Kapex is dead !!!

[luke1984]

My kapex died today ,in style I may add. Cutting some hand rail for a job I'm doing and all was good. Had 1 cut left to do so pulled the switch on my kapex and there was sparks and smoke from the motor. And that was that , Was not happy. Emailed a repair form to night as its under warranty hopefully get it back for Tuesday as iv got oak flooring and 10" skirting to install. Will be lost with out it  [mad]

 

[bobfog]

Another one bites the dust...!

 

[Brandon]

Sorry for your loss.
I know this subject has been beaten to death but this really is a problem. As I've posted before mine died a couple years ago in similar fashion. Sad that the best saw made has the worst motor. Maybe Festool should give Bosch or Hitachi a call and ask for some motor tips.

 

[mac west]

my new kapex.  399.00 price matched at Lowes with free stand. Its a beast cuts spot on out of box . Dust collection not as good but I will work on improving. Mac
.

 

[TomE]

What's with the yellow tape or whatever it is all over the Hitachi?

 

[mac west]

What's with the yellow tape or whatever it is all over the Hitachi?

Its a personal problem i am very disturbed individual. Mac

 

[Rick Christopherson]

Had 1 cut left to do so pulled the switch on my kapex and there was sparks and smoke from the motor. And that was that

Given this description, I am beginning to think the root problem might be something related to an effect from PWM speed controls. Sometimes the power from a PWM controller into a motor can have very large voltage spikes--much larger than the supply voltage, but very short duration. If these spikes are larger than the insulation rating on the motor windings, the tiny spike will put a tiny hole in the winding insulation. A couple of holes in the insulation isn't a problem, but over time the effect becomes cumulative until you have a catastrophic short circuit. That's kind of like what these failures sound like.

 

[live4ever]

Had 1 cut left to do so pulled the switch on my kapex and there was sparks and smoke from the motor. And that was that

Given this description, I am beginning to think the root problem might be something related to an effect from PWM speed controls. Sometimes the power from a PWM controller into a motor can have very large voltage spikes--much larger than the supply voltage, but very short duration. If these spikes are larger than the insulation rating on the motor windings, the tiny spike will put a tiny hole in the winding insulation. A couple of holes in the insulation isn't a problem, but over time the effect becomes cumulative until you have a catastrophic short circuit. That's kind of like what these failures sound like.

Hmmm interesting....given that, would you expect there to be any difference in failure rates between folks who use the saw at max speed all the time vs those who use the saw at different speeds?

 

[Rick Christopherson]

No, I'm not familiar enough with it to make that distinction.

Edit: By the way, I rarely use my Kapex at full speed. Even though that doesn't apply, I should mention it. I'm typically set at about 4 for most cuts. It's a personal preference, and I like the results. My Kapex pre-dates even the European models. I can't remember when I got it, but it was the early spring before Kapex was announced in Europe. It's 240-volt.

 

[bobfog]

Had 1 cut left to do so pulled the switch on my kapex and there was sparks and smoke from the motor. And that was that

Given this description, I am beginning to think the root problem might be something related to an effect from PWM speed controls. Sometimes the power from a PWM controller into a motor can have very large voltage spikes--much larger than the supply voltage, but very short duration. If these spikes are larger than the insulation rating on the motor windings, the tiny spike will put a tiny hole in the winding insulation. A couple of holes in the insulation isn't a problem, but over time the effect becomes cumulative until you have a catastrophic short circuit. That's kind of like what these failures sound like.

Hmmm interesting....given that, would you expect there to be any difference in failure rates between folks who use the saw at max speed all the time vs those who use the saw at different speeds?

I think that it's a pretty universal truth that any electromechanical device is going to have a lesser life and more wear and tear if it has a higher average operating speed than a lower one, if all other factors are equal. I.e. drive 500 continuous miles at 70mph is going to cause less wear vs doing the same journey at 140mph.

However I think this would be a very small aspect of the tools potential longevity  compared with a far more important factor being the stop start cycles. If you spend 20 seconds doing a continuous cut on a piece of 8/4 oak vs 20 seconds making 5 separate cuts in thin picture framing material, the 5 x increase in stopping and starting the motor will cause far more wear given the same time spent at the saw.

