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Adding molding to slab mdf

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Yorkshire1

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Hi , new to the forum thanks for the the approval , initially looking for advice but hope to be able to contribute aswell!
We need to build some wardrobes for a client , the doors will be 18mm mr mdf roughly 1800 x350-500mm wide with dado style molding running 100mm in from the edge on 3 sides the molding is to be roughly 40mm wide and 16mm deep
Now we know usually whats done to one side needs to be done to the other to maintain equilibrium However has anyone any tips for acheiving doors that will remain true
The plan is to use mdf molding in the hope that its flexibility will allow the doors to remain true with the help of 4 hinges / door when fitted
Thoughts gratefully received, thankyou
Photos show how badly the doors would bow with pine molding
 

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Yorkshire1

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Yeah we ve tried that previously and its worse because you get more tension the thinner the mdf the more flex you get
 

Cabinetman

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Even though your last statement seems contradictory I know exactly what you mean, we started off with 18 mil MR MDF just like you for my sons wardrobe doors, he wanted a geometric slashed design right across six of them, I knew I should’ve run away but Dad's being Dad's got stuck in and this is what we ended up with, six mil MR with aluminium angle iron glued on the back with pink stuff, hinges in blocks and almost a nervous breakdown.
I am not recommending you try it this way. NO definitely NOT!! It was a nightmare.
On more expensive wardrobe doors when they glue a mirror on the front they have vertical grooves with aluminium fittings running full length of the height of the door which can be adjusted/tensioned to take movement out. Ian

BEA9BEEA-5D9F-43F9-9E98-F413D274E0AD.jpeg
7B0FC712-1912-4686-AAD5-5C80F9757414.jpeg
 

Droogs

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I would suggest that it's best to make the mouldings out of the same material as the doors, esp if being painted. Or to make the moulding and leave it in the customers house for a couple of weeks to acclimatise and then fit it to the doors just before painting and fitting.
 

Jones

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Have you tried a glue that is not water based? The tension causing the bow presumably comes from the glue drying and shrinking so a pu glue or coating the panel both sides with sealer first might work.
 

Doug71

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I had the same happen on 2 pairs of doors I made for an airing cupboard, wasn't sure if it was the heat or the wood strips shrinking which made the doors bend, either way I won't be doing it again.

Luckily as they were pairs of doors both doors bent the same so you couldn't tell, I think it was only me who noticed it 🤫
 

Spectric

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The nice thing about MDF is that when it does move it is usually only in one direction unlike real wood that bows and twist.
 

Yorkshire1

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I would suggest that it's best to make the mouldings out of the same material as the doors, esp if being painted. Or to make the moulding and leave it in the customers house for a couple of weeks to acclimatise and then fit it to the doors just before painting and fitting.
Hi thanks yes thats the next plan we do have an an insulated cabinet we use to replicate indoor conditions
 

Yorkshire1

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Even though your last statement seems contradictory I know exactly what you mean, we started off with 18 mil MR MDF just like you for my sons wardrobe doors, he wanted a geometric slashed design right across six of them, I knew I should’ve run away but Dad's being Dad's got stuck in and this is what we ended up with, six mil MR with aluminium angle iron glued on the back with pink stuff, hinges in blocks and almost a nervous breakdown.
I am not recommending you try it this way. NO definitely NOT!! It was a nightmare.
On more expensive wardrobe doors when they glue a mirror on the front they have vertical grooves with aluminium fittings running full length of the height of the door which can be adjusted/tensioned to take movement out. Ian

View attachment 126458View attachment 126459
Even though your last statement seems contradictory I know exactly what you mean, we started off with 18 mil MR MDF just like you for my sons wardrobe doors, he wanted a geometric slashed design right across six of them, I knew I should’ve run away but Dad's being Dad's got stuck in and this is what we ended up with, six mil MR with aluminium angle iron glued on the back with pink stuff, hinges in blocks and almost a nervous breakdown.
I am not recommending you try it this way. NO definitely NOT!! It was a nightmare.
On more expensive wardrobe doors when they glue a mirror on the front they have vertical grooves with aluminium fittings running full length of the height of the door which can be adjusted/tensioned to take movement out. Ian

View attachment 126458View attachment 126459
Striking set of doors there Ian yeah Ive seen those adjusters are they the hafele ones
The strange thing is why some doors stay true and others dont when everything is in equilibrium am going to clamp a bowed door flat and add molding to reverse side and see what happens
 

Yorkshire1

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Have you tried a glue that is not water based? The tension causing the bow presumably comes from the glue drying and shrinking so a pu glue or coating the panel both sides with sealer first might work.
We use mitre glue and activator its slightly baffling as to what the issue is currently 8 500 mm wide tall doors are sfraight and all 4 300+mm doors have bowed all the same materials all built the same day
 
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