Advanced Guide to printing ABS Filament

Author: Matt Tyson/Monday, 4 June 2018/Categories: How To

Advanced Guide to printing ABS Filament

While some 3D Printers can have difficulty printing this material, ABS is one of the most common 3D Printing materials which has maintained its popularity due to its balanced mechanical properties, heat resistance and low cost.

Contents:

What Is ABS?
  Regular ABS

Requirements
  Regular ABS

Printer Setup
  Loading & Unloading Filament
  Bed Surface
  Bed Leveling & Nozzle Height
  Pre-heating
  Enclosure
  Filament Storage

Printer Settings
  Nozzle Temperature
  Bed Temperature
  Controlled Chamber Temperature
  Cooling
  Rafts
  Supports
  Dual Extrusion

Post Printing
  Removing a print after completion
  Removing Layer Lines
  Painting
  Joining

Trouble Shooting
  Blocked Nozzle / Filament Jam
  Warping
  Poor Layer Adhesion
  Nasty smell during printing

What is ABS?

Regular ABS

ABS (Acrylonitrile butadiene styrene) is an amorphous plastic derived from acrylonitrile, butadiene, and styrene. ABS is one of the most common 3D Printing materials to print due to its low price and balanced mechanical properties. ABS is a recyclable plastic and is available in a variety of different colours.

Regular ABS is a stiff material exhibiting a moderate toughness (impact resistance). With the right printing conditions (heat) ABS can be an easy material to print, however is susceptible to warping and cracking if printed in uncontrolled environments.

ABS exhibits a moderate chemical resistance and moderate temperature resistance, softening between 90-100°C (Glass Transition and Vicat temperature).

Requirements

Regular ABS

So what do we need to print ABS?

To print regular ABS you will require a printer equipped with a heated bed that can heat up to 90°C.

If you are interested in printing any sizable parts an enclosure is highly recommended. An enclosure will help to maintain a consistent heat within the build volume. 

To print very large parts, thin parts or parts with a high infil percentage a heated chamber is recommended to ensure no warping or cracking with those parts.

Printer Setup

Loading and Unloading Filament

Changing between two ABS materials:
If the printer is currently loaded with a different ABS material, unload that material at 240-260°C and extrude your ABS filament at the same temperature. Stop extruding the ABS filament after the previous colour has been completely purged and cleaned out.

Changing from a higher temperature material:
If the printer is currently loaded with a higher temperature material (for example PolyCarbonate), unload that material at its recommended printing temperature, and then load and extrude your ABS filament at that same higher temperature. It is important to load the ABS at this higher temperature so the previous material can be pushed out.  Stop extruding the ABS filament after the previous material has been completely purged and cleaned out, lower the temperature to 240-260°C, and extrude the ABS plastic for a few more seconds.

Changing from a lower temperature material:
If the printer is currently loaded with a different lower temperature material, unload that material  at its recommended printing temperature, and then load and extrude your ABS filament at 240-260°C. Stop extruding the ABS filament after the previous material has been completely purged and cleaned out. 

Bed Surface

For ABS printing there are a variety of optimal print surfaces

BuildTak™, FlashForge Sheets etc. (Recommended)

These surfaces are an adhesive backed sheet designed to stick onto your printers bed or removable platform. These sheets are our favourite printing surface when printing ABS due to their compatibility with other 3D printing materials, minimizing the need to recalibrate the printers nozzle height when printing multiple materials. 
In our experience we have found the FlashForge sheets are better than BuildTak™ for ABS printing as the sheets are more durable and the adhesive helps to prevent the sheets lifting when the heated bed is set for ABS temperatures.

It is possible to slice damage these sheets as bubbles can form if the ABS parts warp. However if you remove the parts gently and set your nozzle height correctly, these sheets can last longer than other surfaces.

Perforated / Textured Boards
Some printers are designed with a perforated or textured bed, these are an excellent build surface for ABS printing. During printing, the extruded ABS plastic sticks through the perforated holes gripping the plastic to the board. 3D Printing on perforated boards will require a raft to ensure the final part has a smooth bottom surface.

Heated Glass Bed with Glue Stick
Printing ABS straight onto a heated glass bed with PVA Glue stick is an excellent option. Printing on glass gives the bottom of your prints an incredibly smooth and shiny finish. We recommend applying a layer of PVA glue stick which acts as a ‘release agent’ when removing the finished print.

Once the 3D Print is completed, it must be removed from the build plate when the temperature is high. Removing a print after the bed has cooled may cause the glass to break because the print may shrink more rapidly than the glass plate.

This print surface is best suited for enclosed printers and printers with a controlled chamber temperature and setting your nozzle height correctly is extremely important when printing on glass.

Other:
When printing ABS you can also print with a variety of other printing surfaces such as Kapton Tape or an ABS slurry.

