Friday, 20 December 2013

Steps to making a completed figure

This post is directed at the people who want to know more about the processes needed to produce a complete, painted figure. Since I'm rather limited in the photos I have at hand, I will use the example below (apologies to those who dislike candy coloured equines).

There are 5 major steps from start to finish:
  1. Modelling
  2. Slicing
  3. Printing
  4. Post processing
  5. Painting
I'll try to avoid jargon as much as possible for readability.

1. Modelling

First, to print anything, we need a 3D model for the printer to create. Most 3D modelling programs can be used, since they can save the model in a form the next piece of software can understand. Personally, I prefer to use Blender for three reasons:
  1. It's free (and open source!)
  2. Strikes a nice balance between rigidity and flow. What I mean by this is it's able to model (and sculpt) organic, complex objects; as well as being able to model a part to specific dimensions.
  3. Has built-in utilities to help 3D printers, like showing you which parts of the model are too thin to print.
There's a few things you need to check to see if a model is suitable for printing. For example, internal structures are a massive, massive pain to print, and should be avoided where possible. This is especially frustrating when people upload models which have these structures which shouldn't be there. Let's take a look at the example:

Protip: click on the picture to zoom

That mouth cavity (jumble near the centre) adds time and blemishes to the print. So I just removed it and fixed up the model.

2. Slicing

A slicer is a program which turns the 3D model into something the printer can understand. For example, it will tell the printer to move between these points while squirting out a certain amount of plastic. It's most likely called a slicer since 3D printing is done by layers. You put down a layer of plastic, move up a tiny bit and keep going up and up and up.
The one I like to use is called KISSlicer (Keep It Simple Slicer), which generates the best results by far.

For the print to look good, you need to put in the right settings into the slicer. I won't bore you with the details, but this type of print needs support structures for it to print properly. Let's take a look:

The blue bits is what we expect the final model to look like. The grey bits are the support structures, and the yellow bits aren't important for now. This is now ready to be saved and sent to the printer.

3. Printing

Nothing to say here. Just wait a few hours for the printer to work its magic.

By the way, the horizontal ridging patterns you see there have been fixed.

4. Post processing

The support structures have to be carefully broken off...

...and then I spent a few hours filing and sanding it down... (bit too blurry)

...Holes, details and repairs (damn tail) were patched with standard model epoxy.

One last sanding and it's ready to paint.

5. Painting

Technically, this falls under post processing... Anyway, the paint needs to stick to the model. Otherwise, the paint starts to flake off and it just looks terrible. I searched online and found normal white PVA glue works great for this. So I took a bit of glue, watered it down slightly so it's easily spreadable and applied generously.

Afterwards, I used acrylic paint to start adding colour...

... and finished the model with a bit of matte varnish to protect it.

Overall, this process does not happen overnight. It took me about a week of effort after work to produce these figures... hopefully my painting ability improves though, that my second painted figure so far.

Monday, 16 December 2013

Fixing Z wobble, attaching a fan, and upgrading hotends

Fixing Z wobble

In my last post, my prints were suffering from heavy ribbing due to Z wobble. I finally caved in and purchased machined 5mm to 5mm couplers from Markerfarm to replace my old, ineffective Z couplers.

Unfortunately, I'm away from home, so there's no pictures available at this time.

From now on, I'll definitely recommend to everyone who has Z wobble to try and get the most accurate couplers possible before quitting. It really does make a world of difference.

Attaching a fan

To improve print quality even further, I wanted to attach a 80mm fan I salvaged from an old PSU. For those of you who don't know, the fan improves print quality of PLA prints by quickly cooling the rather soft and rubbery PLA so that it becomes hard and holds its shape. Otherwise it droops on overhangs, even with supports, which makes for an ugly looking print.

But I ran into two problems:
  1. The Makerfarm wooden carriage doesn't allow for much to be attached
  2. My fan is a 80mm fan, which is larger than the 40-60mm fans people tend to use for this purpose.
To solve problem 1, I searched for a fan mount for the Makerfarm carriage. Someone really smart decided to use the two screws on the side to secure a fan mount without damaging the carriage (seen here: Problem is, this one was made for a smaller fan, so I had to adapt it to a larger fan.

