Author Topic: 4*6" band saw bodge, Phase one  (Read 8013 times)

Offline PekkaNF

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4*6" band saw bodge, Phase one
« on: December 10, 2012, 03:56:21 PM »
I have had one small bandsaw. Pretty good, it have served well.

It only really needed oil change and a new blade.

Right from the start I build a better stand and an extension to cut long pieces (not shown here, it's detachable).

After few hours I startted to think some kind of cooling pump and went trough few different bodges.

I also build too small tray and then too big tray. Which was chopped smaller and bend for bigger list - just in case I'll end up building flood coolant to it.

I also went trough few iterations on hydraulic downfeed.

Wife didn't like her stepper anymore and when I was taking it appart to recyle metal I noticed the torture cylinders that had an adjustement.... :zap: :zap:
http://www.recycler.com/Uploads/20d1ca5a-c105-469b-ad23-036d84926215-500.jpg

Unfortunately the adjustement range was not not sufficient....how hard can it be to tweak it a little. Someone might be better modder but the stepper cylinder was not very good on this purpose. I used outer skin (reservoir) and after playing some time with cylinder, piston and rod ended up using only cylinder (liner?). Cylinder needed honing, for some reason it was somewhat more shaped like a coke bottle than cylinder.

Then made rod out of hydraulic tube (not very round or straight stuff), why do I get these ideas?

Then made piston...twice. First one was too tight and too long bearing surface...potentially too much friction, galling and whatever.

Rest of it was easy. Whatever pneumatic material I had on hand. Worked first time.

Levers and lost-movement-mechanism was drafted on paper to produce max cylinder piston movement on max diameter, look "right", and clear parts. This was the part I was least confident and desided to bodge and try how it works before really committing...see pictures and you understand what I mean.

I was mostly surpriced when this contrption worked on first try....pneumatic needle valve gave over 5 turns of usefull adjustement range on cutting down speed. Spring seems to balance ok, I'm trying to get constant down feed speed.

I'm trying it out some time and maybe then I finish it and bolt everything on their final places.

Pekka


Offline PekkaNF

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Re: 4*6" band saw bodge, Phase one
« Reply #1 on: December 15, 2012, 06:29:46 AM »
OK, that seemed to work - least until now.

Then to second issue: coolant

At the very begining I tried without coolant, seems like coolant is used definitely for a reason. I use the saw very seldom for anything else than ferrous bar stock.

Did a little homework and that time water emulsion was pretty much the only way to go with iron metals. Tried it with few different setups, but while it definitely forks and even better for harder metals it's messy, has tendency to flow or drip outside the saw and this emulsion needs some care. Also running the pump needs some extra circuitry.

After a year I dismantled it and used manual drip feed from a spors drink bottle. Worked fine, but over 50 mm sections get kind of booring.

I was thinking fog/mist lubrication and while it works brilliantly on technical point of view, I'm not sure about the health issues. Also it needs some compressed air (not that big problem).

Before resorting back to flood coolant, I'm trying out some mechanized drip feed options.

I Turned/milled some AL "nozzles". Holes are made in lathe and magnets glued with epoxy. Idea is to place them on blade guide with magnet and they can be taken out when not used.

Idea is to drip feed coolant directly on the blade just before bar stock. Basically this has a small bore with 1/8"G thread at he other end, drilled reservoir on the middle and at extreme end a slit marginally wider than band saw blade.

I also made another nozzle to be tested after the bar stock. I had trouble with some coolants collecting swarf on the blade and that is not very ideal situation. I used long time a go some plastic brush and then pressurized air with just a simple pipe, but it needed very large volume of air and did not do that good work.

Then I got an idea a decided to have a go: It might better to blow firs another side and then another side. I turned two distantly venturi type nozzles and cut a slit for blade that way the one side of the blade gets blown and the another....this is probably going to take some tries.

Here are the parts, I'll hopefully get a change to try rest of it later (something quick and dirty just to try out concept).

Pekka

Offline DavidA

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Re: 4*6" band saw bodge, Phase one
« Reply #2 on: December 15, 2012, 12:03:36 PM »
Re the drip feed.

