Getting a smooth finish on Baltic Birch Plywood [help wanted]

[daydark]

Hey all, I sell a product that is made from Baltic Birch. After the product is routed, the layers of the Baltic birch are exposed and we have to sand them down (there are burrs and rough spots.) This is taking a lot of time and I was wondering if anyone had any ideas for how to improve the finish.

I understand that some sanding will probably be necessary either way, but if we could eliminate a lot of it, it would save us tons of time.

We are using a 3/8" Compression bit to do through-cuts on 1.5" thick panels of Baltic Birch. We are cutting them in 3 or 4 depth passes.

One solution I had (but haven't tried it), is to come in about 1/16" or 1/32" and just shave off a thin layer of the exposed wood. Does anyone have any suggestions on which bits / feeds / speeds would work, and if this idea would work at all? Thanks in advance.

[Simops]

I have had good results, as an alternative to using a compression bit, is to use a downcut a third down and then finish off with an upcut.....

Cheers

[scottp55]

Welcome Clay.
Haven't used compressions yet, but almost always in hardwood use an allowance or offset of about .015-.02 on first pass, and then clean up without.
If you have the CEL, the new Vectric 8's have the built in "Last Pass" option which should give it to you(worth trying).
Only ever done it with 1 sheet of BB using last pass option, but it worked a treat.
Listen to the other guys with more sheet goods experience though.

[Bob Eustace]

Version 8 of the Vectric software has a cool new feature that lets you take a full depth finishing pass and even lets you run it in the opposite direction if you so wish.

[dlcw]

Climb cut using a 1/4" compression. Leave a 1/32" skin. Conventional cut the last pass cutting 1/32" thru the sheet. Make sure you do this conventional pass in one pass, not multiple passes. This process leaves an edge that can go straight to the edgebander without any touchup with sandpaper. If the bit is dull, you will notice a rough edge. Don't use resharpened bits either. Only factory original bits. I can cut about 25 plywood sheets before I have to change to a new bit. I cut at 6ips at 12K rpm on climb pass and 5ips at 12K rpm on conventional pass. I cut first pass all the way in one pass, not multiple passes stepping down between passes. Most spindles can handle this without a problem. If your spindle is bogging down, either up the rpm's or reduce feed speed until it "sounds right" for your machine. The numbers I gave are the numbers for MY machine. Your mileage may vary.

I use this process on BB, hardwood plywood, Appleply, MDO and other types of plywood. Melamine is a totally different animal when it comes to cutting. I can get about 10 sheets before the bit is dull. It even works on gold ply which is the stuff that has a 1/8" layer of MDF under the veneer providing a super flat surface for the veneer.

I cut several hundred sheets of plywood every year since I got my machine in 2009.

[knight_toolworks]

I never use a compression but cuts are good as long as the spoilboard is not too chewed up and you cut deep enough on the cleanup pass.
http://i154.photobucket.com/albums/s266/knighttoolworks/posting/852A0F91-DAB7-4BEA-880E-2CCD00BD7285_zps8pn5pxw7.jpg (http://s154.photobucket.com/user/knighttoolworks/media/posting/852A0F91-DAB7-4BEA-880E-2CCD00BD7285_zps8pn5pxw7.jpg.html)

[dlcw]

You are right on.

With a smooth spoilboard and a down spiral, you can get really nice cuts. That's what I do with the 1/2" MDF that I process. I use a 1/8" sacrificial board on top of my spoilboard and get super clean cuts with a 1/4" down spiral. I use the same 1/8" sacrificial board when processing plywood so I could use a downspiral on that as well. Lot less expensive then a compression bit. :) Once I use up my compression bit stock, I am going to experiment using a downspiral for plywood processing.

[daydark]

Climb cut using a 1/4" compression. Leave a 1/32" skin. Conventional cut the last pass cutting 1/32" thru the sheet. Make sure you do this conventional pass in one pass, not multiple passes. This process leaves an edge that can go straight to the edgebander without any touchup with sandpaper. If the bit is dull, you will notice a rough edge. Don't use resharpened bits either. Only factory original bits. I can cut about 25 plywood sheets before I have to change to a new bit. I cut at 6ips at 12K rpm on climb pass and 5ips at 12K rpm on conventional pass. I cut first pass all the way in one pass, not multiple passes stepping down between passes. Most spindles can handle this without a problem. If your spindle is bogging down, either up the rpm's or reduce feed speed until it "sounds right" for your machine. The numbers I gave are the numbers for MY machine. Your mileage may vary.

I use this process on BB, hardwood plywood, Appleply, MDO and other types of plywood. Melamine is a totally different animal when it comes to cutting. I can get about 10 sheets before the bit is dull. It even works on gold ply which is the stuff that has a 1/8" layer of MDF under the veneer providing a super flat surface for the veneer.

I cut several hundred sheets of plywood every year since I got my machine in 2009.
Wait a sec, are you saying that you cut all the way through 3/4" thick plywood at 5ipc in 1 depth pass!?

[dlcw]

Yes, I cut 3/4" plywood with a 1/4" compression bit at 5ips, 12K rpm in 1 pass. These speeds work for MY machine. I have a 7 zone (setup for 5'x5' BB if I want to cut that) Gary Campbell Black Box vacuum system that works very well. Even though I'm at 2500' altitude, I can still hold stuff down pretty well. I don't pull 10 inches of vacuum like I see some people pulling, but I pull around 7.5 and that seems to work. I use a 1/8" MDF ($5 at my supplier) sacrificial board that plywood goes on. I can cut 3 sheets of plywood on each side of the 1/8" sacrificial board. When cutting is finished, I simply slide the whole thing off the table, to a working table and load up a new 1/8" sacrificial sheet, put on another sheet of plywood on the CNC and let it start cutting while I put labels on parts and get them ready for edgebanding. You have to figure out what will work for YOUR machine.

I also cut 3/4" and 1/2" MDF in one pass at these speeds. Down spiral bits used for MDF.

I ONLY USE FACTORY NEW BITS!! No resharpened bits.

I've got a 2009 PRS Alpha with 2.2hp spindle running the last release of 3.6 control software. I use my machine to make a living, not beta test software for Shopbot. 3.8 has had to many reported problems on this forum for me to chance shutting my business down over a few of features I may or may not use. I use SBLink a LOT and don't know the situation with 3.8 and SBLink and am not willing to test to see if it works. I've spent a lot of time performance tuning my machine. I've used a lot of Brady's (and other's) suggestions for tuning. I can process 6 to 7 sheets of plywood per hour. This includes parts labeling and edgebanding.