Bed Leveling & Nozzle Height

It is important when printing ABS that your first layer adheres to the printing bed. To achieve this it is important to ensure your bed is perfectly leveled and your nozzle height is set correctly.

We recommend leveling the bed and setting the nozzle height when the bed is preheated (90°C) to account for any expansion or shrinkage that may occur.

When manually calibrating your nozzle height, the ideal distance between the nozzle and bed is 0.1mm or the thickness of a piece of paper folded in half. When changing between bed surfaces, it is important to adjust the nozzle height again to compensate for the added thickness of the bed surface.

Pre-Heating

For optimal results, it is recommended that you preheat the buildplate to 90°C at least 15 minutes before printing ABS. A longer preheating time (30 minutes or even up to 2 hours) may be required with larger printers, in colder climates or with lower wattage heated beds to prevent warping.

In printers with actively controlled chamber heating, preheating the build plate to 90°C and chamber to 60°C for 5 minutes is recommended.

Enclosure

Without the right printing environment (high temperature environment) parts printed in ABS will print with too much internal stress, causing the print to warp while compromising your parts mechanical strength. 

While an enclosure is not required to print small parts in ABS, an enclosure is important when printing medium to large sized parts.

Many enclosed printers have top lids / doors which can be opened or removed. When printing ABS on these printers, we recommend closing the lid to maintain a higher internal temperature.

Photo: The Creator 3 by FlashForge (Left) UP300 by Tiertime (center) and FUNMAT HT Enhanced by INTAMSYS (right) are enclosed, a benefit when 3D printing ABS filaments.

Filament Storage

Like many other plastics, ABS is a hygroscopic material, absorbing moisture from its surrounding environment. When the filament passes through the hot end the moisture rapidly expands creating bubbles in between layers, poor layer adhesion, inconsistent extrusion due to material expansion and thus poor surface quality.

ABS will typically absorb moisture over a period of months however in environments with high humidity (such as evaporative air-conditioning) this process can take days.

Removing Moisture:
It is possible to remove this moisture by drying the filament. To dry a spool of ABS, place it in a pre-heated convection oven at 80˚C for 8 hours.

The temperatures listed are for ovens with accurate temperature control. It is important to pre-heat the oven before drying to prevent temperature over shoots. Drying without pre-heating or with higher drying temperatures can cause the filament to fuse together.

Preventing Moisture Absorption:

To completely prevent moisture absorption it is important to store and print your ABS materials below 20% humidity. Proper storage will ensure you don't need to dry your filament, this is ideal as excessive drying can degrade the plastic.

We recommend storing filaments in a resealable bag with desiccant when not in use. In environments with high humidity we recommend printing with a dry box like the PolyBox™. The PolyBox™ is a spool holder / dry box that stores the filament in an environment below 20% relative humidity, preventing moisture absorption.

If you are interested in reading more on the topic of moisture, check out our 'Starters guide to moisture, drying and filament storage'.

Printer Settings

Nozzle Temperature

ABS is considered a high temperature material, typically printing between 240°C - 270°C.

Of course the printing temperature range of an ABS filament will vary depending on which printer and filament brand you use. Some filament manufacturers add additives to their ABS to increase or lower the materials printing temperature range.

Higher extrusion temperatures will typically result in better flow and layer adhesion, ideal for printing mechanical parts whereas lower extrusion temperatures allow the plastic to cool and solidify faster, beneficial for users interested in overhang surface quality and easier support removal.

When starting we recommend trying a temperature right in the middle of the manufacturer’s suggested settings. If the manufacturer recommends 240°C - 260°C, printing at 250°C is a good starting point. If your extruder can not reach the highest recommended temperature, try printing at the lower temperature. Based on the quality of the print we suggest adjusting ± 5°C at a time.

Troubleshooting Nozzle Temperature
If the nozzle temperature is too hot, you may experience wisps / stringing on the surface of the print, difficult to remove and fused support material, sagging or poor surface quality on overhangs and a harsh smell during printing (this smell is more prominent with some ABS brands).

If the nozzle temperature isn't hot enough, you may experience compromised mechanical properties due to the poor layer adhesion, under-extrusion (uneven / rough surface quality) and if the filament is not melting fast enough; nozzle blockages.  

Bed Temperature

Printing ABS requires a heated bed at 90°C -100°C.

We don't recommend heating your heated bed above the glass transition temperature of ABS (100°C ). 

Controlled Chamber Temperature

A controlled chamber is not required to successfully print parts in ABS, however is important for users interested in printing medium, large or full-size parts in ABS without warping. A controlled actively heated chamber will minimize internal stress ensuring near-zero warping.

On printers equipped with an actively heated chamber or advanced thermal system, a chamber temperature between 60-70°C is ideal. At this temperature ABS will print with low residual stress and in most cases near-zero warping / cracking. Lower chamber temperatures such as 50-60°C may be used when printing fine detailed parts that need more cooling.

