Tailored Placement of Fibres around Pores Robotic Fabrication Possibilities

Size: px

Start display at page:

Download "Tailored Placement of Fibres around Pores Robotic Fabrication Possibilities"

Geoffrey Blake
5 years ago
Views:

1 1 Tailored Placement of Fibres around Pores Robotic Fabrication Possibilities Course Name: Computational Design and Digital Fabrication Course Number: Term/Year: Summer Term/2014 Examination Number: Tutors: Karola Dierichs, Marshall Prado, Tobias Schwinn Institute: Institute for Computational Design Eva Espuny

2 2 3 Contents Chapter 1: Introduction Page 05 Chapter 2: Path Drawing Page 09 Chapter 3: Robotic Fabrication Research Page : Fibre Winding Page : Stitching Pre-impregnate Fibres Page : Pinching of Unidirectional Pre-impregnate Fabrics Page : Robotic Application of Resin on Unidirectional Fabrics Page : Fibre placement between fingers Page 30 Sources Page 36 References Page 37

3 4 5 Chapter 01

6 CHAPTER 01 CHAPTER 01 7 FIGURE 01: Lobster exoskeleton: chitin fiber arrangement around honeycomb structure of pores INTRODUCTION This research has been developed during the summer semester 2014

4 6 CHAPTER 01 CHAPTER 01 7 FIGURE 01: Lobster exoskeleton: chitin fiber arrangement around honeycomb structure of pores INTRODUCTION This research has been developed during the summer semester 2014 seminary Computational design and Digital Fabrication, as a part of the ITECH Master program of Stuttgart s University. Having the topic been chosen to give answer to the fabrication aspects of my thesis preparation about inducing variable stiffness through porosity, this research focusses on the possible processes of laying fibres following curvilineal paths around a predetermined configuration of pores, conforming 3D surfaces, and using a Kuka robot.

5 8 CHAPTER 02 9 Chapter 02

10 CHAPTER 02 CHAPTER 02 11 x Distance from external point to pore center on surface Pore size increasement FIGURE 02: Porosity

6 10 CHAPTER 02 CHAPTER x Distance from external point to pore center on surface Pore size increasement FIGURE 02: Porosity gradient created with Grasshopper PATH DRAWING TEST The first test consisted on drawing with the Kuka on a 3D surface a path created in Rhino and Grasshopper. The path reproduced a porosity gradient on the surface of a cylinder parametrically determined by the distance from the surface to a generic point. FIGURE 03: A kinematic simulation of the robot task was performed using Grasshopper

12 CHAPTER 02 CHAPTER XX CHAPTER 02 13 FIGURE 05 and 06: The resulting path drawn by the robot Half a cylinder

Due to the rigidity of the support, an ink pen with a slightly movable point was chosen to allow for certain

Second, a survey of the cylindrical surface was carried out, then transferred to grasshopper to recalculate the

The path generated in grasshopper was then translated into Kuka s language KRL.

7 12 CHAPTER 02 CHAPTER XX CHAPTER FIGURE 05 and 06: The resulting path drawn by the robot Half a cylinder was built with cardboard and covered by a white paper. An ink pen was installed as effector on the Kuka s head. Due to the rigidity of the support, an ink pen with a slightly movable point was chosen to allow for certain tolerance. Firs of all, the right position of the cylinder to permit the robot s reach needed to be found. Second, a survey of the cylindrical surface was carried out, then transferred to grasshopper to recalculate the path. Then a kinematic simulation of the robot was performed with Grasshopper. The path generated in grasshopper was then translated into Kuka s language KRL. FIGURE 03 and 04: Kuka robot performing the path drawing at the Robolab of Stuttgart University The robot performed the drawing task perfectly after some small effector adjustment.