Long story short (will be covered in a later post), I modified it to fit an 80mm fan, and printed the part. It seems to be a bit tight under the stepper motor, but it works fine

I don't have any photos right now which shows off the improved print quality, but the overhangs don't droop anymore.

Here's the link to the part if you need it:
NOTE: only works on Makerfarm i3 kits and 80mm fans. DO NOT print this if neither of these things apply to you.

Hotend upgrade

During Black Friday, Makershop NZ decided to discount their stocks of the E3D all metal hotend. I've been wanting one of these for quite some time, but got put off by the cost and wait time. Since this sale killed two birds with one stone, I went ahead and got it.

Once again, just a quick lesson on hotends. The J-head which came standard with the Makerfarm kits are quite robust and easy to use. However, they have a few issues which can be solved by upgrading.

Firstly, the J heads don't have easily changeable nozzles as the nozzle and heater block are made from the same piece of brass. This is a problem since I was stuck with a 0.5mm nozzle. A 0.5mm nozzle is relatively large, and while it's good for quick prints, it's not very good for prints with high details. The all metal hotend came with a 0.4mm nozzle which can easily be swapped out as needed.

Secondly, the J head is constructed with PEEK plastic in the barrel. This is because when plastic melts in the barrel of the hotend, it expands and forms a rubbery plug. PEEK has a low friction coefficient, so this plug can slide down easily without clogging everything up. Problem is, PEEK can only be heated up to about 240oC before it starts to soften, so these hotends can't be taken past this point. That's a huge problem when it comes to printing with other materials such as nylon, which has superior strength and low friction between parts. Since the E3D hotend is all metal with no PEEK, it can easily print any thermoplastic in the foreseeable future as it can withstand temperatures past 300oC.

Lastly, the surface quality with the E3D hotend is much better than the prints made with the J head. I don't know exactly why, but it could be due to the reduced ooze (dribbling of plastic while not extruding) during printing Alternatively, it could be due to the improved nozzle design, since I didn't need my cooling fan to print overhangs easily.

Sorry, no photos for now. I'll upload them once I get back.

Of course, these improvements come at a cost. The E3D hotend requires active cooling, so the supplied fan needs to be run continuously while printing. This is an easy requirement to fill, since I just snaked a few cables straight from the PSU to power it.

Overall, definitely consider swapping to the E3D hotend when you can. Highly recommended upgrade.

Monday, 7 October 2013

Things I have learned in the past three months

Hi internet, it's been a while. During this time I managed to figure out most of the major problems with the printer. Here's a quick summary:
  1. Wet filament sucks
  2. The weakest point in any system is the end user
  3. Z couplers are much, much more important than I realized

Wet filament

So in a previous post I reported I was getting some inconsistent extrusion. During a routine extrusion to clear out filament, I noticed a popping sound and I saw steam escaping. This is apparently a telltale sign of wet filament since the moisture in the filament will be heated into steam and expand.

From what I can gather, the production of steam causes inconsistent extrusion since steam isn't plastic (duh). You can't get an even amount of plastic being pushed out if an uneven amount of plastic is present.

To solve this problem, I initially invested in a desiccant. Since the supermarket didn't stock silica gel, I had to settle for the more caustic calcium chloride (as Damprid). Problem is, it'd take months for it to dry properly. 

To speed up the drying process, I preheated an oven to the lowest temperature possible (~50oC) and turned the element off. It's important to keep the element off, since it will radiate heat directly onto the filament and is likely to melt it. I put the filament in the oven to sit in the warm environment for about an hour. I repeated the process once more to fully dry the filament.

Now I keep my filament in a box with a desiccant to avoid these issues in the future.

I thought wet filament was to blame for all my printing woes, but it was only a small part of the problem...

In summary:
  • Wet filament ruins prints
  • Kitchens are possibly one of the worst places to store filament. Only the shower would be a worse storage area
  • Ovens aren't just good for baked goods. It's also good for baking filament.

