Production Bending

eclipsme

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For those of us that use side benders, how do you go about bending multiple sides in one session? If I want to bend 4 sides (or more), surely I don't need 4 side benders.

How do you deal with this? Thanks for any comments.
 
My bender cools for reuse very fast with a fan blowing up into it from underneath.

How long do you leave it in the bender before removing the side? and do you do anything to keep the bend after that or just put it on a shelf until use? ;-}
 
If your forms and heat blankets are wide enough, you can bend two sides at a time.
Brad

I don't use a blanket. I use steam but my bender is not double wide. Seems like there is a better way to do multiple sides...
 
No personal production experience here. But, I've visited the Martin factory and they bend one set at a time. They had one operator running several bending machines.

Looking at bending as a process, it is very inefficient. Most of the time is spent 1. Waiting for the wood to heat up. and 2. Waiting for the bent sides to dry or set up in the forms. Some people even heat cycle the bent sides in the form which adds more wait time. The "value add" time of actually bending wood is small compared to all waiting.
Possible solutions to eliminate waiting:
1. Heat the wood in an oven before moving them to the bending machine. Around 240F would allow you to move wood on to the machine and start the presses immediately.
2. Design your bending machine to have bending forms that can be quickly exchanged. Then you can allow the wood to cool and set up in the form while you're bending the next set.
 
I bend on the iron first and then set the shape in the bender with a heat blanket. My bender handles both sides at the same time. I can easily do 4 sets in a day if I chose to.
 
I bend on the iron first and then set the shape in the bender with a heat blanket. My bender handles both sides at the same time. I can easily do 4 sets in a day if I chose to.

I have never used the iron (though now thinking of it) but thought that when finished, the side is the correct shape, but then you 'set the shape in the bender'?
 
No personal production experience here. But, I've visited the Martin factory and they bend one set at a time. They had one operator running several bending machines.

Looking at bending as a process, it is very inefficient. Most of the time is spent 1. Waiting for the wood to heat up. and 2. Waiting for the bent sides to dry or set up in the forms. Some people even heat cycle the bent sides in the form which adds more wait time. The "value add" time of actually bending wood is small compared to all waiting.
Possible solutions to eliminate waiting:
1. Heat the wood in an oven before moving them to the bending machine. Around 240F would allow you to move wood on to the machine and start the presses immediately.
2. Design your bending machine to have bending forms that can be quickly exchanged. Then you can allow the wood to cool and set up in the form while you're bending the next set.

I assume bending machines with blankets? Was there no springback when released from the bender?
 
Most of the bending time is spent waiting for the benders to cool down, during which I do something else. Sides don't have to be a perfect fit in the mold coming off the benders, they just have to be a nice fit when the end blocks are glued in. Adjusting them in the mold is the real trick, not avoiding some spring back.

Steam sounds like an inefficient way to enhance production. Electricity allows the builder to bring the heat up quickly, make the bend in just a few minutes, and permits the builder to walk away while the bent side cooks and the timer runs down. A lot of work can be accomplished between bending sessions. Using two benders I could build four guitar bodies in a week.

In my uke shop all the gear is stripped down. Electric blankets but no Fox benders. No automatic timers, so I can't walk away. No drying forms. Yet I can easily bend sides and load molds for three different models in a morning, which is a lot faster than my production requires. I don't even have a "production", as I build leisurely, but it only makes sense to do some steps in bulk.
 
I assume bending machines with blankets? Was there no springback when released from the bender?

I don't know....I'm a hot pipe bender and just a hobbyist. But I am a Lean Manufacturing guy in my day job so I figure the same principles will work. Identify the steps that add value and the steps that don't. Anything that involves waiting is a pure waste....heating, cooling, re-bending, drying, clamping, unclamping would all be big targets for elimination if possible. Don't even get me started on the finishing process :rolleyes:
 
I have never used the iron (though now thinking of it) but thought that when finished, the side is the correct shape, but then you 'set the shape in the bender'?

If you haven't used a bending iron then you had better get one and start learning. I'd consider it a pretty much indispensable item in a luthiers shop even if it's only to touch up the shape of some timber that just doens't want to behave.

The reason that I and many others use the iron first is that with high figure timber and or difficult to bend species going straight to a bender will far too often result in sides that end up having to be tossed in the bin. And especially with a body shape such as mine with ver tight waist and upper bout bends. The iron lets you "feel" when to apply pressure and how much without it fracturing.

Only using a bending machine too often you are guessing if it's been heating enough and ready, or too long and the timber has dried out and brittle. You will see all kinds of work arounds by people that only use a bending machine to try and remedy this problem, when the method I describe is dead easy and has worked 100% of the time since I switched to it. About 200 instruments since the switch.

