Thread: Power Hacksaws V's Bandsaws

Ha!

The electrical team has come to the realisation that it's existance is meaningless without the success of the gear team!

I have been looking at wiring diagrams of 2 speed 3 phase motors. It's not pretty but I will have to do more searching before I'm convinced it can't be done! Yet to look at the coolant pump motor but the hydraulic motor (Siemens) has the luxury of all 6 wires in the cover with a diagram for star and delta. So that's a tiny win if I decide to still use it via VFD.

The electrical team is somewhat hamstrung until the cleaning team do their job and get out. Also the electrical team refuses to work on dirty, greasy equipment. Cleaning team is working day/night in between looking after a home from school sick child.

Simon

Just remember, once the electrical team is done there will be wire offcuts, conduit pieces, striped insulation etc scattered around the place and the cleaning team will have to come back in......

How big is the motor Simon? It may be ok just to leave it in star, let's face it you probably won't be pushing it as hard as a commercial user would.

Hi Ueee,

It's only a 0.6/0.8 Kw motor. Not that big but obviously has enough to shear and destroy a bronze worm gear. I think I'm going to have to buy a VFD for it anyway so I may give it a go.

I have been thinking about the switching sequence and the hydraulics. I still can't work out what stops the saw from falling at it's determined feed rate after it has finished it's cut and is lifted to the top by the hydraulic pump.

Also, somwhere between the pump output and the ram, there must be a non return valve (some one mentioned this earlier) I assume it's in there somewhere. The pump outlet hose to the ram is still complete and connected so it's as it should be for correct operation but there is no visible non return valve. It may have one built into the pump.

I know I said I wanted to keep things simple but I can't help but think an automatic sequence run by a couple of solenoids, relays and a PIC program controlling the VFD could be a bit fun!

Cleaning team will be on saw guide cleaning duty tonight while the R&D team will be on youtube looking at Reil Burners for a foundary to pour a worm blank.....

Simon

So what are those slackers on the hydraulics team doing? Having a night off?

Michael

Originally Posted by Michael G

So what are those slackers on the hydraulics team doing? Having a night off?

Michael

Having a stop work meeting becaue EBA negotions have stalled!

Bloody Unions!

OK I have dismantled and cleaned the saw guides and in particular the one with the hydraulics tensioning. I would have taken a pic but the phone has died, so I'll post some pics tomorrow.

The hydraulic tensioner has an adjustment screw which has a plunger that pushes on a ball. When this screw is all the way out, the ball is seated. Screwing in the adjuster pushes the ball out of it's seat which I assume allows increased flow. On the other side of the ball is another plunger that is in contact with the ball and pushes down on a thrust bearing that guides the top of the saw blade.

I'm probably not explaining it properly but the way I see it, the hydraulics don't actually tension the saw blade, the adjustment screw at the top does. But a consequence of the tensioning is increased fluid flow for the down feed. I still don't think it's designed to make feed rate adjustments during normal operations. Why would you put something that will be used on a regular basis right next to a moving saw blade? I think it must be a way of setting the maximum feed rate achieved using the other valve. In any case, the only pressure achieved in this line would be the weight of the saw acting on the ram, so not a huge amount of pressure, not enough for a tensioning system as such.

I got excited when I saw the ball as I straight away thought it was a non return valve but no, it allows flow in both directions, eventhough during operation flow would only occur ever in one direction anyway.

Cheers,

Simon

Originally Posted by simonl

Why would you put something that will be used on a regular basis right next to a moving saw blade?

Well its better than where the adjuster on mine saw is

Originally Posted by simonl

The hydraulic tensioner has an adjustment screw which has a plunger that pushes on a ball. When this screw is all the way out, the ball is seated. Screwing in the adjuster pushes the ball out of it's seat which I assume allows increased flow. On the other side of the ball is another plunger that is in contact with the ball and pushes down on a thrust bearing that guides the top of the saw blade.

Is there a spring between the screw/plunger and the ball? I'm thinking there should be, but that doesnt look like the factory screw.

