How to Fix Common Issues with Third Party Gundam Kits: Fit, Flash, and More

Quick Answer

Most third party Gundam kit issues come down to three things: tight or loose fit, leftover flash, and seam lines. Start by dry-fitting every part, sand flash with fine grit, and use glue only where a joint is truly loose. If a part is warped or the plastic cracks easily, stop and consider a replacement part rather than forcing it.

Third party Gundam kits offer exciting alternatives to official Bandai releases, often at a lower price. But they can bring their own set of challenges: parts that don't quite click, extra plastic left from the molding process, and seams that refuse to disappear. The good news is that most of these problems are fixable with basic tools and a little patience.

This guide walks through the most common third party kit issues, what causes them, and how to fix them without ruining your build. Whether you're working on a Daban PG kit or a smaller 1/100 third party model, these troubleshooting steps will help you get a cleaner result.

Tight Joints: When Parts Won't Fit

A tight joint is the most frequent complaint with third party kits. The peg is slightly larger than the hole, or the plastic has a bit of extra thickness from the mold. Forcing it can crack the part or stress the surrounding plastic, so always dry-fit first.

If a peg is too tight, sand it gently with fine-grit sandpaper (400-600 grit) in a circular motion. Test the fit frequently. For holes that are too small, carefully ream them with a hobby knife or a pin vise. Work slowly — removing too much plastic creates a loose joint that's harder to fix.

• Always dry-fit before applying any glue or force.

Loose Joints and Falling Parts

The opposite problem is a joint that's too loose, causing arms or legs to droop or fall off. This often happens when the peg is undersized or the socket is too wide. A simple fix is to apply a thin layer of super glue to the peg, let it dry completely, then test the fit. The added thickness can tighten the connection.

For ball joints, you can also use a layer of clear nail polish or a small piece of Teflon tape. If the part still won't stay in place, consider adding a drop of glue to permanently secure it — but only if you never plan to disassemble that joint again.

• Use a thin layer of glue or nail polish to build up a loose peg's thickness.

Flash and Mold Lines: Cleaning Up the Plastic

Flash is the thin excess plastic that appears along the edges of parts where the mold halves meet. It's common in third party kits and can make parts look rough or prevent them from fitting together. Use a hobby knife to carefully scrape off flash, then smooth the area with sandpaper.

Mold lines, the raised lines that run across parts, are similar. Sand them down with progressively finer grits (400, then 800, then 1200) for a smooth finish. Be careful not to sand away detail lines. For curved surfaces, use a sanding sponge that conforms to the shape.

• Start with a coarse grit and move to finer grits for a smooth finish.

Seam Lines and Gaps

Seam lines appear where two halves of a part meet. In third party kits, these lines can be more prominent than in official kits. The standard fix is to glue the halves together, let the glue dry, then sand the seam away. This works well for parts that don't need to separate, like a forearm or a rifle.

For parts that must remain movable, you can't glue the seam. Instead, use a technique called seam line removal with a liquid cement that welds the plastic, then sand. Alternatively, accept the seam as part of the build — some builders find it adds character. The key is to decide early whether a part needs to be permanent or movable.

• Glue and sand seams on non-moving parts for a clean look.

Warped Parts and Other Serious Issues

Sometimes a part is warped, meaning it's bent or twisted out of shape. This can happen during shipping or due to poor molding. You can try to straighten a warped part by dipping it in hot (not boiling) water, bending it gently, and holding it in the correct position while it cools.

If a part is cracked, broken, or the plastic is so brittle it crumbles, don't force it. Forcing a damaged part can ruin the entire build. At this point, the smart move is to stop and order a replacement part. Many stores, including Cool Dragon Hobby, offer replacement parts for Gunpla models and Metal Build items. Check availability before you continue.

• Stop and source a replacement part if a piece is warped beyond repair or cracks easily.

Diagnosis: When to Fix and When to Stop

• Symptom: Tight joint: Dry-fit first, then sand the peg or ream the hole with fine tools. Proceed if the joint fits after light sanding.
• Symptom: Loose joint: Add a thin layer of glue or nail polish to build up thickness. Proceed if the joint holds after the layer dries.
• Symptom: Flash or mold lines: Scrape with a hobby knife and sand with fine grit. Proceed if the surface looks clean and fits properly.
• Symptom: Warped or cracked part: Try hot water straightening for warps, but if the plastic is brittle or cracked, stop. Stop and order a replacement part before continuing.

Products That Help

• Daban PG Gundam Unleashed RX-78-2 Model Kit: Material: ABS, Scale: 1/60, includes model kits for the gundam, water slides, and other accessories. If you're building a large third party kit like this PG, expect to do some fit adjustments. The included water slides mean you'll also want to practice your decal application for a clean finish.
• Replacement Parts (Gunpla Models Kits and Metal Build/Metal Robot Spirits): Replacement parts policy: complete a request form before ordering, and for Metal Build / Metal Robot Spirits items, provide clear photos of the needed parts. Availability is checked within 1–2 business days. When a third party kit has a broken or warped part that you can't fix, ordering a replacement is the safest option. Knowing the process ahead of time saves you from a stalled build.

Third party Gundam kits can be rewarding builds, but they often need a little extra care. By diagnosing each issue — tight joints, loose parts, flash, seams, or warped plastic — you can apply the right fix and know when to stop. With patience and the right tools, you'll turn a problematic kit into a display-worthy model.