The end

April 16, 2010

Today we concluded the experiments concerning the design of a small-scale granule extruder for the RepRap machine. The final result is a working extruder that leaves plenty of room for improvements.
In the report that will be available on this forum one can take a look at the documentation we made of this research. We hope you will enjoy reading this paper and give us you opinion.

on behalf of the team,

Jasper Flohil

RepRap granule extruder – TUDelft

Working test setup!

April 9, 2010

In our final attempt to create a working version of the extruder, we had a new screw machined and made sure the whole setup was fastened, so nothing could get bent this time. We fed the machine some of our finest created granule and waited. It took a long time and we wanted to stop the test, but finally ‘something’ came out of our nozzle. After that, it kept on extruding, reaching speeds of about 25 mm per minute.

We are very glad with this result. At the end of this day, we have about 4 of these extruded rods:

Although we have many questions and ideas for further testing at the moment, we do not have enough time to test everything, since our paper’s deadline is in one week from now. We are focusing on analysing the current results. like strength and transparency. However, we noticed something: there were serious metal parts in our result:

Since this probably comes from friction between our screw and the extruding tube (there were some vibrations), we think it is not profitable to analyse motor stats to see which motor is needed for the RepRap. The motor looses power on the friction. That’s why we need to document and analyse everything that happened today, to have some recommendations in our paper.

Have a nice weekend!

The final steps

April 7, 2010

It has been a while since the last update. Since our last post, a lot has happened. March 31 we had to give a presentation about our work, so we were working hard to get everything finished. The motor was turning in the right direction, but since it was taking so long, we already had a backup motor in place.

Since we already projected that our aluminium screw would be too soft for the process, an other one was already made, this time of steel. Last week, we had everything in place for our presentation at a science fair: two working test setups.

However, we did not have time to get some test results yet. During the presentation, it turned out we had done some thing a bit too quick to get everything ready in time. There were some issues with both setups, with the worst being one of the screws that was bent. The presentation however, was a success, being voted the best presentation of the course.

Now, after a long Easter weekend, we will be working towards testing again. However, we have only limited time. Next Friday, we must hand in our paper and our project comes to an end. There will be no time for us to develop our results into a real extruder design for the RepRap, only some concept drawings and recommendations. We are sorry, but we have to make choices to get this project finished in time.

We did however, speak to some gentlemen of the Haagse Hogeschool, the Delft department of Product Development. They have showed interest in putting a student team to really develop the toolhead, using our results (among others, offcourse) as a start.

When we are ready to test, an update will be posted again.

progression 25 march

March 25, 2010

Today the test setting is finished.

The testsetting exists of an adjustable power source; 4 multi meters in combination with two thermocouple wires and a power and RPM counter. The only problem we are facing now is that the motor is computer powered and therefor it’s hard to make it turn left (software problems). To make the design work we made a heating element that is insulated with glass fiber. This element makes it possible to heat the whole system to 220 degrees C.

When it works an update will be posted

Extrusion process update

March 22, 2010

The first extruder screw were finished today. This extuder is a down scale of the extruder in our faculty.

Together with the other parts we made an testing setting.

When everything was installed we inserted the super fine granulate (which was made with the “blender”) .

When we turned the machine on the power, we discovered that the screw was left turning and the machine is right turning. So the granulate did not get in to the extruder. The next extruder screw, based on a design form Cavas and Costa (A miniature extrusion line, for small scale processing studies, 8 March 2004) will be right turning to fit our machine. Further more we had some discussions with a few tutors and we conclude that we have to heat the barrel. The heating will be realized on wednesday. In the next update we hope to give some real results.

Extrusion, progress

March 15, 2010

After two weeks it is time for an update. We found three basic working principles to extrude material: With an extrusion screw, plunger or by using a pressure pump. (which has similarity’s with the second principle). We discussed these three ways of extrusion with our expert, Rolf Koster, this resulted in the following.

Extrusion screw:
This ways of extrusion results in:
– A good heat distribution
– Dense material at the extrusion head
– A better change to get a equal output
– A continue process

Plunger
This results in:
– Easy construction
– Bad heat distribution
– Bad and material
– Bigger change on air bubbles
– Discontinues process

Air or liquid pressure
We decided tot cancel this concept because it becomes to complext for domestic use.

