New low cost printers

 Two interesting developments in low cost 3D printing. One, a next gen printer the The Replicator 2, and the another one, Form 1 seeking funding on Kickstarter using stereolithography technology.

3D Printers put to the test

Make Magazine is running a shootout test of 15′ consumer grade’  3D printers. "A lot of 3D printing is watch and waiting, ???cause as 3D Print Shop honcho Matt Griffin says: Unattended 3D printers do scary things.??? MAKE???s 3D Print Shop Weekend

First successful print!

After many failed attempts, here is our Ultimaker’s first successful print, the famous Panther woman model. It took a couple of hours and required some manual intervention when the filament stopped extruding. I had to manually force the filament by turning the print speed down to 10% and pushing it by hand whilst temporarily raising the temperature. This worked luckily and I got the print finished, but I’m still not convinced the Ultimaker can finish a print without constant supervision.

In the above picture you can see the print in progress. Note the ‘skirt’ around the model on the print-bed, used to outline the footprint of the job and to give time for the extruder to kick in. You can also see the print about to fail; the top-most layer is almost ‘flaking’ as the PLA stops extruding. 

Here is one of the previous failed attempts which shows the hollow internal structure of the model. I printed the model with 0% fill and 3mm thick walls. It is surprisingly strong and light.

Each print track is 0.2mm high and roughly 0.5mm wide, so at 3mm thick the printer has to make 6 passes on each layer. Thankfully, the Ultimaker’s ability to speed up to over 250% on the fly (theoretically even up to 500%) means that a model like this should only take an hour or so to print – less with thinner walls. I will be running some thin wall tests soon to see how thin you can go whilst maintaining structural integrity. 

Overall I’m very impressed with the speed and accuracy of the Ultimaker but very unimpressed with its reliability. Let’s see if we can change that with a few modifications!

//josh. 

Blocked extruder

A few weeks after the first test print of the Mars Rover and I haven’t been able to get the Ultimaker to successfully finish a single print. The problems are manifold: first, the PLA filament simply stops extruding at intervals losing traction in the extruder, ruining the print instantly. Second, the load on the extruder becomes so great that the bowden tube connector pops out of the plywood extruder frame, taking shards of plywood with it. 

What’s so puzzling about these problems is the irregularity of the occurrence. Usually after such a failed print, I can begin a new print straight away without any problems until about 20 minutes later when extrusion will fail again. 

Here is a temporary solution I used to try and keep the Bowden tube connector in place. 

This worked temporarily but a few prints later the pressure became so great that it popped out anyway, shearing the corners of the plywood frame. Note the slight wear on the plywood in the photo above (before it got really bad). 

I realised it was probably a blockage at the hot end causing the pressure at the extruder, despite the puzzling fact that I could resume printing normally afterwards. I tried printing at a variety of different temperatures and had some success printing at a higher-than-normal  220 degrees (185 being normal). This made the PLA ooze out of the hot end a lot more – and in my mind seemed to solve the blockage problems. I was also able to print significantly faster with good results too (up to 250% faster) until the inevitable random extrusion failure  half an hour or so into the print.

The Bowden tube connector no longer stays in its frame like it should, so I’ve had to devise a rather lo-fi method of keeping it in place until I can print a proper uninterrupted fix. Below you can see my makeshift fishing line solution, which actually works rather well. When there is a lot of pressure the connector rises out of the slot like in the picture below and the tension in the line naturally pulls the bowden tube down to help extrusion. It acts a little like a suspension belt. 

Despite the temporary fix, I realised this was a band-aid solution and set about to dismantle the hot end to check for blockages. When I got it dismantled I was greeted with this:

In the above photo you can clearly see a large ‘plug’ of dark blue PLA in the tube of the PEEK insulator. Not good! 

This is actually a very common problem with the current Ultimaker hot-end design and is a result of the molten PLA forcing its way into the space between the copper pipe of the extruder and the Bowden tube, cooling to form a solid. 

After removing the blockage printing went smoothly for a while until the same problem happened again, pressure built up in the hot end, filament jamming. I opened the extruder up again but this time it was a different problem. Instead of forcing its way between the Bowden tube and the copper pipe, the PLA had formed a plug up inside the Bowden tube. This is probably the case because I had the temperatures up too high, causing the PLA to melt all the way up into the tube, then solidifying. 

So it seems there is a very fine line between having the temperature set too low or too high. More tests to come.

//josh