Slicer settings

I'm a huge fan of KISSlicer. It seems to be a lot more intuitive compared to Slic3r in terms of printing movements and in settings. Only problem is, I started tinkering with some of the settings I didn't understand (I know, it contradicts the above statement), like the destring settings.

To quickly summarise what destring is, it's responsible for preventing hot plastic from trailing behind the hotend when it moves off the path. If you disabled destring (or use Slic3r), you may notice small, fine threads hanging within your parts.

For KISSlicer, the suck is the amount of filament which is reversed out to reduce ooze (and therefore strings), while wipe will cause the hotend to backtrack over a set distance to wipe off plastic before it moves again. Lastly, prime is the amount of plastic which is pushed out once an extrusion begins to counteract the action of the suck command we saw earlier.

Now, if you look back to this print:

If you look at that arrow, you can see some of the inconsistent extrusion. When I went back and looked at the gcode, I noticed this part was where the suck was happening. It was also a reproducible issue and I noticed this with all models.

What I didn't know about suck was suck isn't instantaneous. It will occur well before the print head gets to the end of its path. In fact, my suck setting was so high, it meant the ends of all paths didn't have enough plastic so they all failed.

When I returned the settings to default, the problem vanished. Clearly the suck setting is something to be weary of.

In summary:
  • Sucking at setting suck, sucks.
  • Wipe gives most of results for destring. Suck helps, but I prefer to keep it low now

Z wobble and Z couplers

I have a confession to make. I had no idea what 'Z wobble' meant. I know what its effects are (regular horizontal banding patterns), but I had no idea why people called it Z wobble.

The reason why is due to the movement of the Z threaded rods when the assembly moves up and down. If you watch your printer's threaded rods moving from side to side (as if it was wobbling), then you are likely to see banding patterns similar to what I'm getting:

NOTE: the top layers being off is due to the print head hitting the plastic and misaligning. Seems to do that a lot with low layer heights.

Initially, my left threaded rod was wobbling all over the place. This was because the nut was much too loose in the nut trap. I added a bit of bulk to the nut using a bit of tape, and now that rod is completely solid.

Problem is, now the right rod has been getting a few issues. The reason for this is I had to cut the tubing which were being used as my Z couplers. Despite my best efforts, the Z coupler wouldn't let go of the rod, so I had to cut it.

To replace the couplers, I printed off a set using this:, except I printed a much shorter version since the original size is simply too long for it to fit. Long story short, the new couplers aren't working. The right rod continues to wobble around. I suspect it might be due to the slant in prints I've been experiencing, most likely due to a poorly constructed frame. This led to a poorly printed Z coupler which could be responsible...

That's all I got for now, till next time. (hopefully with a fix to the slanting issues)

Thursday, 8 August 2013

Inconsistent extrusion and a fix

Hi everyone, welcome to my blog. I'll be detailing all of the issues I've run into while printing from the viewpoint of a non-engineer so it might be easier for the layperson to understand, diagnose and hopefully fix whatever might be bogging down their Reprap.

Anyway, I've run into some problems regarding inconsistent extrusion. Take a look at the picture below:

The yellow arrow points to a few layers which appear 'spongy' and underfilled. I've also noticed the support structures generated would be very weak, which caused them to break and ruin rest of the print.

Since the coldend of the extruder is responsible for pushing the filament, I decided to take a better look by loosening the idler and this is what I discovered:

The hobbed bit of the hobbed bolt has gone out of alignment with the hole where the filament goes through. This means the filament would have been underextruded.

A potential fix for this problem would be to use a thicker washer on the right so when it is tight, the hobbed bit will be centered again. Since I'm too far away from a hardware store, I'll be making a quick fix by backing off the nut securing the big gear to the shaft of the hobbed bolt. This centered my bolt again, but I'd have to do this constantly until I can have a permanent fix.

There we go, a centered bolt, good to go.

If you have anything to add, please share it with us. We're all learning here

UPDATE: Even though the hobbed bolt wasn't aligned properly, the other reason why I couldn't print properly is because my filament was too moist. Don't forget to dry it out by baking on low or leaving it with a desiccant (e.g. silica gel).

This problem was a lot bigger than I thought it was. Everything I've learned is covered in the next post.