Intro: Better Quality From Cheap 3D Printer Kits
There has been a huge surge of 3D printer kits becoming available on sites such as ebay, Amazon and Aliexpress, many of these are actually quite decent quality, however the instructions supplied are often hastily put together and out of date for the kit which you receive. This instructable is to give you some of the tips I have learnt on my quest for better print quality.
Step 1: Choosing a Printer
If you've not already got a printer, choosing one can be a bit tricky. There's so many different styles and configurations, Delta, CoreXY, Dual Z + Moving Bed (Prusa) etc etc. The most common printer kit available is based on the Prusa i3 MK1 design.It's cheap to manufacture and supports a full size heated bed. I looked for one with an Acrylic Frame, cheaper kits can be found cheaper (around £160) However this seller makes good points to why their kit uses what it does. From some quick Google-Fu I had also found a few people online that had bought this kit and had great success, as well as .dxf files for the frame. This is a good thing to have as if you over tighten the fasteners into the acrylic it is very easy to crack. This gave me the option of repairing any broken parts using my local makerspace's laser cutter(Shameless plug for Milton Keynes Makerspace). This printer was shipped from the UK so took about a week to arrive, however you could order directly from China for a lower price.
For reference if anyone that buys the Sintron Kit it uses this frame https://www.thingiverse.com/thing:39889 . be prepared for the instructions to just loose all detail by the end.
Step 2: Belt Tension
Belt tension is a tricky one to get correct if you’ve never owned a printer before. This is the biggest issue people face with cheap kits. To get proper belt tension first unscrew 3 of the four motor mounting screws, leaving just the one highlighted. Allow the motor to pivot towards the belt assembly a few degrees.Now mount the belts so that they are relatively tight. Now the belts are secured push the motor back to its mounting position and screw it in place taking up all of the slack making the belt very tight .This should take some force to get into place, if it's easy to move the motor your belts are too loose, If it’s too tight you may either snap your screw or 3D printed partt. Be careful! Screw the motor back in place, when pushing down on the belts they should be under much more tension. You may need to try this a few times to get to right. You should use the same method for any belts on your printer (Commonly X & Y)
Step 3: Threaded Rods
Many cheap kits use M5 threaded rods for the Z axis, the threaded rods in my kit were pretty bent over the entire distance. Replacing these reduced a huge amount of Z distortion and was pretty inexpensive. M5 Threaded rod can be found many places, I would personally look for local suppliers over ordering online to avoid the rods being bent in shipping. I bought mine in Toolstation for £1.78 a meter. Cut these to length and install them. A dremel or angle grinder makes this quick and easy, but a hacksaw and file will do the job, albeit at more effort from you.
A more expensive alternative upgrade for this is to purchase leadscrews. These are better than threaded rod and are designed for transferring motion, however cost more and will require a working printer to print new 3d Printed brackets as the leadscrews and leadscrew nut have different geometries.
Step 4: Extruder & Hotend
The Extruder and Hotend gave me a bit of grief when I first built the kit. My kit used the MK8 Extruder which is commonly available from ebay and aliexpress (Such as here goo.gl/fxlWlj). IF YOUR PRINTER USES THE MK8 EXTRUDER ENSURE THE MOUNTED FAN IS ALWAYS ACTIVE. About an hour into any prints the extruder would stop extruding, causing the motor to skip. Without active cooling on the heatbreak, it will slowly heat up to the temperature of the nozzle (For PLA this is around 200 degrees C). When this happens the tip of the heatbreak will start to melt the filament before it enters the heatbreak. When this occurs the filament will clog around the extruder gear as the extruder tries to extrude more and more filament. I've attached a photo above of a case when I caught this relatively early, and one of slightly later(excuse the quality it was a photo sent over Facebook Messenger), I missed this once for a long time and upon disassembling my extruder found it to be solid full of PLA. There are two ways to fix this. The best method is to wire the fan on the extruder to 12V directly, turning it on when the printer is on. If you'd rather have variable control you can connect it to the fan port of your RAMPS board. Ensure in your slicing software (I use Cura) that the fan is always on.
I later replaced this with a e3d clone which is working great. If you can afford it buy a real e3d to support them!
Step 5: Test Cubes!
Test Cubes are great, they allow you to diagnose issues with your printer setup. The best guide I've found for working out why there are defects is by Matterhackers and can be found here
http://www.matterhackers.com/articles/3d-printer-troubleshooting-guide . Google your issues! Its likely your not the first person to have that issue. Once your getting good print cubes you can move to torture tests such as the 3D Benchy. These prints test every aspect of a printer and let you really dial in your machine. How far you take this is up to you.