MDF vs Plywood and wood vs metal Router table

[ger21]

Originally Posted by Coogrrr I would think that if you buy a sheet of 1/2 mdf sandwitch it between 2 1/2inch ply (almost anything) completely coat surfaces with glue lay on garage floor and set several buckets of rocks to hold them together. When dry cut board and put 1.75inc screws thru boards in both directions. wouldnt you end up with a cheaper (thinner parts and cheaper products) yet stong as all hell solution compared to all the BB or laminating the hell out of mdf?

Buckets of rocks don't really provide enough clamping force to do that job properly. You need clamps, lots of them, or a vacuum press.

Originally Posted by Coogrrr last stupid thought was after enough BB or mdf and lamination could you just buy some steel and pay to have it welded for cheaper?

Where's the fun in that??

[Coogrrr]

Originally Posted by ger21 Buckets of rocks don't really provide enough clamping force to do that job properly. You need clamps, lots of them, or a vacuum press. Where's the fun in that??

I dunno just thought maybe it would be kwik and cheeep. Anywho I am interested if there is a way to slap 2 or three sheets of something with glue and screw together that would make a non-warping piece, I ask as I may do something like this on a smaller second table.

[randyf1965]

Use your router to cut a torsion box for a new table...... the interlocking torsion frame work cut from 1/4" mdf (or plywood) with a 1/4" skin on both sides (wouldn't be a torsion box without.....) is very easy and extremely strong (glued and nailed)

[SZID]

Interesting points & advice!

I have come here trying to determine if Baltic Birch Ply can come close to aluminum's performance while saving some $. I have built many items/gigs/furniture/etc using both MDF/HDF and Baltic Birch. Baltic Birch is very good (often refered to as either Baltic, Russian Ply or European Plywood). It is made of birch which is a hardwood and because it is super laminated it already contains a good level of sealant in the adhesives binding its layers together...the low viscosity expoxy would be perfect as a finished coating. BB holds brad nails like a tiger, drills/routers very cleanly for holding t-nuts and is available in 5'x'5 sheets in 1/2" 3/4" 1" thicknesses. I have found the stock at Toronto's Century Fairbank Lumber to be superb, flat stacked and high quality.

BB was once used in building aircraft frames...laminated into 1.5" member it is dangerously strong. I am considering building a CNC router with this once I research a little more. I believe side frame rails in the 2X4 size can work very well with hardened 1/2" rod on the top and bottom to engage with V roller bearings.

My $.02-------hopefully worth gold.

-SZID

[mykrowyre]

Modern MDF is mostly GLUE. So it's far more stable than plywood which is layers of wood, glued together with gaps. As for birch, it is not what it used to be. To get good quality (aircraft or marine grade) birch, it's VERY expensive. Home Depot sells birch, and I've used it here and there, but it tends to delaminate and is not very good quality.

To me it was not worth the effort.

After weighing the options, I decided to go with 80/20. I couldn't bear the thought of coming out to my workshop in the hot summer to find my CNC warped from humidity.

I figured I'd spend the same amount of money rebuilding/repairing a wood cnc as I would have spent to build it right the first time with 80/20. Plus, the 80/20 can be ordered pre-cut to length.

[SZID]

Understood about 80/20. The thing is, we're looking to cut aluminum and 80/20 alone rings like a tuning fork unless it is properly dampened for vibration.

We are considering epoxy-foam filled 80/20 (plus other modifications) OR utilizing the natural characteristics of Baltic Plywood which would do this very well. NOT BirchPlywood from HomeDepot...we're talking BALTIC RUSSIAN PLYWOOD (highgrade) with significantly more thin veneers of birch, it is heavily impregnated with adhesive. These layers are very uniform..no voids.

Baltic Birch may very well have more resistance to temp than alum and humidity should not be a problem if edges and outer surfaces have coating of epoxy. Its heavier weight may also help to damped vibration/chatter. Many useful benefits... easier to work with and less cost than alum. Best way to varify is to try it which is exactly what we must do


-SZID

[mykrowyre]

Originally Posted by SZID Understood about 80/20. The thing is, we're looking to cut aluminum and 80/20 alone rings like a tuning fork unless it is properly dampened for vibration. We are considering epoxy-foam filled 80/20 (plus other modifications) OR utilizing the natural characteristics of Baltic Plywood which would do this very well. NOT BirchPlywood from HomeDepot...we're talking BALTIC RUSSIAN PLYWOOD (highgrade) with significantly more thin veneers of birch, it is heavily impregnated with adhesive. These layers are very uniform..no voids. Baltic Birch may very well have more resistance to temp than alum and humidity should not be a problem if edges and outer surfaces have coating of epoxy. Its heavier weight may also help to damped vibration/chatter. Many useful benefits... easier to work with and less cost than alum. Best way to varify is to try it which is exactly what we must do -SZID

Ahh ok. Makes sense to me. I agree real high grade russian plywood is some fantastic stuff! I'm surprised it's not more expensive than 80/20. But I understand why you don't want to go with 80/20... it does ring like crazy!

[ger21]

I'm a big fan of building with wood. But you need to do it right. I'm currently working on a large wood machine. Baltic birch, torsion boxes as well as some custom laminations. The goal is to have a very high performing machine.
As you said, they used to build planes our of wood. They also build very big and fast boats from wood. It's all about how you use it.

Here's some pics of the parts for my spindle carriage. I haven't assembled it yet, but it should be incredibly strong. It's also very compact. About half the size of the one on my first router. It's baltic birch with Makore veneer.
http://www.cnczone.com/forums/691923-post172.html

[eigstein]

on the subject of wood cnc routers. check out these two german machines. the big one has 40mm. ply and the smaller has 30mm. ply. its most likely laminated baltic birch. at the turn of the 1900's wood and semi-wood frames were used in a lot of industrial machines.
you can google CNC-Wood - Home have google translate the german.