Dimensional Weird One

So, I've just finished a load of upgrades to me printer and decided to check the XY dimensional accuracy. I designed a simple 1 mm thick square measuring 100 x 100 mm OD with and internal square hole of 80 x 80 mm, that is 10 mm wide sides.

On printing, with ABS, both the X and Y axis print to within 0.16 accuracy after cooling on the outer dimensions but, the inner dims are a good 2 mm smaller. That is the side widths are coming out around 1mm wider ( ie. 11 mm).

Anyone got any ideas on what might be going on here??

Sounds like you need to adjust your stepper steps.

1mm is too close to the bed- the plastic distorts from the heat. Calibration measurements should generally be done at least a few mm above the bed.

It is critically important to do a complete calibration of the extruder before you try to calibrate the X and Y axes. Did you use the actual diameter of the filament when you sliced or use an extrusion multiplier based on a test print?

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Ultra MegaMax Dominator 3D printer: [drmrehorst.blogspot.com]

Quote
the_digital_dentist
1mm is too close to the bed- the plastic distorts from the heat. Calibration measurements should generally be done at least a few mm above the bed.

It is critically important to do a complete calibration of the extruder before you try to calibrate the X and Y axes. Did you use the actual diameter of the filament when you sliced or use an extrusion multiplier based on a test print?

Yes, the test piece was sliced in Simplify3D.

The error was noticed after I had printed an item, the bottom part of a box for an LCD display. The box was 20 mm in height. All the external dims were correct but it was under size on the internal X and Y dims.

Might try a different slicer just to confirm its not a slicer problem?

Did you design the box yourself or DL it from Thingiverse/Youmagine? You might want to check the CAD/STL file to make sure it's correct. It's easy to make that sort of mistake when you're designing things and there's a lot of crap on the design sharing sites. The Chinese board manufacturers frequently change specs without changing model numbers, so maybe the part was designed for a slightly different version of the board than the one you have.

When I design printable parts that have to fit other objects, I usually start by modeling the other object, then design the printed part to fit around it. That prevents a lot of problems, at least if I get the other object model right. I've had pretty good success using this method so far.

If you're making a box to fit a reprap discount GLCD module, I placed an accurate model of the module on Youmagine. I used it to design the controller box for my printer and it worked perfectly. You can DL it here: RRD GLCD Module

Edited 1 time(s). Last edit at 04/10/2016 10:32AM by the_digital_dentist.

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Ultra MegaMax Dominator 3D printer: [drmrehorst.blogspot.com]