Problem with wavy laminations

[EwokArcher]

I built this sander to save a buck, ended up spending about 40$ (got the motor for 2$ at a garage sale)

I've been working on getting lams out of it but keep coming up with some wavyness and occasional dips. I found running the lams through slowly several times helps this some but they aren't coming out as perfecth as I'd like. The drum spins true so  so that is not the issue. I'm using 60 grit on it currently.
I appreciate and tips or advice. I told my wife to put a nice drum sander on my Christmas list lol. Thanks for your help guys.
Ty

[EwokArcher]

Sorry here is the link for the sander I built. I used a drum that I could cut my own sand paper for out of standard sized sheets.
http://www.buildyourownbow.com/how-to-make-a-simple-thickness-sander-for-bow-laminations/

[kennym]

If the feed speed changes, it will make dips. Without a conveyor for lams, it takes practice to keep feed even, someone on the other end helps too.

Even with a conveyor, I found most conveyor belts have a few thousandths difference at the belt splice, so I just slowly let the sander down and sand the belt just a little.  

[Roy from Pa]

If you are pushing them through by hand, then that's part of the problem.

[Buemaker]

A good drumsander  also have pressure rollers, one on each side of the sanding drum to press the lamination down onto the conveyor.

[Mitch Edwards]

Something you deal with in machining is rigidity. If you push harder or a few inches everything will flex and get out of the way. Then when you let up everything goes back to where it was. Don't know much about bow building though

[Mad Max]

Originally posted by Roy from Pa:
If you are pushing them through by hand, then that's part of the problem.

I guess it's not OK
Wrong       :p      
I have one of these     http://vanda-layindustries.com/html/the_hog_sander.html    

I also have a 12" baby drum sander
The hog is so nice, if you want to get rid of the snipe, just run it threw the hog.
I never had any wavy lams.


are your lams dry?

[bigbob2]

Wow Mark that is a good looking sander.It's a pity it would be cost prohibitive for me to get one over here.

[Roy from Pa]

LOL, that's not a real drum sander...  

[EwokArcher]

I'm thinking the feed speed is my primary issue I didn't know that was a factor. I'll see what I can do working with that in mind.

[Mad Max]

Take the sand paper off.
Raise the table as close to the drum and see if the gap is parallel and rotate the drum by hand and look at the gap. I bet it wobbles.
check for loose bolts ect.

The Hog really is a nice sander.
I push and pull.
I have sanded down to .025
I make overlays tip overlays parallels and even tapers. I use it all the time.

[EwokArcher]

I appreciate the feed back everyone. I spent a couple hours in the shop today practicing and can notice a huge differenice after trying up my drum more and also focusing on steady feed speed. I think these will be passable. I did a little touch up on my belt sander following and believe I will be able to get good glue lines.

[JamesV]

Guess I am about the only one that cuts lams on a planer. My sled runs on a rail and the planer pulls it thru at an even speed. I get perfect tapers every time. I just don't see sandpaper cutting as accurate as a planer blade.

James

[mikkekeswick]

Jamesv it is the other way round. A planer leaves a washboard if you look closely enough. Sanded lams will give a stronger bond. Also planer blades no matter how sharp compress the surface compared to a sanded surfaces which is easily wettable by the glue. Even the very best industrial planers with 4 blades have the same problem.
The lucky thing is that we have very good epoxies now that don't necessarily need perfectly prepared surfaces to work.

[Roy from Pa]

I run my lams through a drum sander on a sled with a tapered lam pattern under the lam I'm making. Kenny made me 4 different thickness lam patterns on his High tech drum sander. I choose the thickness taper I want and run them through several times. I get perfect lams.

My drum sander would eat up that hog. LOL

[kennym]

That was hard making those sleds, Roy specified in 1/32"s . That is 31 and 1/8 thousandths.

Whew!!  

[Roy from Pa]

.03125, get it right ole boy..  

[kennym]

Just checkin, and you said you didn't know nuthin bout thousandths....  

[Roy from Pa]

I went back to school son.. Couldn't let you get ahead of me..  

[monterey]

Guess I need to go get my GED.  

You have to have a way to apply pressure to the stock on both the infeed and outfeed side of the drum.  I'm still trying to get it right.    

If you want really really nice lams get in touch with Troy.