8 14 CHAPTER Chapter 03

16 CHAPTER 03 CHAPTER 03 17 Control points Sample 1 Sample 2 Sample 3 Sample 4 Half a sphere as scaffolding Sample 1 Sample 2 Sample 3

Sample 8 FIGURE 07: Catalog of handmade samples ROBOTIC FABRICATION RESEARCH As part of the Master s thesis, five types of handmade

for each of them: Fibre winding (sample 1) Stitching pre-impregnate fibres (samples 2 and 3) Pinching of unidirectional pre-impregnate

and 8) FIGURE 08 and 09: Sample1 Fibre winding The first sample was created using half a sphere out of plaster as scaffolding.

This sample is proposed to be robotically fabricated by wet or prepreg filament winding.

A similar set up and winding head could be used to fabricate this sample.

9 16 CHAPTER 03 CHAPTER Control points Sample 1 Sample 2 Sample 3 Sample 4 Half a sphere as scaffolding Sample 1 Sample 2 Sample 3 Sample 4 Sample 5 Sample 6 Sample 7 Sample 8 Woolen thread layed following a honey comb like structure Sample 5 Sample 6 Sample 7 Sample 8 FIGURE 07: Catalog of handmade samples ROBOTIC FABRICATION RESEARCH As part of the Master s thesis, five types of handmade samples, presenting different approaches to laying fibres creating pores, were produced and studied to propose a robotic fabrication for each of them: Fibre winding (sample 1) Stitching pre-impregnate fibres (samples 2 and 3) Pinching of unidirectional pre-impregnate fabrics (sample 4) Robotic application of resin on unidirectional fabrics (samples 5 and 6) Fibre placement between fingers (samples 7 and 8) FIGURE 08 and 09: Sample1 Fibre winding The first sample was created using half a sphere out of plaster as scaffolding. The goal was to lay down a continuous woolen thread following a honey comb like structure. Nails were used as control points. This sample is proposed to be robotically fabricated by wet or prepreg filament winding. Various wet winding experiences have already been carried out at the University of Stuttgart by the ICD and ITKE Institutes to build the Research Pavilions 2012 and For the first, a temporary auxiliary structure made out of wood was used to create the control points needed for the geometry winding. A similar set up and winding head could be used to fabricate this sample. The problems will come from the huge amount of control points needed in this case due to the particular curvilinear paths around the pores, and the subsequent difficult disassembling of the auxiliary structure. Since the goal is to create curvilinear paths, another disadvantage will be the fact that the fibre paths created by this method will be poly-lines instead of curves.

18 CHAPTER 03 CHAPTER 03 19 WINDING HEAD ROVING PART ROTATING TABLE RESIN BATH FIGURE 10: Wet winding of carbon fibre.

com) Homogeneously Flexible Stiffer Deformable and able to recover its initial shape FIGURE 12 and 13: Sample 2 FIGURE 14 and 15: Sample 3 Stitching pre-impregnate fibres

The paths were created by sewing wool thread to the elastic fabric. Then the thread was painted with resin.

VARIABLE STIFFNESS At the sample 3, showing a gradient of porosity, the woolen thread was painted with epoxy resin.

10 18 CHAPTER 03 CHAPTER WINDING HEAD ROVING PART ROTATING TABLE RESIN BATH FIGURE 10: Wet winding of carbon fibre. ICD / ITKE Pavillion 2012 preliminary testing (Source: Homogeneously Flexible Stiffer Deformable and able to recover its initial shape FIGURE 12 and 13: Sample 2 FIGURE 14 and 15: Sample 3 Stitching pre-impregnate fibres (samples 2 and 3) To elaborate the second type of handmade samples, first an elastic fabric was tensed over half plastic sphere used as auxiliary base. The paths were created by sewing wool thread to the elastic fabric. Then the thread was painted with resin. For the sample 2, the resin used was polyurethane with the result of an homogeneously flexible structure. VARIABLE STIFFNESS At the sample 3, showing a gradient of porosity, the woolen thread was painted with epoxy resin. The cured sample was stiffer on the non-porous area and more flexible in the porous one. The fabrication proposed for this samples consists in a robot able to stitch fibres pre-impregnate with a thermoplastic resin, on a thermoplastic foil over a 3D auxiliary surface. The thermoplastic foil would melt afterwards during an autoclave process of consolidation becoming part of the composite matrix. Depending on porosity and fiber density FIGURE 11: Winding head. ICD / ITKE Pavillion 2012 preliminary testing (Source:

