Using a router for resaw

[MechanoMan]

I'm building a 4'x8' CNC router.

One thing that came to mind is that I REALLY need the capability to resaw. As a reminder, this is where you'd take like a 2" plank and saw it up into 1/8" thick pieces of the same size as the plank, or whatever size you need. Of course, a router could plane down a 2" plank to 1/8" but it's absurdly wasteful.

I had been looking at the Rikon 10-325, long praised as a relatively cheap, but high quality resaw-capable bandsaw. Still $1000, takes up floor space I don't have, and it's a 13" max resaw capacity, which is "quite good", but I might need more.

I already saw this thread: 56895-cnc_resaw_mini_sawmill_project, but he based it on already having a $3800 Laguna resaw. Of course it also has to work within the Laguna's resaw capacity.

So, I'm just wondering- could the router gantry be retasked as a resaw?? I can see real value in this, but it's also pretty absurd. Resaw forces can be pretty high, and usually require a ~2HP motor. But, being CNC, I wouldn't be disappointed if the cut took 4x longer without me being there holding it.

I'd imagine the blade would run horizontally, which isn't like a spindle at all, there'd be large torsion forces in two directions and the process is sensitive to deflection. Seems like it'd need to mount the two wheels at two difference spots on the gantry, but that would mean two Z-axis slides, which would probably need two identical Z-axis drives and another Geckodrive channel, probably even a larger power supply.

Any ideas here?

[ger21]

Basically what you're talking about is a miniature portable bandsaw mill, used for turning trees into lumber. This would take up far more space than a regular bandsaw, imo.

There's no "cheap" way to get greater than a 13" resaw capability.

[louieatienza]

Some industrial resaw bandsaws cut on the flat - Grizzly sells a few models.

[zool]

MechanoMan stated: "Resaw forces can be pretty high"

In designing a machine, look at where the forces are initiated, how they are magnified, how they have their directions changes, where they are transferred to, and how to cancel or eliminate them. Gerry's thoughtful suggestion to look a bandsaw lumbermills is well taken as the designers and manufacturers have thought about these forces and how to address them since the idea first came up.

Another example of the design engineering of addressing anticipating forces and how to dissipate them is the front suspension of a rear wheel-drive automobiles and trucks. [I am not an engineer mind you, though got hooked on thinking about it when an engineer friend of mine who worked for GM for years on designing suspensions explained what suspensions do and how they interact with the whole structure of a motorized vehicle to me one day and it been fascinating to me since.]

If you visualize the "resaw forces" by using force vectors, it will greatly assist you in the conceptualization phase of your design.

Take a look at these:

Force - Wikipedia, the free encyclopedia

Addition of Forces

This youtube video puts forces in terms of X-axis and Y-axis, which anyone conversant in CNC knows all about.

components of force - YouTube

components of force - YouTube

Good luck with this!! Woodworkers from around the world are going to beating a path to your door!!!

Back off Louis ......... I am first in line!!

[zool]

Very good demonstration of forces [force vectors] and how to see them in a mathematical sense.

Precalculus - The Resultant of Two Forces - YouTube

Precalculus - The Resultant of Two Forces - YouTube

[MechanoMan]

I'm an engineer and well familiar with forces. Understanding what a force "is" is not the issue here. The interest is in how a router might be adapted to be a resaw.

I might be interested in the idea of a DIY stand-up bandsaw that does resaw. I noted the Jet bandsaw had a riser block you'd put into the column in back to make it taller, and use a longer blade, but everyone who used it says it threatens to rattle apart and produces poor quality cuts.

On thing that comes to mind is that, for resaw, the right-hand side of the blade does not NEED to be open. In theory, one could make a box out of the frame instead of having the upper wheel cantilevered off from a single column on the left. That seems like it would vastly reduce stiffness issues.

Nor does the column need so much clearance from the blade. In general the blade would only need like 1" of clearance. I suppose it could make sense to make a reinforcing support from the axle of one wheel straight down to the other. That's the sturdiest possible design.

The job still seems to ask for a multiple-HP motor, which isn't a cheap and easy thing.

[zool]

From a design perspective what initially springs to mind is that using a three axis router design would limit the length of materials that could be machined, unless the head can be locked for this type operation and there is a mechanism [ pinch rollers??] that moves the material though the cutting head.

