To adjust for kerf or not to


#1

Several questions have been asked about the kerf and why its important to adjust your designs for best fitting together.
If you dont want to rely on glue…adjusting for kerf is the way to go.
Here’s a quick video demonstration.
(Getting pretty good at one handed… But must laser cut a phone holder for video making…lol)

First part of the video, the black piece I’m using is the one that came out of the cut…
The white piece was cut larger by .0037" which is the specific kerf allowance for acrylic on my laser and lens.
The black piece falls right out…yet the white piece fits in and holds.

Now back to your regularly scheduled program…lol


Box joints without kerf correction?
A suggestion to help with inlays
Bling Box and Tray
A few more Pokeball necklaces
#2

Still blows my mind how big of a difference such a small sounding adjustment can make.


#3

Do you still use glue later for the final piece? Or do they stay in that well?


#4

Good info. I was used to offsetting outer lines both for cnc and 3d printing. How did you measure the kerf allowance, and is it constant with different materials or thicknesses?


#5

For this piece I glue everything to a backing


#6

I would suggest doing a search on kerf here in the Forum because I’ve answered this question several times before LOL as have others


#7

Thank you for detailing this for us in the video. The video was great, because it is so much easier to comprehend by watching you do the fitting. Now for a question…Is there an easy way to add the .0037" additional size to the white piece?


#8

Like I said in a previous post…in Corel I use a function called contour and I contour to the outside by .0037


#9

Thank you for the tip. I seem to learn sooo much from you. :relaxed:


#10

Although when doing slots, contour wont work since it will make the overall piece bigger and you want just the slot width bigger, so thats when I manually move the nodes using a preset nudge…
Hope Im not confusing anyone…lol


#11

Please don’t even hint at the suggestion that the GF team need not worry about addressing kerf adjustment into the software. Please! ! !


#12

That may be problematic as its not all parts need to be adjusted…


#13

I thought auto kerf adjustment was already in the works for the Glowforge, at least for the Proofgrade material where the kerf is known.


#14

Idk…but not all parts need to be adjusted so I would think there is still need for setup in the design.


#15

Yes, but I’m would suggest it would deal with kerf in much the way a CNC router does. Inside, outside, or on the line.

You have to keep in mind that not everybody makes pieces/parts that fit together pieces/parts they cut on the laser for whatever the end product. Some make parts that need to be within a thou or two of fitting another part of a different nature all together (e.g. the alnico magnet pole pieces I press fit with a 1 ton arbor press into forgon I cut holes in with my CNC router, but soon to be with my Flowforge).


#16

Thats true…inside outside in that application would be easy to compensate for…
Just pointing out the difference for say making a slotted box…or build pieces that are supposed to fit together without gluing.
For those new to the world of CNC…its not a one fix all easy button sort of thing…lol


#17

Inkscape, meanwhile, has inset/outset. I think the really important thing will be figuring out when to make the kerf adjustment in the design and when to let the GF software do it. Because if the design software and the cutting software are fighting with each other, ain’t nobody going to win.

(I was on the periphery of working with a guy who was making map puzzles, and he was having a heck of a time because he couldn’t just cut out the puzzle pieces in place and have them fit nicely.)


#18

Puzzle pieces are a good example of why you would want kerf correction outside the product design. If you start adjusting for kerf inside the model dimensions itself, it means that the next device that attempts to use your pattern will experience “fit” issues because the kerf is different and you adjusted for kerf inside the design itself. This would be a big deal if you plan on selling your design. Well, I think it would. . .


#19

I completely agree.
You also have to deal with the fact that the kerf will be different for different materials.


#20

Kerf and I are the best of frenemies.

If anyone works in Rhino, I adjust for kerf by using the ‘offset’ command. It’s nice because you can tell it the distance to offset, choose which side of the line you want to offset the new line to (including a ‘both sides’ option, which I’ve used to make tabs) and whether or not you want to keep the original line.

For me, I like to make all the new kerf-corrected lines on a new layer and drawn in a different color, so that when I finish with my first pass I can easily see my original lines versus my kerf lines. I also duplicate all my linework before adjusting for kerf, so that if my adjustments are wrong I don’t have to re-offset all the lines back to their original location (trust me, not fun lol).