More Taulman Nylon 618 testing - single perimeters and de-lamination

posted 28 Dec 2014, 12:35 by Colin Bell   [ updated 28 Dec 2014, 12:53 ]

Inspired by my previous efforts with the lovely 618 material from Taulman, and I had left several meters of material that I'd pre-dyed, so I thought I'd try making a bigger decorative vase. The model I selected for this one was the Double Twist vase by  FabLabMaastricht which is an interesting and complex object. I wanted to see how the layer bonding on 618 worked on single perimeter objects, and decided this would be a good test.

I scaled the model up to the maximum that the Printrbot Simple Metal can handle which is about 1.4 times the normal model size, set the layer height to 0.1mm, perimeters to 1, 3 solid bottom layers, 0% infill, nozzle fans off, and the print speed at 20mm/sec. I dropped the temperature down a couple of degrees to 243c for this print, which reduced stringing dramatically, compared with the 245c of previous prints. Amazing what a difference a couple of degrees can make!

As I've noted before, I'm still on a cold unheated bed covered in Kapton tape, and I give the tape a light coat of glue stick immediately prior to printing. This set-up, for 90% of the prints I've attempted with 618 produces a rock solid base for the model to be build on - more on this later....

As you can see from the pictures, I got some black blobs deposited on the print as it progressed. I think these are caused by fine strings getting wiped up by the nozzle, which then cook for a while before being dropped down onto the print again. These actually can be removed quite easily and don't overly impact the finished print quality.

This model is really interesting in both on the inside and outside, and I was fascinated to watch it build up.

So, the print ran for just under 12 hours, and looked fantastic sitting on the printer, apart from some small holes which appeared at very uniform spacing around the outer indents of the triangles, from about two thirds of the way up the vase, and continued all the way up. Further testing has shown that these don't appear on models with more than one perimeter, so I'm putting that down to a slicing issue, rather than a problem with over retraction or material limitations.

So I pulled it off the bed...a bit too hard it seems.

It seems that the single perimeter wasn't quite enough to adhere to the 3 layer bottom of the vase, and it de-laminated as I removed it. Bugger. 

The base itself hung onto the Kapton like a champ of course, and required some careful prying up with a thin craft knife to get it off the bed. 

I could have fixed this with a heat gun (I use an SMD solder rework station with a fine tip to repair and weld 3D prints - this works remarkably well on ABS, PLA and Nylon) but it would have been very fiddly to weld such a large area with a very thin wall and I'd likely have cooked fingers by the time I'd finished, along with potentially damaging the wall of the vase and spoiling an otherwise very pretty print.

So, let's be having a lamp then!

I had an Ikea lamp fitting lying around in the junk box, so designed a base in 123D Design to hold both it, and the main body of the model with the split bottom layers removed. I printed the base in gold PLA. 

Unfortunately, in my excitement to get the lamp fitting and shade installed I neglected to take a picture of the base as it printed, however it can be seen being printed in the video at the end of this post. If you would like the model of the base, you can download it here.

Installing the lamp fitting was trivial - I designed cable escape holes into the base, and just hot glued the fitting into place.

Getting the 'shade' on was a bit more tricky and involved several goes around the perimeter of the bottom with little dabs of hot glue. If I make this model again, I'll likely modify the base again so that the shade friction fits over the lip of the base, instead of sitting within it as it does currently - I chose this route deliberately as I thought it would hide any rough edges that I'd left when I broke the model lifting it off the bed. 

In retrospect though, it would have been completely hidden anyway, so I could have saved myself a lot of gluing. Also, if the shade had been created in a less flexible material, there's no way I could have used this method of gently flexing the base and dabbing in glue.

I ran the lamp with a 30w energy saver bulb for about 5 hours, and it didn't even warm the base or the shade, so I'm satisfied that it's a relatively safe thermal design for this application.

I decided to give this lamp away as a Christmas gift, but unfortunately it didn't survive the trip intact. Somehow, at the top of the model above the diamond shapes, it managed to de-laminate, causing a quite noticeable split on one side, running around the perimeter. I guess if it's used at the right angle it won't be seen...but I'll be making replacement anyway, with two walls at least if I use 618 again for it. As a test, I also intent to print the object again, but at 245c, to see if that's the reason for the multiple de-lamination I experienced.

YouTube Video