Black crumb tray questions

qa

#1

Does the fact that is black mean there won’t be any splashback? I.e. does it totally absorb IR?

If so does it get hot?

Is there a risk the blackness will get engraved off?

Normally crumb trays are made from aluminium that reflects IR and is thermally conductive. I assumed this was to make it immune to being struck by the beam but it does reflect IR giving splash back. Steel is quite a poor conductor of heat so could get hot locally.


#2

i’ve always assumed it was Al because that’s good enough and it’s much cheaper. the black shouldn’t make much difference in terms of how it responds (over the fact that it’s steel i mean) so you could ask a pre-release or production unit owner how they feel. personally i don’t see it being much of a problem unless you’re doing a extremely long running cut and even then…


#3

Well shiny metals reflect far IR very well. Whereas black anodised aluminium absorbs IR well, so I expect it to make a big deference if the black coating means it doesn’t reflect IR.

Pros, you get no splash back, cons perhaps it will get hot and melt the bottom of your acrylic. Or maybe 45W into steel isn’t enough to get it hot.


#4

sure i’m just saying i don’t see it being a big difference over the not black steel grid; i can’t make any comparisons between it and aluminum.


#5

Well the not black steel grid is reported to give splash back, so it must reflect a significant amount of the power. Possibly the black one doesn’t reflect much at all. It depends if the “blackness” extends to the far IR range.


#6

yeah. it just seems like their priority has been making it look nice as opposed to a different sort of feature, and they haven’t mentioned any other properties of the black version.


#7

Currently the :glowforge: crumb tray is steel since you can use magnets on it. The ones on my machines are aluminum which can still give some flashback.
I dont think they are going with black annodized aluminum instead…plus it wouldn’t stay black long since the anodized part comes off easily with the laser…curious on what material will stand up to the laser without being vaporized.


#8

sure, i should clarify my comment in terms of ‘making it look nice’ i only meant the black coating on steel and not any properties of steel vs aluminum


#9

Ive found that covering your bed in a layer of tape has many benefits, one of them being reducing flashback immensely. It will actually sadden me to have to do this to the black bed, but Im going to.


#10

From my recollection of the past discussion, steel was chosen as a material for its strength and durability. It is a more expensive part but from Dan’s spin on it is better. Don’t recall much other discussion about flashback potential with different materials.


#11

Drat. Can’t get Discourse to include the actual question from @curt: " Is it still steel and magnetic?"


#12

Blue tape?


#13

Blue tape will work, ive just been using plain masking tape. Being able to see score lines in the tape provides extra benefits, so as long as thats visible, its good enough for me =)

You can see on the right where some flashback was occurring, and it would have damaged my acrylic, but instead it just hit the tape and stopped. lifesaver…


#14

I wonder if you’re restricting airflow somehow by doing that…


#15

The crumb tray has a solid bottom, and airflow in the unit goes over the top of the area, not underneath it, so it hasnt impacted it in any meaningful way for me.


#16

Ah, cool.


#17

Problem with taping the crumb tray is that it blocks the airflow underneath. The whole reason for the honeycomb in the first place. I mask any material that needs to be clean on both sides to prevent staining or marking from flashback…
-edit–
…just read the crumbtray isnt open at the bottom for air flow…thats weird…


#18

The crumb tray has a solid bottom, so no airflow is really going through there. Its all over the top.

Masking tape on the bottom of the pieces hasnt been enough in the past to stop flashback problems for me, and in some cases made them worse, as the masking on the piece chars and melts the acrylic. However, having the separate tape layer generally alleviates this unless the power setting was set waaaay too high.


#19

Thats weird…my masking never chars when cutting acrylic…settings may be too high.?


#20

Yeah. The airflow is in from the front right side of the machine. Across the top of the bed. Out the left rear of the machine.

From the head assembly, Its ‘pushed’ to the forward area of the machine (door) then to the left rear of the machine.

You can see the smoke that forms under the bed get sucked upward the towards the left.