Dave
Please check with the Manufacture on the size of the rebate inserts. If they are too small in height to cut enough wood away to get over the top of the rebate guide fence that the same issue will happen. The board hits the rebate guide (if you have one) and raises the lumber off the bedplate.

Hope that helps

Thanks Russ. I will go over those points with it today. The articles are very helpful!
Rpm is 6000 with 4 knife head. 6m/min which is 19.68 fpm. I can also run it at 38 fpm. I'll run a piece like you suggest away from the rebate cutter.

Ok. Checked rebar cutter and all good radial and lateral. Made a slight alignment. Lots of room to go over the shoe. Ont thing though, the shoe is exactly in line with the right fence past the first vertical spindle.. As per pic
Tightened belt to main joint head, helped a bit. Next pic is the pattern i see off the bottom head running at 12mpm.

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Is the air pressure on the feed rollers 40lbs?
Is there a star knob on the first set of rollers, if so make sure the roller are all the way down, feel free to call me if you wish

The vertical cutter on the rebate cutter should lightly touch the straight edge in your picture. How much are you taking off on the infeed table fence? It should be around 1/8".

Dave
Would you please provide a pic from the infeed of you machine, I would like to see the a portion of infeed table, rebate cutter and the right cutter head. I am not familiar with the Sicar machine. I might help see what you have going on.
Thanks in advance
Russ

Dave
It almost looks like that fence you have the ruler on in the pic is the fence and not a guide fence for the rebate cutter. If that's the case do this,

Put a straight edge flush to the fence behind the right cutter head.
Adjust the right radial cutter head until the straight knife barely touches the straight edge.
The fence in front of the right cutter head should be behind the plane you just set, by the exact amount of wood you want the right cutter head to remove.
I hope this helps make the saw marks go away.
You should have a lateral pressure element that pushes the lumber to the fence attached to the left cutter head assembly. this should eliminate the chatter we are seeing from the sides.
The bottom chatter is telling me there is not enough feed roller pressure to hold the workpiece on the bedplates.
I am running out of options :)

2 pics wheels on and off.

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Russ I think I have the side rebate cutter aligned well now. Nice smooth cut on the side when removing 1/8" last task is bottom. I will put more pressure on the feed rollers. When the machine winds down in rpm you can hear a zum zum zum zum zum. Of the bottom cutterhead. About 1/3 second apart. Very odd.

One more thing, I have top hang the knife top the right on the joint head like this so there is no gap between the rebate cutter and the main knife.

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Dave
I think I see the problem,

The knives look very dull. The motor will still spin the cutter head even with dull knives. What happens is the wood is being plowed into a dull knife and lifts the wood off the bedplates to crawl over the top of the cutter head instead of cutting thru the wood, creating the ripple effect. The sound must be very loud when milling, the machine is talking to you begging for a sharp knife:)

Please replace or sharpen the knives, I think you will see a huge difference,
The other issue would be feed roller pressure, how can you control the pressure on the rollers?

Were getting there
Have a good evening
Russ @ MR

I have a question that may sound a bit off but I want to check to make sure its aligned correctly.
If you place the straight edge on the bedplate after the bottom head is the knife just barely touching the straight edge?
I know is basic but I have to ask, sometimes common knowledge to me is not to others.
Thanks
Russ

Yes - have a very flat ground bar and I set the cutterhead/bedplate so that the knives just move the bar about1/8" linearly. We do the same with our felder jointer, knives are just a thou higher than outfeed. New set of kinves arriving Monday morning.
I almost feel like I want to go back to the 4 knife head where the knives are ground rather than the tersa. We process about 1500 bf per month. Always stock that is 2-1/2 wide x 13/16 finished dimension.
Another thought is that perhaps the rebate cutter should be rotated in ration to the cutter block so that the vertical carbide is not near one of the cutterblock knives. Seem to get a solid buildup of shavings right in the corner.

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That's a good idea on the rebate cutter, I think new knives will be a big help. did that rebate cutter come with the machine? It just look like a mismatch, never seen a gap so big between the two cutters, there must be a shoulder on the cutter head or something like that.
I would be interested in seeing the wood after you change the knives.
have a good weekend Dave
Russ @ MR

Good Morning Dave
Curious to see if you solved your problem with the new knives?
Thanks
Russ

Waiting on new blades to arrive in before re-evaluating. Should be either today or tomorrow. I'm changing all cutters on the jointer and rebate cutter. Also took off the head and re-use the position of the rebate cutter relative to the counter knife. That helped shavings control. Will clean of residue on all other heads. Smal steps and I am seeing improvements.

This has a chain drive for the pressure wheels, should the chains be tight or have some 'slack'? The feed seems slightly choppy as I keep a finger on the board as it goes in but that could be something else.a

Dave
I have never seen a chain drive, that could be the issue especially if you feel its choppy.
Sorry I am no help on the chain drive maybe somebody else will chime in.
Russ

This is what I mean by chain drive

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Changed all the knives for genuine tersa knives on the jointer head. Remarkable difference in the quality of cut. I still get the very odd pattern that I'm showing in the picture but it's much shallower. I took off the other three cutter heads and rotated all the knives so that everything was sharp and I cleaned them very very well.
i ran this piece of cherry at 12mpm instead of the usual 6mpm and three sides are perfect. i think running at 6 was dlling the knives due to overheating. The pattern that you were seeing on the wood repeats two and a quarter inches. I highlighted it with white chalk.
very odd. I am thinking now that I have an oscillation in the joint or head perhaps something is loose. perhaps the bearings are pooched. or the chain drive is doing something.

Even though there is that slight Ripple on the bottom that it is so shallow that we can tolerate that and sand it out with our thickness sander once our parts are assembled.
any thing else i should be checking? with the main cutterhead running solo there is alot of vibration in the long infeed bed.

my gosh, so much time spent!

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This may seem like an odd question, has the machine been placed on leveling pads and is the machine level? The leveling bolts need to be on a leveling pad, not just the bolts touching the floor. Basic stuff that gets overlooked sometimes.
Those knife marks would drive me nuts.
Oh well if its good enough for you I guess my job here is done.
Thanks for allowing me to help (somewhat)
Russ @ MR

I'm going to keep working on it to get rid of the knife marks. Drives me nuts as well and not up to my standards. I like things running perfect! Thanks for the help Russ! Much appreciated!

I am going to re-level it tomorrow and check all the bolts and pads. We have 1/2" steel plates 3x3"

Dave
I question weather a steel plate has the ability to absorb any vibration. Please read my article on leveling a profile grinder, same concept for a moulder. There are some pics of cast leveling pads and shock absorbers. You may want to review to see what you think.
All the best
Russ @ MR

https://www.mr-moulding-knives.com/information/profile-grinder-leveling

Problem solved!! Out of balance pulley on main motor. Was shaking the whole machine.

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Excellent Dave
Good sleuthing,
Its been real.
All the best
Russ @ MR