Tag Archives: emaker

Setting Up Megatronics

Steps per mm

Possibly the most exciting thing for me when building a 3D printer is the electronics. I have built 2 kits (a Huxley from eMaker and a Mendel from RepRapPro) and am now building my own design. Until any printer gets attached to its electronics it is a mere metal doorstop. What I wanted to write up about was how I calculated the steps per millimetre for the DSF.

While in my usual ‘I’m bored lets search the net’ mood, I stumbled across the excellent RepRap Calculator3  by Josef Prusa. If you are building a printer from scratch this will greatly simplify figuring out what number the steps per millimetres should be.

Like many of the printers out there my DSF uses belts for the X and Y axis’ (T5) and a lead screw for the Z (M5). For the belt drives all I needed to change was the belt preset to 5mm – or the T5 belt. The pulley I was using was already 8 teeth and 1/16th stepping. As a result this would give me 80 steps per millimetre or a 0.0125mm resolution.

The Z axis uses an M5 threaded rod as its drive so again all I needed to change was the preset to M5. This means a step of 4000 steps per millimetre or 0.00025mm resolution. Obviously that is much finer then any of the prints I would ever do, the finest I have done was 0.1mm/layer. In reality I could set the stepper to full steps and still retain a resolution of 0.004mm.

So thanks to the calculators I have a 80 steps/mm for X and Y and 4000 for Z. Ignore the 800 for the extruder above. I have not yet got an extruder so that is just place holding!

One last thing; I have limited the feedrate of the Z axis to a low 2mm per second. Any faster and the motors stall. I need to oil the threaded rod to try and get some extra speed out of it, but I am not holding my breath.

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A Year of Printing

Has it really been a year – already? Well according to my first tweet on this day last year it is!

I remember being introduced to the RepRap project a few years ago. The printer at the time was Darwin. I absolutely loved the idea of it – but the machine was a bit of a monster. Not only did it look huge and complicated – it also had a bit of a ‘bodge job’ electronics solution. When I read up on making the printer the electronics were the most confusing – seeming to take several different boards and then modify them for this application. A far cry from the need single board solutions we have at the moment.

The second iteration of the RapRap was Mendel – a far less cumbersome looking machine. This was then modified further into the Prusa Mendel. This basically looked like the Mendel but was easier to build. Since then there has been the Huxley, Prusa Air, Mendel Max and the Wallace to name a few. That doesn’t even take into account the other more commercial machines like the Thing-O-Matic or the UP!.

So in this year I have gone through over 4kg of filament (although about 750g is waiting for the Filabot so I can recycle it) – I’ve had to repair the printer several times (3 times for the heated bed!) and changed or upgraded several parts of the machine.

Overall it has been a great experience and being able to have an idea and a few hours later have the item in my hand is great.

image

My Huxley

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Printing on the Cheap

While I was browsing eMakers forum I can upon a post of somewhere to buy cheaper filament. I ordered some from Reprapkit.com at £49.90 for 2.3Kg. That price has now gone up – £62.37 – as they are out of pre-order – that said the listing is confusing stating they have stock but still on pre-order! Anyway back to the filament.

From the East

The filament seems to be made in China, I hadn’t realised this when I brought it and got a little worried having read in the past of people having issue with filament from there. So far I have printed two sets of my Mini Rack and not had any issues. Not to say that it is totally perfect either. Before we get the the bad stuff…

The Good Stuff

The filament is very good – it feeds well and the finish is shiny. There have been no problems with it stringing etc.

However – as I have said – there are a negatives. The main one being that there seems to be a lot of moisture in the filament. This leads to some popping and spitting at lower print speeds – mainly on the first layer as it is printed slower. This leads onto any print that has a low feed speed – mainly those of a lower layer height – however I suppose you could simply increase the print speed.

But in the end

Considering this costs 6.5p per meter its faults so far are easy to put to one side. It sticks well, looks good and is cheap. It may have a little to much moisture for slower prints – which reduces its ability to work with thin layers – but its cheap making it great for test prints or prints requiring large amounts of plastic.

