on the Speed Build Kit, would be a great help.
I learned a few things in cutting out the DTFB. First, cutting foam is a very risky business - starting a fire in the laser is a real danger, and as the foam tends to burn from the backside of the foam board, it is often hard to detect. The blower to remove fumes out of the laser, tends to "fan the flames". Not good. Never walk away from the laser when it is cutting foam board.
When cutting foam board, turn off the overhead lights, and the lights in the laser, so when the foam board does catch fire, you can see it.
Dollar Tree in my area also sells black paper on the foam board. The black color absorbs more heat from the laser than does the white foam board. I ended up creating a different speed / power profile for black vs. white foam board to account for the differences. This build will be the last I do, using black foam board, as you can not see any flame through it. Note: when foam board burns, it burns from the back, not the front, which makes it hard to detect quickly.
Another thing I learned, was that when the cutting foam, is that "Chads" are evil. (No reference to Chad Kapper). Chads are those small pieces of foam which fall out and down below the grid which holds the foam as it is being cut. With a 120 watt laser, any chad not cleaned out from the last foam board cut, will immediately catch on fire whenever a through cut causes the laser beam to touch them. So, in all designs which I'll cut in the future, there will be no loose chads to fall into the bottom of the grid. That means any small pieces will need a razor cut, to remove them. No chads mean less mess to clean up. Note to self: any Center of Gravity marks, need to be through cuts, else they end up on the inside of the wing, making them worthless.
When using Epilog's print drivers, for a given color layer of your drawing, there is no control over which line within that layer is cut first, the order within the layer, is completely random, and with only 16 colors to chose from, there is a limit to the order control you have. As such, there can be significant time wasted, as the system randomly picks and travels to the line it happens to pick to next cut. So, if you are cutting a square, it could be laid out a single closed line to make up the square or as 4 separate lines. A single closed line square will cut a lot faster than a square consisting for 4 separate lines positioned to make up a square, as the laser will not randomly chose another, far away line to cut on that layer, then return to cut an adjacent line.
But, when a line is setup as a closed line square, there is a lot of heat placed/generated in corners of a single closed single line square. It is a good idea to break up any corner, into two separate lines, so any sharp corner does not accumulate so much heat as to catch fire.
If you're going to cut through the foam board, hit it with all the power you have, so that the foam and paper are vaporized without heating the surfaces adjacent to the cut. It is counter intuitive, but lowers the fire risk.
I would be interested to hear of your laser experiences.
The suggestion that I have, is to add a "kiss cut" to anywhere the plans call for cutting out that 45 degree foam edge with a razor (found on any movable surface), so that you have a guide for your razor cut from just above the paper fold, to the kiss cut. The video for the FT Explorer build said to make that cut deep, to allow for flaperon use, a kiss cut on the foam parallel to the bend, to mark where that would be on the Speed Build Kit, would be a great help.
I learned a few things in cutting out the DTFB. First, cutting foam is a very risky business - starting a fire in the laser is a real danger, and as the foam tends to burn from the backside of the foam board, it is often hard to detect. The blower to remove fumes out of the laser, tends to "fan the flames". Not good. Never walk away from the laser when it is cutting foam board.
When cutting foam board, turn off the overhead lights, and the lights in the laser, so when the foam board does catch fire, you can see it.
Dollar Tree in my area also sells black paper on the foam board. The black color absorbs more heat from the laser than does the white foam board. I ended up creating a different speed / power profile for black vs. white foam board to account for the differences. This build will be the last I do, using black foam board, as you can not see any flame through it. Note: when foam board burns, it burns from the back, not the front, which makes it hard to detect quickly.
Another thing I learned, was that when the cutting foam, is that "Chads" are evil. (No reference to Chad Kapper). Chads are those small pieces of foam which fall out and down below the grid which holds the foam as it is being cut. With a 120 watt laser, any chad not cleaned out from the last foam board cut, will immediately catch on fire whenever a through cut causes the laser beam to touch them. So, in all designs which I'll cut in the future, there will be no loose chads to fall into the bottom of the grid. That means any small pieces will need a razor cut, to remove them. No chads mean less mess to clean up. Note to self: any Center of Gravity marks, need to be through cuts, else they end up on the inside of the wing, making them worthless.
When using Epilog's print drivers, for a given color layer of your drawing, there is no control over which line within that layer is cut first, the order within the layer, is completely random, and with only 16 colors to chose from, there is a limit to the order control you have. As such, there can be significant time wasted, as the system randomly picks and travels to the line it happens to pick to next cut. So, if you are cutting a square, it could be laid out a single closed line to make up the square or as 4 separate lines. A single closed line square will cut a lot faster than a square consisting for 4 separate lines positioned to make up a square, as the laser will not randomly chose another, far away line to cut on that layer, then return to cut an adjacent line.
But, when a line is setup as a closed line square, there is a lot of heat placed/generated in corners of a single closed single line square. It is a good idea to break up any corner, into two separate lines, so any sharp corner does not accumulate so much heat as to catch fire.
If you're going to cut through the foam board, hit it with all the power you have, so that the foam and paper are vaporized without heating the surfaces adjacent to the cut. It is counter intuitive, but lowers the fire risk.
I would be interested to hear of your laser experiences.
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