Based on this outcome we chose to try and create the extrusion screw. The problem with this concept is that the screw can be hard to create. In designing this concept we have several options to create a screw.

1. Take a wood auger
This was tried in 2006 by Forrest Higgs.(http://blog.reprap.org/2006/02/initial-experiments-on-filament.html)

Problems that were occurring:
– To wide barrel fitting
– Not the right depth of the thread
– Not a variable thread dept
– A wood auger does not have a center. This cause a leak of pressure

2. buy an existing worm wheel
Problems:
– The are not long enough
– The threads are not deep enough
– There are to many windings per cm
– Expensive

3. Create our own screw,

To avoid the problems that are mentioned above we decided to make oure own screw. In this way we van examine the feasibility of the screw concept concerning the best circumstances. The problem however is that it has to be possible for other people to make the screw as well. To make sure that other people can make the screw also we want to make an file which can be but in a small automatic rotational machining appliance. This kind of appliances are availably in CadFab labs. These labs can be used by everyone.

The Biggest problem to overcome is to design the screw in a way that it can be produces in a CadFab lab. Small machines have limited power and therefore it can be hard to use steel. An other big problem is pitch of the propeller. This is limited tot the speed and the power of the machine. We hope to have some test results later this week. If this way of building a screw does not work out we can try to make it like Adrian Bowyer did (http://reprap.org/bin/view/Main/GranuleExtruder).

Blending!

March 12, 2010

The juicer we showed you wednesday didn’t work that good. Today, we brought something different: a cheap, secondhand blender.

We tried to blend the milk bottle HDPE in different sizes and in both straight and fumbled state. This had some mixed results (we will eleborate these next week), but most important: it worked!

Next thing, we have to discover with size the milk bottle has to be reduced to, to be able to extrude it. Also, we will have to look at the consequences of the impact the knives have with the plastics. Although the temperature changes seemed to be pretty low, there knives were getting a bit warmer. Does it change the material properties of the plastic due to temperature changes? How fast will the knives go blunt? What can we do to prevent the heating (for example adding water to the plastic while blending or putting the plastic in a refridgerator)?

Have a nice weekend!

Some updates on printing and shredding

March 10, 2010

After a morning of a lot of printing problems, we decided that it just takes too much time to make perfect prints, without having the specific knowledge of how it is put together and which wire controls which module. For the moment, we will put all object printing activity to a hold. If we will develop a direct add-on to the RepRap, we have decided to just design the parts in the spirit of RepRap parts (that is: a RepRap can print them) and then we will have to wait for feedback from the community if it is really printable and okay to use in a realistic setting.

About the shredding, Gijs has done some research to various shredders and blenders, but it is really hard to find some sort of mechanism that is used in industrial shredding and that can be scaled down for domestic use. We decided to take a more practical approach and see how it goes from there. We will try to modify an existing domestic appliance for use in shredding or cutting the milk bottles, because we think people that currently use a RepRap will be able to modify their blenders :-). We will also try to recycle printed RepRap ABS to be able to reuse that in a later stadium.

With this in mind, we went to a secondhand shop in the centre of Delft. We came back with this baby:

More coming soon!

Taking babysteps

March 10, 2010

Last monday we had a short session. Jasper and George are working on the extruder concept. I think they went for the screw principle above a piston, but they should time something here today aswell.
Gijs and me were working on trying to get our RepMan to work. We are having serious trouble with the coordinate system. The X-axis seems to shift a bit each layer. We tried to tighten some belts and nuts and we just keep trying, since we should be able to print extruder and/or shredder parts in the near future. To bad the team that build our Darwin has left no documentation at all how they got it working, so we spend a lot of time checking everything of their work, because we just don’t know if it is done right. Today we are going to develop some concepts for the shredder principle.

Today’s activities

March 5, 2010

Today we will be focusing on setting up the outline for the paper we have to hand in in a couple of weeks. To do this, our goal is to make a plan for this project as good as possible, including milestones and detailed planning. We will use the checkpoints to be found HERE for our paper.

We also had contact with Adrian Bowyer, founding father of the RepRap project. Since he already looked into the subject of a granule extruder (see here: http://reprap.org/bin/view/Main/GranuleExtruder) he gave us some tips and advice. We also added this blog to the RepRap Blog of Blogs (http://pipes.yahoo.com/davidbuzz/reprap_aggregation_pipe), a collection of all RepRap related RSS feeds.


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