Photo: Advanced Thermal System on the INTAMSYS FUNMAT HT Enhanced maintains a high internal chamber temperature to print ABS with near-zero warping. 

Cooling

When printing ABS, users generally print with the part cooling fan off to maximize layer adhesion.

If you can control the power of your cooling fan, setting the fan at 10% - 20% speed can help to improve the quality of overhangs and reduce sagging.

Rafts

A raft is not required when printing ABS materials however if the printing bed is not perfectly leveled, a raft can be used to compensate and improve bed adhesion while minimizing warping.

A raft can be required when using certain printing surfaces such as perforated boards.

When printing both the raft and model in ABS, the raft should peel away easily.

Supports

When printing both the supports and model in ABS, supports should peel away easily and cleanly.

If supports are fusing to the model, try decreasing the printing temperature by -5°C adjustments or increase the distance between the model and supports.

If your supports are failing / collapsing during the print, try increasing support density and printing with a raft , this will improve adhesion for the supports.

Dual Extrusion

Support & Raft:
Dedicated support and raft materials compatible with ABS include HIPS; a limonene dissolvable support material.

Dual Colour / Material:
In most cases, ABS filaments will stick to other ABS based materials; ideal for dual colour printing.

Post 3D Printing

Removing a print after completion

Once your 3D Print has completed, it can be removed from the build plate. The best method to remove your ABS 3D Prints will depend on your build platform with some of these methods specific to removing ABS prints. 

Rigid Build Platform
On rigid build platforms like glass or aluminium, a sharp paint scraper can be used to easily remove the model.

When printing on glass, the ABS print must be removed from the glass platform when the temperature is high. Removing a print after the bed has cooled may cause the glass to break because the print may shrink more rapidly than the glass plate.

Some printers are designed so the platform can be removed from the bed while other printers the build platform may be fixed in the printer. If the platform is fixed, we recommend supporting the platform with your second hand to prevent uneven pressure on the bed which could affect your bed leveling.

Flexible Build Platform
Some printers on the market print on flexible build plates. With these platforms users can flex the plate to remove prints.

Removing Layer Lines

ABS like other materials can be post-processed after printing to remove layer lines and achieve a smooth surface. ABS is considerably easy to sand for professional applications. In addition printing with finer resolutions and using a filler primer can drastically cut down on sanding / post-processing time.

ABS also be chemically smoothed via a technique known as 'acetone vapour smoothing'. There are many variations to this smoothing technique, some of which use heat to expedite the smoothing process. Typically cold vapour smoothing can take between 1-3 hours with careful attention required to prevent over smoothing and achieve an even surface finish.

Safety Warning: Acetone is combustible and flammable so all users interested and investigating acetone vapour smoothing should never heat acetone. 

Painting

ABS plastics can be easily painted with acrylic and enamel based paints. Removing layer lines and model clean up are recommended before painting.

Joining

Parts printed in ABS can be joined with a variety of techniques

Glue
Gluing parts printed in ABS is simple, with Super Glue or Two Part Epoxies. We recommend sanding contact surfaces with a coarse sandpaper to increase the surface area for the glue, this will result in a stronger join.

Solvent Welding

Acetone can be used to solvent weld two parts printed in ABS.

  1. Use a paint brush to coat one contact side in Acetone.
  2. Carefully join the two parts together.
  3. Clamp or hold together the join for a few minutes while the contact surfaces fuse together and dry.

Trouble Shooting

Blocked Nozzle / Filament Jam

When 3D Printing it is possible to encounter filament jams or nozzle blockages, these blockages can be caused due to a variety of reasons.

Causes and Steps to Prevent Nozzle Blockage and filament jams.
In all of these cases if the filament cannot pass through the extruder, the extruder gear will continue to try push the filament and will eventually 'chew out' the filament. If you hear a clicking or clunking sound coming from the extruder, this is a good sign that the filament is jammed or will be if ignored. 

  • If your extruder temperature is too low during printing, the ABS filament will not flow and will have difficulty extruding. Printing with the correct nozzle temperature will solve this issue.
  • If there is too much friction on the filament, the extruder may have difficulties feeding the plastic. Try feeding the filament with a spool holder in different positions (above, beside, behind the printer).
  • If the nozzle height is set too close to the bed, the filament will have difficulty feeding through the nozzle eventually causing a filament jam. When printing at finer layer heights (0.1 and 0.05mm) the correct nozzle height is even more important. To prevent this issue it is important to print with the bed leveled and the correct nozzle height.
  • If the part is warping or lifting off the bed, the part will be pushing against the nozzle limiting extrusion and material flow, in this case it is important to prevent the part from warping.
  • Nozzle Blockages can occur more commonly with finer nozzles. The majority of 3D Printers are equipped with 0.4mm nozzles, it is important when printing or experimenting with a smaller nozzle (0.2mm) to adjust printing speed and extrusion settings 
  • If the filament is of poor quality is oval shaped or manufactured with an inconsistent diameter, this can cause the filament to jam in the extruder. The industry standard for filament tolerance is ± 0.05 mm. If the filament is 1.75mm an acceptable diameter variance would be between 1.70 - 1.80mm. Premium and higher quality brands can offer ± 0.02 mm tolerance. If you have difficulties printing ABS with only specific brands of filament this could signify issue with their quality control.

