Bamboo plywood and wheatboard feed rates

[laura]

Hi guys!
I am cutting two sheets, 3/4" solid grain bamboo plywood and 3/4" wheatboard. I have previously used the ShopBot to cut 3/4" Medex (formaldehyde-free particle board). I have a question about feed and speed rates. The Medex took 8-9 hours at 1 ips, 15000 rpm with a plunge rate of .125 inches. I used these same rates with the bamboo ply previously. The folks at Plyboo said the solid grain cuts like maple or "any other hardwood." But, they weren't sure of the rates.

There were no burn marks and the cuts seemed clean enough. But, the tech at my school (yes! I'm a student) thinks that 1 ips is way too slow and thinks it'll be a danger because of the dust that forms. Additionally, I'd like to cut the time down to less than the 8 hours it took. But, he didn't have any suggestions on rates. Any suggestions for cutting both plyboo and wheatboard?

Thanks for your time. I am amazed by the expertise I've seen on these postings.

[Gary Campbell]

Laura..
We have had some experience with Bamboo. It is hard like Maple, but more fibrous. You didnt mention what kind of stepdown you were using, but I would would definately kick up the feed speed. Do a practice cut at 3/8 Stepdown, 2.5 ips and lower the RPM to 12-13,000. Check your chipload and ears and adjust accordigly. We have had the best luck with single O Flutes in these types of material. Specifically the Onsrud 65-000 series in upshear or the 64-000 series for downshear.
Gary

[laura]

Dear Gary,

Sorry, I was using a .125" stepdown, not plunge rate. I used a 1/4" carbide straight double flute bit, but it's been recommended that I try an upcut spiral double flute. Have you tried that or do you still recommend the O flute from Onsrud? Any suggestions for wheatboard?

Thanks so much for your speedy reply. I appreciate your input. I'll give your suggestions a try.

Laura

[Gary Campbell]

Laura..
For your exact needs you will have to experiment. The 2 flute may work fine for you at faster speeds, but we have found that the O Flute works better when we are looking for a high quality cut. The single flute allows a better chipload at slower move speeds, and the O flute design is the best I have seen for many of the imported woods as they are, like you say, as hard as maple. Make sure that you are getting curled chips off the cutter, not dust, and they will last fairly long.

You should get great results with the 2 flute in the Wheatboard. We mostly cut solids or veneer over solid or ply core, but with the little we have done have been at move speeds 1.5 to 2 times higher than listed above. We seldom run the spindle over 13K rpm, but I will defer to the guys who cut those types of material. Good Luck
Gary

[laura]

Thanks Gary!

I'm going into the shop today to run some tests. I checked out the Onsrud O flutes online. They look beautiful.

Laura

[seana]

Laura,

We cut a lot of bamboo.
We cut at 3IPS and 12,000 rpm. What we found was that we needed to cut in two passes first cut to a depth of .6 (.75 thick material) with an offset of .04 and then the second pass on profile to full depth.
Were using .25 compression (we need both sides without tear rout) bit but have cut with the good results using up spiral if the top edge can have tear out.
We use the two pass cut system because the laminations of the bamboo seem to cause bit deflection even using larger dia cutters. The second cut will give you a nice edge with minimal sanding and tool marks.
Also do the two path system if you make dados or pockets, it still amazes me the amount of defection in a product that is considered a grass.

Bamboo is full of silica and is hard on tooling so don't purchase really expensive bits.
I have been having good results with bits from http://centuriontools.com/.

Hope this helps good luck

Sean

[jhicks]

Sean, good info to start trial cuts with, thanks.
Any experience with the end grain butcher block/checkerboard style laminated bamboo sheet?
Trying to cut 1.5" thick sheet for a counter top for sink hole and cut out?
This stuff is pricey so hope to get it right the first time but have some scrap area to experiment before diving into a $450.00 sheet
Thanks

[seana]

Jerry,

Haven't cut the butcher block style bamboo sheet yet but there is talk that i will be soon.
I would be leary that the "little blocks" may want to tear out.
If It was me i would start with the sink cut out with a large off set and see what happens.

Let us know what happens.