Won't you have problems maintaining a steady drip rate as the rate will vary as the head in the supply changes ?

Dave

Offline PekkaNF

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Re: 4*6" band saw bodge, Phase one
« Reply #3 on: December 15, 2012, 01:25:36 PM »
Re the drip feed.

Won't you have problems maintaining a steady drip rate as the rate will vary as the head in the supply changes ?

Dave

Jep, There are few ideas there, sort of IV-route, but that's where "mechanized drip feed" is something to play with...I'm googling DIY peristaltic pump and thinking a way to bolt onto drive chain. The big idea  :loco: is to use it as a valve and as a dosing unit.

Any ideas...this is really not my comfort zone just contemplation.

Pekka

Offline PekkaNF

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Re: 4*6" band saw bodge, Phase one
« Reply #4 on: December 16, 2012, 07:32:38 AM »
Little more testing:

1) I was concerned about the space requirements for these, they will require almost extra 40 mm on span and if the feed would be greater then band saw blade flex might be an issue. I'm workking here with a hobby machine and hobby conditions, I don't know if this is an real issue or just a theoretical one.

See first picture "Nozzle spacing". Because of the way the saw is build, blade guides don't clear clamp and table structures anyway, without any modifications situation does not change that much. This picture also gives an idea of test rig.

2) Tested coolant applicator, reservoir  was  20 ml syringe and head about 200 mm. It was a royal pain making small enough flow restrictor at the end of the pneumatic tubing. After repeated tests I stuck a piece of plastic tubing that had heated and nipped most closed to give any usable restriction. Well least there is some real flow potential here.

Tested and 10ml of emulsion was just enough to cut 20 mm MOC on a bit too slow feed. See picture "1stMOCtest".

 I was anticipating the emulsion to cling on teeth, but it's really hard to even see it, on the other hand exit side cleaning nozzle shows steady stream of coolant. I see none of the coolant dripping out of the applicator when band is moving. I'm really wondering how much of the coolant is actually on the teeth and how much on the non cutting part. Some more testing and photography to do.

3) I was anticipating swarf removal to be more of an issue, but least with this amount of oil and this iron very little of air is needed. I can go very much smaller and then it doe not work anymore, but 1 bar (14 psi) and very little flow seems to do the trick without atomizing the coolant. The coolant drips out of the "venturi" holes.

So this goes now for a little while as it is just to figure out how does it endures normal work before I commit more involved compressor approach.

I think I'm going to test a little more of this total loss drip feed idea, I think I have some stuff lying around. I have no doubt - this can be made to work, but I need to eliminate all small orifices, eventually they would block. Another thing is that it needs a little more adjustment range and an easy way (or automatic) way to switch drip on and off.

Pekka

Offline PekkaNF

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Re: 4*6" band saw bodge, Phase one
« Reply #5 on: December 16, 2012, 08:47:47 AM »
And some more testing.

I found IV-drip that I saved long time ago. It's pretty much this type:
http://i147.photobucket.com/albums/r287/uscmba04/iv_drip_system.jpg

I used thumbwheel and tube. On the first picture this is staged to bandsaw to show componenets. But in use magnetic base with 20mm syringe was placed over a tool box, to give about 500 mm head.

The thubwheel allowed complete cut out of the flow, and pretty easy adjustment of the flow. It seems to work pretty good this way.

I cut some keystock and some 20-25 bars of different origins and noticed something rather interesting:
* This swarf removal nozzle removes not only swarf, but also removes the coolant pretty efficiently.
* If the swarf removal nozzle is removed, whole lot less coolant is needed, but eventually some swarf accumulates on the band and knocks off the applicator nozzle.

See last picture, it's easy to notice that whole more coolant is being circulated on the blade...actually it show in real life better than the picture, but difference is noticeable.

I think that there is really much truth on fog/mist coolant application argument that very little of the coolant is needed when sawing if the coolant is placed right.

Now I used about 5ml per cut (20-30 sections) and even that looked excessive. Hmmm.. Am doing everything right?

I have been using old and very dull band saw blade for these tests. Maybe should test with a good band before jumping into further conclusions.

Pekka