Nub removal is one of the most important techniques to master. It’s a fundamental not only for Gunpla building, but in all branches of scale modeling.
So what are the nubs anyway? Well, nubs are new / bad gamers, so nub management is very important. Seriously though – in our hobby term ‘nubs’ refers to small bits of plastic, left on the parts after cutting them from the runners. Nub removal is a process of shaving and sanding them down until they disappear.
Sadly, many new builders try to build their kits as fast as possible, like it’s some kind of race. Some even go as far as creating posts like “I built it in 3 hours, how fast can you build?”. Kits featured in those posts often look awful, with zero nub management and tons of stressed plastic. I find this kind of attitude simply wrong. Unless you’re a reviewer, trying to rush the content out, you should always aim to build well rather than build fast. Doing stuff properly the first time around beats having to fix it later.
Nub Removal 101
|Tools we need are pretty basic:
- Hobby knife with a fresh blade
- Various grits of sandpaper or sanding sticks
There are also some optional nice-to-haves:
- Sanding sponges or Flex-I-File for rounded surfaces
- Flat file for quicker sanding
|Nub removal process starts with cutting parts off the runners. For best results, we make the cut some distance away from the part, rather than right against it.
Most nippers tend to pinch plastic until it breaks, instead of actually cutting it. This causes material stress and discoloration to appear – first in the middle, then radiating outward. By making the cut away from the parts, we reduce the risk of those stress marks reaching them.
Using high quality nippers, with thin and sharp blades further reduces this risk. Those tend to do more cutting and less pinching.
|I tend to leave good 1-2mm of excess plastic when cutting the parts out. You can see white, discolored plastic in the middle of those leftover nubs.
Shaving the nubs down
If you own a pair of thin, sharp nippers, you can cut off some more of the nubs at this point. Don’t cut right against the part though, as even those quality nippers can leave some stress marks.
If all you have are basic, thicker side cutters, skip to the next step, as those will do more harm than good at this point.
|Next up, we switch to our hobby knife and start shaving off the excess plastic. As with nippers, don’t try to slice off entire thing at once, doing so can easily result in gouged plastic and bleeding fingers. Just take it easy and keep slicing off thin layers until the nub is almost gone.
Find a comfortable way of operating the knife. Some people will recommend cutting away from yourself, but I find it impossible. I tend to hold the knife with four fingers and push it gently towards my thumb. It gets sliced every now and then, but it’s nothing major. Normally I also support the part with my left hand… but I had to take that photo somehow.
Another way of doing this step is leaving the part on your cutting mat and slicing the nubs off with a chisel-type blade. This way doesn’t allow as much control, but it works pretty well for gates placed on the edges of flat parts.
Sanding down the leftovers
Final step is sanding down the last bit of excess plastic. If there’s much of it, we can start by using a flat file. Otherwise we hit the part with progressively finer sandpaper or sanding sticks.
Rougher grits will make quick work of excess plastic, but they’ll also scratch up the part. To bring back the shine we repeat the process with progressively finer grits.
If you’ll be painting your kit, you can stop around 1000 grit (medium / fine, as some manufacturers call them), as the primer will easily fill the smaller scratches. If you’re not painting, you can go up to 2500-4000 grit (very fine) and rub the part with microfiber cloth for a smooth, shiny surface.
When working on curved surfaces, skip the file altogether and sand in a circular motion that matches the part to avoid flattening it. Preferably use soft sanding sponges or Flex-I-File for best results.
|When working on pieces that consist of two halves – like head and thigh armor on the pictures – it’s important to assemble them before sanding.
This way both halves will still match perfectly after nub removal. It also halves the amount of work needed, saving us a fair bit of time.
If we were to sand each piece separately, there’s a good chance they’d end up mismatched – not lining up, having rounded edges etc.
Unfortunately, proper nub removal is a rather lengthy process, especially on bigger MGs. Thankfully Bandai engineers make it easier on us by placing some gates in the hidden areas and employing undergating. With some building experience you’ll be able to recognize which parts will be visible which ones won’t. For the latter, you can cut the gates right against the parts and skip the process altogether.
Finally, it’s worth noting that nub removal varies in difficulty depending on the plastic color. White is the easiest, as stress marks are nearly invisible on it anyway. On the other hand, we need to be more careful with darker colors (especially Bandai’s dark blue). They tend to be a bit more brittle and therefore prone to stress.