Cleaning a ABS Nozzle Blockage
If the nozzle is blocked with ABS one of the most successful solutions is to feed a tougher / harder and higher temperature material (for example PC-Max) through the extruder. In most cases, the properties of the tougher material and its higher printing temperature help to purge and remove the clogged ABS plastic. It is important to feed the tougher material at its required printing temperature, for PolyCarbonate (PC) this is 250°C and to push the filament into the extruder during this process.

A blocked nozzle can also be soaked in Acetone for a minimum of 24 hours to dissolve the ABS.

Warping

When printing higher temperature amorphous materials like ABS, some users can have difficulty preventing warping, firstly lets look at why ABS materials can warp.

Warping is caused by internal stress in the 3D printed part; there is one cause for internal stress when printing amorphous materials.

1. As the filament is extruded through the small diameter of the nozzle, the polymer chain of the filament is stretched and will want to return back to its ‘normal’ state, much like a stretched elastic band will go back to its position when it is released. At temperatures moderately close to the materials glass transition temperature, the polymer chain will 'relax', releasing the internal stress and preventing warping. Due to the higher glass transition temperature of ABS (100°C), ABS requires a heated bed and will print with moderate minimal internal stress at room temperature.

So how can we prevent warping and achieve near-zero warping when printing ABS.

Preventing ABS warping.

  • If parts are warping early into the print, this may be due to insufficient bed adhesion or an incorrect nozzle height. If the first layer of extruded plastic is not sticking to the bed, the internal stress during printing will be enough to quickly lift the part off the bed. It is important to ensure your nozzle height and bed is leveled correctly and that you are using the correct printing surfaces for ABS
  • Drafts, cool air from air conditioners and low environmental temperatures in winter can cause the ABS to print with more internal stress. An enclosure with a closed front door can help to contain heat from the heated bed, raising the internal temperature required to minimize warping.
  • In an enclosed build volume of 150 x 150 x 150mm, heat from the build plate will raise the internal chamber more efficiently and faster than with a larger 250 x 250 x 250mm build volume. Preheating for a longer time may be required on larger printers to reach the required internal temperatures. 
  • Printing with a lower infil will produce parts with less material and thus less internal stress in some cases minimizing warping. Parts printed at 100% will suffer from significant warping when compared to parts printed at 25-50%. Parts should stil be printed with a moderate infil (above 20%) as parts printed with a low infil are more suseptible to cracking.
  • Typically warping will occur on the outer edges of a 3D Print. In some cases, a raft can be used to extend the length of the part. The outer edges of the raft will warp instead of the part.
  • Printing on a printer equipped with an actively heated chamber is one solution to printing ABS with near-zero warping. Active heating is important to successfully print full size parts in ABS (eg. 300 x 300 x 300mm)

Poor Layer Adhesion

Causes and steps to improve poor layer adhesion.

  • If the filament is under-extruding during printing there will be inconsistencies and gaps between the layer, compromising  mechanical strength and layer adhesion. It is important to ensure you are printing the ABS filament at the right nozzle temperature to ensure consistent flow and to minimize drag or tension which may prevent the filament from feeding.
  • Poor layer adhesion can also be caused when printing with a ABS spoiled with moisture. When the filament passes through the hot end, the moisture erupts creating bubbles in the extruded plastic, compromising  the parts mechanical properties. If a spool of filament has absorbed moisture, it can be dried however it is important to store the ABS correctly and prevent this issue from occurring.

Nasty smell during printing

Compared to other 3D printing materials, ABS traditionally prints with a noticeable smell.

Causes and steps to minimize printing odors

  • ABS materials will release a harsh smell during printing if printed too hot. Printing at lower nozzle temperatures can sometimes minimize noticeable odors when printing ABS.
  • Users will notice certain brands of ABS will print with harsher odors when compared to other brands. Printing with a cleaner ABS material is recommended. For example Polymakers PolyLite™ ABS has been designed to print with low odor when compared to other ABS materials.
  • Placing the printer in a ventilated space can help to minimize odors when printing ABS, odors should also be less noticeable when printing with enclosed printers.
  • Some 3D printers are equipped with HEPA / carbon filters which can help to minimize the smell when printing ABS plastics.

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