Thoughts on technical things

Levelling 3D printers almost seems like some form of witchcraft..….Doubly so when you have a small amount of mechanical knowledge and have some electrical PCB tinkering ability

The Wanhao D9 is a Prusa style printer – it has a moving bed and a fixed gantry

A slight difference is that the D9 has Dual Z axis stepper motors – BOTH sides of  the Z axis are driven, which adds another dimension to the levelling whajmacallits.

Firstly – Frame Levelling –

See below for a picture of the D9 – Nice and studio like – this one has some quite significant differences to the shipped version that I received…(first one to list 3 wins a prize!)

 

These things really are quite easy to assemble quickly, however, you should pay attention to the small details….

For example……….See these images below for the top right of the printer gantry and the top left………

If you quickly assemble these printers, you’ll create problems for yourself.

There’s just enough ‘play’ in the mechanics to allow the whole frame to be tightened up so that it looks a little like a skewed rectangle, or if you’re lucky, a parallelogram……

This one’s an easy fix………Simply grab a thing with a known good ‘right angle’

A builders square or set square are great….If nothing, grab any square thing that’s sturdy, very thick cardboard, parts of flat pack furniture, or even a tablet device or phone!…as long as it has long-ish sides – longer the better

Slacken off the two hex nuts inside the gantry at the top

use your ‘squaring device’ to make sure the side and the top are touching your device…see image above – there won’t be a gap when the top is level……….

Tighten that side up…Repeat for other side and you’re good!

 

My first attempt at assembly actually had the printer gantry resembling more of a trapesoid as the space between the two upright parts at the top actually measured 1.5mm narrower than  the space at the bottom – and made it look something like the below!..

Other Levelling

Dual Z axis Motors……Twice as much to go wrong!?……….

See my previous post about how the Z axis went a little ‘wonky’.

I did wonder how well two steppers could be synchronised when the printer electronics are effectively an open loop system with no feedback…….My fears were assuaged when, one of the first thing the printer did was……….that above!

There’s some visual marking stickers on the rear of the printer to help you align the Z axis and make it level……

Anyways, all is well with the printer right now, it IS printing, and fairly well, but as always, there’s improvements to be had…….

Bed Levelling

it’s another subject entirely, but this one’s fairly simple really….there are 4 thumbscrews, raise or lower ’em ………

 

Improvements?

For a successful print on the D9, there’s quite a few things that need to be setup and the more accurately, the better..

• Chassis / Frame – Make sure everything’s tight, square and level
• Z axis – make sure that’s level – visually –
  • There are two points ‘sides’ to measure here to make sure the axis is level
• Bed – tighten up screws and measure – how? – calipers?, ruler?, measure to what point?
  • There are FOUR points to measure to make sure the bed is level (assuming the bed isn’t warped….that’ll be another blog
• SIX points in total to measure to ensure a day-day level machine!

 

Humans aren’t very good at being very precise when eyeballing stuff.  

So, there has to be a way that’s better than manually trying to jam your measuring device into some slot and tweaking / eyeballing things

Thoughts – Old school, mechanical but cheap and good enough

• Z axis – Spirit level? – some type of ‘bubble’ that’s bolted on somewhere to allow a decent eyeballing of levelness
• Bed – Multiple Spirit Levels – or a centre bubble device

 

Thoughts – Mechanical

• Create a custom sized / printed Block that ‘just fits’ into the frame where measurements are needed…..To ‘level’ the machine, simply tighten / loosen or move bits till it hits the block!

Thoughts – New fangled elecronictrickery

The VL53L0X

Enter a fairly new component, the World smallest Time-of-Flight (ToF) ranging sensor

This device uses Lasers to measure stuff with a pretty good accuracy level……..

I’ve just ordered a handful of ’em, I’m thinking of maybe having a digital readout of each of the 6 major points that need measuring……..

I haven’t seen anyone else quite use these devices in this manner…..questions that need answering will be

• Accuracy – reports of 3% accuracy for measuring distances…That’s 3cm every meter!…given that the printer has a 400mm / 40cm Build volume height, I’d expect to see an error of up to 1.2CM!!……..you’d think that would dismiss a device like this when it’s suggested you need to level within fractions of a millimeter But………I think it could work out…….
• Repeatibility………..this is the IMPORTANT part……..when you’re levelling anything, you’re making one thing parallel to another, all you need to know is that the distance between the two things is identical all the way along the thing….for my use, I just need to know that the distance between A and C or B and D is the same as it was, or if it’s changed, OR, if they’re different!…….

So, I think, using SIX of these VL53L0X  devices I can measure each bed corner and each side of the z axis and use that to level everything…IF the sensors are highly repeatable in their inaccurate measurements…

Or, in other words….Provided that EVERY TIME I make a measurement I get the same number out of the thing, I’m happy!…..Now, if I measure a (say) 40cm distance ten times and get ten different readings, I’ll be unhappy, But, can work with that somehow

Now to wait for the slow boat……………..

 

 

 

 

 

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