I’m new to the forum and somewhat new to CNC’s. Well, in 1980 I added motors to a milling machine and wrote a sw language to drive it, but that was a long time ago and it used a teletype machine, so, I’m really starting over.
Anyway, I’ve gotten interested in woodworking and I’d like to speed up the process of making straight cuts. I’d like to replace (or just not pay for in the first place) a table saw, a miter saw, track saw, and a panel saw. A cnc panel saw comes to mind and the low rider seems to be a good place to start. The question is what would I have to change? Better yet, has someone already done this?
General requirements are:
able to handle a 4'x8' sheet of plywood
cut at any angle within that area
cut up to 2" thick boards, or
cut 2" into a 6" glued up board
be able to get around or over hold downs and fences.
use a circular saw
So, I need 4 axis of control (X, Y, Z, and alpha (blade angle)). A fifth axis for blade tilt would be nice but I'm going to ignore that unless someone says it's easy. Accuracy is probably fine at around 1/32". My understanding of the low rider is I'd need a controller that has 6 motor drivers (2 for x, 2 for y, 1 for z, 1 for alpha). The z axis would be longer than the 3 odd inches mentioned for low rider. I don't know about torque on the saw but I assume the blade should line up with the alpha axis.
I assume someone has already done this. Or struggled with it. I’d really like to hear people’s insights and pointers. The less I have to design the better so your feedback is greatly welcome.
I think you would be covering new ground implementing an angle change like that. And I dont think anyone has mounted a circular saw.
The mpcnc has 2 x, 2 y, 1 z motor and the lowrider has 1 x, 2 y, 2 z, but for axes that have two motors, they are driven in series from a single motor driver, so only 3 drivers are needed for the standard build. You should have open slots (extruders as far as marlin is aware) for at least one more axis.
I think some have implemented a 4th axis rotating a workpiece along a horizontal axis. This azimuth-controlled saw will be cool, but I’m afraid it’s new territory.
In the same spirit, I can see potential with an angle grinder eliminating the need for a metal-cutting bandsaw I can’t justify buying.
You really just need a table saw. A used craftsman 113 with the cast iron top and hang on the back motor would perform those jobs pretty well, except you cant lift and push a huge 4x8 sheet easily. So a circular saw for rough cuts is another good investment.
To use a standard low rider, you need to make a design (which can be as simple as a rectangle) and open it in the cam tool, which you then set up your cuts (like outside the rectangle, with a certain size bit, depth of cut, speed) and it spits out the toolpath file, which the controller can then use to drive the router to specific locations and cut out the material. You might be able to push it to 2", but you won’t be able to tilt the router bit. It can cut angles like cutting a triangle or hexagon easily, but not make bevels.
Adding a circular saw is unecessary. The forces on the circ saw are strong and unpredictable. Kickback would immediately destroy it and send a circular saw across the room. Plus, a router can cut through material just fine without a circular saw blade. It take as many passes needed and you can be present, but doing other things.
Adding an angle for the circular saw is either very niche or completely custom. There was some work on a tangential knife, and that was promising, but it would not work with a circular saw.
You can cut straight parts out all day on it. Cutting 2" deep is a big ask, but possible. You just don’t need the circular saw setup and it won’t cut bevels and it won’t be faster than a table saw.
AFAIK, no one has tried this. If you do, please be safe and please share what you’ve found.
I did not know that, thanks. I’m a bit surprised that one motor driver can drive two motors. I guess they’re current controlled? Anyway, that is a great bit of information.
I think that gets close to an important issue. To me, it seems like CNC machines are all about spending a lot of time up front getting something big ready to be done and then letting it go. As you say, let it do its thing while doing something else. That’s different from how most saws are used. I need a board so I cut a board. Setup time is short. Execution is short. On a miter saw it’s even less time - measure the board, line it up, turn on the saw and cut. Now, I might not get things that fast but I certainly don’t want to wait 5 minutes for what would take less than a minute. What that setup looks like with a cnc panel saw is certainly something to think about.
I’ve never seen a circular saw get jerked so hard from my hand that it would throw itself across the room if rather than my hand it was connected by steel tubing and what not. I do have my father-in-laws radial arm saw and that is the jerkiest saw I’ve ever seen. It just wants to run across the wood. Kind of like using a router in the wrong direction. But it isn’t enough to jerk the tool out of my hand. A good question is how strong are stepper motors? My impression of a stepper motor is it’s basically open loop, so would that be an issue? Another option is a brushless motor which would use feedback. So if the saw does jerk then the motor would hold it in place. Hmmm. I originally thought of brushless motors just for speed until I saw the price of the controllers.