Sean

[jhicks]

Hey Sean, with much trepedation we went forward but happy to report good results. Used 1/2" wood route 2 flute straight cutter at 100IPM/25 plunge rate, 1/4" per pass in conventional cut direction for inside hole cut out and counter edges cut from outside the vectors down to 1.6" on 1.5" stock into vac spoil board.
Chips were nice size and warm, cut was clean except for the vertical fiber being irregular so minor clean up will be required to sand edges a bit smoother. Not a problem though
On the exit side of the counter back corner cut (which was the 30" stock width so we only cut the angle and end edge, not an entire rectangle) there was a small .125 radius chip out but not a problem for this counter.
The bit was a bit warmer than I would prefer for short cut time but not hot, so I would probably either dial down rpm or kick up move speed a little but with my small 1AMP motors I would rather err on the side of caution and a warm bit than bog down for some reason and lose steps on this material.
I think the block tear out suspicion is a real possibility depending on the cut shape and exit points so that consideration should be studied for best results in a worst case scenario. I certain it will happen intermittently so design cut directions, start and end/exit points with that in mind and you'll be happy.
With this bit the chips really packed in so we blew out the route area after each pass to reduce heat and grind until the last pass but no top or bottom surface tears.

Thanks

[seana]

Thanks Jerry that is great info.
I'm going to print your post and keep it in my notes.

Thanks again, and glad that it came out well for you.

Sean

[laura]

Thanks Sean (and Jerry) for the advice. I did some test cuts yesterday with various feeds and speeds. I also talked to a guy at Onsrud....great bits. I'll check out Centurion too. A friend who cuts bamboo highly recommended a 3/8" spiral compression bit, but for my project and budget, the Onsrud guy thought I'd be better off with a solid carbide double flute upcut. Previously I used a carbide tipped double flute straight...with good results, but again...slow times (8-9 hours).

I failed to mention that I'm using an old Shopbot. I was running tests yesterday at 2.5 ips, 12,000 rpm and a stepdown of .375. Chip size looked good. But, it was a little rough on the edges...I could see circular bit marks and their was a little tearing on the top edge. I need at least one side to be clean. Anyway, other tests were between 12,000-15,000 rpm, 1-2.5 ips, stepdown .125 - .375. I'll have to look at the tests more to see what'll work for me. Thanks for your advice on the trial cuts.

Laura

[jhicks]

Hi Laura, the edges we got with the stratigh 2 flute edge were quite acceptable BUT did require some sanding. The fiberous nature of the material in the vertical end grain butcher block material is just not going to machine like a hardwood. The fibers tend to break off but nothing too drastic. sanding the edge worked well and didnt take too much effort.
Good luck

[knight_toolworks]

I cut a large circle in some bamboo plywood. I think I was using a 1/4" rougher it was a longer bit with a 1 /14" cut length. it was 3/4" stock and I did it in one pass at 1ips. but the circle ended up with these even flats all the way around it. I think they were a inch or so long. I cut a bunch of smaller ovals that were fine but the big circle had those flats. ever see anything like that? I think now I will use a larger bit ad two passes at a faster rate. but I did cut it nice and clean.

[cnc_works]

Steve, I would suspect that your circle was segmented in the artwork. Check the nodes on it and see if they are spaced around the circle the same as the cut flats.

Donn

[knight_toolworks]

thats what I thought but I looked at the nodes and there were only 4.
but I had problems with most of the drawing. we had to edit a bunch of the other pieces and later after they were cut we found one that the shape had changed in the drawing. so maybe the circle was effected too.
every drawing I have had from him has had problems.

[beacon14]

How were the drawings created and what software was used to make the toolpath? I find when drawing curves, arcs and elipses they will machine with straight segments UNLESS I convert the curves to vectors before exporting/importing into VCarve.

[knight_toolworks]

I can't remember what he used it was not your normal cad program. one from corel I think? we ended up opening it up on turbocad to fix some of the problems. but it seems even though they looked good there were problems not noticed. but looking at the circle it only had 4 nodes like a standard circle and it looked good on the preview. but I have seem some crazy things when importing.