20 CHAPTER 03 CHAPTER 03 21 FIGURE 16: Sewing machine FIGURE 17: Sewing machine shuttle hook FIGURE 18:

Leibniz-Institut für Polymerforschung Dresden e. V.

flat fabric or foil reproducing a path digitally created, the fabric has to be laid out over the

tow/roving in front of a sewing head, attaching them by needle and thread onto a base material that is

composites can be done with conventional processing techniques such as resin transfer molding, vacuum

In case of thermoplastic composites the matrix material and the reinforcement fibers can be placed

11 20 CHAPTER 03 CHAPTER FIGURE 16: Sewing machine FIGURE 17: Sewing machine shuttle hook FIGURE 18: Sewing machine for shoes: Blind stitching FIGURE 20: Taylored fibre placement. Leibniz-Institut für Polymerforschung Dresden e. V. FIGURE 19: How it works a sewing machine Although there exist already machines which stitch fibre to a flat fabric or foil reproducing a path digitally created, the fabric has to be laid out over the machine table in a set up in which the position of the sewing head is fixed and the fabric is moving underneath using numeric control. In this process of taylor fiber placement, the special fibre placement machine lays out bundled fibers, tow/roving in front of a sewing head, attaching them by needle and thread onto a base material that is held in a frame of the machine. composites can be done with conventional processing techniques such as resin transfer molding, vacuum bag molding, pressing and autoclaving. In case of thermoplastic composites the matrix material and the reinforcement fibers can be placed simultaneously e.g. in the form of films or fibers. The base material can then be a thermoplastic foil which melts during the consolidation process and becomes part of the matrix. The base material can be a 2D-textile such as a woven fabric or for thermoplastic composites a matrix-compatible foil material. The consolidation of TFP-Preforms to FIGURE 21: Source:

22 CHAPTER 03 CHAPTER 03 23 FIGURES 22 and 23: KSL sewing head KL 500, for Kuka robot FIGURE 25: KSL Blindstitch head RS510 Some sewing heads for

The company KSL is using a two needle head (fig.

12 22 CHAPTER 03 CHAPTER FIGURES 22 and 23: KSL sewing head KL 500, for Kuka robot FIGURE 25: KSL Blindstitch head RS510 Some sewing heads for Kuka robots have been developed which are used to sew together carbon fibre fabrics over 3D surfaces. The company KSL is using a two needle head (fig. 24): a single thread chain stitch seam is formed with only one single needle thread, which is brought into the material by two needles from the top side of the material. Number of needles: 1 sewing and 1 catcher needle Stitch type: modified chain stitch Stitch length 4-8 mm Material thickness: 2-15 mm KSL has patented as well a blindstich head. The blindstitch seam is formed with only one single needle thread, which is brought into the material by one curved needle from the top side of the material. Number of needles: 1 curved needle d = 50 mm Stitch type: blindstitch (KSL patent) Stitch length 5-12 mm (depending on material thickness) Material thickness: 2-7 mm (depending on stitch length) This blindstich head could be used as the starting point to develop an sewing effector for Kuka robot incorporating a fibre roving. FIGURE 24: KSL Two needle head RS 530

24 CHAPTER 03 CHAPTER 03 25 34. Needle shaft. 36. Needle holder 40. Needle 126. Drive gear 150. Guide 154.

Spring FIGURE 27: Blind stitch sewing machine Patent EP 1182287 A2 FIGURE 28: Blind stitching.

