Hi guys,
While lowering my table saw blade to change it, I had the idea of doing it mechanically.
I'm wondering if a stepper type motor would work.
Right now there's a crank wheel attached to a center shaft that raises and lowers the blade approx 5 inches.
Would it be possible to attach one shaft to the other using some sort of a dc motor to produce a high torque low rpm output?
Thanks
Ricxh
Without seeing a technical drawing of the machine and getting details of the forces involved how can one tell?
When people ask vague questions like that about dangerous things like a saw I get very worried.
...R
Thanks for the advice and you need not worry..
I've used this machine plus a variety of others I own without mishap for approx 20 years.
If I knew the forces involved, I would have included them in my question.
As far as a technical drawing, I have a 3D drawing of the saw itself.
I don't know what that type of a technical drawing would accomplish since I just need a motor to turn the shaft to raise and lower the blade mechanism.
I appreciate the time you took to answer my vague question.
Regards,
Richt
Yes, a stepper motor would work but it seems inappropriate. A stepper would be used for precision e.g. raising the blade 3/32". Since you only want to raise or lower the blade, you would be complicating things with a stepper. The system you suggest demands limit switches. Since only two positions are required, the limit switches could also serve to determine when those positions are attained. In lieu of the stepper, there are many geared motors with high torque available at low cost.
Would it be possible to attach one shaft to the other
This I do not understand. I guess it means the motor shaft to the raise/lower crank shaft. If so, it seems too difficult and would obstruct manual operation of the raise/lower function. I wouldn't do this project at all since I know damn well that sooner than mid way through I would be scolding myself for doin' all this stuff for an occasional task. However, if I was just doing it for entertainment, I would prefer to attach a sprocket or toothed pulled to the existing crank wheel and go from there.
In any case, you have to know what torque is required to select a motor.
- Scotty
richt:
If I knew the forces involved, I would have included them in my question.
I understand. But you would be surprised how many people leave out important information even when the do know it.
However, you will need to figure out the force in order to determine how much torque is required from the motor.
Post your 3d drawing (assuming it includes the relevant parts), A photo of a simple hand-drawn sketch would be a big help. See this Image Guide
One idea to put in your mind is a screwed rod driven by a simple DC motor with limit switches to stop the motor at top and bottom. Probably no need for an Arduino.
...R
richt:
Would it be possible to attach one shaft to the other using some sort of a dc motor to produce a high torque low rpm output?
Of course! If there is a shaft, it can be turned. However, if the height adjust is combined with the tilt, it might be rather complicated.
It wouldn't have to be a stepper motor, a DC motor with gearbox would work as well.
The effort required to engineer a lazy method of moving the table will probably be greater than that required to manually do it - unless of course you are changing blades on a daily basis.
Have you considered the use of a windscreen wiper motor which comes complete with a worm-drive gearbox
My engineering prof used to say "laziness is the true motherhood of invention". Using a table saw in the first place is the lazy method of cutting wood, is it not? So it is kind of silly to say to an engineer "don't be lazy", replacing people with machines is the whole point of engineering.
Anyway, I regard Arduino as primarily a learning tool, so while a motorised table saw height adjuster may not be ultimately practical, something will have been learned on the way.
A windscreen wiper motor would probably work, just need a 12V supply and a switch.
bobcousins:
replacing people with machines is the whole point of engineering.
What a negative view of the profession 
...R
Robin2:
What a negative view of the profession
Nevertheless, it is essential to the modern, western lifestyle. Even for an average person who uses around 30,000 kWh per year, that is the equivalent of about 400 people working for you. In the past, those people were servants, serfs or slaves, and you would have to be very rich to afford that many servants. Other sources of energy are available, but the way we have found to exploit those sources is via machines designed to use them. I would view the elimination of servitude a positive thing, but you may think different.
Of course, machines also replace animal labour in general. I guess if we all kept 40 or so horses we could get the same energy use. That would be a lot of horses...which have their own drawbacks. Indeed, in cities the "automobile" was hailed as a solution to the problems of ordure and fatalities caused by horses.
