Why do some kits have fit issues?

[walkerccw]

I have a question about the industry in general.  Some kits have fit issues (no specific manufacturer.

Just an example: If the prototype of the kit shows large gaps between the wings joining the fuselage, why is the mold not corrected?

 

CCW

[Graham Boak]

Often they are, depending upon the size of the problem.  If not, then probably because that takes time and money.  Possibly some manufacturers care more than others.

[JackG]

For sure if it is a resin kit, then it's very nature can (and will) cause problems with each new casting.  The first one will be the best while those at the very end will be quite less so. 

 

For injected plastic molds,  I've no idea where the problem arises.  Obviously this method allows for a larger quantity in output, so perhaps quality control cannot keep up.  Some companies may recycle plastic that has already been molded, and that would cause problems?

 

regards,

Jack

[Don149]

A typical case is the recent Special Hobbies Tempest, the wing to fuselage joint takes major surgery to get a good fit, and both the spinner

and chin intake look oversize, perhaps someone with 1/32nd drawings can confirm!. After the long gestation period of the kit, surely it

should have been correct !.

[Abakan]

Engineering is the word you are looking for. Some do it better than others. Some shortcuts have consequences as well.

[JohnT]

1 hour ago, Don149 said:

A typical case is the recent Special Hobbies Tempest, the wing to fuselage joint takes major surgery to get a good fit, and both the spinner

and chin intake look oversize, perhaps someone with 1/32nd drawings can confirm!. After the long gestation period of the kit, surely it

should have been correct !.

 

I should stick with my PCM one then?  Or not so simple as that?

[hendie]

4 hours ago, walkerccw said:

I have a question about the industry in general.  Some kits have fit issues (no specific manufacturer.

Just an example: If the prototype of the kit shows large gaps between the wings joining the fuselage, why is the mold not corrected?

 

CCW

 

because there may well be nothing wrong with the mold. Shrink and warp can be partly due to design and partly a result of processing - as are dimensions.  If the processor doesn't understand what he's doing, and unfortunately, there are thousands like that in this industry - it's surprisingly easy to get bad and inconsistent parts from a good mold.

 

As for flash - I have lost count of the number of posts I've seen on this forum stating the molds must be old because there's flash. That is a complete nonsense and you can get flash on a brand new (and in tolerance) mold.  If the press doesn't have enough clamp tonnage available, or it's set too low, then you'll get flash.

[Ptmvarsityfan]

Hi, good question, I am currently struggling with the AZ Airspeed Oxford and nothing seems to fit! Cheers, Paul

[Stonar]

13 hours ago, Don149 said:

A typical case is the recent Special Hobbies Tempest, the wing to fuselage joint takes major surgery to get a good fit,

 

Really? Here's mine, dry fitted, I had no problem at all with this part of the build.

 

 

This raises another cause of fit issues, the way the builder puts the kit together. I claim no particular expertise, I have managed to create such problems on kits with which others have had no such trouble.

 

I can't comment on the millimetric accuracy of the Special Hobby and PCM kits, but from the point of view of someone who has built both, the Special Hobby kit is light years ahead of the PCM offering in terms of engineering and what you get in the box.

 

Cheers

 

Steve

Edited September 25, 2016 by Stonar

[waistgunner]

Where kits are stored has a big affect on how they go together as well . Some of the larger kits like the B-24 will tend to get warping along wing seems and the fuselage . What happens is the weight of the kit and heat will affect fit . Heat will tend to cause warping and ill fit . Think about how hot you would get riding in a sea container across the ocean . I try keep my kits under 90 degrees .  

 

 There are some kits that are just plain junk . When those kits show up trim the alignment tabs and do your best . I try to use a plastic tab of my own make to align with the mating part . Test fit , Test fit and Test fit can not be stressed enough with any kit .  

 

Best of luck , WG 

[Beardie]

I think that method of assembly definitely has a part to play. I have had kits give me problems not mentioned in any build review of them and, on the other hand I have had problem free builds of kits which every reviewer has found fit problems with.

 

I also suspect the method of design has a part to play. I don't know much about the industry but I am guessing that any problems that appear once the molds have been created could require a complete redesign and a new mold made and I am guessing that, at that point the company, who may not be the largest or most resource rich,  has to decide on whether to take the time and spend the money to sort out the design and make new molds or whether the kit can still be built with a little modelling skill by modellers who are used to some  filling etc. when it comes to 'limited run' kits.

[Darby]

20 hours ago, ptmvarsityfan said:

Hi, good question, I am currently struggling with the AZ Airspeed Oxford and nothing seems to fit! Cheers, Paul

You think that's bad. You should try their Attacker. My first and last foray into AZ models.

[Graham Boak]

The Oxford, and I suspect the Attacker, come from Pavla originals which always did have a bad reputation.  The newer breed of AZ kits are in quite another league.

[Ptmvarsityfan]

Hi, I quite agree, would be happy to buy the more recent releases from AZ. Cheers, paul

[Pin]

On ‎24‎/‎09‎/‎2016 at 5:47 PM, walkerccw said:

I have a question about the industry in general.  Some kits have fit issues (no specific manufacturer.

Just an example: If the prototype of the kit shows large gaps between the wings joining the fuselage, why is the mold not corrected?

 

CCW

 

Do you have a rough idea how much does it cost to correct a mould? Thousands of pounds. Answering your question - in most cases fixing the problem makes no economic sense

 

[MilneBay]

Yes some kits do have fit issues - especially the limited run types. But that just makes them a bit more challenging. Often also fit problems can be overcome by carefully dry fitting and checking alignments etc. before you put glue to plastic. The rest is up to your skill as a modeler to get right.