example, eliminating the laborious an tedious process of disassembling the part; the complete freedom in the fibre

26: KSL Blindstitch head RS510 Amongst the disadvantages would be: the difficulty of the fibre blind stitching head to

13 24 CHAPTER 03 CHAPTER Needle shaft. 36. Needle holder 40. Needle 126. Drive gear 150. Guide 154. Adjustment plate 156. Base plate 170. Supporting roller 172. Circunferential groove 174. Pivoting lever 182. Spring FIGURE 27: Blind stitch sewing machine Patent EP A2 FIGURE 28: Blind stitching. Patent US A The advantages of this fabrication system would be: the absence of control points as in the previous example, eliminating the laborious an tedious process of disassembling the part; the complete freedom in the fibre placement only subjected to the reach limitations of the robot; the possibility of true curvilinear fibre paths; FIGURE 26: KSL Blindstitch head RS510 Amongst the disadvantages would be: the difficulty of the fibre blind stitching head to be developed; the slowness on the action of laying and sewing the fibre, comparing with the speed of a winding process; the lower level of possible pretension of the continuous fibre.

26 CHAPTER 03 CHAPTER 03 27 VARIABLE STIFFNESS Depending on porosity and fiber density Epoxy resin was applied over the flax fabric Partial Honey-comb structure Fabric gripping to produce pores.

FIGURE 30: Sample 4 after resin has cured Pinching of unidirectional pre-impregnate fabrics (sample 4) FIGURE 31: Robotiq 2-finger adaptive robot gripper 200 A third kind of samples was produced by

14 26 CHAPTER 03 CHAPTER VARIABLE STIFFNESS Depending on porosity and fiber density Epoxy resin was applied over the flax fabric Partial Honey-comb structure Fabric gripping to produce pores. Unidirectional flax non woven fabric Three distinct gripping modes: - parallel - encompassing - internal FIGURE 29: Sample 4 before applying resin. FIGURE 30: Sample 4 after resin has cured Pinching of unidirectional pre-impregnate fabrics (sample 4) FIGURE 31: Robotiq 2-finger adaptive robot gripper 200 A third kind of samples was produced by hand using the same auxiliary base as in the previous example: an elastic textile tensed over a half plastic sphere. In this case an unidirectional flax fabric was laid up over the base. To create pores in a honeycomb like structure the fabric was pinched in specific points and then stitched to the textile base. Epoxy resin (in a proportion with hardener of 100:30) was then applied over the linen fabric. The cured sample was showing higher stiffness on the porous areas, due to the higher fibre density of the pores borders compared with the non-porous area fibre density. The robotic fabrication proposed consists in robot with a gripper having two heatable fingers which will be pinch- ing and then heating and pressing together specific points of an unidirectional fibre fabric, pre-impregnate with heat-curable resin, to create the desired distribution of pores. One of the advantages of this method would be the lower complexity in the effector development as well as in the fabrication process, comparing to the stitching one. The complexity would consist in achieving the right accuracy of the gripper to pinch exactly the specific areas of the successively laid up layers of fibre fabric one on the top of the other. One inconvenient would be the need of a posterior consolidating process as autoclave to cure completely all the pre-impregnate fibre fabric. ROBOTIC GRIPPER Requirements: Effector: - Temporary scafolding - Non woven unidirectional fabric prepeg with: Heat curing epoxy Hot surface GRIPPER: Pressure + heat: Heatable tongs to press and heat the pinched fabric

28 CHAPTER 03 CHAPTER 03 29 Area of fabric painted with glue Area of fabric without glue FIGURE 32: Sample 5. The glue has been applied on the fabric. FIGURE 33: Sample 5.

Robotic application of resin on unidirectional fabrics (sample 5 and 6) The next experiment was to apply glue on two pieces of unidirectional linen fibre fabric following two different reticulated

An effector more accurate than a brush could be developed to apply resin on the laying flat fabric.

