@NeverDie This is the one I've got: https://www.aliexpress.com/item/4000321437538.html?spm=a2g0o.productlist.0.0.3fb4457dTnpLL8&algo_pvid=d91fe6a2-335b-49cf-99fb-e01ae6fc9467&algo_expid=d91fe6a2-335b-49cf-99fb-e01ae6fc9467-3&btsid=0b0a556216043099802122070e932b&ws_ab_test=searchweb0_0,searchweb201602_,searchweb201603_

I've bought it via ebay from an European reseller, faster shipping and no taxes di*king around.

By "tuning" the endmill I mean: take out the collet/nut, blow the dust out, insert the endmill untill the chamfered edge passes through the collet. Insert collet/nut/endmill as it is in the spindle and tighten LIGHTLY!!! Do NOT overtighten! Start spindle, turn to max rpm, if it's noisy stop! take out whole collet/nut/endmill from spindle and rotate the endmill in the collet like 30-45 degrees, reinstall and run test again. If patient enough you can get to 60k rpm without much vibration.
Lately I'm not going over 35-40k rpm, the VFD shows the speed from 0 to 1000 and I stick around 700-750. For drills I run even lower, like 550-600 and don't bother tuning at all.
You can find the sweet spot as I said earlier, turn up the rpm, then slowly decrease until silent. You will find there are rpm ranges where vibration is high and ranges where is low, just use the lowest vibration one while still having a good rpm (find the vibration function poles).

Imagine the in the picture rightmost is 60k rpm, the blue line is the noise/vibration level, as you go to the left (lower rpm).

My 60k rpm is ER8, I guess the lighter collet/nut combo is less prone to vibrate, never seen a decent priced 60k rpm ER11.
ER 11 good is for heavy endmills, big collets, more than 3.175mm (1/8") shaft diameter, maybe 1/4" for table flattening.
The 60k rpm spindles are usually 300W, not a lot of power at lower rpm to do tough milling, so no use for larger endmills, ER8 is a good choice for fine milling with 1/8" shafted endmills.
My VFD is a Sunfar one, pretty decent I might say, I ran it for a few dozen hours now without issues.

PS. The best way to check for runout is the sound test, run the spindle empty, then with collet+nut, then with the endmill inserted. If I "tune" the position of a new endmill I can reach 60k rpm without any vibration at all, so I get almost no runout.

Regarding feedrate vs rpm the last engravings I ran at about 40k rpm, was to lazy to balance the endmill (turn spindle on, if it hums loudly then stop, undo the clamp, rotate 20-30 deg the endmill in the clamp, retighten clamp, rinse, repeat). I just tend to find the poles of harmonics: start spindle at full speed, hums badly, lower rpm slightly less hum, lower even more starts humming again, lower again, even more quiet... so find the sweetspot with least humm (vibration). If you go down enough at about 35-45k rpm you will get the quietest.
For best feedrate I've manually written a simple zig-zag gcode with different speeds: F1000 G1 X20Y5 G1 X0Y10 F1100 G1 X20Y15 G1 X0Y20 F1200... and inspect with the microscope for the best, burr free, engraving speed.
I normally run at 1400mm/min.

@NeverDie How about a dial gauge in a magnetic mount attached to the spindle and measuring against x/y/z frame points, and a simple gcode like g0x100 g0x0 a hundred times? At least that's how I did it to check for lost steps.

@NeverDie my UV lamp is made from a UV led strip glued to a cardboard box, I just place the UV over the board not the board in the lamp.

The so called 1080p cheap projectors are actually 640x480 real resolution, or even 320x240, they are able to accept a 1080p signal and scale it down so are falsely advertised as FullHD. That was the state of things a year ago when I last checked. Much better to get a sh brand projector instead.
About resolution: FullHD 1920x1080 over a 150x100mm board gets you 10pixels/mm roughly, that is 0.1mm resolution, I don't know if that is good enough, also focusing at such a close range would require some lens hacking, from the factory they focus at 50cm at least and get you a 60-100cm diagonal size.

It highly depends on the lead/ball screws, if the tolerances are in range of 0.01mm and backlash at about 0.1mm a 0.X deg of resolution at the steppers/servos doesn't matter since a normal lead screw is 4-8mm/turn.
Even 200 full steps/rev (1.8 deg stepper and full steps) with 4mm/rev screw means 50 full steps/mm or 20 micron/step (0.02mm/step) linear resolution which is much better compared to the rest tolerances of the machine.
On high precision rails, very tightly built machine it might make a difference, but for these cheap routers it doesn't.

LE. @NeverDie 0.27 deg error translates to 0.003mm linear error (3 microns) assuming 4mm/rev screws are being used. Do you think you can notice/measure that? (4mm/360)*0.27=0.003 Even if using HUGE 16mm/rev ball screws translates to 0.012mm of error, unnoticeable.

@NeverDie The UV laminator just gave me the craziest idea: Why don't we take a normal laminator, remove the heating coils and add a strip of UV leds to it??? The expected result: perfect pressing of the artwork to the board and curing at the same time, speed it travels through sets the hardening level. I can get rid of all those glass panels and stuff.
I'm going out hunting for a cheap laminator :)

@NeverDie for $99.99 I would roll the s#it out of it with my hand roll, heck I would even step on it with my pressure controlled 200 lbs weight in pink slippers.

@NeverDie My printer has a problem with transparencies (jams) and also the high cost for transparencies made me go the paper route, if the toner is facing down the distance is the same as when using transparency printed artwork, also the paper "softens" the uv led light and makes it more uniform I guess.

