Bow in sheet after ripping on panel saw

[dohertycarpentry]

I have been having an awful issue this past few months with my panel saw, say I cut an 8x4 sheet of MFC down the middle, I'm being left with a 2-3mm bow on both sides of the cut. I spoke with an engineer about it, he was too busy to take a look at it but he put it down to board tension.

The blade is good, the riving knife is in line with the blade, the fence is parallel with the blade etc. I've checked everything I can think of but I'm still getting it. I have heard that because of the pandemic and the demand for sheet materials is so high that the sheets aren't being properly kiln dried, is there anyone who has heard that also?

At the moment I have to cut everything twice, rough cut to size and then final measurements, which is a pain.

Any ideas what it could be or what I could do to remedy the problem?

 

[TheUnicorn]

I feel I'm being stupid here. but when you say panel saw are you meaning table saw? I think of a panel saw as a hand saw.

As far as the problem goes I wonder if adding additional weight to the board as it is being cut might help

 

[dohertycarpentry]

I feel I'm being stupid here. but when you say panel saw are you meaning table saw? I think of a panel saw as a hand saw.

As far as the problem goes I wonder if adding additional weight to the board as it is being cut might help

No I do mean panel saw, with a scribing blade and 3.2m outrigger crosscut sliding table.

Perhaps, I will try that tomorrow, thanks.

 

[dohertycarpentry]

I feel I'm being stupid here. but when you say panel saw are you meaning table saw? I think of a panel saw as a hand saw.

As far as the problem goes I wonder if adding additional weight to the board as it is being cut might help

That kind of saw.

 

[marcros]

Felder Panel Saw K700s "curved" cuts problem??? is worth reading through. The consensus seems to be that it is both common and material based

 

[dohertycarpentry]

Felder Panel Saw K700s "curved" cuts problem??? is worth reading through. The consensus seems to be that it is both common and material based

Thanks.

 

[TheUnicorn]

That kind of saw.

yeah that is definately not my understanding of panel saw. so is it essentially a table saw scaled for sheet material?

 

[dohertycarpentry]

yeah that is definately not my understanding of panel saw. so is it essentially a table saw scaled for sheet material?

It's mainly used in joineries or large scale workshops that make units/kitchens made out of MFC (Melamine Faced Chipboard) which is why they have two blades, main cutting blade for cutting through and scoring/scribing blade for cutting 2-3mm off the laminate first so it doesn't tear out.

Hope this helps.

 

[Doug71]

I don't have a panel saw but use my Festool TS 55 with a 3m guide rail and often have to make three cuts. First to split the sheet, second to straighten and third to make it parallel.

maybe @doctor Bob will have some input on this?

 

[TheUnicorn]

It's mainly used in joineries or large scale workshops that make units/kitchens made out of MFC (Melamine Faced Chipboard) which is why they have two blades, main cutting blade for cutting through and scoring/scribing blade for cutting 2-3mm off the laminate first so it doesn't tear out.

Hope this helps.

thank you, initially I was thinking of this https://i.ebayimg.com/images/g/PVMAAOSwUV9WolnJ/s-l300.jpg ... hence the confusion

 

[SamTheJarvis]

thank you, initially I was thinking of this https://i.ebayimg.com/images/g/PVMAAOSwUV9WolnJ/s-l300.jpg ... hence the confusion

"I can never seem to get a straight cut! Must be something wrong with the saw..."

 

[ztifpatrick]

I don't have a panel saw but use my Festool TS 55 with a 3m guide rail and often have to make three cuts. First to split the sheet, second to straighten and third to make it parallel.

maybe @doctor Bob will have some input on this?

When I read this post, the 1st thing I thought of was a Festool issue I had with my TS 75.
Apparently the Festool TS needs to "toe in" slightly to avoid this. Adjustment isn't too difficult -https://www.festoolownersgroup.com/festool-how-to/ts-75-eq-toe-in-reference/

 

[custard]

This isn't a common problem but it does happen, I've always suspected a problem in the distribution pipeline like excessive humidity/moisture, or sheets being badly stored and adopting some twist or wind. A solution that seems to work is to rip down the middle, then trim a couple of mill from each cut edge. A faff I know, but better than the alternatives.

 

[doctor Bob]

What brand sheet material is it. Egger is great, Kronospan moves all over the place.

 

[Sean33]

I have been having an awful issue this past few months with my panel saw, say I cut an 8x4 sheet of MFC down the middle, I'm being left with a 2-3mm bow on both sides of the cut. I spoke with an engineer about it, he was too busy to take a look at it but he put it down to board tension.

The blade is good, the riving knife is in line with the blade, the fence is parallel with the blade etc. I've checked everything I can think of but I'm still getting it. I have heard that because of the pandemic and the demand for sheet materials is so high that the sheets aren't being properly kiln dried, is there anyone who has heard that also?

At the moment I have to cut everything twice, rough cut to size and then final measurements, which is a pain.

Any ideas what it could be or what I could do to remedy the problem?

I have had this problem too, what has seemed to work for me is putting downward pressure on the board. I found that the biggest issue was with 8*4 sheets and cutting thin rips. The left hand bottom corner would sag under weight lifting the board slightly.
Hope this helps
Sean.

 

[doctor Bob]

I have had this problem too, what has seemed to work for me is putting downward pressure on the board. I found that the biggest issue was with 8*4 sheets and cutting thin rips. The left hand bottom corner would sag under weight lifting the board slightly.
Hope this helps
Sean.

Thats why the fence should be infront of the board. front on the fence, right hand edge supported by the bed and left hand lifts the other corner, whilst pushing through.

 

[dohertycarpentry]

This isn't a common problem but it does happen, I've always suspected a problem in the distribution pipeline like excessive humidity/moisture, or sheets being badly stored and adopting some twist or wind. A solution that seems to work is to rip down the middle, then trim a couple of mill from each cut edge. A faff I know, but better than the alternatives.

That's what I've been doing, it's a pain in the arse.

 

[dohertycarpentry]

What brand sheet material is it. Egger is great, Kronospan moves all over the place.

Finsa

 

[dohertycarpentry]

I have had this problem too, what has seemed to work for me is putting downward pressure on the board. I found that the biggest issue was with 8*4 sheets and cutting thin rips. The left hand bottom corner would sag under weight lifting the board slightly.
Hope this helps
Sean.

I'm wondering if I extend my outfeed table would it help?

I recently noticed the sliding table was about 1.5mm higher than the cast iron bed of the saw and I adjusted it so it's JUST a fraction of a millimetre higher than the bed, it helped a bit but still not great.

 

[doctor Bob]

Finsa

If it's just on MFC boards and not on MDF then I'd really consider switching to Egger.