FDM from a polymer 

processing perspec3ve: 

challenges and opportuni3es

Bryan	D.	Vogt,	Fang	Peng,	Emily	Weinheimer,	and	

Miko Cakmak

Department	of	Polymer	Engineering	

University	of	Akron	
Challenges of FDM 3D prin3ng

v

Text


Bed temperature:Tbed

Low 

High

Temperature

Incomplete infill results in 

voids inside printed parts: 

• Due to rapid cooling, molten 

fiber usually is not able to 

completely fill space within 

adjacent fibers 

Fast solidification leads to limited chain 

diffusion between fibers and layers 

• Significant chain diffusion across fiber interfaces 

occurs only at high temperature 

• Poor mechanical properties at interface due to low 

level of chain interdiffusion across interface 

void 

Poor Mechanical 

Properties

Process	is	non	isothermal!!	
Challenges for FDM and process control

3. Printing Speed 1. Extrusion Temperature

2. Bed Temperature

4. Layer Thickness d

V

d0 d

1. What	is	temperature	history	through	the	hotend?	

2. How	is	the	bed	temperature	related	to	the	lowest	temperature	of	the	part	

during	the	print?	

3. How	does	prinKng	speed	(and	size	of	object)	impact	temperature	history?	

4. Does	the	thickness	of	the	printed	layer	(thermal	conducKon	path)	impact	

the	temperature	history?	

0.	Thickness	varia/on	of	the	filament	

0.			How	does	varia/on	in	the	filament	impact	the	final	product?	
Filament extrusion and uniformity

Extruder	to	make	~1.75	mm	filament	

Die Pump	 Extruder	

Zone	3			Zone	2			Zone	1	

1.67	+/-	0.037	mm	

1.60	+/-	0.015	mm	

Both	diameter	and	variance	ma\er!	

Diameter	depends	on	speed	of	uptake	

wheel	and	melt	pump	

Variance	is	more	problemaKc	than	exactly	

reaching	1.75	mm	

Switching	melt	pump	

impacts	filament	
Customized FDM printer

E3D-V6	Hot	end:	Tmax	=	400	C	 Cartesio	3D	W09	

Modified	stage	to	isolated	

aluminum	plaborm	with	

resisKve	heaters	(Tmax	=	

300	C)	

			

Temperature	and	temperature	history	

control	criKcal	to	improve	control	to	

develop	desired	properKes		
Challenges for FDM and process control

3. Printing Speed 1. Extrusion Temperature

2. Bed Temperature

4. Layer Thickness d

V

d0 d

1. What	is	temperature	history	through	the	hotend?	

2. How	is	the	bed	temperature	related	to	the	lowest	temperature	of	the	part	

during	the	print?	

3. How	does	prinKng	speed	(and	size	of	object)	impact	temperature	history?	

4. Does	the	thickness	of	the	printed	layer	(thermal	conducKon	path)	impact	

the	temperature	history?	

0.	Thickness	varia/on	of	the	filament	

0.			How	does	variaKon	in	the	filament	impact	the	final	product?	
Temperature profile through extruder head

Embed	thermocouple	in	

filament	through	the	extruder	

Test	filament	=	polycarbonate	

Total	Kme	in	the	melt	out	of	the	extruder	is	<1	min	

PotenKal	for	processing	history	in	the	filament	manufacture	to	be	transferred	to	final	part	

What	is	the	extruder	variaKon	for	idenKcal	FDM	systems?		

What		about	system	differences?	

Tg

90	mm/min	

180	mm/min	

270	mm/min	
3D prin3ng is extremely non-isothermal
Temporal and spa3al complex temperature 

history of part

1st	layer	print	

over	

thermocouple	

2nd	layer	

print	over	

thermocouple	

Local	temperature	history	is	very	complex	

Exact	locaKon	of	the	measurement	will	impact	the	measured	profile	

Need	for	simulaKons	that	provide	the	temperature	history	distribuKon	

The	size	of	the	part	ma\ers	for	the	history	
8th layer

Printing temperature : 300 °C

Printing speed: 40mm/s 

Bed Temperature: 185 °C 

Temperature history of 

8th layer during printing 

Temperature in the 3D prin3ng process

9th layer

10th layer

8th layer

9th layer

10th layer

Location of thermocouple
Role of temperature history on defect 

distribu3on

2mm 

More voids Less voids

Hot → Good diffusion

Cold → Poor diffusion

Low High

Temperature

Process	temperature	history	criKcal	to	

properKes	of	part	
Part failure - remnants of ini3al filament

Printing pattern: 0°-90° Printing pattern: -45°-+45° 

SEM images of fracture surface 

of FDM printed tensile bar 

(polycarbonate)	

Poorly	selected	print	condiKons	

to	maximize	voids	

0°-90°

±45°
260 °C 

310 °C 

Polymer: PC/ABS blend 

Layer thickness: 0.15 mm 

Printing pattern: 45 °

285 °C 

Role of Extrusion temperature

Extrusion	temperature	

determines	interdiffusion
Composite-like failure in PC/ABS blend

Edge-on	prinKng	of	impact	bar	 0-90	orientaKon	 45-45	orientaKon	

Notch	posiKon:	 top	 bo\om	 top	 bo\om	

Impact	strength	(i-lb/in)	 15.1	(0.2)		 2.8	(0.1)		

N	=	4	

1.6	(0.5)		 2.2	(0.5)		

Order	of	magnitude	difference	in	the	impact	strength	depending	on	

print	direc/on	and	notch	loca/on	(highly	anisotropic	materials)
Exploited 3D prin3ng – cellular solids

25%	

100%	

30%	 50%	 75%	 100%	

Sample	infill	

0

6

1 2

1 8

Im pa c t	s tre ng th	 (ft-lb/in )

In fill	 (% )

2	lb	loa d

5	lb	loa d

25	 30	 50	 75	 100	

15	

ParKal	break	occurs	upon	2	lb	load	
Failure of cellular print

30%	infill	

50%	infill	

75%	infill	

100%	infill	

50%	infill	does	not	completely	break	under	a	2	lb	load.	

16	
Responsive polymers – thermoplas3c 

hydrogels

Synthesize	copolymer	 Extrude	filaments	

FOSA DMA 

Dry	“Hydrogel”	

3D	print	

Completed	product	

1st	layer	
Using print processing to control response

100%	infill	 25%	infill	

Swelling	of	sample	is	tunable	by	print	opKons	–	potenKal	for	folding	and	bending	on	swelling	

Comparison	of	hydrated	and	iniKal	sample	
Summary and unmet challenges

• Complex	temperature	history	for	FDM	printed	parts	

• Need	integraKon	of	modeling	and	experiments	

• IntegraKon	of	thermal	history	and	expected	

properKes?	

• Anisotropic	properKes	

• Design	of	print	based	on	expected	stress	loads?	

• Wealth	of	new	possibiliKes	to	explore	with	FDM	

• New	materials	(filament	extrusion	and	uniformity)	

• Tunable	failure	by	print	condiKons?	

• Improved	process	knowledge	is	key	to	future	success	
New 3D prin3ng laboratory at Akron

ATOS	Core	|	Blue	Light	3D	Scanner	 Formlab	(stereo)	 Fusion	3	(FDM)	

Markfordrged	(FDM)	 Objet30	Pro	(jet)	 uPrint	SE	3D	printer