Another way to look at it, is that only the availability of cheap energy + machines creates the wealth that enables our modern lifestyle. Without that cheap energy, we would have to go back to a peasant lifestyle and probably some sort of indentured labour for everyone but the very rich.
Anyway, I think we have strayed way off topic
bobcousins:
Without that cheap energy, we would have to go back to a peasant lifestyle and probably some sort of indentured labour for everyone but the very rich.
I don't think we are any happier now than we were then.
Anyway, I think we have strayed way off topic
I agree.
...R
Robin2:
I don't think we are any happier now than we were then.
That may well be true. That's really one for philosophers to solve 
jackrae:
The effort required to engineer a lazy method of moving the table will probably be greater than that required to manually do it - unless of course you are changing blades on a daily basis.Have you considered the use of a windscreen wiper motor which comes complete with a worm-drive gearbox
New to the forum here:
This was the first thread I read and I find it kinda sad to see such negative input to something that could be a great idea. For us beginners, simple steps like this lead to learning how to use these things and that can lead to more complex uses and may even something that lots of people find useful.
I bought my arduino uno with a stepper motor shield to do this exact idea with the blade height and the blade angle. To be able to set up the blade to a precise angle and height with one touch and it be repeatable can be invaluable to one who's hobby is woodworking (even better for those that make a living at it). Think how good it could be to add a keypad where you could have preset angles/heights as well as to be able to type in an angle/height and have the blade move directly to it's position.
Also, to keep safety in mind, once the saw blade is started, the arduino would be locked into position so the blade cannot be moved while running.
Please remember, we newbies are learning. It's not easy for all of us and sometimes simple tasks that seem useless to you are invaluable to us when it comes to figuring out programming, coding and configuring the arduino... Thanks.
1 Like
Can you get a torque wrench on the shaft ?
cblackard:
This was the first thread I read and I find it kinda sad to see such negative input to something that could be a great idea.
I don't see anything unreasonably negative in the earlier Replies here.
In your own Reply you have already displayed more knowledge of the subject than there is in the Original Post and you have also acknowledged the need for safety in your first Post.
I don't see any question from you and if you need help with your own project I suggest you start a new Thread.
...R
I'm afraid that negativity can be a problem for "old hands" who have seen a lot of newbies come and go with what they think is a great idea and "should be easy", yet our experience tells us that it is likely not easy, often even impossible.
Then the question is, is the best way to help someone by collaborating with their probably futile endeavor, or gently suggest that they would better direct their effort somewhere more productive. We really don't want to encourage people to spend a lot of time and money on something that is never going to work.
It's a judgment call, and not easy to get right. I often compose a reply such as "sorry dude, that is next to impossible, you are wasting time", but don't hit "Post". It's their time to waste, and if they get no replies they may figure it is difficult.
I try to balance between providing useful help and cautioning against unrealistic expectations. Obviously, the point of asking others is to get their more informed opinion, sometimes that opinion might be "don't bother". It really shouldn't be a surprise to people that not everything that can be thought of is actually practical to implement.
cblackard:
I bought my arduino uno with a stepper motor shield to do this exact idea with the blade height and the blade angle. To be able to set up the blade to a precise angle and height with one touch and it be repeatable can be invaluable to one who's hobby is woodworking (even better for those that make a living at it). Think how good it could be to add a keypad where you could have preset angles/heights as well as to be able to type in an angle/height and have the blade move directly to it's position.
How far did you get?
Robin2:
I don't see anything unreasonably negative in the earlier Replies here.In your own Reply you have already displayed more knowledge of the subject than there is in the Original Post and you have also acknowledged the need for safety in your first Post.
I don't see any question from you and if you need help with your own project I suggest you start a new Thread.
...R
I wanted to take a moment to answer the comments made by robin2. Its not an attempt to start a war of words, but simple clarify the original post I made. To me, the comments below seem negative as if to say it's a waste of time to attempt this:
Excerpt from scottyjr "I wouldn't do this project at all since I know damn well that sooner than mid way through I would be scolding myself for doin' all this stuff for an occasional task."
