Lasercutting foam board

[IsmaelPR77]

So I bent my needle coil smaller than the bearing, so how do I get the needle onto the bearing now that the coil is smaller than the bearing?

 

[dkj4linux]

Not all folks do it this way, but I've always ground a very shallow groove in the outer race of the bearing with a Dremel and cutoff disk... lightly dragging a finger on the backside to keep it from spinning up to damaging speeds. I then use a "mandrel" (a drill bit shank) about 2/3 the OD of my bearing to wind my loops around... about 1-1/4 to 1-1/2 turns and I usually leave a little tail/handle, which makes it easy to slightly spring open the loops to go around the bearing race. The loops spring back a bit when removed from the mandrel but, when fitted around the bearing, it "snaps"/settles and holds in the shallow groove in the outer race simply by its own spring pressure. I have some pictures in this post that show the basic procedure.

Some folks have had problems with the grooving procedure above and have used super glue, flanged bearings, etc... with some success.

More recently I've used a 3d printed "keeper" that surrounds the bearing with a close fit... and the needle has a simple 90 deg bend in it...

Keepers have been made for 8mm and 10mm OD bearings... the most common sizes used, I believe. Post some pictures and give some details of your cutter and we'll do what we can to help.

This discussion should also probably belong in a different thread... feel free to use my needle cutter thread, or start your own.

-- David

 

[Headbang]

Needle cutter for the win. Mpcnc goes together very easily. My needle cutter has a ply frame, coil on the motor shaft, 0.025 piano wire needle with 0.030 mig tip and oiled cotton. Works very well, but I did solder a heat sink to the mig tip. All in all it has been painless and productive.

 

[dkj4linux]

Needle cutter for the win. Mpcnc goes together very easily. My needle cutter has a ply frame, coil on the motor shaft, 0.025 piano wire needle with 0.030 mig tip and oiled cotton. Works very well, but I did solder a heat sink to the mig tip. All in all it has been painless and productive. View attachment 120021

Outstanding work, Headbang!

Since this is the "laser-cutting foamboard" thread, let's please take any further needle-cutter discussion(s) over to the needle-cutter thread.

-- David

 

[jhitesma]

So I bent my needle coil smaller than the bearing, so how do I get the needle onto the bearing now that the coil is smaller than the bearing?

I always make my coil a little smaller than the bearing. Then I just leave the end a bit long so I can use it to pry it back open and slip it on the bearing before doing the final trim. That way it fits nice and tight since I've yet to successfully put a groove into the outside of a bearing and am too lazy/cheap to buy a grooved bearing. I do sometimes add a single tiny drop of super glue which I wouldn't expect to do much on metal to metal...but does actually seem to help (my cardboard experiments kept tossing the needle off the bearing until I added the drop of super glue - but once I did I didn't toss another needle.)

 

[agates1967]

Do you have a cheap Chinese cnc laser cutter you have successfully done this with?

The cheap ebay 40W laser cuts pretty good at 20% and 20mm/s

 

[uggymoo]

I have an older epilog 75watt 18" X 24" bed it has 3 settings for vector . Speed , power and rate ,
to cut I use S/25 P/55 R/10
to score S/50 P/50 R/05
In the Vancouver BC area

 

[Dvirski]

It takes long and sometimes much simpler to cut by hand but it does achieve a clear cut without melting the foam. Using a generic old Chinese 40W laser and doing 4-5 passes.
I can't tell the settings in Watts but on the control panel the setup goes like this...

Cutting distance: 3-5mm (hand measured)
Power setting: 12.1 (possibly percentage)
Speed: 30 (possibly mm/m)
Score: 1-2 passes
Cut through: 4-5 passes
Mark (reference): 1 pass with power setting lowered to 8.7

Would like to be able to cut faster without compromising cut quality or melting the foam.... maybe someone can suggest better settings?

 

[Mik3y]

It takes long and sometimes much simpler to cut by hand but it does achieve a clear cut without melting the foam. Using a generic old Chinese 40W laser and doing 4-5 passes.
I can't tell the settings in Watts but on the control panel the setup goes like this...

Cutting distance: 3-5mm (hand measured)
Power setting: 12.1 (possibly percentage)
Speed: 30 (possibly mm/m)
Score: 1-2 passes
Cut through: 4-5 passes
Mark (reference): 1 pass with power setting lowered to 8.7

Would like to be able to cut faster without compromising cut quality or melting the foam.... maybe someone can suggest better settings?

30mm/min is a bit over 1"/minute. Very slow.

On my 100W machine I use 500mm/sec at 12% (about 8W) in one pass