Problems with my Festool saw, aaarrrgghh!

[Neil]

Woody, I have just tried my saw on speed 1 and I have the pulsing too. The pulses have the 'rough gearbox' noise of the normal startup phase, and you can feel the pulses very obviously through the handle. Its fine on 6 though...

Cheers,
Neil

 

[Jake]

Has anyone actually cut on speed 1, as festool's claim for their "intelligent MMC electronics" appears to be (judging by the constant repetition of this phrase in net articles) that it "maintains constant speed under load "?

Tony, as you no doubt accurately surmised from my post, the maths you edited into your post went over my head. In essence, my mistake is to overestimate the amount of torque necessary for a circular saw compared with what Festool get from their motor. OK. I know my Bosch slows down if I cut too quickly, but that is probably not a fair test, and under those condition so would the Festool, I guess.

 

[ColG]

Just to throw another firework into the ring....... Has anybody seen/used/bought one of these? http://www.eurekazone.com

 

[johnelliott]

Just to throw another firework into the ring....... Has anybody seen/used/bought one of these? http://www.eurekazone.com

Having read about this system, I think there is every chance that it is at least as good, if not better than, the Festool system. If they'd been side by side at the place I bought my Festool I might well have bought one instead. But only if the circular saw that I fitted to it was as good as the Festool. I doubt there's anything made anywhere that's as good as the Festool saw in terms of quality of cut.

John

 

[Jake]

I had a look in the Festool catalogue this evening, and it doesn't give away too mnay secrets. The "MMC intelligent electronics" keep the speed "constant automatically". There is an automatic speed reduction on idle on most things, including the TS55, jigsaws, and the CS70 with 'MMC' electonics. So without load, speed 1 is not full speed 1. The only other mention of the electronics is on the belt sanders which are said to use "intelligent full-wave electonics". Whatever that may mean.

 

[Anonymous]

Has anyone actually cut on speed 1, as festool's claim for their "intelligent MMC electronics" appears to be (judging by the constant repetition of this phrase in net articles) that it "maintains constant speed under load "?.

I see where you are coming from and if Festool make this claim, then the system must use feedback for it to be true under medium to heavy duty cuts


The comment posted by Neil at the top of this page makes me think that the pulsing may be mechanical in nature and related to a gearbox rather than the motor. Having said that, I don't think that I have ever seen a circular saw with a gearbox - they are usually direct drive with the blade mounted on the armature

 

[Jake]

I'm not particularly going anywhere, I'm just intrigued and trying to work out more. Is the idle speed reduction thing significant at all, do you think, as a potential reason for the pulsig sound at idle on speed 1

 

[Woodythepecker]

John wrote:

Anyway, tried my saw on the irrelevant and unecessary speed one this am, and it was definitely pulsing. The way i see it, maybe it would behave oddly if i ran it upside down too. So what. Mine is always on speed 6 and there it will stay.

John, i do not see setting one as being irrelevant or unecessary as there may come a time when i need to cut some other sort of material at that setting.
As for behaving oddly if you ran it upside down, i would hope not, because this would mean that the owner of this saw who bought a Triton Workcentre 2000 would not be able to use it, which if you look at the price of this excellent saw, would certainly shock him :shock: :shock:

Like you i think that most of us would keep on setting on 6, but because of the price and the overall excellent quailty of this saw i would not think "So What" if there was a problem with another setting, whether i used it or not.

Put it this way if Festool had not made such a big thing in their advertisments about this no loss of speed, i would probably never have taken any noticed of the pulsating, as the quailty of cut has not been effected. But i did take notice of their advertisment and because i paid over £500 for the tool and all its accessories, i excepted this top of the range tool to last more then 6 weeks before i found what could be a fault.

Anyway i hope that you get your saw back soon and that it is working as perfectly as it did before it went wrong.

Neil thanks very much for your feed back. I have contacted Festool and i will keep you up to date when they reply.

Tony thanks very much for your input, which i was very intrested in.

Colg, i agree with John, that is certainly a nice system. Thanks for the link.

Regards

Woody

 

[SquareCircle]

Guess I have to break the lurking habit sometime………….
Bought one of these saws at the Feb show. Switched it on in the shed and first thought was blimey, better send it back. Got to be something wrong with it. Easily the worst sounding tool I have (with or without ear defenders on). Seems to warble, pulse and splutter its way along. But it does it cut incredibly clean and true, and effortlessly too. Sometimes I am not sure that the blade is turning (especially since the dust extraction is so darned efficient).
Eventually decided that maybe these guys just didn’t spend as much effort on tuning the sound of their machines (like getting the right exhaust note or making sure that the door shuts with the right thunk). And if the saw does what I want it to do and comes with a three year warranty, then can’t complain. Even though it’s an expensive, feels like the best purchase I have made to date simply because it does what it supposed to do exceptionally well (makes upgrading the TS rather pointless for the time being).
Pity about the sound and the pulsing but that is really not why I bought it (never read the advertising blurb). I also feel that if the product subsequently turns out to have a design fault, then don’t see how Festool will keep their reputation intact without a product recall or something along those lines.
Just another view.

 

[kityuser]

If they have, then there is no reason why the speed should vary at all.

