Erich's Benchtop Gear Hobber Project

After watching the video of this, it turns slower than I imagined. I wonder if that motor can go slow enough and still have adequate torque? Maybe you could cut a gear set for the motor to reduce it maybe 4:1 at the motor and then drive with a pulley? That would substantially improve torque and still go up to 1250 RPM. What is the max RPM you anticipate needing?
Alternatively these motors work very well:
www.ebay.com

Industrial Sewing Machine Servo Motor 110V 550W 3/4HP CS1000 4500RPM 928879560299 | eBay

Find many great new & used options and get the best deals for Industrial Sewing Machine Servo Motor 110V 550W 3/4HP CS1000 4500RPM at the best online prices at eBay! Free shipping for many products!
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rwm said:
After watching the video of this, it turns slower than I imagined. I wonder if that motor can go slow enough and still have adequate torque? Maybe you could cut a gear set for the motor to reduce it maybe 4:1 at the motor and then drive with a pulley? That would substantially improve torque and still go up to 1250 RPM. What is the max RPM you anticipate needing?
Alternatively these motors work very well:
www.ebay.com

Industrial Sewing Machine Servo Motor 110V 550W 3/4HP CS1000 4500RPM 928879560299 | eBay

Find many great new & used options and get the best deals for Industrial Sewing Machine Servo Motor 110V 550W 3/4HP CS1000 4500RPM at the best online prices at eBay! Free shipping for many products!
www.ebay.com
Click to expand...
I'm using a 4:1 ratio pulley, figuring ~1k RPM is more than enough. If that doesn't end up being torquey enough, I figure it is easy enough to put together a small jack-screw gearbox on the front of the motor to give another 2:1 or 3:1 reduction. I'm hopeful I'll be running this at about 200 RPM, but finding a small motor (those sewing machine motors are big!) with a good amount of torque that isn't 10k RPM is a challenge.
 
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pdentrem said:
My Singer has a tiny motor! About this size.

DOMESTIC SEWING MACHINE MOTOR WITH PEDAL AND MOTOR BLOCK FOR SINGER AND MORE by Feit : Amazon.ca: Home

DOMESTIC SEWING MACHINE MOTOR WITH PEDAL AND MOTOR BLOCK FOR SINGER AND MORE by Feit : Amazon.ca: Home
www.amazon.ca
Click to expand...
Thats a neat little motor! A little less than 1/3 the power of the motor I got, so I'm not sure if it would do it.

One thing that is really neat about the motor I got, is it is the one from the FIRST robotics, so there are a number of gearboxes available in a ton of different ratios as I need them. There is a bolt-on planetary gearbox available that is pretty low profile, and available from 4:1 all the way to 56:1 (or something like that!). So for $30 I got a motor with a ton of flexibility.
 
That sounds great about the bolt on gear boxes. I would go for that.
 
So, threw the PWM board on the bench, and hooked a scope to it. Overall, it looks pretty well built. The board design is clean, layout it clean, etc. I think the rated current it a bit optimistic, in true chinese fashion.

Looks like they have a PWM asic or programmable logic chip in there. The brains are based on a completely unlabeled IC. Looks like they have four FETs in parallel, but the copper traces seems a bit light for the rated current. I you intend to run it continuously, I'd probably pop it out of the case and put a pair of 12V fans blowing right on it. (And/or reinforce the traces by soldering some #12 copper on the bottom. I can show you where if you get to that point...)

Overall the output waveform looked good. Much better than some I've seen.

It has a very smooth, but slow responding PWM adjustment. It takes about 5 seconds to get to the level you set the knob to.

It uses relays for direction change. You probably want to turn the speed pot down/off, and then switch direction. I have a buddy who welded relay contacts on a similar controller once.

Maybe the biggest possible issue will be that the motor cannot have it's case electrically connected to the power leads. If your motor ground is connected to the case you'll probably have to isolate the motor case. This probably won't be an issue for you, but check for this before you wire anything up just to be sure.

I think the bottom line is, if it works for you, it wouldn't hurt to buy are spare or two. For the price, just keep a few around. I might even order a couple more just to have in the parts bins...

Dan
 

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I finished up with the die-filer repair, so I turned back to this. I spent a bit more than an hour in the shop last night and finished the flex-linkage:

PXL_20230124_231458928.jpg

Inside those two large cylinders is the forks. Here they are moving on Erich-power:

View attachment PXL_20230124_231502468.mp4


It still catches a little, so there is some fettling I need to do on the forks themselves. I can see more or less where I need to round off, so I might spend some time with a file (or filer!) working on that at one point.



Brings my TODO list down to:

1- I have to make the work-holding and hob holding MT2 adapters. There will be a challenge there, as I have to make the work holding spindle particularly long (thanks to not doing the CAT20 holder, I ended up not 'wasting' as much room)
2- getting all of the drivetrain 'little bits' done. I have a lot of keys I need to make. I need to file out the quadrants to fit the gear holders. I need to drill and broach all of the plastic gears.
3- Mounting the electric motor
4- Setting up the electronics

After that, I have to go through the process to make ALL of the gear set :)
 
So seemingly my power supply is pretty complicated :) it has 30 different pins, and is seemingly a power supply for a 1U or 2U server. I don't get 12v power it appears without shorting the correct pins.

I probably need to order a socket for the connector, and start messing with it at one point. It is ALSO way bigger than I thought, so I might look into a less-nice PSU and go with a standard "120v goes in, 12v goes out!" kinda supplies.
 
ErichKeane said:
So seemingly my power supply is pretty complicated :) it has 30 different pins, and is seemingly a power supply for a 1U or 2U server. I don't get 12v power it appears without shorting the correct pins.
Click to expand...
Do you have a link to the one you bought?

xU server power supplies usually have load sharing, and other odd features that can usually be ignored. Should just need to pull the 'enable' pin up or down to enable the output. Might be able to help you sort that out...
 
dkemppai said:
Do you have a link to the one you bought?

xU server power supplies usually have load sharing, and other odd features that can usually be ignored. Should just need to pull the 'enable' pin up or down to enable the output. Might be able to help you sort that out...
Click to expand...
It is a Emerson Astec DS450-3-002. I saw that when poking around today, but think it might be a little 'overkill' and a a little 'oversized' :D

Instead I ordered this: https://www.amazon.com/dp/B096VL68B1?psc=1&ref=ppx_yo2ov_dt_b_product_details

I had a similar one show up in a kit to make a power supply, and it seems to be good enough. More importantly, it has a much smaller footprint:)
 
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