[Mike]

As a group, we tend to blame the kit first, rather than consider pointing the finger at ourselves and the way we put them together.  I've recently made a few errors on that front with a little fun build I've been doing, and in hindsight I realise that I could have done it better, although I don't beat myself up about it too much as it's a short(ish) run kit.  Of course, it's not always our collective fault, but we must be open to the possibility that it's our ham-fists, lack of comprehension of the instructions or something else or we'll just end up looking foolish when someone comes along that had no problems

[Stonar]

48 minutes ago, Mike said:

As a group, we tend to blame the kit first, rather than consider pointing the finger at ourselves and the way we put them together. 

 

I have built two of the Tamiya 1/32 scale Spitfires. On the first one I had a devil of a job getting the panels to fit around the engine, making the entire nose something of a battle. On the second they fitted perfectly. I still don't know what mistake I made on the first kit, but the problem was certainly caused by something I did.  Obviously, entirely fortuitously, I avoided repeating the mistake on the second kit 

 

Cheers

 

Steve

[Don McIntyre]

I find that other than on short run kits, I tend to blame myself for fit issues. As an example, on another forum I belong to, myself and another guy were building (he's finished, I still have work to do) Monogram's old AV-8A/Harrier GR.1. 

He didn't use any filler, while I needed filler on pretty much every seam. I think he was just more careful in his assembly than I was.

Edited September 26, 2016 by Don McIntyre

[hendie]

14 hours ago, Pin said:

 

Do you have a rough idea how much does it cost to correct a mould? Thousands of pounds. Answering your question - in most cases fixing the problem makes no economic sense

 

 

correcting the mold is built into the initial cost.  When first built, the mold is sampled and the first article produced. It is at this time it is the responsibility of the customer to check the data from the first article and make sure it's correct. This includes dimensional data, surface finish, flash, runners and gating etc.

If there is anything out of spec it's the tool builders responsibility to correct it.

Most of the issues you see on kits is down to the processors not understanding the process (sad but true).  The problem is that like anything else in life, people tend to go for cheaper rather than best (for most commodity items) - and if companies are looking to save a few pounds, dollars or whatever, they'll go to the lowest bidder..

The lowest bidder tends not to "invest in people" (in most instances) by providing the appropriate training.  Their philosophy is melt, squirt, cool, and send it out the door.

That's the reason you will see one person stating it all fitted together with no problems and another stating that it was all out of whack - the molder ran an inconsistent process providing parts which were dimensionally all over the place.

 

 

 

 

[Phantome]

On 9/24/2016 at 10:27 PM, hendie said:

 

because there may well be nothing wrong with the mold. Shrink and warp can be partly due to design and partly a result of processing - as are dimensions.  If the processor doesn't understand what he's doing, and unfortunately, there are thousands like that in this industry - it's surprisingly easy to get bad and inconsistent parts from a good mold.

 

As for flash - I have lost count of the number of posts I've seen on this forum stating the molds must be old because there's flash. That is a complete nonsense and you can get flash on a brand new (and in tolerance) mold.  If the press doesn't have enough clamp tonnage available, or it's set too low, then you'll get flash.

 

Case in point, Revell. Amazingly engineered kits. But terribly produced kits, in particular the canopies which are straight up deplorable.

[Eric Mc]

19 hours ago, Mike said:

As a group, we tend to blame the kit first, rather than consider pointing the finger at ourselves and the way we put them together.  I've recently made a few errors on that front with a little fun build I've been doing, and in hindsight I realise that I could have done it better, although I don't beat myself up about it too much as it's a short(ish) run kit.  Of course, it's not always our collective fault, but we must be open to the possibility that it's our ham-fists, lack of comprehension of the instructions or something else or we'll just end up looking foolish when someone comes along that had no problems

100% agree.

 

Often a little bit of forethought and planning can get around what at first seem like serious fit issues. There are, of course, some kits where the fit really is poor. My worst example so far is the PM Focke Wulf Ta154. It's one of the few models I gave up on because of fit issues. However, I've since bought another one and will have another try at some point in the future.

[malpaso]

9 hours ago, Phantome said:

 

Case in point, Revell. Amazingly engineered kits. But terribly produced kits, in particular the canopies which are straight up deplorable.

A bit unfair.  I've not had any more issues with Revell kits than anyone else's, and less than classic Airfix reissues.  I built the 1957 1/28 Dr1 a couple of years ago.  It fitted together fine, the only filler was required to correct one aileron, as it's presumably based on the captured one with assymetric ones.  I wasn't embarrassed for it to be judged against WNW in the club competition, though needless to say it didn't win...

[Phantome]

To answer the original question, I will reply with another set of question?

 

Why are some houses terribly built?

Why are some companies terribly run?

Why do some people have terrible personalities?

Why do some restaurants serve terrible food?

 

Because if they didn't, we wouldn't really know what is truly great and amazing.

[Phantome]

21 hours ago, hendie said:

 

correcting the mold is built into the initial cost.  When first built, the mold is sampled and the first article produced. It is at this time it is the responsibility of the customer to check the data from the first article and make sure it's correct. This includes dimensional data, surface finish, flash, runners and gating etc.

If there is anything out of spec it's the tool builders responsibility to correct it.

 

 

That's not how making the mold works. Once the mold is done, it's done. If a piece is too wide, how do you shrink a steel mold to correct it? You can't. Some (very few) manufacturers may correct a kit by re-molding a certain piece but that's it. If an easy to replace part is wrong, the aftermarket community steps in and hopefully produces a resin replacement, not the manufacturer. Major dimensional errors are never corrected.

 

Also who is this mystery customer who buys the first kit produced? No company sells just one kit and then sits around expecting feedback...