Links

RepRap Kit

 

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Simple Slicing with Slic3r

Can you get to print faster with Slic3r?image There is a general workflow I use for printing in 3D, you design your item, you slice it and finally print it. Originally it was the second step that would take the most time for me as I was using Skeinforge. That was the slicing software of choice for eMaker – and still is. It produces arguably the best prints out there at the moment. But it is slow – really slow.

Bytecode to native
Skeinforge is slow as it uses the Python scripting language. As I understand, Python uses the bytecode method to execute the scripts. This means the the code is translated and run in a virtual machine. It is the virtual machine that then runs the program. This is what slows down Skeinforge. So the new kid on the block is a program called Slic3r. This is programed using PERL and then compiled to run on Linux, Mac and Windows natively. As an example I sliced the model “Ducky Swimming” using Skeinforge and Slic3r. Skeinforge took 18 seconds to complete whereas Slic3r needed just 2.4 seconds – that’s 750% faster. Taking a more complicated model the “Babylon 5 – Starfury“. Slic3r was in at 38.97 seconds and Skeinforge was 8 mins 18secs.

It can safely be said that Slic3r is much faster the Skeinforge. Another advantage with Slic3r is it’s simplified interface. Skienforge as many plugins that means up to 180+ variables that could be entered many of which aren’t exactly clear as to what they do – although you don’t always need them all. Sli3cr on the other hand has about 60 and most have a clear simple English title.

Quantity over quality?
Does this speed come at a cost? Slic3r does a very good job overall with prints, even having some little tricks to reduce the blobs you get from printing in PLA. Another function of Slic3r is the ability to specify different print speeds for different parts of the print. So you can choose to have the outside shell printed slowly to get a good finish and the infill printed faster to reduce the print times.

Simple setup
image Once Slic3r is installed on you computer – and by installed I mean the ZIP file extracted to a location of your choice – you can run the program. A window will open and be filled with a standard compliment of settings. Before you load up your first STL there are 3 setting you need to check:

Nozzle Diameter
Filament Diameter
Filament Temperature

That’s it! You can now load up a STL file and get ready to print. Although that is the minimum you need to do, you may wish to look at other settings to help you produce better prints, my suggestions would be:

Layer Height (I normally run at 0.3mm for a 0.5mm nozzle)
Perimeters
(2 for most prints)
Solid Layers
(3 for 0.3mm layers, more for thinner layers)
Print Speeds
Travel Speeds
Start and End G-Codes

RepRap community member RichRap has written up on his blog a more in-depth look at Slic3r and its settings – link at the bottom of this post – it is excellent and well worth a read.

Now the bad news
Slic3r is very much under-development – as given by it’s 0.7.2b version number. There are some areas where it isn’t able to match Skeinforge. The most obvious one is when a STL has a thin wall. If an object has a wall of about 2-3mm Slic3r will only do the outside shell – when set with my 0.5mm nozzle – sometimes it will ignore walls altogether if they are less then about 1mm. I have got around this by reducing my nozzle size in Slic3r to 0.49mm and that seems to solve some of the problems. Neither does it have Skeinforge’s ease at switching to different profiles.

But in the end
For 95% of my prints I use Slic3r. It is fast and generally produces good quality. It isn’t perfect yet, but it is being developed and many of the issues get ironed out fairly quickly. Not bad for what seems to be a one man programming ‘team’!

But there’s more! (Update)
Since I wrote this Slic3r has been updated to 0.8.2. This has been a significant update that has seen the addition of a pattern plate to help print multiple objects as the same time. Another feature is to move the start position of each layer reducing the lumps on a side/corner up an object. Internal perimeters are now printed outside first to help with overhangs. There are a number of other changes which I will look at covering in another post.

Links
Slic3r Website
RichRap Blog
eMaker Website

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