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konrad

Bed levelling

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I can't remember where I saw the vid but I use the trick with aluminium foil and a multimeter. Put foil down flat on four corners (or over the entire bed if you're not lazy), hook up one probe to the foil and the other to the nozzle (make sure the end is nice and clean). Now set the multimeter to continuity mode, move the head to the bottom left corner, raise the bed until the multimeter beeps, adjust your z-stop so that it triggers for this height, now check the other corners and adjust screws as necessary.

It might be a bit involved if you need to do this often but in my case it works fine (I've only needed to do it once so far, might be time for an adjustment now though).

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What I do is take a spirit level, take one screw as reference, and measure from this screw to the other screws. That way I am sure that the bed is levelled out.

just to clarify, the idea of "bed leveling" is not that the bed is perpendicular to the gravity vector, but parallel to the nozzle tip.

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I can't remember where I saw the vid but I use the trick with aluminium foil and a multimeter. Put foil down flat on four corners (or over the entire bed if you're not lazy), hook up one probe to the foil and the other to the nozzle (make sure the end is nice and clean). Now set the multimeter to continuity mode, move the head to the bottom left corner, raise the bed until the multimeter beeps, adjust your z-stop so that it triggers for this height, now check the other corners and adjust screws as necessary.

It might be a bit involved if you need to do this often but in my case it works fine (I've only needed to do it once so far, might be time for an adjustment now though).

a sheet of paper will do just fine: put the paper between the bed and the nozzle, and adjust the bed until you can slide the paper under the nozzle with the same amount of force in all 4 corners.

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What I do is take a spirit level

I wonder if spirit level tis precise enough to measure such small (<0.1mm over 200mm) variations. And it will work if X-Y plane of hot end movement is perfectly horizontal which might not be the case due to several reasons. Anyway I haven't tried this trick and I will give it a try.

 

trick with aluminium foil and a multimeter

That surely is precise but it takes a long time. One issue is that nozzle must be clear and this means it must be cold to prevent dripping. Somebody mentinoned here that while hot the hot end expands slightly. That will influence Z homing settings set with foil trick (but not the levelling itself).

I do something similar with just a piece of paper - I put it between (hot) hot end and bed and just slide it and adjust screws. If I can slide it with just moderate force the nozzle-bed gap is just right. But that needs to be repeated four times, needs practice and have limited accuracy.

I love simplicity of the two lasers setting described in the link in my firt post and keep wondering if this can be done with X-Y stationary bed.

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If you want to do the same with the Ultimaker you'll need to attach 2 fine lasers to the printer head. Because you don't move the bed in the X/Y plane but the printer head.

What you simply do is using the lasers at an angle from each other as a cheap range finder.

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I don't have my machine yet, but I do have some experience tramming machine tools (for instance squaring a tool spindle to the work table or vice). I intend to apply that knowledge here. What requires is a dial indicator such as this one:

http://www.amazon.com/Sowa-SO-200-718-Dial-Indicator-Range/dp/B002SPQFKE

These devices are accurate to .001" (.03mm) or better.

The instructions below seem long, but concept is actually simple. If I didn't own a dial indicator gauge I would use feeler gauges and the same basic procedure.

1. It requires is that the indicator be rigidly mounted to the print head with the plunger pointed toward the print bed. It should be easy to design a Thing for this.

2. Move the print bed up to a point where the indicators plunger is depressed somewhat. Lets say to the middle of it's travel. It would be best to lock the Z axis at this height if possible.

3. Slacken or back off the Right Front adjuster screw so it has no influence on the print bed height and leave it loose. This will temporarily effect a three-point leveling system and will eliminate twisting the plane as the adjustments are made. Leave the Left Rear adjuster tight. Break the Right Rear and Left Front adjusters loose, but leave the lock nuts finger tight.

4. Move the print head to the Left Rear corner of the work space.

5. "Zero" the indicator by turning the reference mark on the dial glass to align to the current position of the indicator needle.

6. Move the print head to Right Rear corner of the print envelope. Note the dial reading and adjust the leveling screw to attain a zero reading. Finger tighten.

7. Move the print head to the Front Left corner and note the reading and adjust until the indicator reads zero. Finger tighten.

8. Theoretically if the print bed is a true plane the bed will now be as close to level as is reasonable necessary, but the Left front corner has no support.

9. Without deflecting the print bed, take the slack out of the Left Front adjuster.

10. Move the print head to the Left Front corner and adjust to read a zero on the indicator. Finger tighten.

11. Re-check the reading in all four corners, make adjustments if necessary and snug the lock nuts.

12. Re-check again and tighten all four corners in the process.

13. Re-check again.

Note: I started the procedure in the back corner because it is closer to the support structure and so eliminates some deflection and slop in the bearings from the starting reference point.

Hoping to help.

Matt

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This is a Gcode file I made to more rapidly move to each corner at your set height.

It basically raises z to 10, homes the nozzle and zeros out x, y and z.

Then it goes to your preferred corner (the one not bracketed out) and sets z to your desired height. I set my z to 0.05mm in the code and then use a 0.05 mm feeler gauge which should squeeze between nozzle and platform with a bit of drag.

Then make your adjustment. The initial adjustment is the end stop using this thing http://www.thingiverse.com/thing:11033 and the next 3 are the bed levelling screws.

After you've adjusted a corner you hit the build button which makes it lower the platform by 10, home and return to that corner at z =0.05.

Once that corner is done bracket it out in the code and unbracket the next corner.

I set the x and y of each corner to be as close to the bed levelling screws as possible but giving room for the screw driver.

G21
G90
G1 Z10 F2000
G28
G92 X0 Y0 Z0
(RightRear)
G1 X150 Y180 Z2 F5000
(LeftRear)
(G1 X35 Y180 Z2 F5000)
(RightFront)
(G1 X145.0000 Y10 Z2 F5000)
(LeftFront)
(G1 X35 Y10 Z2 F5000)
G1 Z0.05 F200

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I don't have my machine yet, but I do have some experience tramming machine tools (for instance squaring a tool spindle to the work table or vice). I intend to apply that knowledge here. What requires is a dial indicator such as this one:

http://www.amazon.com/Sowa-SO-200-718-Dial-Indicator-Range/dp/B002SPQFKE

These devices are accurate to .001" (.03mm) or better.

I designed something to mount a dial indicator on my extrusion head a little while ago. It works quite well! I've been meaning to put it on thingiverse but haven't gotten around to it yet. My design uses 2 clips that clamp the 10 mm rod that came with the dial indicator parallel to one of the m3 threaded rods on the extrusion head and use the corners of top and bottom wooden plates to prevent it from rotating. I will post here once I have uploaded it.

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This dial indicator came from Harbor Freight for $15. Seems accurate enough for bed leveling. Attaches to you choice of one of the long screws coming down from the hot end. If I did the picture right you can take a look.

6845420846

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