Anyway, I’d think kickback on a table saw is equally as dangerous. Not flying saws but flying wood. Especially on an old tool that doesn’t have a riving knife. But it is a good point, put a riving knife behind the saw blade.
Another issue is hold downs. With any type of saw both sides of the cut needs to be held. There are some simple hold down ideas for use on woodworking tables (bench dogs and a wood mallet) that I think would be useful. It just requires a thick table. And probably some software that says “no fly zone for the saw.” Which comes back to the user interface.
Pretty sure you can forget it, unless you’re able to develop a custom firmware and custom tool path creation software.
Cutting with a circular saw is very different than cutting with a milling bit. The bit can be assimilated to a point while the saw is a segment, moreover it’s not really a segment but some kind of curve if you take the thickness of the material into account.
The only way I see for it to be “easily” adaptable would be to use a reciprocating wire saw instead of a circular saw. But then you would have to pre drill everything and remove/reattach the wire for each travel. Might be possible to make this task automatic, but that would need a very clever design and lots of custom parts. That’s the only way I see you could still use standard firmware, otherwise I just don’t see it working with current solutions.
In any case, the Lowrider frame doesn’t seem adapted for that use. If you’re gonna attach a 1500-2000W circular saw to something, it needs to be sturdy. Kickback can throw off the saw, it’s not because you never heard of it nor seen it that it does not happen all around the globe on a daily basis. I wouldn’t trust anything else than a 100% metal frame frame (steel or aluminum profiles at least) to handle such a dangerous and wild tool. Especially since, in this case, it would be driven by electric steppers who have no clue about whether they are moving too slow or too fast.
Kickback on a circular saw is scary… I’ve never had it happen and I’m very glad. Google for some videos of what it looks like. It will literally throw the saw at you.
Kick back is going to happen when you get wood movement or if the blade isn’t straight in the cut. I’m sure you’ve had it happen where the blade binds, or twists in place. You instinctively turn the saw off or slow down the cut. The cnc will happily keep going.
Table saws are dangerous and cause something like 40% of woodshop injuries, but I would argue they get used at least 40% of the time too. Having a rivinf knife is helpful. Keeping your hands behind the blade means your hands can get pulled into the blade during kick back (IMO this is much more the danger than the wood hitting you). But using push sticks and proper cutting techniques can turn it into a tool you can use daily for a lifetime without injury.
Here is a perspective I mostly agree with. A crosscut sled on a table saw is more accurate and cleaner than a miter saw:
I wouldn’t want to do something like installing flooring using only my table saw, but most stuff is more enjoyable on my table saw.
You could definitely build a panel saw, with a digital read out or even motors. That sounds more like what you need.
This shouldn’t be too difficult as all I can do is a series of straight cuts. Each cut is 2 points, a depth, and a speed. That’s fairly simple gcode to generate.
I was thinking about how to deal with going through denser wood. A stepper motor has the problem of being open loop and can lose steps. I found a stepper motor with a sensor and feedback that will detect lost steps and then add more where needed. Then I found a brushless motor controller (that implicitly has feedback) and is also fairly inexpensive and open source (they’re used in electric skate boards). They can detect when the motor starts slowing down as they’ll start increasing current to the motors to compensate. I suppose sensors could also be put on the blade motor. Anyway, a current limit can be put on the motor controller. Something that could work would be to throw a fault if the current limit is tripped and then either slow the motor down, or halt for a bit, or just stop the saw. I don’t think gcode can handle exceptions so that would be a change.
The other types of problems that cause kickback are not keeping the blade straight and not supporting the wood correctly. A cnc with feedback can make sure the blade is straight. As for supporting the wood the cleverest thing I’ve seen is using a sheet of foam as a sacrificial board.
And anything involving a router is much messier.
It could be. I need to think about how I’d like to use it. I saw a miter saw with a motor controlled fence. Just dial in the length and it will line everything up. Lining things up quickly and accurately is a big part of what I want.
It actually isn’t too bad, with a 1/8" bit, which is about the kerf size of a table saw blade. With the dust collection attached, it’s definitely less dust than a miter saw or a circular saw, but not as clean as my table saw with DC.
I was getting lots of dust even with dust collection then added a ceiling mounted workshop air cleaner for a couple hundred. It cycles all the air and takes out the dust in almost seconds… air is clean as outside. Scary how often I wind up vacuuming out the filters.
