1 Topic by Photog

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Topic: calibrating bed level and z stop with razor blade.

Since the z-stop is supposed to be set for the nozzle is 0.3mm above the bed, wouldn't it make sense to just use a razor blade? Razor blades are usually 0.3mm thick. You could level the bed at the same time this way.

Would this work? or am I just an idiot?

1) Set z-stop by eyeball for nozzle is close to bed but enough room to slide the razor underneath the nozzle.
2) Set the razor blade flat on top of one of the levelling screws.
3) Manually move the extruder for the nozzle to be above the razor.
4) Crank the screw to bring the bed higher until it won't go any further. The hard metal razor will prevent the nozzle from being any closer than 0.3mm from the bed.
5) Repeat steps 2 through 4 for each leveling screw.

Unless I'm missing something, this will not only adjust it for the z-height is perfect at 0.3mm (where I've read it should be on the forums.) but also level the bed at the same time since it will be at 0.3mm at each of the 3 screws. It seems like it will work better on a glass bed than the kaptop tape bed since the glass is a harder surface.

My SD3:  Clear plexiglass case, case heater, X axis stabilizer, Z axis stabilizer, thumb screws, filament guide, heatsinks on all motors, extruder fan, controller fan, heatsinks on motherboard, Y rod pillow block, USB and Power on/off switch, fully calibrated including trimpot tuning. Am I missing anything?

2 Reply by Hazer

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Re: calibrating bed level and z stop with razor blade.

Steps are correct, but you shouldnt just say "crank the screw till it wont go further". The entire extruder assembly rocks back and forth on the X rods. Also, the bed is on springs. A more accurate procedure at this step would be "tighten screw until razor starts having trouble sliding underneath nozzle".

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3 Reply by Claghorn

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Re: calibrating bed level and z stop with razor blade.

Or what seems to work best for me is "till it has trouble sliding out from under the nozzle". I find it easier to lower the bed, put my shim under the nozzle, home Z, then see how "stuck" the shim seems to be.

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4 Reply by Photog

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Re: calibrating bed level and z stop with razor blade.

Am I right that the best height for the nozzle from the bed is .3mm ??  Or do you guys run higher or lower than that?

I just tried this razor blade trick with a single edge razor blade I got from work. Tested it with calipers and it's 0.301mm thick.
I did it with the razor blade just barely having "grip" on the nozzle likes you guys suggested and my prints are coming out better than with using the paper method.

I think it works better because you want to heat your bed up when leveling, but if you use paper it will deform the paper somewhat on a hot bed, plus paper is soft and the nozzle is hard metal and will scrap up the paper. No problems like this with the razor blade.

My SD3:  Clear plexiglass case, case heater, X axis stabilizer, Z axis stabilizer, thumb screws, filament guide, heatsinks on all motors, extruder fan, controller fan, heatsinks on motherboard, Y rod pillow block, USB and Power on/off switch, fully calibrated including trimpot tuning. Am I missing anything?

5 Reply by ronsii

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Re: calibrating bed level and z stop with razor blade.

I use a piece of 20lb. computer printer paper... never had a problem with paper deforming... I guess if the paper was wet or something, just slide the paper back-n-forth while adjusting screws when I get a slight drag I back it up a tad... so no drag then go to the other front screw... no need to do the back screw as it is set by the ztab screw wink

6 Reply by dubbsd

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Re: calibrating bed level and z stop with razor blade.

I use a $4.00 set of feeler gauges  from Harbor Freight.
http://www.harborfreight.com/32-piece-s … 32214.html

Ultimaker S3.

7 Reply by Rincewind

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Re: calibrating bed level and z stop with razor blade.

Photog wrote:

Am I right that the best height for the nozzle from the bed is .3mm ??  Or do you guys run higher or lower than that?

AFAIK the height for the nozzle should be .1mm. Your first layer already moves .3mm above that (if your layer height is .3).

8 Reply by adrian (edited by adrian 2013-12-07 22:46:57)

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Re: calibrating bed level and z stop with razor blade.

Rincewind wrote:
Photog wrote:

Am I right that the best height for the nozzle from the bed is .3mm ??  Or do you guys run higher or lower than that?

AFAIK the height for the nozzle should be .1mm. Your first layer already moves .3mm above that (if your layer height is .3).

My start gcode has opening lines as thus:

G28 ;home all axis
G90; set absolute coordinates
G92 E0; reset extruder distance
G1 Z5 F300 ;move platform down 5mm
G1 X203 Y199 F3000 ; move to back right corner
G1 Z[first_layer_height] F200 ;move platform layer height from nozzle

So if the Home sets '0', and the G1 Z<layerheight> moves us the layer height from the platform, then you want a distance of slightly *less than* the layer height between the nozzle and the bed..  But whats important is - This is when everything is at Temp and thermal expansion has come to rest... The 'piece of paper' test with the Bighead Nozzle and the standard bed means that the .1mm gap when the bed is not fully at temp and the nozzle is off will come down to 0.2mm effectively when everything is at temp (as with the nozzle expanding down and the bed fractionally expanding up, "0" is now "+0.1", meaning that the commanded move to "Home + LayerHeight" will land you at just slightly less than the first layer height which is what you want smile

Now, the above works great for the more standard 0.3 or 0.4 first layers are used, as the expansion is all good for that to ensure that first layer is slightly squished onto the bed to ensure it adheres.

But if you want the cleanest base on an item, and have first layer heights of 0.2 and 0.1, the thermal expansion can often be more than the layer height itself! smile Setting up the 'standard way' can lead to you actually having too much squish and even have the nozzle dragging on the bed. At first layer heights of 0.5/0.6 its the opposite problem - threads will not adhere at all.

I personally just use a piece of glossy photo paper - it rubs quite nicely with a noticeable grip and is the perfect thickness to setup the nozzle against the COLD bed and when printing at temp its a nice squished but still rounded first layer thread...