Excerpt from jackrae "The effort required to engineer a lazy method of moving the table will probably be greater than that required to manually do it."
Do not mistake my words as an attempt to argue with anyone on this forum. I just want to point out (maybe even enlighten) to those that are experts, advanced users, etc... at using an arduino that there are beginners out here need to start with basic projects in order to learn and grow into more complicated projects. Although our ideas and projects may seem like child's play and a waste of time in their eyes, it's never a waste of time if you can learn from it.
As for your 2nd comment, I do have the knowledge for what I want to 'achieve' with the hardware/software which is the same as the OP, but what I do not have is the knowledge to 'execute' it. I am a newbie to arduino and programming and I hope to be able to learn how to program this project well enough to be able to create other projects for my shop to automate other tools such as my lathe and milling machine.
To your final comment, you are correct in that you do not see a question from me. I do not have a question and do not yet have a need to open a new thread. I made my comments in this thread because it has one of the elements found within my project and I wanted to share that with the OP in the hopes that it can encourage them to go forward with it and maybe even take their project further than a simple motion control for changing the blade.
Again, please do not take this as a war of words, but more as an explanation of the comments I made. I will comment no further on it as it is off topic to the thread.
bobcousins:
I'm afraid that negativity can be a problem for "old hands" who have seen a lot of newbies come and go with what they think is a great idea and "should be easy", yet our experience tells us that it is likely not easy, often even impossible.Then the question is, is the best way to help someone by collaborating with their probably futile endeavor, or gently suggest that they would better direct their effort somewhere more productive. We really don't want to encourage people to spend a lot of time and money on something that is never going to work.
It's a judgment call, and not easy to get right. I often compose a reply such as "sorry dude, that is next to impossible, you are wasting time", but don't hit "Post". It's their time to waste, and if they get no replies they may figure it is difficult.
I try to balance between providing useful help and cautioning against unrealistic expectations. Obviously, the point of asking others is to get their more informed opinion, sometimes that opinion might be "don't bother". It really shouldn't be a surprise to people that not everything that can be thought of is actually practical to implement.
How far did you get?
bobcousins
To answer your question about how far I have gotten, I just received my arduino with the cnc shield a couple of days ago in the mail. I still have my keypad and display on order so for now I am just playing with the arduino coding trying to learn how to make it do things. I have a couple of small stepper motors to work with, but will need larger ones for the final project.
I hope I can show proof of concept before ordering the larger stepper motors. If I can get this project working, then I hope to apply similar ideas to several of the tools in my shop such as my lathe and milling machine.
richt
By all means, work on this project. Learn from it. If you think about taking the project to another level by controlling the height of the blade, then I would go with a stepper motor. Limit switches would be a must, I think, with any setup to insure nothing is over driven and jammed or broken. having a stepper just allows you to expand if you want to later.
Oh, and good luck with your project...
You can buy electrically driven screwjacks which deliver large linear forces - those , with a couple of microswitches as limiters might do the job.
Try Ebay
Allan
But you omitted to mention that, in response 6, I tempered my so-called 'negativity' with the positive suggestion that you consider the use of a windscreen wiper motor complete with worm-drive gearbox and also the caveat that you might be changing saw blades on a daily basis (in which case a power driven system would be a useful asset).
A couple of advantages of stepper motors if used as a direct drive; they can be used without a limit switch because they stall easily, and they can be de-energized to allow manual override. If you have a lot of gearing those features can be lost though.
With a DC motor you would typically use a lot of gearing to reduce RPM, and ofc with a worm drive back driving is not possible. In that case you would need a clutch or something to allow manual operation; and an emergency stop button would be a good idea.
For me the electronics and software is the easy part; finding a neat way to fit a motor and drive to an existing machine not designed for it is the hard part. My guess is a belt drive would be easiest to fit.
Converting manual mills to CNC operation is quite common, I didn't find any examples relating to other machines like table saws.