Weigh material down with proofgrade?


#1

In a thread about flattening warped material to the bed, and discussing the use of magnets, I got an official response of:

“Regarding the magnets, we don’t recommend putting anything in your Glowforge unless it’s laser-compatible. We recommend using small scraps of Proofgrade material if you need to weight down the edges of your material.”

Anyone know what they mean by this? (sent them a DM but no response yet) None of the proofgrade stuff I’ve got in the starter package is heavy enough to weigh anything down, especially not just a scrap of it.


#2

They are just covering themselves from a legal standpoint. If they said it was OK to put something in that caused a problem, you’d be saying it was their fault.

You can make hold-down clips from PG scraps that will help in many situations. Otherwise, magnets can be used as long as you make sure you don’t get anywhere near them with the beam!


#3

CYA by lawyers.

Since they officially only support PG materials, they can’t recommend using something other than PG in the bed. It’s nonsense though because one of the things Dan said once long ago was they spent extra on a steel honeycomb bed vs. the more traditional aluminum one because it’s magnetic.

Weighing down PG material with other PG material is the most ridiculous answer I’ve ever seen come out of GF Support. Physics tells you that you cannot weight PG with other PG sufficient to flatten a piece especially when having to maintain the 1/2" head clearance. The weight density just won’t allow it for any real warping.

The hold down pins are great for some uses but for mid-field on fresh materials where you don’t have any edge to catch the pin, magnets are the trick. I use neodymium magnets for about 90% of my hold downs and the pins for the remainder.


#4

I suppose if one wanted to be extra careful one could make proofgrade material caps to cover the magnets ¯_(ツ)_/¯


#5

CYA, but also you do need to be really careful your magnets or weights are not in the laser path. I always double check against the image placement & make sure they are well away! (will get tougher for material that requires more magnets, though).

I sometimes use small metal weights, too, and always make sure they are outside of the head’s path.


#6

I have a collection of them - quarter sized, half-dollar sized and pencil eraser sized. I can use the thicker bigger ones for major hold down, the smaller ones to tuck in spaces in the design (and can stack them to boost the holding power) and then the smallest ones are good in between design elements that are too close together for the larger ones.

Keep in mind that the image may be up to a 1/4" off so keep about that between the magnet and any nearby design element that will get lasered. The height of the ones I have won’t hit the head with the materials I use - even when doubled up. All from Amazon. :slight_smile:


#7

Whew. I’m not the only one that the laser path/end results can vary from the placement! (worse of course the further away from the camera you get!).


#8

That would protect the magnet–but your design is still screwed up if it’s in the path of your etching or cutting! (Been there, done that, but at least was just a bit of leather this particular magnet was sewn to (it was one of the “sew-in” magnets that I use in my leather bags)


#9

my main concern is I don’t want to screw up the laser if it hits a reflective magnet. Not sure if that’s an issue or not, just something that occurred to me?


#10

The magnets are not very reflective to the IR wavelength of the laser.

Now if you had polished copper or molybdenum clad magnets that’d be different :slight_smile:

You can always hit them with a coat of spray paint if you’re really worried about it though.


#11

More than one user has sucked a magnet up from the bed to the head…


#12

If the magnet has a strong pull to the honeycomb it won’t jump off the material when the head passes. A decent rare earth magnet on medium or thick Proofgrade material will be fine. If you use something thicker the pull to the bed might be insufficient and it could jump to the head or air assist port when it passes. Have had it happen with weaker ceramic magnets.


#13

The laser beam itself won’t care… if highly reflective, risk the beam will deflect to another area of the GF that could be damaged… or worse up towards the lid & anyone watching it. Though hadn’t heard about magnets getting sucked up to the head, but it does make sense how/when it can happen.

Just be sure it’s strong hold to the tray (different thicknesses & types of material will affect how well the magnet holds. And it isn’t so high a material or stack of magnets that it will be impacted by the head, or perhaps even affect the head travel if strong enough magnet…


#14

The lid glass is nearly opaque at the laser wavelength.


#15

Nice to know the laser shouldn’t damage anything if gets reflected up to the lid–still not nice to see a beam though! (even as unlikely & short duration as that could be from passing over a mirror-like magnet).


#16

I’m not sure if anyone has posted this yet. These hold down pins are magical and are made of PF!


#17

You need to order some Proofgrade depleted uranium.


#18

Damn… I was about to post that. Alternatively, wait for Proofgrade Neutron Star Slices.


#19

Do you guys happen to know the force rating of your magnets?


#20

I have rectangular ones rated at 27.5 lbs wrapped in gorilla tape. They’re overkill. I’d go with less strength. The 1/2" diameter, 1/8" thick are good for most things. You can stack them for particularly stubborn material. I didn’t wrap those in tape and they all broke/chipped so I don’t have many left. If you go for a magnet twice their strength, and put them in tape, I think you’d be pretty good. Say the 8-12lb rated range.