Why would a SM Mark 7 bog during operation?

[KCollins]

I have a SM Mark 7. I was running the jointer at 3500rpm to joint the edge (3/4") of a black walnut board. When I would feed the material the headstock would bog down and almost stop. I wasn't feeding it very fast either. It hasn't done this before and it just struck me as odd. Thought this headstock was supposed to amp up if it detected a drop in rpm.

This has been a very and I mean very lightly used headstock... I haven't be begun to put it through it's paces. Maybe 20 hours of use so far. So it can't be over use or misuse...

Anyone had the happen to them before? Thoughts?

Thanks

Kevin

[RonKlein]

Kevin,
Drive belt slipping? I have seen reports of the motor pulley set screw loosening, so check that and the drive belt tension.

[DLB]

My thoughts here presume it is a Gen 1 PowerPro. Is there a fault message on the display when this is happening and/or does the RPM indicated drop off? (Trying to isolate between the motor bogging and something slipping) I don't want to encourage looking elsewhere when cutting, so maybe have someone else watch it or record it during the bog. I have a Gen 1 PP that I bought used that would actually stop running even under relatively light work load, in fact it would sometimes stop running just trying to come up to a high speed (9500 or 10K) while doing no other work. It just seemed to have little power, which I isolated to the Power Supply / Control Module and bought another one. Fault message was always 'Low RPM,' same thing you see when it is spinning up.

I have heard of, but not experienced, poor contact in the drive lines at the (Molex or similar) disconnect between the Controller and Motor. Either the two halves of the disconnect might not be locked together or a single pin/socket may not be locked in its half and pushing out when the halves are connected. IIRC this is a six pin disconnect with fairly large diameter wires for high current. I think you have to tilt the motor to see this connector.

The good news here for you is warranty coverage.

If it is slipping, PowerPro's have a reputation for causing setscrews to loosen, as RonKlein mentioned. I would start with the Headstock and Jointer drive hubs for that.

- David

[KCollins]

DLB... I is a Gen 1. I didn't look at the display when I was attempting to run it through the Joiner. So I'm not sure what it said. However I do remember that it seemed as if the headstock was bogging down not slipping. If it was slipping there was no noise to indicate slippage. It is raining most of the day tomorrow so I'm unsure if I'll be able to get the SM out of the garage to run it but if I get a window of time I will give it a good look over. Check all my connects and verify that lower pully isn't slipping. Thanks for the help guys.

Kevin

[Swiley3362]

I had an issue where the drive coupler was not tight and spinning on the shaft. When the unit was under load, the coupler was not turning the cutter head on the jointer.

[JPG]

Jointer @ 3500 rpm ? ? ?

[KCollins]

Yes JPG 3500 rpm. And this has never happened in the past... It would chew up whatever I feed it as fast as I feed it... This time I had to gauge my feed speed by the amount the joiner slowed or bogged down as I feed it into the joiner. Sounding liking I'm going to have to tear the head apart and check on my connections and pullies. Swiley the drive coupler slowed the same amount as the joiner as the head stock. It all bogged together.

[DLB]

Yes JPG 3500 rpm.

This is a confusing convention that I blame SS for. On the PowerPro, RPM (set or measured) is always referring to upper spindle RPM. Same if you set a function through the menus. And I just checked my laminated speed charts, they also give Jointer speed of 3450 - 3500. But since the Jointer is physically connected to the lower accessory drive its actual speed is ~1.6 X upper spindle RPM, so something around 5500 RPM. Unless, of course, you mean you are really running the Jointer at 3500 RPM, not at indicated 3500 RPM...

- David

[KCollins]

David,
According to the display on the power stock it read 3500rpm and had a number below it of 3495 that fluctuated some when I was looking at it. From 3500 to 3490ish. I didn't read it when I was feeding the material. I should have gotten a second person to look at it.

[DLB]

For clarity, you also have a 'saw cuts funny' thread going. Am I correct to presume that the PowerPro is neither slipping nor bogging during table saw operations at approximately the same set/indicated speed? To me, that would suggest slipping. And you've already determined the coupler is slowing down with the cutter head. So the most likely source of slipping is the drive coupler piece on the lower aux shaft.(?) IIWM, I would check that setscrew first. The motor pulley, at least on the original motors, is keyed and won't slip even if the setscrew gets loose. It might rattle a bit or slide in toward the motor, but should continue to turn at the same speed as the motor.

Note: Most parts internal to the headstock that are unique to the PowerPro are metric. This includes the small setscrew on the motor pulley, at least on mine.

- David