Warning about Routers

[Bill Space]

That Makita router isn't designed for fault tolerance, it's call FMEA or failure mode effects analysis. We can be grateful those Makita engineers don't work in the appliance or automotive industries. The just of Design FMEA is to assure a single point failure can't allow the device to fall in a dangerous mode. In the OP's example something has failed intermittently and the result is the router runs full speed without any input from the user. A recent example of a bad design relying on a single sensor for critical data with no backup mode is the 737MAX.

I'm sure Makita has seen this failure already, I'd give them a call a listen to their reaction. I might contact the CPSC and see if they want to investigate. If there's a UL listing I'd contact them too.

We need to keep in mind that any device can fail, and protect ourselves by only using components (in the case of a router, bits) that can survive failure of the equipment being used (within reason anyway) when it fails in the full speed mode.

It would be prudent to only put in a router things that can withstand the maximum speed the router can attain.

Besides high speeds caused by speed control failure, there is always the potential for high speeds due to operator error. At least in my case (whoops! I forgot to turn the speed down!)...can't speak for others. In either case the result could be the same.

I would be willing to bet most router manufacturers have seen this same failure mode at least once. But don't think that is the root issue. The message in this thread is that router speed controls can and will fail full on. So don't put anything in your router chuck that cannot withstand the maximum speed the router can turn. (Or in any other tool for that matter).

[Stephen Tashiro]

t the type of speed control on a router like the one you used is an open loop design. It simply reduces the input voltage supplied to the motor by limiting the peak voltage and / or duration of each of tje 60 Hz voltage cycles. It has no way to monitor the actual speed or do anything to 'control' it. I suspect, in your situation, the rotational speed of the lathe, coupled with the speed of the router itself caused the router to be overcome by the lathe rotational speed. There is no way the router could do anything but "go along for the ride".

I get the general idea that routing against something that is rotating (or just moving quickly) can affect the speed of a router, but I don't understand the details. Are you saying that the moving "work" spun the grinding wheel and the router shaft at the same speed the shaft would have rotated if the router motor wasn't turned on?

[Edwin Santos]

We need to keep in mind that any device can fail, and protect ourselves by only using components (in the case of a router, bits) that can survive failure of the equipment being used (within reason anyway) when it fails in the full speed mode.

It would be prudent to only put in a router things that can withstand the maximum speed the router can attain.

Besides high speeds caused by speed control failure, there is always the potential for high speeds due to operator error. At least in my case (whoops! I forgot to turn the speed down!)...can't speak for others. In either case the result could be the same.

I would be willing to bet most router manufacturers have seen this same failure mode at least once. But don't think that is the root issue. The message in this thread is that router speed controls can and will fail full on. So don't put anything in your router chuck that cannot withstand the maximum speed the router can turn. (Or in any other tool for that matter).

This advice basically means completely eliminating all router bits over 1" in diameter.

[Dan Friedrichs]

This advice basically means completely eliminating all router bits over 1" in diameter.

Did you see Bill Space's post #57 in this thread?

[David Buchhauser]

I own and operate several PlasmaCAM cnc plasma cutting systems. Although it has not happened to me yet (probably because of the limited use they see), some of the other PlasmaCAM owners have seen the controller have intermittent malfunction due to an accumulation of plasma cutting dust (fine metal particles) inside the control box. In most cases - the remedy has been to open up the control box, clean and blow out the plasma cutting dust, reassemble the box, and then it works fine again. I have thought about this and I believe that it may be possible that over time, with the metal grinding operations this particular router has been exposed to, that fine metal particles from the grinding operations may have made their way into the router motor affecting the speed control reliability. In particular, if the router speed adjustment wheel that you turn with your finger is actually a potentiometer (variable resistor) then is is possible that fine metal particles from the grinding have contaminated this and are causing the resistance to change sporadically. There may also be other circuitry inside the router head that could be adversely effected by this metal dust. I theorize that since the original intended use of this wood router is for use with wood or maybe other non-metallic materials, the designers may not have considered that it might be used for grinding metal and thus not taken this into consideration when designing and testing this tool. As an electrical engineer, I would be very interested to examine the particular router in question (in its current "contaminated" condition) to try to evaluate exactly what is causing this sporadic loss of speed control.

David

(MSEE, BSME)

[Mark Hennebury]

I did a quick look online and found a few conversations on this problem dating back to 2006


CNC Zone 03-10-2006
https://www.cnczone.com/forums/diy-c...18394-cnc.html

I have a home built cnc router with a 2 1/2 hp Makita router. One of those ones thats suppose to be real quiet. The problem it has been devoloping is that the rpm goes up and down instead of remaining constant. Its constantly reving up /down. Has anyone had a problem like this with a router? Am i going to need to buy a new one or is there a fix?


Router Forums 06-21-2009
https://www.routerforums.com/general...d-control.html
Hi.

