The Eggstruder:

Welcome to the Eggstruder homepage. In 2014 we came up with the plan to build an extruder to produce filament wires for 3D printers. The well-known extruder from the USA appeared to us to be in need of improvement in various respects. In the years that followed, we built and continuously improved several prototypes. This website shows our results and how we got there. Our Eggstruder enables all process steps of filament production for 3D printing to be carried out in one device. In addition to the extrusion of the plastic granulate into a filament of freely selectable thickness, this is then wound onto a storage spool in ordered layers. From this spool, the wire can later be rewound onto smaller spools and printed. In addition to a productivity of at least 1 kg/hour, our goal was a dimensional accuracy of the wires < + 30 µm

Operating principle :

Operating principle : First, plastic granulate is filled into the funnel and the heating is started. The extruder screw is then heated up to the temperature preset in the preset. The electric motors are then started. An encoder-controlled DC motor with gear drives the 3-zone stainless steel extrusion screw which is milled from solid material. As a result, the granule is conveyed through the extruder nozzle towards the outlet nozzle. The granule is heated and kneaded into a pasty mass by the movement of the screw, which emerges from the extruder nozzle. The extruded filament is pulled past the camera via an air cooling channel by a stepper motor (Advance). The filament thickness is determined by the pulling speed. In controlled operation, the camera measures the wire thickness without contact and adjusts the pulling speed. At the end of the cooling channel, a caliper gauge is used to check the wire thickness. Another stepper motor (winder) drives the supply reel on which the extruded filament is wound. The wire is distributed in even layers on the supply roll by means of an oversized, stepper motor-driven screw thread (weaver). By folding over, the same winder motor can drives smaller rollers onto which the wire is rewound. The process parameters can be freely selected within wide limits, so that they can be adapted for different types of plastic and saved for further production. The granulate is optimally kneaded by the auger specially made for the Eggstruder, which enables processing at low temperatures that are gentle on the material. In addition, coloring of the wire with master batches is particularly even. The DC motor that drives the auger is speed-controlled via an encoder. The temperature is measured with a PT 1000 temperature resistor and kept constant at +/- 0.5° C with a PID controller. The advance motor, whose speed determines the wire gauge, can be operated in two ways. It can either run at a constant speed or the speed can be tracked by the wire gauge information from the camera via a PID controller. The Eggstruder can be operated via a four-line LCD display and a keypad. The respective operating status is displayed via an LED display. The process parameters are output in real time via a USB interface and graphically displayed and saved using a data logger program.

System Components :

Extrusion Unit

The Eggstruder has a modular structure made up of individual function blocks. The first functional block is the extruder unit. Its most important component is the auger. A 3-zone extrusions screw with feed, compression and discharge zones is used. The auger was made of stainless steel on a 5-axis CNC milling machine. The outer diameter is 16 mm and the active length is 420 mm.



The screw sits in an extruder tube made of seamlessly drawn 20 mm precision tube whose inner diameter is reamed to 16.3 mm. The tube has a fine thread M20X1 on both ends, on the outlet side the tube has a brass cap into which an extrusion nozzle, also made of brass, is screwed. On the opposite side of the tube, a flange is screwed onto the thread with which the tube is connected to the housing and the drive motor. A tapered roller bearing absorbs the pressure of the auger towards the motor. The drive motor is a brush commutated 24 Volt Elvi windscreen wiper motor with built in encoder. The speed of the motor is constantly controlled with the encoder signal. The extruder tube is encased in an aluminum round block in which a mains-powered 400 watt heating cartridge together with a PT 1000 temperature sensor heats the tube wall to a constant temperature. When adjusted, the temperature fluctuation is less than +/- 0.5 °C. The diameter of the nozzle is larger than the wire diameter to be extruded. The auger can be pulled out of the tube on the drive side for maintenance and cleaning.

Cooling Unit

The second functional block is the cooling unit. After exiting the extruder nozzle, the still soft plastic filament runs through the cooling unit, at the end of which there is a stepping motor that drives a roller that pulls the wire through the cooling unit. The plastic is stretched to the desired diameter based on the pulling speed. The cooling unit consists of a channel formed by two long angled metal sheets. The plastic wire is moved along the top of the channel. On the underside of the channel there are axial fans with which an air flow is generated transversely to the pulling direction of the wire, which cools the wire to such an extent that it can no longer be deformed by the roller of the pulling motor at the end of the channel.

Camera

A camera for monitoring the wire diameter is located on the cooling unit. Under ideal conditions, the wire reaches a diameter within 20 minutes in unregulated extrusion operation that is within the target tolerance of + 0.03 mm. In order to shorten this time and to minimize the effect of long-term fluctuations - for example the room temperature - the wire thickness can be measured with the camera and, if necessary, adjusted by changing the pulling speed. The camera unit consists of a CCD chip, a light source and telecentric optics through which the wire in front of the light source is imaged onto the CCD chip. Through a special evaluation of the light-dark contrast, it is also possible to measure wires made of transparent materials.

Winder

The last functional block is the winding unit. The winding unit has a total of 3 stepper motors. Here the extruded wire is first wound onto a large supply reel. The first stepper motor drives this supply roll via a roller. The wire is evenly distributed into individual layers by a rotating screw thread arranged parallel to the axis of the supply roll. In this way, the winding volume of the supply roll is fully utilized. The second stepper motor rotates the screw thread in one direction until a complete layer is wound onto the supply roll. When the layer is full, the direction of rotation of the auger is reversed and the next layer is wound onto the supply roll in the opposite direction. When the supply roll is completely full, part of the wire can be rewound from the supply roll onto smaller rolls by the third stepper motor. Again, the wire is fed through the snail in the individual layers. To control the auger, the data for the rolls (inside and outside diameter and roll width) can be entered in a menu and called up later as a preset.

Controller

A controller coordinates the functions of the individual units. The heart of the controller is an Arduino Mega Board. This is connected to a keyboard, a display and the drivers for the motors, fans, status LEDs, sensors, the heating element and the camera via an adapter board. At the same time, the data output for data logging during the extrusion and the evaluation of the camera data for determining the wire thickness runs on the Arduino.

Circuit Diagram

Design Parameters :

• 1 kg/h productivity
• Filament diameter freely selectable between 1.5 and 3 mm
• Camera-controlled filament gauge control
• Camera measures transparent and opaque wires
• Process-optimized extruder screw milled from solid material
• Temperature selectable from 20 - 270 °C
• Extruder screw speed selectable from 10 - 40 RPM
• Filament parameters can be saved in presets
• Automatic wire distribution to storage reel and production reel
• Production parameters can be displayed in real time with Logview
• Easy to adapt to your own requirements thanks to the modular structure with extruded aluminum profiles

In case of questions, write us an E- mail :