Stuart

Power hacksaws and band saws have their own advantages and disadvantages. But band saws have much greater overall utility.

Originally Posted by Stustoys

Well its better than where the adjuster on mine saw is


Is there a spring between the screw/plunger and the ball? I'm thinking there should be, but that doesnt look like the factory screw.

Stuart

No Stuart. It's the srew connected to the ball, conneted to the plunger, connected to the thrust bearing. So it's basically a solid connection (through those bits) from the adjustment screw to the thrust bearing and increasing flow rate along the way.


You thinking there should be a spring between the screw adjuster and the ball?

Simon

G'day Bosox
You've missed the fun. Even though we all said "No, no Simon - don't buy it" (because that's the sort of guys we are - wouldn't dream of encouraging another member to buy a machine), Simon lashed out and got an old fixxer upper bandsaw. (starts here - http://www.woodworkforums.com/f65/po...2/#post1648833)
The thread title is a bit mis-leading, as it should now be "Adventures with a Heska" or some such.

Simon, you need to remember that this was a production machine so if it needed to be adjusted because someone wants to interrupt the steel cuts with an urgently needed piece of CI, it could. That's the reason for the adjustable speed control, feed, vice, etc, etc. While it might be regarded as bad practice I'd bet probably the saw was left on while adjustments were made. While it may seem odd to have adjustments next to the blade, that's where the operator's attention would be, so that's where frequently adjusted things are likely to be.

Michael

Just took some pics of the "tensioner":



Pic 1: Main Body
Pic 2: Adjustment knob. The plunger at the end makes contact with the ball.
Pic 3: Adjustment Knob "exploded view" with shaft out.
Pic 4: Looking down the body from where the adjustment knob screws into and makes contact with the ball.


The contactor on the end of the adjustment knob has a clearance fit so that it can pass through to make contact with the ball. The "rings" on the shaft of the adjustment knob are set of hardened rings. I think that perhaps they provide some spring tension and they can squash a little They are almost a very flat cone type washer. Perhaps they have lost some of their springiness over time?

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Cheers,

Simon

Originally Posted by simonl

. The "rings" on the shaft of the adjustment knob are set of hardened rings. I think that perhaps they provide some spring tension and they can squash a little They are almost a very flat cone type washer. Perhaps they have lost some of their springiness over time?

Cheers,

Simon

Those rings would be Belleville washers, acting as springs. It would not hurt to replace them. With them in place the valve is effectively acting as an adjustable one way valve.

Michael

Originally Posted by simonl

Yea OK i know!

Just a thought try Max Billman Castlemaine Billmans foundry and or Griggsbys foundry in Ballarat.some times they have a blue mistake] or do some extras in non ferrous worth a try before it goes back to the pot might be able to score a blank ??? for your worm wheel.

Originally Posted by j.ashburn

Just a thought try Max Billman Castlemaine Billmans foundry and or Griggsbys foundry in Ballarat.some times they have a blue mistake] or do some extras in non ferrous worth a try before it goes back to the pot might be able to score a blank ??? for your worm wheel.

Thanks Ashburn.

Also I have received a price on a new replacement worm from Jaespa, Germany. It's EU144 plus shipping. That would most likely be a last resort as it would no longer be a cheap saw by then. I'd also want to be very confident that nothing else is wrong with it.

In terms of casting a blank, my three options in order of preference are:

Cast it myself
Ask very nicely if someone else on this forum can help me,
Pay a commercial foundry to do it.

Simon

Hi Simon,

Originally Posted by simonl

The hydraulic tensioner

Where did that term come from? I think its around the wrong way, the tension(well deflection really) of the blabe adjusts the hydraulic system. The reason its there is because it cant be anywhere else. Manually tighening that screw increases downfeed. When the back of the blade is pressed against the other side of the valve hard enough it slows down feed. *

Those washers should be one up one down one up one down right?

So how do you feel about 60%ish power?

Stuart

*I think