I have a Makita RF1101 which functioned beautifully for years, until a few weeks ago. Now the speed is erratic, changing at random intervals to random speeds during operation. The brushes are in good shape, and I suspect that the problem is the motor control (part #63139702) but I was looking for at least some confirmation of this before I drop $70.00 plus shipping on the part.
Any help is appreciated.



posted 10-16-2012 10:04 PM
https://www.lumberjocks.com/topics/42433
My router (after 7 years) has decided to speed up and slow down. I checked the brushes and they don’t look that bad. Controller board?? Anyone got a suggestion?



03-11-2016
https://www.cnczone.com/forums/diy-c...394-cnc-2.html
Re: makita router rpm constantly reving up/down any one had this problem?
[IMG]file:///C:\DOCUME~1\Owner\LOCALS~1\Temp\msohtmlclip1\01\cl ip_image001.gif[/IMG] Originally Posted by tsalaf [IMG]file:///C:\DOCUME~1\Owner\LOCALS~1\Temp\msohtmlclip1\01\cl ip_image001.gif[/IMG]
This is a defect in some earlier Makita routers and was repaired on both of mine free of charge, even after the warranty had expired.

That is a very interesting observation, tsalaf. My Makita RF1101 has the same problem.
Do you recall how you want about receiving this service? How did you learn that they'd take care of this for you?

[David Buchhauser]

Mark,
I will have to admit that your anecdotal evidence is compelling. It's hard to believe that in over 10 years, Makita has not corrected this problem. I wonder how many of the other router manufacturers (if any) have similar problems with the speed control. In any case, we will probably never know the exact cause of the problem with your particluar router. Unfortunately, the damage has been done. On the positive side, I think that your cautionary tale has inspired many at SMC to rethink some of their practices with the power tools they use. Good luck with your speedy recovery.
David

[Pat Barry]

I get the general idea that routing against something that is rotating (or just moving quickly) can affect the speed of a router, but I don't understand the details. Are you saying that the moving "work" spun the grinding wheel and the router shaft at the same speed the shaft would have rotated if the router motor wasn't turned on?

I wasn't sure whether the work was turn in ng in the lathe at the time, since clarified by the OP that it wasn't, but, yes, if the grinding wheel in the router was contacting the work, and the work was rotating, the frictional force would cause the grinding wheel to keep up with the lathes rotational speed.

[David Buchhauser]

The grinding wheel would typically be turning at around 8000 rpm. No way this particular lathe can keep up. I would guess the top speed on this lathe is no higher than 2500 rpm, maybe slower. Depending on the pressure applied to the work piece from the grinding wheel, the surface speeds of each could and most likely would be much different.

[Larry Edgerton]

A universal motor speed is independent of line frequency, so that wouldn't work for this. I am almost certain that there is no such thing as a 3 phase line voltage hand held router.

https://www.allbids.com.au/c/industr...-router-693833

[Brian Holcombe]

I wasn't sure whether the work was turn in ng in the lathe at the time, since clarified by the OP that it wasn't, but, yes, if the grinding wheel in the router was contacting the work, and the work was rotating, the frictional force would cause the grinding wheel to keep up with the lathes rotational speed.

The grinding wheel would typically be turning at around 8000 rpm. No way this particular lathe can keep up. I would guess the top speed on this lathe is no higher than 2500 rpm, maybe slower. Depending on the pressure applied to the work piece from the grinding wheel, the surface speeds of each could and most likely would be much different.

I get the general idea that routing against something that is rotating (or just moving quickly) can affect the speed of a router, but I don't understand the details. Are you saying that the moving "work" spun the grinding wheel and the router shaft at the same speed the shaft would have rotated if the router motor wasn't turned on?

https://en.wikipedia.org/wiki/Cylindrical_grinder

Grinding a cylinder on the OD is typically done with the part rotating counter to that of the grinding wheel. This is done to avoid having the grinder influence the speed of the part or vice versa.

[Mark Hennebury]

Top speed of old bessy is 1400 rpm.

The grinding wheel would typically be turning at around 8000 rpm. No way this particular lathe can keep up. I would guess the top speed on this lathe is no higher than 2500 rpm, maybe slower. Depending on the pressure applied to the work piece from the grinding wheel, the surface speeds of each could and most likely would be much different.

[Frank Pratt]

https://www.allbids.com.au/c/industr...-router-693833

I should have qualified currently made for the North American market. All of Scheer's current routers are universal motor.

[Jeff Davies]

Hey Mark, thanks for posting that. Its a drag that it did not miss you like the video you linked, but you sound pretty tough -my sincere wishes for a speedy healing. Being nonchalant after near 5 decades on shop floors as I am , I don't pay much attention to shop stories--but I was taken by yours, and the shocking video --I will never rely on an electronic speed control. Thank YOU . Best wishes , J.J.

[David Buchhauser]

It looks like Makita is not the only manufacturer with this problem. Apparently the Dewalt routers have had similar problems with the speed control.

https://sawmillcreek.org/showthread....-speed-failure