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3dp FDM printers
#1

To give some explanation to 3dp printing this is a short introduction to one type of printer system the Fused Deposition Modelling or FDM is one of the 2 home hobby 3dp printing systems available (the other being SLA Stereolithography liquid resin printing). This article is an overview of FDM printers and ancillary equipment, to give a flavour, i.e. sufficient understanding for the uninitiated to go and look further.


How does it work?

FDM printing is in simple terms is a hot melt glue gun held in a gantry fed from a a spool of filament that can be accurately moved via stepper motors in 3 axis X, Y & Z by software generated for the printer. The object is printed by the print head (glue gun) being driven in the required pattern in fine layers onto a base plate with the print head rising one layer at a time to form the object.


Below is a generic ‘Bowden’ feed FDM printer loosely based on a Creality CR10.

   

Note: This a generic design and there are many permutations on feed, table movements, gantry styles and so on.


The control box (LH side) houses the display, all the electronics for the controller, and has a USB port and or a mini SD card reader and sometimes a Wifi link. The control box supplies power to the stepper motors, the heated bed and printer head.


The printer chassis has a moving bed (dark grey) which moves in the Y axis, a gantry (light grey) which moves in X and Z. The X & Y travel is from using a toothed rubber belt (black) on direct drive from stepper motors (green), the Z axis has a lead screw turned by a stepper motor to raise the gantry. The movement is held to each axis via hard plastic ball raced rollers (black) either side of the gantry frame (pic 2).

   

The filament (pink) comes off the reel (black) through the filament drive (toothed drive dog on the stepper shaft) which pushes it into the Bowden tube (yellow) that feeds the filament to the print head (gold). The print head has a cartridge heater to heat up the print nozzle, but has a fan (grey) to cool the upper half (finned) so that the filament does not melt until it reaches the nozzle and can be deposited on the bed initially, then the object being printed. To the side of the printer head and below is a second fan with a nozzle to blow cool air onto the deposited filament to ‘freeze’ it off and prevent it sagging. Shown in pic 3  with the print head shroud moved to one side is a pink cup being formed 1 layer at a time with pink filament.

   

FDM printer speeds vary greatly a cheap printer will shake and produce misaligned layers if run too fast so will have to be run slower. A good home machine i.e. an Ender 3 typically will print a 1/32 car chassis for a Slot It pod @2-3 hours, a bodyshell may take 12 hours or more.


Filaments

Typical home use filaments are

PLA Polylactic Acid made from corn starch resin
ABS Acrylonitrile Butadiene Styrene (thermoplastic)
PETG Polyethylene Terephthalate Glycol
CF Carbon fibre composite material with strands of CF embedded in one of the above or other base filaments

There are many more variations in material, colour and filler i.e. there is a wood infused filament.

Of the 4 quoted the one filament most people start with is PLA as it is the easiest to print, for novices, and relatively cheap i.e. @ £17/kilo reel. PLA can be used for slot car chassis’, bodies, and scenery items. ABS is stronger than PLA, ditto PETG which is a lot more flexible so ideal for rear wings with thin sections. CF is stronger than PETG, PLA & ABS and quite rigid.

Downside to the other filaments are ABS is more toxic to print so not recommended to print this indoors in an open frame unit but either in a sealed booth or in a workshop with extraction. CF will wear out the print nozzles due to its abrasive nature so the recommended upgrade is going from brass to steel nozzles. PETG can string where the nozzle has a fine string coming out in addition to the object causing flash so may need more post print cleaning and flash removal. ABS when printing thin sections is prone to warping and de-laminating during printing due to uneven cooling so careful design, print settings and the need for an enclosed booth to be considered.

Note: If you are considering running a printer for long periods, then for any filament used it is better to have this in a workshop away from the home as even PLA can be toxic if overheated or from prolonged exposure or build up of fumes from multiple machines.


Costs

FDM printers start around £90 for a 100mm x 100mm x100 print volume going up into the thousands for professional high speed/accuracy units. Typically a suitable home printer is the Ender 3 range from Creality which starts at @£180 for a print volume of 220mm x 220, 250mm and requires minimum assembly (typically @30 minutes) to have up and running.

