Building a Band Saw Hydraulic Downfeed with Lift Function

[M.B. Naegle]

I've got an old Band Saw that I want to fix up and while I'm at it, add some function too. One feature I want to add is hydraulic down feed assist (currently has a big adjustable coil spring), and I'm thinking it would be handy to add a lift function to it too. Obviously I'll need more than the typical closed loop control that bleeds from one side of the cylinder to the other, so I'm thinking a pressurized system with a directional control and two metering valves. Then I can set an adjustable slow down feed, and a faster return feed. I have actuators, pumps, valves, etc. already, so cost of the update isn't an issue to me. Just looking to add some practical function utilizing stuff off the shelf. I plan to leave the current coil spring set-up in place so the hydraulic lift isn't doing all the work.

I first considering doing this with pneumatics, but I've read that they perform poorly in an application like this, so I'd need to add a hydraulic pump. My first question though, why can't I use the cutting fluid and it's pump to also power the hydraulics? Assuming I keep the fluid quality up, the reservoir full, and add/maintain a filter to keep swarf out of the valves, how much trouble am I getting into? I'd like top run water soluble fluids, but the saw is old enough to have run cutting oil originally, so I could stick with that. I'm thinking going slightly bigger on everything would help too, like 3/8 to 1/2 NPT parts instead of 1/4" to limit the chance of a foreign particle causing issues. The coolant pump I'm using is an old Brown & Sharpe #1 gear pump, which can run 300 to 900 RPM producing 1 1/2 to 4 1/2 GPM. I have an extra pump that I can use to run the cutting fluid and hydraulics separately, I'm just wondering if combining them is at all feasible.

 

[gustafson]

Personal bias perhaps but I think I would go electric

 

[Gordon Heaton]

First rule of hydraulics is to keep it clean, but I think for this application it might work ok for years if you use and maintain a good filter for that part. Does the oil pump have the capacity to do both jobs at once? (I realize you have the flow, but at what pressure?) If not, giving priority to the lift without screwing around with valves might be complicated and/or expensive.

Since you have another pump I would personally go with that.

 

[DDoug]

What does DoAll doo ?

 

[Gordon Heaton]

What does DoAll doo ?

All, of course.

 

[dkmc]

A customer of mine has a Horiz doall that has the typical 'closed loop' oil filled cylinder for slowing the down travel, plus a pneumatic cylinder to lift the head, and a double chambered air cylinder on the vise. It's very handy to use, and quick acting. The oil cylinder for downfeed eliminates the problems you mention when using pneumatics for that function. IMO adding a full on hydraulic power unit is overkill, but I've done that with projects myself. Using the coolant pump for hydraulic power is a novel idea. But it might turn out sounding better than working well in actual practice.......sorta like the Amphicar.

 

[Garwood]

Keep it hydraulic.

I've had a few semi and auto saws and none are simple. One thing I would do is mount a small cylinder on the outboard end instead of a large cylinder near the pivot. Better control this way.

That hydraulic auto up part is a big undertaking for the little it accomplishes.

 

[dkmc]

All, of course.

Does that mean Doosan will Do Some but not Doall ?

 

[Nmbmxer]

Air over oil works very well for this type of thing imho. Your metering orifices are much more effective on oil than air and it isn’t as squishy.
Can be as simple as a small tank filled with oil going to an air cylinder with a checked orifice on the line. Pressurize the tank and the saw raises, relieve vent the tank and it falls against the orifice.

 

[bsg]

What does DoAll doo ?

We have a Doall 400M at work, it just uses pneumatic cylinders and spring assist......works fine and seems easy to duplicate.

Kevin

 

[604Pook]

Our Hydmech, has hydraulic. can adjust down feed pressure etc. I wouldn't use my coolant for anything but coolant.

If you got one of the oil cylinders used on the cheaper horizontal bandsaws to control down speed, and a air cylinder to lift it, that would work good, and be easy.

 

[M.B. Naegle]

We have a Doall 400M at work, it just uses pneumatic cylinders and spring assist......works fine and seems easy to duplicate.

Kevin
View attachment 387227View attachment 387228

The issue with pneumatics on a saw is that they are hard to get to have consistent pressure and fluid movement (or so I've read). Does the spring on this saw mitigate that issue, perhaps since the cylinder has less gravity against it?

The saw in question is an ancient Napier. "It's got good bones!" or at least has a nice heavy iron construction that I'm wanting to build on with other features like the hydraulic assist, VFD speed control, and adding guards! The arm is a fairly substancial casting, but with the fulctum point and the assist spring, it dosn't take much force to move. I'm thinking about adding the cylinder on the left beside the spring.

 

[MrWhoopee]

The coolant pump will not generate sufficient pressure for this purpose.

Similar to you, I built my downfeed control entirely with parts on hand.

Frankensteinish, the cylinder is definitely over-kill. Top valve is fine downfeed control, middle valve is rapid down, bottom is the check valve for raising the head.
I put compressed air to it once when building it. I was lucky I wasn't in the way when the head shot up.