15 28 CHAPTER 03 CHAPTER Area of fabric painted with glue Area of fabric without glue FIGURE 32: Sample 5. The glue has been applied on the fabric. FIGURE 33: Sample 5. The fabric is stretched opening the pores. FIGURE 34: Sample 6. The glue has been applied on the fabric. FIGURE 35: Sample 6. The fabric is stretched opening the pores. Robotic application of resin on unidirectional fabrics (sample 5 and 6) The next experiment was to apply glue on two pieces of unidirectional linen fibre fabric following two different reticulated patterns, similar to a chessboard pattern. Once dried, the fabric was manually stretched with the result of openings of the fabric in the areas left without glue. An effector more accurate than a brush could be developed to apply resin on the laying flat fabric. Before the curing of resin, the fabric would be stretched over the desired auxiliary 3D geometry with the subsequent fabric opening and pores creation. Such a concept could be further developed and fabricated using a robot to paint with resin a fabric reproducing a digitally created pattern. Applying paint with a robot is a normal task carried out at the car industry, and more artistic robotic painting experiences have been tried, as the one showed during the Robarch 2014 workshops. FIGURE 36: Diagram showing the areas painted with glue (yellowich) in sample 5. FIGURE 37: Diagram showing the areas painted with glue (yellowich) in sample 6. FIGURE 38: Craft Class 4 Robots Workshop. Robarch 2014.

30 CHAPTER 03 CHAPTER 03 31 hollow tube to place the fibre in between the fingers Seconnd layer of flax fibre thread (orientation 45º) First layer of flax fibre thread (orientation 90º) flax fibre

Sample7 Fibre placement between fingers (samples 7 and 8) For the sample number 7, a scaffolding was builded by sewing cylinders of polyurethane foam on a polyurethane foam sheet.

VARIABLE STIFFNESS Depending on porosity, fiber density and matrix For the last handmade sample, (sample 8), a pre-mould was created using clay and an adjustable wooden frame.

The silicon mould was then stretched and hold over a cardboard cylinder. At the shorter edges of the mould screws were placed to act as edge control points.

16 30 CHAPTER 03 CHAPTER hollow tube to place the fibre in between the fingers Seconnd layer of flax fibre thread (orientation 45º) First layer of flax fibre thread (orientation 90º) flax fibre thread silicon mold with fingers cardboard cilinder first layers fibers+pu screws as control points Polyurethane foam fingers Flax fibre thread last layers fibers+epoxy silicon mold hinge FIGURE 39: Sample7 Fibre placement between fingers (samples 7 and 8) For the sample number 7, a scaffolding was builded by sewing cylinders of polyurethane foam on a polyurethane foam sheet. This foam was placed and fixed over a plastic sphere to curve it. Then a flax thread was layed around/between the cylinders/fingers. VARIABLE STIFFNESS Depending on porosity, fiber density and matrix For the last handmade sample, (sample 8), a pre-mould was created using clay and an adjustable wooden frame. The clay was pierced creating a regular pattern of circular holes following an hexagonal grid. Then a mould was created pouring silicon over the clay, producing a flexible mat with fingers. The silicon mould was then stretched and hold over a cardboard cylinder. At the shorter edges of the mould screws were placed to act as edge control points. A release agent was applied over the silicon mould and control points. A resin bath was improvised to impregnate the linen fibre just before to be placed around and in between the silicon fingers, to create the fibre around pores organisation. The continuous fibre was placed in position with the help of a thin plastic tube through which the fibre was running. The laying of the fibre was fast and easy. Once the resin was cured, the disassembling process of the fibre composite was presenting no difficulty. The fibre was pre-stressed around the fingers and control points, and its path was truly curvilinear. FIGURE 40: Checking the placement of fibre in between the silicon fingers. FIGURE 41: Fabrication of sample number 8. FIGURE 42: View of sample 8

32 CHAPTER 03 CHAPTER 03 33 WINDING HEAD ROVING PART ROTATING TABLE Wet filament winding RESIN BATH Ø6 mm + Ø40 mm Ø12 mm 40 mm 10 mm 72 mm 95 mm 50 mm 150 mm FIGURE 43: Wet winding of carbon fibre.

