Scroll saw design

[roombacurious]

I've recently taken interest in scroll saws after realising that a bandsaw can't actually do everything I wanted... I've studied a few web sites and other sources and I think I now have a fair idea of how a scroll saw works.

However I can't help wondering whether in this era of high tech electronics the current designs are the only way of making an effective scroll saw. I just can't believe that the best way of making a blade go up and down is attaching it to a frame/set of arms a few hundred times heavier than it and then making the whole thing reciprocate which will obviously result in unwanted vibration.

My thought for example would be that the upper arm should be made to have little weight and zero or minimal travel, i.e. a design with a fixed upper arm and all the moving parts attached to the bottom of the blade.
An even better way would be to attach magnets to the ends of the blade holders and make these travel up and down with the use of electromagnets, one on each arm. (I can give details if this sounds complicated, I think it's pretty simple) This way you do away with both the motor and practically the majority of the vibration since both arms are fixed and don't have to move. Tensioning the blade should also be simple to adjust electronically.

Does anyone know whether anything similar has ever been tried? There may be pitfalls I haven't thought about.

 

[Gill]

This is a thought which has crossed my mind too, although I'm not an engineer so I wouldn't know how to go about designing a new type of fret saw.

Are you aware of the Eclipse in the USA? It is very highly regarded over there, although it isn't exactly what you're talking about. In many ways, the Eclipse reminds me of old industrial fretsaws which were similar in design to sewing machines.

I've got an electromagnetic saw which may be akin to the type you describe. It's called a Spirolux and it operates along the same principle as those saws used in hospitals to cut plaster casts. Sadly, it can't cut very thick material and it vibrates terribly. I'm not sure if it's still in production - a couple of years ago they were quite common on eBay, but no longer.

I suspect you might need to reflect upon the need to keep the blade under tension yet provide for quick changing. The predominant parallel arm system is very effective in this respect. However, if you think you can produce a better type of saw than those which are currently available, I'll give you every bit of encouragement. After all, it was only when Doug Woodward and his colleagues realised they could improve upon standard scroll saw designs that the Diamond was invented, and it set the standard for many years.

Gill

 

[jigsue]

Hi

I have seen one done, somewhere. Try "Googling". In the meantime, I will have a think and if the light comes on, I will get back to you! I know in this are of the country, I have seen treadle "pole saws", dunno how similar they would be!

Sue

 

[roombacurious]

Well it's good to see that the idea is not entirely insane since it has already been done! The principle at least should be the same as the Spiralux. I've read elsewhere that it can't cut thick material because it "vibrates" instead of cutting. Should I translate this as "the stroke is only a couple of millimetres" that's why it doesn't cut well? Also, I wonder why the Spiralux vibrates terribly as you say. In theory it should vibrate very little if any since the stroke is (probably) very small.
I think I need to find one to take apart and study! Anyone wanting to get rid of theirs?! (it seems nobody uses them anyway) :wink:

 

[Gill]

Some time ago I was sent an article from an old magazine explaining how electromagnetic saws work. They're not a new idea - the magazine was published in 1935! Fortunately, that means I can now make it available on the internet because it is out of copyright . Such diferences as there are between a Spiralux and the saw in the article are trivial; blade clamps, plastic body and so on. Anyway, if you're interested I've uploaded the article here.

I've also found a related US patent application here.

Gill

 

[roombacurious]

Thanks Gill, that was indeed quite helpful.
I think I'll try to make a prototype at some point. I'll let you know if I come up with anything worthwhile.

 

[Brucio]

Gill-????
Where is the article?
When I click on your link ("here"), I get to Easy Share.
A couple of girls from Sunderland, an advert for casino gambling.
No mention of the article you refered to about a scrollsaw.
A little button marked "download this file". What file?
When you click on this button (after filing in the little code numbers), a quick glimpse of a downloading screen, then nothing!
What have I just downloaded?
Where has it gone on my computer?
The three boxes at the bottom, containing html code, bb code etc, i tried them-nothing!
I'm most disappointed.
Bruce

 

[StevieB]

Works OK for me, fill in the anti spam code and click download and the file opens on a new page.

Steve.

 

[Gill]

I thought it would be easier to share the file by posting it to Easy-share rather than having to go to the trouble of exchanging emails. If I've upset you, I apologise.

I've found the original article online since making my last post, so you should be able to link to it directly by clicking here. No download .

Gill

 

[Brucio]

The file DID NOT open in a new page-that's what is so annoying.
Just a quick glimpse of the downloading screen, then nothing...
What have I just downloaded?
A virus?
A trojan horse?
A key-logger?
A pop-up advert?
Porno material?
Spyware?
I don't even know the NAME of the file, so that I can hunt it out and delete it.
I won't sleep again, worrying about what I've just done.
Gill, why couldn't you just put the link on, and NO downloads, like you did in your second post?
Instead of all this bother and worry.
I won't sleep, ever.
It's horrid.
Bruce

 

[StevieB]

Or you could just have your browser set to not open additional windows from a page so you have downloaded nothing? If it bothers you that much do a date search in windows explorer for any file created today, or just do a sweep with your anti virus software.

Steve.

 

[Gill]

This is what I get for trying to help. It's nice to feel appreciated, Bruce.

Gill

 

[Taffy Turner]

Crikey Bruce,

Take a chill pill!

Gill tried to help out, and now you are unloading on her big time.

As others have downloaded it without any problems, I would suggest that it's your computer set-up that is at fault.

As for "not sleeping, ever" - Get real!!! Even if by some chance you have downloaded a virus, it's not the end of the world. Get a grip and stop behaving like a spoiled 7 year old!

Steve has given you good advice on how to resolve it. If anything malicious has been downloaded (which I highly doubt), then your Anti-virus software should stop it in it's tracks. If you don't have any AV software, then what on earth are you doing surfing the internet in the first place?????

I think you owe Gill an apology.

Gary

 

[Brucio]

Gill-I DO apologise....
I didn't mean to upset anybody.
I'd just come off a 12 night shift, and I was thinking straight....
I didn't know that there were so many people with acid instead of blood inside them.....
I shall go and stick my head in a bucket of water.
Or stand outside in the snowstorm for five minutes...
There.
Is that penance enough?
Bruce

 

[roombacurious]

Ok let's all come down please!
Bruce there are no viruses on that page, don't worry.

Here is the article:

It's placed in my personal web space so it won't be there forever - if you want to keep it just right-click-save as.

Again, thanks again to Gill for this.

George

 

[bugbear]

I just can't believe that the best way of making a blade go up and down is attaching it to a frame/set of arms a few hundred times heavier than it and then making the whole thing reciprocate which will obviously result in unwanted vibration.

Some design have totally rigid (and motionless) arms, with the upper arm holding a (spring loaded for blade tension) sliding attachment for the blade, and the lower arm carrying a (small) oscillating mechanism.

Does that appeal to you?

BugBear

 

[bugbear]

Well it's good to see that the idea is not entirely insane since it has already been done! The principle at least should be the same as the Spiralux. I've read elsewhere that it can't cut thick material because it "vibrates" instead of cutting. Should I translate this as "the stroke is only a couple of millimetres" that's why it doesn't cut well? Also, I wonder why the Spiralux vibrates terribly as you say. In theory it should vibrate very little if any since the stroke is (probably) very small.

That would depend on the rate - vibration comes from change in momentum, the product of mass and acceleration.

It's the ends of the stroke that matter, when the mechanism is changing direction; the length of the stroke in between doesn't matter.

BugBear