Air over oil sounds like the way to go for lift.

 

[Strostkovy]

Poor man's hydraulic servo is two cylinders plumbed together, with a linear actuator pushing on one.

With the price of stepper driven linear actuators (very cheap) and simple one axis g-code interpreters or step generators (also very cheap) this is the way I would go, as it lets you use all off the shelf parts and keep the electronics in a safe place.

Granted I have never used nice hydraulic speed controls, but the cheap ones are terrible. I just want to set my feed rate and leave, without staring at it and tweaking a knob until it looks sort of right I guess.

 

[bsg]

The issue with pneumatics on a saw is that they are hard to get to have consistent pressure and fluid movement (or so I've read). Does the spring on this saw mitigate that issue, perhaps since the cylinder has less gravity against it?

The saw in question is an ancient Napier. "It's got good bones!" or at least has a nice heavy iron construction that I'm wanting to build on with other features like the hydraulic assist, VFD speed control, and adding guards! The arm is a fairly substancial casting, but with the fulctum point and the assist spring, it dosn't take much force to move. I'm thinking about adding the cylinder on the left beside the spring.
View attachment 387231

I stand corrected, the large cylinder is pneumatic for lifting and the small one is hydraulic for the feed!
The spring is considered a counter balance.
This saw also has an adjustable travel limiter for stock size to speed up production.




Hope that helps........

I think I still have an aftermarket hydraulic down feed assembly I bought years ago for a Wellsaw if anyone is interested?

Kevin

 

[Scottl]

A customer of mine has a Horiz doall that has the typical 'closed loop' oil filled cylinder for slowing the down travel, plus a pneumatic cylinder to lift the head, and a double chambered air cylinder on the vise. It's very handy to use, and quick acting. The oil cylinder for downfeed eliminates the problems you mention when using pneumatics for that function. IMO adding a full on hydraulic power unit is overkill, but I've done that with projects myself. Using the coolant pump for hydraulic power is a novel idea. But it might turn out sounding better than working well in actual practice.......sorta like the Amphicar.

100% agree. Hydraulic damper for down travel and pneumatics to lift the head is far simpler and eliminates the complexity of pumps and related valves.

 

[memphisjed]

Hydraulic like hyd mech, with positive downfeed. Most of the time the cylinder is pushing head down faster - not slowing it down.
If hydraulics are on the shelf you have regulator from down valve to cylinder down to set your force. A flow vavle after regulator to set speed.
The return line is just cylinder to valve- wide open.

Waterhydraulics is very cool.

 

[dkmc]

memphisjed​

Hydraulic like hyd mech, with positive downfeed. Most of the time the cylinder is pushing head down faster - not slowing it down.


Not on any 3/4" 1" or 1-1/4" blade horizontal bandsaw I've ever seen, used, or owned. They are all regulating gravity, not pushing down, it's not needed the weight of the head is plenty of force on the blade. Autofeed Cold saw, maybe.

We have a Doall 400M at work, it just uses pneumatic cylinders and spring assist......works fine and seems easy to duplicate.

Kevin
View attachment 387227View attachment 387228

Actually I think that's just like the customers saw I mentioned

EDIT
Yes, post #15 .....that is probably the same system as the customers saw.
Nice schematics BTW!

 

[memphisjed]

memphisjed​

Hydraulic like hyd mech, with positive downfeed. Most of the time the cylinder is pushing head down faster - not slowing it down.


Not on any 3/4" 1" or 1-1/4" blade horizontal bandsaw I've ever seen, used, or owned. They are all regulating gravity, not pushing down, it's not needed the weight of the head is plenty of force on the blade.

The weight is not enough. A 1.25 inch blade runs with 2500 plus pounds of force in a 3 inch cut to maintain proper feed rate. This is vertical, horizontal feed is 2/3 of vertical. Hydmech claim to fame originally was the positive force feed on scissor saw. Pedinghaus uses a tiny .9 kw servo on ball screw for horizontal-which can keep good feed rate in horizontal speeds.

A drill press needs some help to push the bit.

 

[dkmc]

The weight is not enough. A 1.25 inch blade runs with 2500 plus pounds of force in a 3 inch cut to maintain proper feed rate. This is vertical, horizontal feed is 2/3 of vertical. Hydmech claim to fame originally was the positive force feed on scissor saw. Pedinghaus uses a tiny .9 kw servo on ball screw for horizontal-which can keep good feed rate in horizontal speeds.

A drill press needs some help to push the bit.

Perhaps larger saws with 2" wide blades work that way? Can you specifically list some brands/models of saws that are Hyd down feed? I've never seen one.
Here's my Welles 1270, it runs a 1.25 blade. The head weighs around 400lbs. There is a lift cylinder that's single 'up'
acting.... to raise the head.
The weight of the head is more than enough to make the blade cut up to 12" OD steel barstock.