(trying to remember back to my control lectures at uni), surely this is impossible as it implies that the system has a controller with infinite bandwidth (i.e. enough to respond to the changes in load in zero time so as not to slow the blade down).

surely all systems have a response time?

I agree that it sounds mechanical (or it could possible that at the very low speed you set it to the lag in the gear box sets up some low frequency oscillations in the control electronics, however I`d not expect this from a lump of kit costing this much dosh! :shock: as this would obviously be poor design).

do they claim that the saw will hold a constant speed for any depth of cut up to the maximum capacity?

steve

 

[johnelliott]

Having said that, I don't think that I have ever seen a circular saw with a gearbox - they are usually direct drive with the blade mounted on the armature

Actually, I think you will find that every circular saw has a gearbox. Two reasons, one is to keep the speed down to a reasonable level, and the other is to be able to get a decent cut depth without the motor getting in the way

John

 

[kityuser]

my skil one does`nt, single speed with the blade mounted straight on the motor spindle.

 

[ColG]

If anybody is interested, here's somemore info on the Eurekazone system. I intend to go for it soon as I can't really justify the cost of the Festool. When I do, I will post a mini review.

http://www.sawmillcreek.org/showthread.php?t=13318&highlight=eurekazone

 

[froglet]

I've just had a look at the parts list and exploded diagram for the saw and the blade does not appear to be mounted directly on the motor spindle. Power is transmitted through a part called the ' gear housing' and the blade is mounted on the 'gear shaft'. Also from inspecting the saw the shaft the blade is mounted on does not appear to be in line with the motor spindle.

Graeme

 

[Anonymous]

If they have, then there is no reason why the speed should vary at all.

(trying to remember back to my control lectures at uni), surely this is impossible as it implies that the system has a controller with infinite bandwidth (i.e. enough to respond to the changes in load in zero time so as not to slow the blade down).

surely all systems have a response time?
steve

Hi Steve

Yes of course there is no such thing as an instantaneous response in any system.

However, the reponse time for a high torque motor such as those in a circular saw and the very small inertia of the blade during a light cut will result in speed corrections that are not noticeable to humans - probably adjusting every few millisceconds or so. Even on a hard cut with much increased loading, the fast rate of corrections will ensure the blade remains at constant speed as far as a user is concerned until the force applied by the user requires greater troque than the motor can provide at which point the motor will slow or stall

 

[Neil]

Tony et. al. - I've uploaded a scan of the parts list Graeme mentioned so you can have a look if you are interested. Scan is fairly large (130kb)

Neil

 

[kityuser]

tony:
I agree completely, sorry for the pickiness, I was just trying to keep mindful that there are "non-technical " (no insult implied) people in here that might take statements (such as your quote) at a face value.

sounds mechanical is there any kind of clutch in these things?


steve

 

[Anonymous]

No worries Steve :wink: I do get carried away somtimes :?

Thanks for the scan Neil

It is as I suspected, no gearbox (rules out backlash) and no obvious feedback mechanism to control speed.

I think that they have either used a type of speed control called Armature feedback control or run it 'open-loop' (i.e. no monitoring of the speed) using a PWM drive system.
Armature feedback is notoriously difficult to get accurate speed moitoring from but it is the cheapest way to monitor the speed of the motor. Expect speed control to be around 8%. this type of feedback control may well produice the 'hunbting' reported here.

Open-loop is still most likely for these saws in my opinion although I may have missed something in the drawing. Open-loop speed control using PWM is very good and more than adequate for a circular saw

Tech bit for the interested - please feel free to ignore:

A motor and a generator are pretty much the same thing. If you spin a motor armature inside a magneitc field (field windings or permanent magnets) it generates a voltage and current. Motors are not as good as generators at this due to slight constructional differences.
Now, if the rotation of the motor is due to a voltage applied to it, the motor still acts as agenerator and generates it's own voltage opposing the 'driving' voltage (that you applied) - this is called the back-emf (emf, electro motive force, is just another term for voltage). The back-emf causes a current to flow in the armature windings in the opposite direction to the current you are putting in to drive the motor.

It is very easy to measure this back-emf generated current and it is pretty much proportional to speed. However, due to losses in the system that are varying with speed, the use of back-emf to measure and thus control speed is not too good and the control is usually within about 10% of ideal (best I have seen reported is 8%)
End of tech bit hope it wasn't too boring

Cheers

Tony

who is waiting for Alf's cutting and funny comment on ' I do get carried away somtimes ' :lol: :lol: :wink:

 

[Bean]

Yes Tony but I want to know who keeps bringing you back :wink:


Bean
(Having a bad day)

 

[johnelliott]

Thanks for the scan Neil

It is as I suspected, no gearbox

If you are referring to the Festool saw, it most certainly does have a gearbox. How on earth would the drive get from the motor to the saw blade, even a glance at a picture will show that the motor and the blade are not in line

I had a quick look through the circular saws in the Axminster catalogue, and there too it can be seen that in most of the saws the blade and motor are not in line

OK , they aren't MT75's or even BW65's but if they are encased, and contain gears, then gearboxes they are.

In the illustrated parts list downloadable from the www.festool.co.uk website you can see the 'gear housing'

John