 

[Rick Christopherson]

Had 1 cut left to do so pulled the switch on my kapex and there was sparks and smoke from the motor. And that was that

Given this description, ...

Hmmm interesting....

I think that it's a pretty universal truth that any electromechanical device is going to have a lesser life and more wear and tear if it has a higher average operating speed than a lower one, if all other factors are equal. I.e. drive 500 continuous miles at 70mph is going to cause less wear vs doing the same journey at 140mph.

No. Sorry but this is a completely different aspect that is not related to tool loading. It is related to a mathematical phenomenon of the wave signals sent to the motor. It's a topic that is slightly over my head, and I'm actually an electrical engineer. I know about it, but I haven't done that kind of mathematics in 30 years.

The good news is that if I'm correct, Festool could pull out a fairly simple fix with some filtering circuits.

 

[rizzoa13]

Would your theory flow down to broken armatures and worn out brushes? The main things needing replaced on y saw were the armature and brushes and it seems thoss are the two common major items for the saws when they stop working like this.

 

[geoffshep]

I have seen a few threads on Kapex problems - is this mostly (or entirely) with 110v saws?

 

[Holmz]

Would your theory flow down to broken armatures and worn out brushes? The main things needing replaced on y saw were the armature and brushes and it seems thoss are the two common major items for the saws when they stop working like this.

Probably... If [member=191]Rick Christopherson[/member] is correct, then then the spikes would not only be tough on the wiring, but it would be hammering the motor mechanically like a solenoid. Some of that hammering could affect the armature, but the bearing maybe not so much.
He has impressed me this morning.

 

[pettyconstruction]

Would your theory flow down to broken armatures and worn out brushes? The main things needing replaced on y saw were the armature and brushes and it seems thoss are the two common major items for the saws when they stop working like this.

Probably... If [member=191]Rick Christopherson[/member] is correct, then then the spikes would not only be tough on the wiring, but it would be hammering the motor mechanically like a solenoid. Some of that hammering could affect the armature, but the bearing maybe not so much.
He has impressed me this morning.

Me to

EDIT> fixed quote box

 

[Rick Christopherson]

Probably... If [member=191]Rick Christopherson[/member] is correct, then then the spikes would not only be tough on the wiring, but it would be hammering the motor mechanically like a solenoid. Some of that hammering could affect the armature, but the bearing maybe not so much.
He has impressed me this morning.

No, the spike durations are too short to have a mechanical impact on the motor. But yes, it absolutely translates to damaged armatures. The armature is the rotating motor winding. The stator is the stationary motor winding. But the armature is the more delicate of the two because the wire needs to be finer and wound into the small slots of the metal rotor.

The brushes could be impacted, but just because the service department replaces them doesn't mean they were damaged. They should be replaced simply because the armature is replaced.

This is a topic that is common for VFDs. Even though it is usually from long wires, it can also be caused by higher carrier frequencies. My guess is that Festool raised the carrier frequency on Kapex so it didn't growl like the TS saws do. Here's a generic oscilloscope screen for a VFD output to a motor I found on the internet. It's supposed to be a square wave, but the fuzzy parts are the spikes.

 

[Tinker]

What's with the yellow tape or whatever it is all over the Hitachi?

Its a personal problem i am very disturbed individual. Mac

Purely psychedelic.  Better for your fix than other avenues I can think of  [bite tongue]

 

[jmbfestool]

Oh crap this reminds me I need to reply to Germany about kapex.

Totally forgot!  Just had a baby so been busy doing other things.

Well its interesting another kapex bites the dust.
Atleast yours is within the warrenty.

 

[luke1984]

Yeah still in warranty but a huge pain in the  because iv got loads of work booked in and I could do with my kapex on most of it

 

[GarryMartin]

Just had a baby so been busy doing other things.

[member=5671]jmbfestool[/member] Congratulations! Best news update on a Kapex thread *EVER*  [big grin]