A tiny tabletop bandsaw Part II (finishing the C-frame)
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- Опубліковано 4 жов 2024
- Short heads-up of the progress regarding the construction of this machine.
Anyone who has a suggestion regarding the cause of the too low speed of the motor-driver combination is more than welcome to educate me in the comment section.
No music this time. Sorry, too much to tell.
Thank you for showing your process of applying the tire to the wheel, I'll be using that. Very glad you found the issue with the dents in the blade.
Nicely done Michel. Interesting discovery about the blade construction.
Thank you!
Thank you, I am enjoying this build of yours. 👍💪✌
Michel
I have now started making a band saw based on your design. Good progress so far. While cutting out some aluminium with my Scheppach mobile band saw I had a problem with the blade coming off the track. I then examined it and found that it had the same tooth set method you describe and there are a series of 5 cracks like those that you found. I am pretty sure that the problem with these mobile saws is that the blade is twisted from the wheels to the roller guides to enable the size of cut to be made. This blade did though last me for many cuts in a variety of materials including stainless steel rod and aluminium. John
Ah, great! Good luck John! You know that working drawings will be released soon? Just also look at the more expensive band saws. I think the Makita ones are of good quality. You pay a bit more for them, but they are definitely worth it.
I'm enjoying this build series, what a neat tool! FYI this Part II doesn't seem to be in your Builds! playlist so it took a little time to find it.
I will look into that. Thanks!
Hi Michel. I am also thinking of building a benchtop bandsaw. Right now, I use a Milwaukee Deep throat bandsaw with a 47" mol blade. I clamp it in my old heavy-duty vice, use a small c-clamp and cut small pieces of 3/8", 1/2", and 3/4" thick steel. A lot of them. I have also had issues with blade fatigue. The back edge of the blade fatigues, and eventually breaks. I believe the reason is because the top blade support bearings are so far away from the metal and bottom support bearings that too much pressure is applied trying to "stretch" the back of the blade as well as continuous flexing around the wheels. They always fatigue from the back and then break. If I ever get time, I will give it a try. I make small tools to form "cowboy hats" from US coins and have been making them for over three years now.
That seems like a good analysis to me.
If those support bearings are too far away from the point where the sawing pressure is applied, you will indeed get a long arm for the force and so an undesirably large bend that leads to premature breakage. It is striking that the blade tears at the back in this case, while the front (the stress riser at the tooth bases) is the weakest spot.
It is not possible to bring the support bearings much closer to the workpiece?
Maybe like this: Mount ball bearings (like I did in the previous video) in a holder and clamp that holder to the saw table itself.
Many thumbs up! Very interesting about the alternative blade tooth set... Wonder what they were thinking :) I think the new design and "better" thin blades will work very well. As long as the overall weight stays reasonably low, it will definitely still be a "table top bandsaw"!
I think I can keep the total weight well below 20 kg.
brilliant!! i need one too
Michel, misschien de resolutie van de encoder van de servo lager kiezen? Twee maal wellicht? Misschien met een functiegenerator te simuleren? Hartelijke groet, Job
Hoi Job,
Ik moet er nog induiken, dus wie weet vind ik het. Het geheel is verkocht als een set. Dus dacht ik dat de driver een defect had, en dat dacht de verkoper ook. De gratis nieuwe driver echter geeft hetzelfde probleem. In de motor zitten drie hall sensoren die naar de U,V en W ingangen van de driver gaan. Daar valt niets aan te veranderen. Maar ook bij de driver zie ik geen instellingen die iets oplossen. Ik vrees dat deze driver en motor niet bij elkaar horen.
Met drie losse Hall sensoren als feedback valt er aan de hardware kant denk ik weinig makkelijk te wijzigen. China is goedkoop, dat wel. Qua documentatie heb ik het nooit getroffen en qua back-office idem... Maar dat zal wel pech zijn geweest ;-) @@Michel-Uphoff
I am assuming you had to go with a longer saw blade?
Yes, you are right. Makita's new blade is 1140 mm long.
What is your input voltage and what are the switch setups on your controller? Also, I wouldnt take apart the motor first as it have a chance loosing some of the magnetism on the rotor. First I would try to check the controller switches if those are doing anything (i mean sw 1 and 2) might be a wrong connection or a wrong switch there. For me its seems like you run a 4 pole motor in 2 pole mode if it is exactly half amount of rpm what it should be. Also it can be the encoder settings or the encoder itself problematic.
I have already tested all those settings with no meaningful results. I now think I have an 8-pole motor and a (max) 4-pole driver.
@@Michel-Uphoff Based on my internet research for your topic, you seems correct, it might be an 8 pole motor. Considering 120mm and 1500 RPM its almost 9,5m/s cutting speed, what is on the low side, but its not terrible for this desktop use, but obviously half the speed as it could be.
@Sastas 9.5 m/s is way to fast. That's more than 500 mtr/min. The usual cutting speed for a bi-metal saw blade is 60-90 mtr/min for steel and say about 200-300 mtr/min for aluminum and copper. You have forgotten that there is a 1:10 reduction gearbox. So the wheels now rotate at 150 rpm, and that's 56 mtr/min. Just usable for steel, way to slow for soft metals.
@@Michel-UphoffYeah, you are correct, i miscalculated and remembered wood data... (but based on my recent check for some of the aluminiums 600 is still okay) For soft metals its not too slow, as you probably wont change the blade with bigger tooth.
So for steel, based on the hardness and alloy 10-100 m/min is optimal. For structural steel 60 is a good number. And right now you are basically around 60 on max speed.
Why four wheels and not three?
Good question, didn't make that choice because the frame then must be made about 5 cm wider to keep the same throat size.
@@Michel-Uphoff
understand, thank you 👍
SW1... 2-poles - 4-poles?
Tried that, and every other setting I could adjust, but to no avail
@@Michel-Uphoff Does speed change when you change the settings on SW1?
Maybe it's an 8 pole? I can not find this specific motor/driver combo on the web.
@@bmalovic In the coming days I will open the motor to see how many poles it has.
@@Michel-Uphoff I wouldnt recommend to open it up. Some of the motors can loose torq if you disassemble them (the housing is closing some of the magnetic poles and its kinda demagnetize when you disassemble). I'm not sure if it applies to BLDC motors as well, but steppers can "die" because of this,
@@Sastas There is no such thing that will "demagnetise" if you disassemble and reasemble it (in the propper way of course).
There may be some other problem with dissasemblng stepper, but demagnetisation definitly not.
Please cut any thing steel or wood
Be patient please, in the next video probably.