The design that arises to me is a fixed horizontal cutting head, with devices [fences] to direct, and thus limit side-to-side travel, as the material is fed through and past the blade, with pinch rollers to move the material into and through the cutting head. A device to raise the cut material from the piece being cut [a "splitter" so to speak, though as long as the bed on the "cut" side of the blade] would remove friction, thus keeping the blade cooler and sharper, and reduce the possibility of the blade being deflected from the downward force of the materiel that is now cut from the larger piece.

MechanoMan stated: I might be interested in the idea of a DIY stand-up bandsaw that does resaw. I noted the Jet bandsaw had a riser block you'd put into the column in back to make it taller, and use a longer blade, but everyone who used it says it threatens to rattle apart and produces poor quality cuts.

I have this saw and the riser. All problems disappeared when I bought these blades Suffolk Machinery - Timber Wolf Bandsaw Blades, and took a lot of time to REALLY set the saw up. I got a 2-inch blade for resawing. Sore shoulders and "drift" are now a thing of the past!

MechanoMan stated: On[e] thing that comes to mind is that, for resaw, the right-hand side of the blade does not NEED to be open. In theory, one could make a box out of the frame instead of having the upper wheel cantilevered off from a single column on the left. That seems like it would vastly reduce stiffness issues.

Nor does the column need so much clearance from the blade. In general the blade would only need like 1" of clearance. I suppose it could make sense to make a reinforcing support from the axle of one wheel straight down to the other. That's the sturdiest possible design.

These both appear to be the reason for the design of horizontal band saws and bandsaw timber mills. Same reasoning why the Y-axis is not often cantilevered.

MechanoMan Stated: The job still seems to ask for a multiple-HP motor, which isn't a cheap and easy thing.

Why not consider gearing rather than horsepower. It seems for this application that torque is more important than speed.

[louieatienza]

In the world of guitarmaking, this guy is one of the most prominant resaw guys around especially for valuable timber. He's made his own fixtures for doing so and might be worth a look: (he's using a laguna resaw bandsaw BTW with a custom manual feed slide)

Borson Precision Resaw

[zool]

Originally Posted by louieatienza In the world of guitarmaking, this guy is one of the most prominant resaw guys around especially for valuable timber. He's made his own fixtures for doing so and might be worth a look: (he's using a laguna resaw bandsaw BTW with a custom manual feed slide) Borson Precision Resaw

WOW!!!!


He really thought everything out....

The wood he gets to cut sure would bring me to the shop every day!!!

[louieatienza]

Originally Posted by zool WOW!!!! He really thought everything out.... The wood he gets to cut sure would bring me to the shop every day!!!

Yeah, cutting a $1000 brazilian rosewood back set to about .100" is pretty damn cool... and the surface he gets is amazing, almost no saw lines...

[MechanoMan]

Hmm... he uses a Laguna "Resaw Master", a $4700 bandsaw. 4.5hp-7hp motors. Wow. Doesn't quite fit my budget and DIY objectives, though. I've no delusions that a DIY solution would automatically be EASY, of course.

Home Built Bandsaw Bandmill - Build your own Bandsaw Sawmill- did a sawmill trailer for slicing trees into lumber.
Hmm this guy did an entire DIY bandsaw- out of WOOD.

[louieatienza]

Originally Posted by MechanoMan Hmm... he uses a Laguna "Resaw Master", a $4700 bandsaw. 4.5hp-7hp motors. Wow. Doesn't quite fit my budget and DIY objectives, though. I've no delusions that a DIY solution would automatically be EASY, of course. Home Built Bandsaw Bandmill - Build your own Bandsaw Sawmill- did a sawmill trailer for slicing trees into lumber. Hmm this guy did an entire DIY bandsaw- out of WOOD.

HELLO! I understand, but I thought the pics of his slide fixture and details of HOW he goes about it (check out the pics of the brazilian rosewood cutting) would be of help! This guy does it MANUALLY with no CNC and he can cut to within a few thous; pretty impressive. You could probably DIY your own cast riser block (or make a pattern and send it to a foundry), and beef up an existing used bandsaw. Or even find an old one on craigslist...

The woodgears guy is a MANIAC! BTW I have his wood gear generator software; very good and handy. And inexpensive! But I don't think I'd be resawing a billet of BRW on a home-made wood bandsaw anytime soon...

I think if you were to make a portable timber mill it would be pointless to CNC it, as you need to only cut to rough oversize dimensions, sticker everything, air dry it at 1 year per inch thickness, bring it inside to acclimate to about 6-7" moisture, surface plane, etc... You could buy an inexpensive guide that can be attached to a 24" or 30" chainsaw and you'd be done for about $800 used. I assumed that since you wanted to CNC it, that you were talking precision resawing....