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Motor gears stripped

@bar wouldn’t happen to have extras would ya?


Gear is rounded over.

This project must be jinxed. Another sheet ruined🙁
20180627_105858

Approximately how many hours of cutting run time do you have on that motor? Curious if it failed premature or you hit the life expectancy.

Edit, never mind. I think you answered my question here Motor Gear failure?

I would say around 30 to 40 hours maybe? The motor seems to be fine just the gear box is broken. Not sure what the life expectancy of a gear is but i would assume its longer than 40 hours.

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Are those all metal gears? Running my motors for a year now, but not every weekend.
However I fried 2 or 3 motor shields with them and recently bent and twisted my u-steel motor mounts testing the TLE5206 and the gears held up to all that stalling.
Wondering if there is a difference of the motors now compared to the 1st beta tester batch.

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One plastic

Stripped one

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One plastic is the same. Here a pic from July 2017


Edit:
From March (that looks like the same gear failed)

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The gear that is stripping looks different to me. What would be the reason its shaped like a wave?

Or are the teath like that cuz they are stripped and they originally looked like the others?

There is one gear which there always seems to be the one which fails. I’ve let the manufacturer know that they need to up the QC on that gear and they sent me spares so I can send you a spare one. Will you email your address to info@maslowcnc.com and we’ll get you a replacement right away

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Resistance on the output shaft? What was material, the depth, feedrate, cutter size and rpm at the time of failure?

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3/4 in
19,000 rpm
30 ipm
.125
Plywood

The left motor always clicked and sounded different then the right. The click got loud today and the started slipping.

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Do you think this was gradual, then? Have you looked at the right gears?

I haven’t looked at the right one. Not sure if its gradual or I bent them in the beginning and they finally gave.

Going along with the striped gears… Has anyone’s motors started making this noise at some point? Is this a sign that is about to completely strip? Or is it just being lazy and whinning :wink: It’s just my left one and seems to only be in this direction. https://aws1.discourse-cdn.com/standard11/uploads/maslowcnc/original/2X/c/c53657825b9850b967ab51d3e69b55fecefb4afe.mp4

The worm wheel wears on only one side of the tooth for the same reason that maslow does not need to account for backlash. The torsional load on each shaft is always in a constant direction regardless of driven direction. We never push the chain, only pull, even when letting it out. This means MTBF for balanced loads can effectively be cut in half for maslow because we are only using half of each gear. Also, plastic creep could occur if the sled weight is left hanging in a hot garage. The next startup would produce accelerated wear as the engaged teeth have shifted somewhat.

The worm wheel gear(gear that meshes with the worm) that is normally plastic and apparently sometimes problematic is brass in these pictures.
Edit: I just noticed that the wave shaped gears described here are not the worm wheel plastic gears. The wave shaped outer teeth of the compound gear on the paper towel appear to be the driven gear of the 3rd stage, made of metal. I thought the post was saying plastic gear was the one that stripped, but I was mistaken.

I know that thread is very old, but does anyone have a source or even specific model number for the motor/gearbox combination used by @mcmiley in that thread? Know what his specific problems were? Overcurrent, or are those really brushless?

I’d like to compare it to a stock maslow motor. Closest to current etonm website appears to be either ET-WGM58BL or ET-WGM58. ET-WGM58BL does not say it is brushless, but picture shows 3 wires. ET-WGM58 text description says it is brushless but picture has 2 wires. Something ain’t right. No way to know what you will actually get.

It has dual output shafts which could be useful for the parallelogram type.

The motor appears to be sealed(smooth black motor case, vs natural metal with flux ring). This is a tradeoff. It has no fan and openings to collect sawdust. It has no fan and openings to keep itself cool. Instead, it has a larger thermal mass motor housing. This lets it absorb the heat created during a temporary stall, a condition where a fan would not be running. The lack of fan also means that it takes longer to dissipate the absorbed heat. If too much time is spent at high load, it can contribute to heat soak where eventually the entire thermal mass is at an even high temperature and things(insulation, grease, brushholders, plastic parts) can start to break down. That is why similar motors with a higher stall current rating often have a lower duty cycle rating.

Has any analysis been done to see the percentage of time an average maslow project spends in percentage buckets of max rated axis motor RPM?

I don’t think so. It would vary greatly depending on so many variables.

