This is a guide on how to remove nubs and how to avoid getting nub marks on your Gunpla parts. This method requires no sanding, just a hobby knife and a side cutter.
Disclaimer: This is not the only way to properly remove nubs, rather this is the method I currently use on my kits. What works for me may not work well for others.
Gates - it is where the melted plastic enters the mold cavity.
Nub - small lump you get from cutting the part from the runners.
Nub marks - discoloration of the plastic due to stress.
Step 1:
Remove the part from the runner by cutting the gates with your side cutter. Cut as far away as you can from the part. This is to avoid putting stress on the part itself.
Now that the part is not restrained by the runners anymore, it's safe to remove most of the excess nub. Don't cut the nub all the way; leave a small gap from the part. The sharper your cutter is, the closer the gap between the part and the cutter so as to avoid getting nub marks on the part.
Flat Surface
Slice the nub in a curved manner. When the blade's edge penetrates the nub, slice forward then gradually tilt the blade's edge upwards. While doing this, try to keep the edge of the blade parallel to the flat surface to avoid damaging the part.
The reason for tilting the blade upwards is to avoid digging and slicing into the actual part especially when the blade reached the end of the gate.
Start on one side until you've sliced most of the nubs. Do a fingernail check to see if it's all flat, most of the time there will still be a small nub on the opposite side of where you started. Rotate the part 180° and do the other side of the nub.
In the video below, there was an additional step where I rotated the part 90° counter clockwise and another 90° to finish it off. This was because the blades I was using was already dull. You'll be able to accomplish this with fewer strokes if your blades are sharp.
I use the flat surface of the part as my blade's guide when removing nubs. Get a feel of the angle of the blade and avoid digging in to the part.
If everything is done correctly, it should give you a smooth finish. The area where the nub previously was will slightly have a different shade compared to the original part color, specially under the light.
There you go! An almost invisible mark. It takes some practice but for me I think it's all worth it.
Persistent Nubmarks
Now if, after doing the above steps, there are still nub marks on the part, and trying to rub it doesn't work anymore, it might have been caused by a couple of things:
Pre-cut stress
Looks like everything is fine, but when you try to zoom in at the part, you'll notice something unusual.
Notice the white outline along the gate? Those are stress marks. This happens when an amount of force is unintentionally applied on to the parts while its still on the runners. This usually happens during shipping, especially if it was mishandled. Part is still on the runner but it has visible stress marks around the gate.
Unfortunately, this is hard to remove. Depending from the amount of stress applied onto the part, fixing it my vary from light sanding to hiding the mark by applying paint on the affected area.
Also, avoid carelessly throwing the runners after cutting a part from it, at least until its an empty runner. Carefully set it aside to avoid unnecessary stress marks.
Twisted Parts
This happens during step 1, when parts twist during the cutting process.
At 00:17, see how the part behaved when the bottom gate was cut?
The part was pushed upwards by the cutter, but since it's still attached to the gate on the right side, it pivoted causing a stress mark.
To avoid any pivoting, first thing to do is to find two opposite gates. Usually there are three gates that hold a part, once you find the opposite gates, cut the one that doesn't have a pair.
These gates will hold the part in place and prevent any pivoting when cutting parts off the runners.
Of course, this is not always the case, you have bigger parts that have more gates. So when removing these kinds of parts, always remember to find the pair of opposite gates, then cut them last. Or if there aren't any opposite gates, find the gate that will be most likely hidden when the kit is assembled, cut that last to make it the pivot point of the part. It will have marks, but you won't have any problems with it because it's hidden.
That's all for now guys. I hope this helps!
Disclaimer: This is not the only way to properly remove nubs, rather this is the method I currently use on my kits. What works for me may not work well for others.
Before we get started, let's try to familiarize with some of the terms we will be using in this post.
Runners (Sprues) - molded plastic which contain the parts necessary to build a kit. Specifically, it is the channel where plastic flows through to get to the mold cavity.
Gates - it is where the melted plastic enters the mold cavity.
Nub - small lump you get from cutting the part from the runners.
Nub marks - discoloration of the plastic due to stress.
Now that we've discussed some of the terms, let's get started!