FIGURE 46: Perspective of the piece to add to the existing winding head 33 mm For the robotic fabrication of this kind of samples an effector was built: the winding head used to produce the ICD/ITKE

The next steps related to robotic fabrication will be to test the effector laying of fibre around different finger configurations focusing on the versatility of the supporting mould to create

17 32 CHAPTER 03 CHAPTER WINDING HEAD ROVING PART ROTATING TABLE Wet filament winding RESIN BATH Ø6 mm + Ø40 mm Ø12 mm 40 mm 10 mm 72 mm 95 mm 50 mm 150 mm FIGURE 43: Wet winding of carbon fibre. ICD / ITKE Pavillion 2012 preliminary testing. FIGURE 44: Winding head made out of steel. FIGURE 45: Collage showing the idea for modification of ICD/ITEKE Pavillion 2012 Final effector. FIGURE 46: Perspective of the piece to add to the existing winding head 33 mm For the robotic fabrication of this kind of samples an effector was built: the winding head used to produce the ICD/ITKE Research Pavilion 2012 was modified by adding to it a thin steel tube. The fibre will be guided to the interior of this tube by two plastic spools. The next steps related to robotic fabrication will be to test the effector laying of fibre around different finger configurations focusing on the versatility of the supporting mould to create different porous systems. Two possibilities could be deeply explored: the placement of wet fibre or the use of fibre pre-impregnate with heat or UV curing resin. This kind of samples and this robotic fabrication process has been the chosen to be further developed during the Master s thesis. FIGURE 47: Steel piece builded to add to the existing winding head. Plans and elevations. FIGURE 48: Render of the final winding head.

18 34 CHAPTER 03 CHAPTER mm 5mm 40mm 5mm 243mm 20mm 310mm 5mm 50mm 26.25mm 233mm FIGURE 49: Drawings of silicon scaffoldings with two different finger diametre to lay fibres. FIGURE 50: Different examples of fibre organisations around the fingers.

19 36 37 Sources Figure1: Raabe, D, Sachs, S & Romano, P 2005, The crustacean exoskeleton as an example of a structurally mechanically graded biological nanocomposite material. Figures 10, 11 and 43: Available from: < Figure 16: Available from: < Figure 17: Available from: < Figure 19: Available from: < Figure 20: Available from: Figure 21: Available from: < References Raabe, D, Sachs, S & Romano, P 2005, The crustacean exoskeleton as an example of a structurally mechanically graded biological nanocomposite material. TFP-Principle. Available from: < Sewing lessons for aerospace engineers. Available from: < KL 500 Robot Sewing Unit: Available from: < Basic_3D-Roboter-Naehanlage_KL_500/Datasheet_KL_500_Dashboard.pdf> RS 530 Two needle head: Available from: < Naehkopf_RS_530/Datasheet_RS_530.pdf> RS 510 Blindstitch head. Available from: < Naehkopf_RS_510/Datasheet_RS_510.pdf> Figures 22 and 23: Available from: < Figure 24: Available from: < Figures 25 and 26: Available from: < blindstitch-head-rc-510/> Figure 27: R. Keilmann (2001). Blind stitch sewing machine, Patent EP A2. Available from: < google.com/patents/ep a2?cl=en> Figure 28: Baxter (1998). Blind stitching apparatus and composite material manufacturing methods, Patent US A. Available from: < Figure 31: Available from: < Figure 38: Available from: <

WORKING of nidaplast

nida 8/gb - 03.07.07 Technical Information. 2 WORKING of nidaplast nidaplast is a polypropylene honeycomb covered on both faces with a soft polyester nonwoven fabric. It is available in 2500 x 1200 mm