Coming off the iron doesn't need to be perfect. Far from it. Just getting the piece to be shaped somewhat like your form is all that is required. The solid form and heat blanket and appropriate clamping does the rest.
 
I on the other hand want my bodies to be pretty close to finished shape as I have been building without a mold. The first one I did moldless.

xLBtE1I.jpg


The first guitar I made I did enough sides to do four guitars, a busy day. I bend the rough shape on the pipe and then set the actual shape on a mold with a heat blanket. I do two sides and then let them sit over night on the mold.

jUBNs79.jpg


The outer one is a little bigger than the inner but easy enough to tweak.

I was a LM kind of guy, spent years on a production line with about 250,000 items into 20,000 cartons a shift. Things did not always go well so when handling was needed any movement I needed to make multiplied by all the repetitions added up and bogged you down. My partner and I went on vacation at the same time one year, the plant efficiency dropped from around 90% to under 50%. They never let us go at the same time after that.

I would not sweat the time to bend wood, put a fan on the mold to cool it down to speed things up. Some woods spring back so a rough form to hold them is useful if not using in a period of time. Look up some Youtube vids of manufacturers building their guitars, Martin has a good one.
 
This is going to be on repeat forever unless someone locks it down. There is no right or wrong way. And whoever started this post ought to put some time in going through all the old posts, youtube videos and stuff out there - there is enough info out here to make more than informed decision. We don't even need Grahams' book! (though it would be nice to have it in our 'library') And we should shut up and stop encouraging them.
 
This is going to be on repeat forever unless someone locks it down. There is no right or wrong way. And whoever started this post ought to put some time in going through all the old posts, youtube videos and stuff out there - there is enough info out here to make more than informed decision. We don't even need Grahams' book! (though it would be nice to have it in our 'library') And we should shut up and stop encouraging them.

I fully agree with this.."The Right Honourable Member for Snowdon and District" has spoken :agree:
 
I on the other hand want my bodies to be pretty close to finished shape as I have been building without a mold. The first one I did moldless.

xLBtE1I.jpg

I see you are also building with Spanish Heel construction. Cool! I could never get a clear picture of how the ribs get attached to the soundboard in exactly the stage of construction depicted in this picture. That looks like Cyanoacrylate glue, yes? Do you then use Titebond to attach the linings? Traditional, kerfed or solid?

The first guitar I made I did enough sides to do four guitars, a busy day. I bend the rough shape on the pipe and then set the actual shape on a mold with a heat blanket. I do two sides and then let them sit over night on the mold.

jUBNs79.jpg


The outer one is a little bigger than the inner but easy enough to tweak.

Yes, why didn't I realize this before? So obvious to double them up! Thanks.
 
I found this thread very helpful, so thank you! Here is how it ended up for me.

I steam my ribs. Then I begin by bending the rib on my side bender.

Side Bender.jpg

Once that is in place, I begin steaming the next rib.

5 minutes before the steaming is done, I remove the rib from the side bender and put it into a form and caul. The rib will stay in the form for at least 24 hours. I now have 4 of these.

Form and Caul.jpg

After 24 hours, the rib is transferred to this - I don't know what to call it but it makes the rib maintain its shape until I am ready for it. I wet the rib down several times during the next 12 hours or so. At the end of this process, I find the rib has very little springback.

Bondage.jpg

I was easily able to get 5 ribs bent in a morning this way (I used the side bender as a form and caul for the 5th rib). I am now beginning on the necks while the ribs sit and stabilize.

I hope my experience can help somebody else.
 
So from all of your research you chose, perhaps, the most painful and pointless way to do something. Listen my friend, the wealth of experience on this forum is there for the taking. Have a couple of days off from posting your ill-advised decisions and repetitive questions and do yourself a favour - THOROUGHLY research what those who have been doing this for MANY years have shared here. Go away for another day and allow yourself to process it. Then come back to us , informed and curious as to why we nearly all agree own one thing - this business is more than just arriving at the first idea that seems the easiest solution. Some operations are difficult but there former posts here made by professionals and gifted amateurs identify the pitfalls and properly guide you to the BESRT way of doing something, not there EASIEST. You are not painting yourself in a positive light my friend and people, like me who want to help people like you are reluctant to do so because you appear to be of the 'entitled ' generation who expect everything without effort, to come instantaneously to your door for free. The price you have to pay to get my help and the benefit if 25 years building ukulele ism to show you have out some measured and thoughtful effort ito this. You are not my peer but a potential pupil....
 
Those are not bends ..those are gentle curves :) ..I do my soprano waists at 1" radius.

https://www.youtube.com/watch?v=vUmyFjC5THI

Wow, thanks for the video! So you bend the waist first and then go to the side bender. I had not seen that before. Clever way to backup the wood with a metal strap.

BTW - Do you find that a tight waist bend improves the sonic qualities of the instrument?
 
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