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5mm Calibration Cube Steps

by MCroucher, published

5mm Calibration Cube Steps by MCroucher Jun 3, 2012

Description

This is a simple calibration object designed to test accuracy of your x, y and z axis linear travel, angular alignment and slicing settings, with some small bridges thrown in.

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Haha, that was also my first thought ;D
What I need after printing this is a miniature Q-Bert to go with it ;D
Problem solved. Marlin configuration for extrusion rate was wrong ( larger than default) reducing this value solved the problem.

On the lower cubes it cant be noticed because the extra material extruded merges with the infill.

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Instructions

Update: 19/03/2013 Hi Everyone, it's great to see so many people finding this piece useful in their calibration. It was one of the first things I designed after building my printer, so I was still fairly new at this when I put this up. I've updated some of the hints & tips below to reflect what I've learned since then. Cheers, Matt

I have since discovered Triffid Hunter's Calibration Guide, http://reprap.org/wiki/Triffid_Hunter%27s_Calibration_Guide This has proved invaluable in helping me finetune my printer. I'd recommend anyone who is trying to improve their print quality run through his guide, especially the Temperature & E-STeps fine tuning sections. I use those two processes with each new batch of filament and it has greatly improved my print quality.


The 1/4 pyramid is made up of 5mm cubes.

Use calipers to measure the dimensions of each block and the depth of each level.

With multiple prints I tested the effects of different slicing, firmware & printer settings against the printed object.

Description: Object overall x, y, z dimension = 25mm. Each layer of cubes is 5mm high. Base layer cutout: 5mm high, 5mm deep, 10mm wide. 2nd layer cutout: 5mm high, 5mm deep, 5mm wide.

I used this object to test: x,y,z travel against a known design: Once you have the correct E-Steps to match your mechanical setup, I found that the next two issues that affected linear accuracy were: Temperature & Extruder E-Step Fine Tuning. See the linked Calibration guide above. Fine tuning my Extruder E-Step calibration was the difference between an accuracy of +0.4mm to +0.5mm and +/-0.1 to 0.05mm.

Angular accuracy: Once you have aligned your printers axis to be perpendicular, this object is of limited use. I found it easier to print out circular objects to test for angular accuracy, as now I was finding that one axis was sliding at a different rate to the other, resulting in ellipses, or squashed circles. Improvements from here focused on reducing the friction in the axis and improving the belt tension.

  • Reducing axis friction (specifically for Reprap Prusa Mendel): First - Ensure that your guide rods are parallel and your carriage doesn't bind up on any point. Your build instructions will have instructions on how to set this for your printer, but on mine there were little grub screws for adjusting the location of the rods. Use a treadlocking compound (like Loctite) or spring washers to ensure they don't come loose under vibration. Second - Reconsider your y-axis carriage. The Makergear Reprap Prusa Mendel y-axis carriage has a tendancy to bind up on the y-axis when you are leveling the bed. Rearrange the fastener/spring arrangement to rectify this. From the side, working from the top down, my solution was: Screw head (M4x40 socket head) - M4 Washer - Wooden Build Platform - M4 Washer - Spring - M4 Washer - ~6mm of spacers (I used more washers) - Plywood Y-axis carriage mount - M4 Washer - M4 Locknut. This arrangement removes the tendancy for plywood carriage to warp and bind when your are levelling the bed, provides a degree of give to the build platform should you drive the head into it, and gives sufficient tension to the mount that I haven't had to relevel the bed in 6 months since I switched over.
  • Improve Belt Tension: Add the spring from some old school wooden clothes pegs to your belt. Pic - http://www.iheartrobotics.com/2009/11/timing-belt-tensioner.html - The new Makerbot Replicator has a similar spring to tension their belts.

Bridging: The cutouts help with checking your small bridging settings, and slicing settings for overhangs: These were added more for interest than anything else. To properly calibrate your bridging/overhang settings, I recommend printing some dedicated bridging calibration pieces such as: http://www.thingiverse.com/thing:9804 or http://www.thingiverse.com/thing:12925

Slicing settings: If you are finding that the top layer or two are being printed as solid cubes and bulging at the sides, see if you can adjust the minimum solid infill area setting on your slicing program. I use Slic3r (Current Ver. 0.9.8), and the setting is: Print Settings -> Infill -> Solid infill threshold area. This was set to 70mm^2 by default. Drop it down to 20mm^2 and the top cube should be printed like any other.

