Happy 2017! With added 3D printer project

Ah, another Christmas and new years is behind us.   I did get socks but I actually wanted them.   I’ve been helping a friend fix an Audi RS6 and it has been a VERY messy job.   I toyed with burning some of the clothes I was wearing while working on the Audi rather than washing them.

Anyway, it would not have been Christmas without buying myself something a bit silly.   And finding a 3D printer for under £140 delivered was just too tempting!   This is a clone of the Prusa i3 which I believe is a fork of the early reprap.   Community support is always a good thing in these situations.

I’ve always been a bit ‘meh’ about 3D printers.   The friend with the Audi has used a number of fairly high price units and has had mixed results.   So I never thought that spending the far side of £500 on one was worth it so I’ve generally ignored them.   But sometimes a deal is too good to pass up!

So what can you expect for £140?   A big kit of bits!   No pictures, sorry.   Lots of screws, lots of bits of laser cut acrylic, lots of wires and a memory stick with the worst instructions EVER!   Thankfully there are build videos on youtube.   If you’re not mechanically proficient I would avoid this.   Acrylic is brittle and a bit too much force and you will break it!

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The spare monitor behind it doesn’t help the photo….

The kit contains EVERYTHING you need including 10m of PLA filament.   It even includes tools, a euro plug mains lead and a UK plug multi-adaptor of death.   It took me a good afternoon to build it up.   And probably the same again to make it even vaguely print right.

There is a whole laundry list of things wrong with this 3D printer:

  • The frame wobbles
  • Z axis lead screw nuts are misaligned
  • Z axis stepper motors are in parallel so the torque is very low
  • Tensioning the belts for the X and Y axis bends the frame
  • The bed sags in the middle by about 0.2mm

Thingiverse has a whole pile of parts for improving the frame and fitting various extras like cooling fans or other extruders.

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The bed comes covered in masking tape which helps adhesion of the first print layer.   And here we see some free holes in the tape thanks to poor packing,   Never mind, tape is cheap.   The bed is a sheet of aluminium that has been shear cut.   0.2mm bend in it is quite normal in my experience.

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Yup, those are not parallel.   Which causes the lead screw to stick and stall the stepper motor.   The X axis is lifted with a pair of lead screws each driven by their own NEMA 17 size stepper motor.   The lead screws are quite nice and the brass nuts are a good fit.  But with that much misalignment they just don’t work right.   To add insult to injury the flex couplings were sat too far down on the stepper motor shaft which resulted in there being very little flex left for the lead screw.   An easy fix but this setup should be detailed in the instructions!

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No support at the top of the lead screw.   You can see the misalignment very well here.   And this is after some fettling.

It was still stalling on the Z axis which meant printing was impossible.   There is a guide to fixing this on the facebook support group.   The key part is increasing the stepper drive current as the parallel wiring of the two Z axis steppers results in half current and the resulting loss of torque.   The guide says to set the trim pot to a particular setting which did result in the Z axis no longer stalling but the itty bitty heatsinks on the driver PCB are just too small!

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The Z axis driver got to the point of burning my finger.   I do not like running electronics that hot!   I’m not an ‘as cool as possible’ person and the reality is that the ‘ow that is hot’ temperature is not that hot.   But leaving a mark on your finger is too hot!

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The heatsinks came off really easily.   Looks like thermally conductive silicone.   Utter crap really!   The drivers are Allegro A4988.   In theory they can do 2A per phase with the right thermal management.

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That is better!   Utter overkill!   It is an offcut from an old heatsink I had lying around.   Some 2 part thermal adhesive will hold it on.   Much better thermal conductivity than the silicone.   I might replace some of the other heatsinks too.   I’ve read that the FET for the heated bed can burn out.   I didn’t give it the finger test while it was running.

So the current todo list is as follows:

  • Fix the Z lead screw alignment
  • Flatten out the bed
  • Fit some braces to the frame.   I plan to use some aluminium angle as I have lots
  • Fix the thermal issues on the driver PCB
  • Generally mess with printing stuff and see how much filament I can waste!
  • Keep the cat away from the printer when it is running

There are an insane amount of bits you can buy for 3D printers.   From both good suppliers and the usual crowd of Chinese cloners.   So I could go totally mental and replace virtually everything and spend hundreds or more if I desired.

I have some other project updates to do but this has been the first time off I’ve had since early 2016….   We shall see how 2017 goes.