Check out Amazon or Ebay to see how many 3dp printers are now available...


Other equipment

To support the printer a PC or MAC with an Internet link is required, to download CAD files from websites either free or pay by model, and software plus the updates.
Also,
Set of metric allen keys (usually comes with the printer)
Screwdrivers Pozi head in various sizes
PCBA Side cutters /Pliers
Set of feeler gauges
Paper glue sticks (certain filaments need help to stay stuck to the bed)
Paint scraper (to get the object off the bed after printing)
Sturdy bench or desk to hold the printer (no wobble)


Software

Two main items of software needed, a CAD program to create or modify and a ‘Slicer’ program to create the software code that is loaded into the printer.

The CAD or computer aided design software can be a free download or purchased software that will read multiple file formats (there are many) and create/convert files. Like cars there are many CAD programs available and punching into a search engine ‘Best CAD software for 3d printing’ will give you a selection and reviews to look at as new programs are turning up each time I check. YouTube is a good source of tutorials on various CAD programs so worth a look.

Slicer programs usually come on a mini SD card with the printer or can be downloaded i.e. the slicer program Cura. The CAD program or file download is normally a STL file or converted into STL which the Slicer can load, then add the printer parameters plus print setting to generate code to drive the printer. This file can either be sent via USB link, from mini SD card to the controller card input or Wifi link download.


What can it be used for?

Basically if it will fit within the print volume and it can be anchored to the printer bed then you can print most anything you can think off. Have a look at Thingiverse to see what has been designed and is available to download.



Support

There are many forms of support available to the home user ranging from forums, to YouTube videos, internet articles, how to’s and magazines, that cover most of the available printers. Support from the printer manufacturer varies wildly depending on the country of origin and the initial cost of the of the printer.


Finally how complex is 3dp?

If you are reading this article online then you have software skills to do 3dp from downloaded files, the rest is basic mechanical knowledge i.e. do you strip a slot car down to its basic parts fettle and re-build it so it runs better, can you diagnose handling issues? If you can do that then you have the basics the rest is experience from doing.

Below is a pic of my 1st printer from 4 years ago an Anet 8 kit for £137. Note the ‘Mosquito’ frame around it to stop it shaking itself to pieces when run fast. This was a massive learning curve to keep it working and is now a pile of bits as superseded by much better kit.

   

Cheers
JMay.
[+] 11 members Like JMay's post
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#2

Thank you John. For the first time I almost understood the processes involved in this 3D business. I now actually know what a slicer program is.

Many Thanks

Alan
[+] 1 member Likes Beejay7's post
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#3

Oustatanding John - Thanks so much for this - while it is not my intention to buy one, it is good to have a basic understaning of how it works and what is actually done by those that syupply the bodies we want :)
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#4

'slicer' is appropriate because the software slices the part to be printed into specified layers, usually 0.2mm thick but can be much smaller. The printer uses the gcode generated to print one sliced layer at a time.
The biggest difference in layer printing between filament and resin printers is resin printers can do one whole layer in a few seconds in one go whilst a filament printer can take tens of seconds to do one layer as the nozzle has to traverse every single part of each layer.
Filament can be laid down in 0.5mm or greater layer thicknesses whereas resin layers are limited to much thinner layers. 
Filament is much more durable than resin but overall surface finish is much better with 3D resin.
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#5

Excellent stuff John, thanks. I have pinned the thread so complete novices like me have an initial point of reference and explanation.
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#6

(25th-Oct-21, 09:37 AM)Kevan Wrote:  The biggest difference in layer printing between filament and resin printers is resin printers can do one whole layer in a few seconds in one go whilst a filament printer can take tens of seconds to do one layer as the nozzle has to traverse every single part of each layer.
Filament can be laid down in 0.5mm or greater layer thicknesses whereas resin layers are limited to much thinner layers. 
Filament is much more durable than resin but overall surface finish is much better with 3D resin.
As a complete novice, I was wondering if a resin printer is a different type of printer, or can you use both resin and filament on the same printer?

Hub
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#7

No. 
Completely different technologies, totally incompatible with each other.
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#8

Thanks John for putting together a simple explanation of the process. I now have a much better understanding of what is involved in 3D printing.
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