I don’t think RPM is the issue as much as tension from the driven chain. High feedrates, the tension required to reach the upper parts of the workarea, friction and weight of the sled are all parts of that. Too, individual occurrences where a chain wrapped or the sled tried to climb above the workarea could weaken the weakest part of the gear train. If we’ve found that weakest part, we should think carefully about alterations that might make something else the weakest link - ‘the devil that you know…’ might apply here.

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I agree wholeheartedly. The reason for the RPM question was to see if possibly changing to the black motors with the brass gears would introduce a high duty cycle situation where the now fanless motor would overheat. Maybe a typical runtime would be an easier measure. Anything over about 30 minutes consider a sealed motor heat soaked.

One benefit of profiling a typical project, rather than ‘try the new motor and see if it burns up’ is that it can be done theoretically without any hardware.

Even though one project cannot possibly be representative of all, it might make sense to choose something as a ‘standard’ project; a benchmark that can be used to compare performance improvements.
It should be:

  • useful in multiples, so that cutting a bunch of them is useful to a maslow owner, not just a waste of wood.
  • contain longish straight cuts horizontal and vertical to compare against framing square.
  • contain a circular element of a common size, comparable against a universally available item. Perhaps a cutout to fit OD of 4" schedule 40 PVC pipe. Or ID of pipe cap for same.
  • any other requirements?

Off the top of my head, I’m thinking some kind of shelf bracket/lumber rack. A right triangle with 24" legs, hypotenuse replaced with large radius curve, the above described hole located at least 2" from any edge. The flat part holds lumber, the PVC pipe holds smaller stuff like dowels, allthread, pipe…

Alternatively, some type of woodworking clamp? One can never have too many clamps.

Wow, that went off topic fast. Back to your regularly scheduled forum.

:100::+1:t2:

What about adding chain counterweights instead bungee cords to avoid gear damage? this will have several advantages.
Just from the top of my head.

-More chain tension, we can add more weight to the router, as long we compensate it on the counterweight side.
-Significantly reducing the load, taking the router and bricks weight off the the motor gears.
-Less heat on the shield.

The only down side i can think of, is that we are adding a lot more side force/weight to the sprocket’s shaft/axle, but this problem can be easily overcome using a separate axle with two sprockets (maybe with ball bearings) and use the original motor and gears to spin that one, that way all the side loads will be on the independent shaft.

I know the load the router put on the gears is greater as it gets higher on the board, so ideally the counterweights would need to became heavier as the router gets higher to maintain a perfect balance, but even if we can not find a way to do this, I believe we still are taking a lot of forces out of the original motor/gears using counterweights.

Unfortunately, I just found about this amazing project yesterday and i cannot test it since i don’t have one.

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adding weight to the sled causes problems mostly when high on the board. There
is a spreadsheet that lets you see the min-max tension on the chains easily.

The low tension positions are low enough that your counter-weights may reduce
the load on the gears to below zero, at which point the output sprocket will
rotate the wrong way (or fail to rotate the right way) until the backlash of
every gear in the gear chain is taken up

I agree that weights are much better than spring-like things as weights are
constant while the springs apply the most force when you need them the least and
the least force when you need them the most.

Hi dlang!

I don’t have this setup and I’m unfamiliar with the problems you guys are having.
Can you please elaborate on the problems you encounter when the sled is high on the board?

I know as high the sled gets, the more force the motors need to keep pulling it up, as closer the sled is from the same height of the sprockets harder it is for the motors, to the point that the motors will be pulling against each other.

But if you add weight to the sled AND compensate it on the counterweight side, you’re not adding any extra load to the motors, besides the extra side load on the sprocket that i mentioned before.

Counterweights are used everywhere, it’s a simple and effective way to reduce loads, think of how a building elevator works. The weight of an empty elevator is compensated on the counterweight side, and the motor is only lifting the weight of the load in it (cargo, people, drag…).

In the case of the sled, the tension of the chain is never reduced, the sled still weights the same, chain still have the same tension and gravity still pulling it down the same way, the sprocket is the one that has to deal with the increased side weight due to the fact you are doubling the weight on it, but you are also reducing the force the motor need to lift the sled due to the counterweight, everything else still the same.

I have no experience with step motors, but since it is worm geared, how can it rotate in any direction without being commanded by motor side?

As I said before, just came across this wonderful project two days ago, so excuse my ignorance on this, unfortunately there are no kits for sale so I cannot experiment.

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