Top surface layer fill Vs perimeters & infill. See Triffid Hunter's Calibration guide for how to adjust Extruder E-Steps on the fly to calibration top surface infill.

Vertical Walls Wall building and the effect on print speed Vs the quality of the vertical wall printed. See the temperature section of the calibration guide. I found that higher print temperatures cause too much oozing of filament on the corners of the cubes. Fine-tuning the temperature as per the guide will allow you to see the effects of extrusion tempeature changes on corners & extrusion quality.

Cooling settings on small layers (such as the top cube layer, as above). Here you can adjust your small perimeter settings and minimum speed/layer time/fan speed settings. I am still trying to find a good combination here for my printer. My current settings for this are Small Perimeters - 30mm/s, with a speed reduction if the layer time is below 10s, and a min. print speed of 15mm/s.

Base Layer Height: If your base layer is too low, then that will affect the first few layers of your print. I replaced the default z-axis stop on my printer with one which gave me much finer control over the setting of the z-axis height and calibrating your base layer heigh properly can be the difference between putting a perfect print off the desk, an aborted print, and spending time reworking the model to trim back the squished out base layers.

There are other calibration objects out there that do similar or more things, but I had fun printing multiple pyramids out to check the results of different settings.

Haha, that was also my first thought ;D
What I need after printing this is a miniature Q-Bert to go with it ;D
I have an issue that always occurs between layers 22 and 28 or so. The solid infill starts to turn into a blob and ends up being higher than the perimeter. At this point the nozzle starts dragging along the infill and it just turns into a mess! I've tried turning down my E step value and it doesn't seem to help much, unless maybe I'm just not going low enough (tried as low as 930 from 945). I'm printing ABS at 216C.Any suggestions would be greatly appreciated!
I ve the same issue. On the last 2 steps there is excesive material due to the infill and the nozzle mess with it.

At first I supposed its a matter of high or infill area so i printed a single column of 25x5x5 mm and it printed it perfectly.. so im running out of options... Any ideas would be appreciated. (ps: Im using slic3r)
Problem solved. Marlin configuration for extrusion rate was wrong ( larger than default) reducing this value solved the problem.

On the lower cubes it cant be noticed because the extra material extruded merges with the infill.

What does it mean when the cubes are bigger overall and if the cubes are larger along one side than the other? Using ABS.
I used this and another object to calibrate and everything is great except the top block of the object is slightly warped (looks twisted). It's not so bad that you can't tell what it is, but bad enough that it's obvious. Everything else is nice and crisp, straight lines, the hollowed out areas look good as does the bottom. What could be causing the warping? Vibration? Temperature?
There is another piece, smaller, that I would suggest to be printed prior to this one - reprap.org/wiki/Sfact, _40x10.stl
I'm using both to calibrate my printer and both are awesome, IMO.
Thanks for sharing!
Great 2nd print for any printer to test a range of setting.I must of printed atlaest 50 of these so far :D
This is a great resource I've been using a lot in calibrating my first RepRap. One thing that would help (with all the calibration objects on Thingiverse) is to have some set of instructions to go along with the object. Such as, "if the long bridge sags try reducing your flow," or, "if the top cube is messy try changing the infill rate for small areas." In my most recent test the bottom layers start out a little messy with a few little peaks and threads, but the print improves after a little while (.2mm layers with a .5mm nozzle and 3mm filament). It would be great to have some suggestions in hand to address that for this object.
Hi thinkyhead, I have updated the instructions above, I hope this helps.
Hi, what slic3r setting did you use to print this cube steps?

I know every machine is unique, I'll use it as starting point.

It will be great if you post them. thanks anyway...

loupe
Hi loupe, I have included some of the settings above, however, consider running through the linked calibration guide, as that really helped me with improving my print quality & determining what settings, (temp, e-steps, etc) to run my printer at.
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