Yeah, I think that’s the key.
… now back to our original programming…
So what was that about motors with bearings and all metal gears???
Just a side note, AC is used for long distance power transmission because there are no DC transformers (or at least not in the early pre- electronic days). The Westinghouse vs Edison arguments of the day are quite interesting along with the claims that AC’s only advantage was electric chairs.
DC would have saved many generations of EE students a lot of heavy math. I’ve forgotten it all after 50 years, alas.
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Budget concerns may contravene what follows.
IMO its best to select a loaded target output RPM based on the highest usable feed rate at the worst case area of the machine. This is eminently calculable, but I have not done the math. Here is a speeds and feeds guide to get you part way there https://www.freudtools.com/public/assets/freud/downloadables/freudtools-router-bit-feed-and-speed-for-cnc-20170822.pdf
Once you have your target max RPM, based on the needs of the wood, cutting tool, and machine geometry, you select a gearmotor with enough torque to support that RPM with sled just below top center. You then choose an encoder with the minimum resolution required to get the job done to desired accuracy. Again calculable, but I haven’t.
Whatever motor, supplier, driver, code was used previously shouldn’t enter into it. Build the tool to the job, not to the previous version of the tool.
If the firmware needs to be rewritten to accommodate the right motor, that is what should be done. I’ve written previously about the need for more modular firmware code for just this situation. If the right motor requires a better driver, the tool requires a better driver. The firmware should accommodate a variety of drivers without drama. To be clear, that is an aspirational opinion, not a statement of current fact. The firmware currently supports just a couple drivers AFAIK, but it has been a while since I looked at it so I could be mistaken.
FWIW I am expecting a new brushless driver and pair of motors in the mail today from http://www.skysedge.us/robotics/index.html It wasn’t intended for a Maslow, but if anyone is interested I can do some tests. $105 for a 2 channel brushless low speed open source controller with Arduino Mega built in could be an all in one control package.
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I had the “opportunity” to open up one of my motors today. Not sure if it was an original from the kit or one of the spares I bought but it has double bearings. I replaced a plastic gear in one of the motors at one time, and when I opened up this particular motor, I found it had a metal gear, so I assume it’s that one… I don’t think the surplus motors from surplusmaslowparts.com came with metal gears, but maybe @bar would know for sure.
The reason for opening the motor was because it was one of the motors driving my robot and it was making a horrific popping sound. Turned out I could actually turn the motor counterclockwise with some force (and the nasty popping sound). It would not turn forward with the same amount of force. When I opened it up I removed the ‘suspect’ gear and all the grease and compared it to one of my remaining replacement gears. Obviously, it was worn … and worn badly… I did a tap test to verify it was metal… sounds like metal, just like the replacement:
So… I’m not entirely sure “all metal” gears are a complete solution if this can happen to them. I found little bits of metal within the grease so I need to completely degrease everything and relube it. I’m sure there are different alloys of metals that have different wear characteristics… but I don’t know how much luck you will have getting an economically priced motor with high-grade gears.
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Thanks for feedback. Turns out Etonm secretly switched to bushings instead of bearings without telling me sometime between 2017 and 2018. When I called them out, they blamed me saying I should of taken apart the test motors I got and inspected them, or I should of told them I wanted bearings. Hard to ask about something that is not an option on the website or ever told it was an option. Also recently told me 2000 minimum order quantity . Complained then reduced to 1000 MOQ. Complained again now 750 MOQ is fine. I’m fed up with them. This BS has been going on for years. they have lost my business. there are other companies that will sell the same motors for less and be professional about it.
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