Delta prints not quite square

I've recently realised the right angles in my prints aren't quite right angles. Reprap firmware auto calibration doesn't correct the problem(I have no idea if it should?), so I'm thinking the printers frame isn't quite right. Does anyone know what could be causing it?

What electronics and firmware are you running? Is it the XY angles that are out, or the XZ and/or YZ angles?

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Large delta printer [miscsolutions.wordpress.com], E3D tool changer, Robotdigg SCARA printer, Crane Quad and Ormerod

Disclosure: I design Duet electronics and work on RepRapFirmware, [duet3d.com].

Duet with your IRprobe and firmware, although I see you've just released updated firmware so I'll load that up tomorrow. X/Y(horizontal) in regards to 3D space. In relation to the towers, straight lines that point towards the Z tower are angled slightly towards the Y tower.
I think I got that right, having XYZ 3D space and naming the towers XYZ too gives me a headache!

Can you post a photo to show exactly what angles you mean?

If the towers are tilted, you may need to use orthogonal axis compensation to get right angles spot on.

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Large delta printer [miscsolutions.wordpress.com], E3D tool changer, Robotdigg SCARA printer, Crane Quad and Ormerod

Disclosure: I design Duet electronics and work on RepRapFirmware, [duet3d.com].

Hopefully these pictures show what I mean. I've marked the towers. I've also now noticed those long side bits aren't straight.

did you get to the bottom of this? I've noticed my angles aren't quite right, not as extreme as in your pictures but its there.

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wayno complaino
did you get to the bottom of this? I've noticed my angles aren't quite right, not as extreme as in your pictures but its there.

Might be different length of rods, lash or the towers not beeing exactly in alignment.

No, my investigations are on hold whilst I build a CoreXY machine. I have realised that the aluminium profile doesn't push all the way into the corners/the straight bits aren't straight((see images)I suppose that's what I get for buying a kit from China). So I'll probably end up buying the metal corners from robotdigg like a few others have.

Before you buy aluminum corners, you might want to check the length of the frame bars -- mine are all various lengths in a 2 mm range. Still putting mine together, yet to see what kind of precision problems this causes.

A little tip for accurately setting your frame bars is to get a pair of digital calipers..... and before every stops reading because their 150mm digital calipers cant measure more than 150mm, there is a trick, that lets you use your 150mm. calipers to measure in excess of twice their range.

The important thing to remember is you don't actually need to know the measurement between each upright at the top and bottom, you just need to know they are all the same

If you take your calipers and open them right out you should see that from the top of the jaws to the tip of the probe you have a distance over 300mm, if you use that to 'measure' the inside distance between your uprights, the calipers may read 125mm, which is clearly not the actual distance, but that doesn't matter, just press the zero button so this length reads zero, you can now measure the other spacing and know how much longer or shorter than the original measurement they are.

Of course, if you actually measure the length of the calipers whilst closed then you can use this trick to accurately measure simply by adding the caliper length to the reading value.

However, even after you get the frame measuring correct, you may still need orthographic correction, the trick to getting this right is to print a regular octagon 100mm across and about 5mm high and hollow (dont waste plastic and time printing the inside) with one of the sides parallel to your x axis flats then, whilst the part is still on your build plate measure across each pair of sides.

If the across flats values parallel ti the X and Y axis measure anything other than 100mm then you need to adjust the scale for that axis...

If the diagonals are not equal to each other then you need to adjust the orthogonal squareness... ideally they should also equal 100mm, but its more critical that they equal each other

if your sides are not straight then you probably have your arm length set incorrectly.

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