Step 1:
Remove the part from the runner by cutting the gates with your side cutter. Cut as far away as you can from the part. This is to avoid putting stress on the part itself.
Step 2:
Now that the part is not restrained by the runners anymore, it's safe to remove most of the excess nub. Don't cut the nub all the way; leave a small gap from the part. The sharper your cutter is, the closer the gap between the part and the cutter so as to avoid getting nub marks on the part.
Step 3:
Shave off the remaining nub with a hobby knife. The goal here is to thinly slice it, not push it forward and force the blade. Like how you slice food by moving the knife forward and not straight down. Forcing it will stress the plastic which will leave a nasty nub mark.
Flat Surface
Slice the nub in a curved manner. When the blade's edge penetrates the nub, slice forward then gradually tilt the blade's edge upwards. While doing this, try to keep the edge of the blade parallel to the flat surface to avoid damaging the part.
The reason for tilting the blade upwards is to avoid digging and slicing into the actual part especially when the blade reached the end of the gate.
Start on one side until you've sliced most of the nubs. Do a fingernail check to see if it's all flat, most of the time there will still be a small nub on the opposite side of where you started. Rotate the part 180° and do the other side of the nub.
In the video below, there was an additional step where I rotated the part 90° counter clockwise and another 90° to finish it off. This was because the blades I was using was already dull. You'll be able to accomplish this with fewer strokes if your blades are sharp.
Curved Surface
When removing nubs on a curved surface, start on one side of the nub then do a couple of curved strokes (tilting blade upwards) until the edge of the blade reached the end of the gate. Afterwards, rotate the part a bit, then start doing a couple of strokes. Rinse and repeat until you reach the other side of the nub. Do a fingernail check, rotate the whole part 180° and finish off the other side.
Tip: Rub the tip of your nails to remove fresh stress marks you get from Step 3; just add a bit more pressure until the stress marks disappear. I did it at the 2:14 mark of the video above, and I was able to remove the fresh marks but it left out the marks that were previously there before the shaving. I will discuss that later on.
I use the flat surface of the part as my blade's guide when removing nubs. Get a feel of the angle of the blade and avoid digging in to the part.
If everything is done correctly, it should give you a smooth finish. The area where the nub previously was will slightly have a different shade compared to the original part color, specially under the light.
There you go! An almost invisible mark. It takes some practice but for me I think it's all worth it.
Persistent Nubmarks
Now if, after doing the above steps, there are still nub marks on the part, and trying to rub it doesn't work anymore, it might have been caused by a couple of things:
Pre-cut stress
Looks like everything is fine, but when you try to zoom in at the part, you'll notice something unusual.
Notice the white outline along the gate? Those are stress marks. This happens when an amount of force is unintentionally applied on to the parts while its still on the runners. This usually happens during shipping, especially if it was mishandled. Part is still on the runner but it has visible stress marks around the gate.
Unfortunately, this is hard to remove. Depending from the amount of stress applied onto the part, fixing it my vary from light sanding to hiding the mark by applying paint on the affected area.
Also, avoid carelessly throwing the runners after cutting a part from it, at least until its an empty runner. Carefully set it aside to avoid unnecessary stress marks.
Twisted Parts
To avoid any pivoting, first thing to do is to find two opposite gates. Usually there are three gates that hold a part, once you find the opposite gates, cut the one that doesn't have a pair.
Of course, this is not always the case, you have bigger parts that have more gates. So when removing these kinds of parts, always remember to find the pair of opposite gates, then cut them last. Or if there aren't any opposite gates, find the gate that will be most likely hidden when the kit is assembled, cut that last to make it the pivot point of the part. It will have marks, but you won't have any problems with it because it's hidden.
Take note that you won't be able to remove all of the visible nub marks. But taking time to avoid or minimize the visible nub marks will definitely help in getting a clean build.
End Result
I built this GN-X using all the methods I mentioned above. No panel lines and no decals yet, just a straight build. I took my time in cleaning all the nubs and this was the end result:
End Result
I built this GN-X using all the methods I mentioned above. No panel lines and no decals yet, just a straight build. I took my time in cleaning all the nubs and this was the end result:
That's all for now guys. I hope this helps!
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