@NeverDie or just try some canola oil spilled on normal laser printer paper ;)

The stack goes like this:

-glass
-normal printer paper made transparent to UV light (https://www.amazon.co.uk/Kontakt-chemie-Transparent-21-Spray-200ml/dp/B00ID6KY4K)
-toner (the image is mirrored and placed toner face down)
-transparent film from "document wraps"
-UV solder mask paint
-pcb
-glass

The top and bottom glass pieces are held tight by some binder clips.

@NeverDie I put a piece of clear "document wrap foil"

In my experiments the best results I got were using a rubber roller with a handle, the film is 0.1-0.2mm thick but that is no problem for the home made led uv exposure box to cure. Here is something similar, unfortunetly mine got lost a while ago when moving out.

I clean the boards after milling with some Scotch Brite metal sponge and the abrasive part of a dish washing Scotch Brite sponge, this also removes the small burs along milled traces. Wash with some IPA in the end and the paint gets good adhesion to the board.

The hurdles of getting the uv mask aligned, printed dark enough (damn these new eco printers) makes me want to build a laser for doing this kind of curing. I've just saw a great video of a UV laser using a spinning mirror from a printer, that would make the scanning of the board so much faster.

https://www.youtube.com/watch?v=G9-JK2Nc7w0

@NeverDie 100 microns = 0.1mm 1m=1,000milimeters=1,000,000micrometers (microns) 1mm=1,000microns

The UV laser solder mask making has some issues:

1. for curing with a laser you need a larger spot, imagine a 0.1mm beam scanning a whole 50x50mm pcb, that takes 500 passes to cover the whole board at 0.1mm resolution. A slightly out of focus laser with 0.3mm beam is more likely to get the job done faster and more uniform. To get the best results using cheap kinematics is best to "scan" the board with some margins for acceleration and deceleration, any attempt at vector cutting the shapes results in a lot of positional error due to backlash and slacks in the kinematics of these kind of laser.
2. reflections, the stronger the uv the more it will flare and reflect and the reflections will cure adiacent regions, maybe some which should not get cured, a weak laser is preferred, 50mW or even less, to reduce flaring and reflections.
3. burning away already cured paint.... I don't really know if it's possible, the UV paint is made to get cured by UV, not burned, you either need a very strong laser or a different wavelength, maybe CO2 laser. I happen to have a CO2 40W laser but never tried to burn already cured solder mask away.
4. focusing and perpendicularity, a slightly not perpendicular beam has an oval shape and the vertical/horizontal size is thrown off, also slight height differences in substrate can and will make the focus spot bigger/smaller as the beam is a cone and you intersect it higher or lower.

LE. I would get an EleksMaker 405nm 500mw laser and start from there. https://www.banggood.com/EleksMaker-EL01-500-405nm-500mW-Blue-Violet-Laser-Module-PWM-Modulation-2_54-3P-DIY-Engraver-p-1287791.html?rmmds=search&cur_warehouse=CN

@NeverDie These closed control loops have got really good traction lately, these days there is a sprawl of new/cheaper devices/clones. I've used mine without issue for 2 years now.
My problem was frequent binding of the machine. I have a 60,000rpm spindle and I normally use 1400mm/min speed and 300mm/s^2 acceleration. The machine itself is far from perfect, sometimes I can hear it knocking, and with older steppers and drivers I lost a few steps every time it jammed, resulting in 0.1-0.3mm of error at the end of a longer milling process.
The culprit is either some misalignment and lack of parallelism or some of the balls have flat spots. The binding does not occur in the same place or direction every single time, so I believe the balls are more likely to be the cause. The solution would be a complete rebuild using higher quality linear rails, but the the price and the time needed to do it makes me leave it as it is since I can mill 0.15mm isolation with 0.25mm traces for smd and also large 20cm x 30cm boards for through hole projects (mostly).

@NeverDie Here are my steppers I currently use on my 3040 cnc: https://www.ebay.co.uk/itm/Nema23-2Nm-Closed-Loop-Stepper-Motor-Driver-3phase-Hybrid-Easy-DC-Servo-Kit-CNC/254675291058?hash=item3b4bd48bb2:g:FcsAAOSwAuZX4lcl

@NeverDie Just get any Atmega328 board (Uno, Nano) and flash grbl 1.1f and wire it to whatever drivers you have (now I'm using hybrid closed loop servos, but I've used TB6560 in the past).
I use OpenCNCPilot, it has autolevel, and a lot of other useful functions: simplify, arc to lines, split long lines, etc. I mainly use it for splitting long lines, as a long move doesn't account for the board topography (local highs and lows), by splitting the line accordingly to the detail needed (5mm for dip, 2-3mm for smaller smd boards) I get a much better engraving. Also the autoloevel grid size and step setting is very simple.

Sorry to hijack the thread a bit,
I'm using a TCRT5000 sensor to read a water meter (Zenner), it works ok until it stops detecting pulses, I have to increase the sensitivity (clockwise turn the trimpot) and it works ok for another few days/weeks, then again it needs an increase in sensitivity, like somehow it's loosing it's sensitivity .
I'm already with my second sensor, the first one got to the end of the trimpot and couldn't adjust anymore.

Has this happened to anyone else? It's powered by 5V, it's the LED losing power or the photosensor losing sensitivity? Any ideas?
Thanks.

Milled some PCA9615 differential I2C converters for the sensors ouside: magnetometer for the gas meter, temp/hum, baro.
Until now I've used a 7 meter long cable, but whenever the gas water heater fired up the Arduino would just freeze losing the count of gas pulses, I've tried shielded cable but it hasn't solved the issue.
Since Sparkfun's breakout boards are on the wrong side of the pond I decided to make my own.
Really hope the Arduino doesn't lock up anymore.

LE. That TSSOP10 was a b*tch to solder 😁

@crankycoder https://github.com/jeelabs/esp-link