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How to print ABS?

Posted by Juan J 24/08/2017 0 Comment(s) Tutorials,Divulgation,

How to print ABS? 
 

Its scientific name is Acrylonitrile Butadiene Styrene (ABS). It is considered a engineering plastic. 
 

ABS filament is very popular in 3D printing and it was one of the first filaments to be used; although it is losing protagonism in favor of PLA, it is still a very interesting filament which offers great results if we work with it correctly. 

 

Among its advantages we point out:

  • It is easy to be extruded
  • As it is widely used in the industry, it is easy to find different variants with high features
  • It is relatively flexible, so it can be used for parts that fit to pressure 
  • It has a good resistance to impact 

What do we need to print it?

  • A 3D printer.
  • A compatible extruder: although it works with practically every extruder, the filament requires a temperature of 230ºC or higher, so we recomment to use hotends with additional fans and ceramic heaters. The old type Budas hotends can reach too high temperature during long printings and the old electronic resistances can get damaged. 
  • A heated bed, with borosilicate tempered glass, clips and fixing spray lacquer. In the case of ABS the heated bed is imprescindible to achieve a good adherence in the first layer and to avoid problemas as "warping".

How to configurate the printer?

  • Temperature: according to the indicated by the manufacturer. it is usual to find temperatures between 220ºC and 260ºC. If your hotend has teflon in the hot zone it shouldn't overcome 240-245ºC. For the heated bed it is usually recommended a temperature between 80ºC and 100ºC, depending on the size of the part and the length of the printing. 
  • Printing speeds: as it is easy to be extruded a wide range of speeds can be accepted, between 30 and 60 mm/s can be considered medium speeds.
  • Layer height: we mustn't use higher layer height than the nozzle diameter, between the 25% and 75% of it can be printed without difficulties. 
  • Extruder width: it is recommended the 120% of the nozzle diameter by the cutter programmes, and this is correct, but it may be interesting to increase this parameter in order to get a good union between layers, the higher is the width/height relation, the better layer union can get. 

How to avoid jams?

  • ABS is easy to extruder, thus we shouldn't have problems if we keep the extruder body cold, we use an adequate configuration with calibrated retractions and high quality components and filament. 

For what applications is recommended?

  • Parts which requiere a high resistance to impact, as mobile parts in machinary. 
  • Funcional prototypes in the industry. 
  • Matte finish models.
  • Applications where the working temperature is hight and PLA can't be used. 


Limitations: warping, delaminations and cracking; the usual problems with ABS.

 

In order to work with ABS properly it is very important to know the material properties and its limitations. The ABS has two characteristics which are the main limitations of the material: it has a high thermal contraction and it doesn't stick to other material when it is melted. 

  • Warping: it occurs when the union of the first layer printed and the heated bed is weaker than the contraction force of the material when cooling, causing that the parts unsticks (mainly from the edges). In order to avoid it we can follow these tips: 
    • Avoid air flows and cold environments, to help the part keep the temperature close to the heated bed temperature. 
    • Use the heated bed at 80ºC or higher temperature, this decreases the material contraction and active the lacquer effect. 
    • Use lacquer valid for 3D printing. There are specific brands, however, in Spain the brand Nelly it is very easy to find and works spectacularly good. The component we must hav is a "sintetic polymer" called differently depending on the manufacturer: Polyvinyl alcohol (PVOH, PVA, or PVAl). Generally the low costs brands usually have a good proportions of this material if you can't find Nelly. 
    • Use a relation between high height and width relation, the higher this relation is (within the reasonable) a better union we will get (values between 200% and 300% are recommended).
    • A good calibration of the first layer, as if the heated bed isn't close enough to the nozzle the first layer won't get adhered properly. 
  • Delaminations: the problem has the same origin than warping, the union force between layers is weaker than the generated by the material contraction, thus a layer separation is generated. In order to minimize this problem we recommend to take this considerations: 
    • Print using high temperature (not surpassing the maximum temperature of the material) to help the layer union. 
    • Avoiding difficult geometries: straight and solid walls are complicated, as well as big parts. 
    • Avoid aire flows, as they make the material cool down faster and it generates more tensions and make more difficult the layer union. 
    • Prepare few parts printings at once, so the time for each layer is lower and so is the cooling. 
    • Use  80ºC o higher as heated bed temperature.
  • Cracking: it happens for the same reason than the delaminations, hight tensions of the material derived from thermal contraction and poor layer union force. The separations aren't visibles, but when a load is applied the layers break up (usually internally generating a low characteristic sound).  
    • In order to avoid it the same indications than for the delaminations must be followed. 

Examples: 

  • Small clip, thanks to the material flexibility it is possible to create this kind of parts easily. 

     
  • Gears, as the material has a great resistance to abrasion it can be used for parts that are submitted to efforts and small impacts. 

     
  • Delamination example, this failure printing shows the layer separation in two corners where the tensions are accumulated. 

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