Kerf size


#1

Back in October 2015 the kerf was definied by dan “ in practice, the kerf is about 0.008 - 0.022 depending on material, settings, etc.

I have a few questions now that some proto types are out and being used.

  1. has the Kerf changed size since 2015? (was there laser or optic changes?)
  2. Is the kerf uniform in both directions (is it round? I have noticed on other lasers it can be a oval)
  3. on other lasers I have used, it is common to have to clean the apature the laser comes out of (dust and smoke causing the laser beam to become factured/defused and thus in turn modifing the kerf). Is this a routing maintance issue that is being observed in the feild?

Fold-out dice box (and dice tower)
#2

First, let me explain my methodology so we will be on the same page. I created an f360 file I call the kerfinator that is nothing but two small parts with box joints. I simply adjust the settings in the kerf plugin and test for a fit I like.

Most of the things I have tested have been 1/8-1/4 inch thick. If there is any rounding it is too small to detect with my measurements.

I am finding I get good fits at about 0.22-0.21mm or about 0.009 inches.


#3

Having read all or nearly all of the posts from the pre-release users I will summarize.

  1. It doesn’t appear to have changed; if anything it may be better. The pre-release users seem to all be pretty satisfied.
  2. Software features that will affect this haven’t been implemented in the pre-release units the last I read.
  3. There is a thread somewhere on the forum of a pre-release user cleaning the laser head. I can’t recall a good search term to find it. My understanding is that yes, you will need to periodically clean the laser head, however, it is a very simple operation especially compared to other lasers. Remember the laser head is attached to the glowforge internals using magnets and is fully enclosed. As I understand it you pull it off, wipe the bottom lens/window, reattach.

#4

Yes to all three. Great summary. :relaxed:

I’m also seeing an average kerf of about 0.2 mm. If i adjust for kerf at all now, I’m now just using .005 and calling it quits. Seems to work just fine for perfect fit without having to force it. (That’s on 1/8" plys and acrylic. Bit more for 1/4".)


#5

oh, that just rocks :+1:


#6

I’'m happy that someone caught and appreciated that. :squee:


#7

Here is a statistic that I suspect only you may be interested in knowing @markevans36301. Index cards, at least the old ones from the 1950-60’s, were 0.009 inches thick, 9/1000"s inches exactly.

I used to use them to set the distant between the magneto and flywheel on chainsaw and go-kart engines so the engine operated perfectly when I was a kid and didn’t have a set of feeler gauges.

It was an inexpensive but effective feeler gauge!


#8

Yes, this is intresting and apparently, no one owns real feeler gauges anymore. I’ve been prompted to use a sheet of copy paper, a folded business card, and several other things to set gaps in official instructions for things.


#9

I’ve got three sets. (I tend to overdo it on purchases sometimes, but i keep losing the one that i need out of the stack.)


#10

I use them for calibrating my 3D printer…


#11

Here’s that thread…
https://community.glowforge.com/t/cleaning-the-lens-of-the-glowforge/5782?source_topic_id=6699


Odd, the automatic fancifying of the link isn’t happening. It is appending the “source_topic” part for some reason though.


#12

I have a set of feeler gauges but I have never felt the need to use them when calibrating my 3D printers. I roll an 8 or 10mm bar under the nozzle and touch off that. Then I measure the diameter with calipers and adjust the Z axis to give the same value.

For a final adjustment I extrude a line and measure its thickness.


#13

Also, something like this feeler gauge is essential if you’re very concerned about extruder distances:


#14

I don’t see why. If I touch off an 8mm rod that measures 7.82mm with a caliper then I know Z is at 7.82mm and can adjust the endstop position to match.

If I then make Z go to 0.2 then it will be 0.2mm above the bed, I don’t need to measure it with a feeler gauge. I can extrude a line of filament and measure its thickness with calipers, which is the end result that matters.

I posses a set like that but I have been running 3D printers for about 10 years and never used it for calibrating Z. Nor have I used a sheet of paper, which is widely advocated on the internet, but is bonkers.


#15

It depends on the machine, and how it does endstops. I have a delta with Z endstop switch plus auto-calibration, but there’s a certain amount of play it has going on. My Z0 is buried somewhere under the glass, so I usually auto-calibrate it for leveling, then adjust the Z offset above the glass using my feelers.


#16

I will have mine handy for kerf measurements, initially anyway.


#17

I don’t understand. Auto calibration implies you have a Z probe, so the machine should know where the glass is by probing it. That should then becomes Z = 0 and when you print the gcode should start with Z at the first layer height.

On my machines with Z probes the only thing I need to calibrate is the offset from the probe to the nozzle. Again I touch off a round rod after the bed has been probed and adjust the probe offset by the difference between the measured rod diameter and the Z value when it touches.

Calibrating with a feeler gauge implies you do it with the actual layer height you are using but Z calibration should work for any layer height.


#18

Just to reiterate before I get into it, I have a delta frame printer – not a box-frame printer.

Deltas can be somewhat “loose” with their head rigidity because they’re connected along 120-degree towers with arms on ball hinges. Plus, my Z-stop is on the extruder and relies on a certain amount of cantilever action to hit the switch, which only happens when the extruder tip “plus looseness” triggers it.

Also, having a delta, it calibrates the height based on the high-endstop at the top of each tower, so that it knows how long the rail of each tower is… because the distance the stepper motors need to travel along each tower’s rail needs to be taken into account or order to ascertain the bed level relative to it.

So I’m actually doing bed-levelling calibration more than I am height calibration. I auto-calibrate to level my bed, then I manually adjust the Z height afterwards, based on that level bed – because of my loose lower Z-endstop – in order to extrude at a proper height.


#19

I also have my Z limit at the top and origin in the centre just like a delta. They have different maths in the firmware but they can be auto levelled just the same as a Cartesian machine.

Once you have run your levelling routine I assume it must set the Z axis origin to an incorrect value. If you place a rod or a feeler gauge on the bed and jog till you just touch it then you can see how far out the Z origin is. If you change your probe offset by that amount then at the end of your bed levelling you should then have the correct Z origin. I don’t see how you could level the bed if the Z probe doesn’t give a repeatable height reading when it strikes it. If those readings are repeatable the origin can be calculated from them and the probe offset.

Anyway, whatever works for you is fine but it isn’t normal to have a Z probe and still need to calibrate the Z origin manually, even on a delta.


#20

I use a piece of tinned protoboard as my spacer. All nicely measured on the micrometer. Kind nice because the 0.03mm or so between the tinned areas and the rest of the board serves as a sort of go/no go gauge…