long term stability of wood framed router

[dave925]

I am considering building a CNC router and have just discoved CNCZone. There seem to be a lot of good information here, but I have not had a chance to get through it all yet. My question may have been answered in another thread. If so please let me know. I design business jets for my day job, so I may be overanalysing some of this.

My plan as of now is to build a small router to do carvings in hardwoods and etch glass and acrylics. (approx X= 18" Y=12" Z = 4") If things work out I will build a bigger machine in a few years.

I have noticed that a lot of people are building thier router out of wood or MDF to keep cost down. My concern with doing the same is with the long term stability of the wood (or MDF) frame. Does the accuracy of the machine change with the humidity level or temperature due to the wood expansion? I will house the router in the garage. Will the humidity and temperature fluxuations over time cause the linear components to become missaligned? Will you have to rebuild the router every year or so? Is there anyone out there that has a wood framed router that they have been using for a couple of years? If so I would like to here about your experience.

[ynneb]

.
IMO....

Steel doesnt lie.

Its cheap.
Not that much more expensive.
Easy to join. ( Weld)
Extremely strong.
A bit of a bugger to cut, but not too bad.
Taps well.

If you want your machine to last a few years, its better to put in a little longer in the building effort and make an extremely strong and reliable machine.

[yukonho]

I have been using my MDF machine daily for over a year now. It has also survived a trip across the country. It is still as solid as the day I finished it. It is a very sturdy design and I am sure that helps, a flimsy design would no doubt show more signs of loosening up. This is a good point to consider when you are in this stage.

I chose MDF because of the availability of woodworking tools to me. I may have made it from MDF even if I had welding and steel cutting tools at my disposal, but that is simply because I have more woodworking experience than metal. I am beginning to make plans towards a steel machine down the road. Just want to make some final refinements on this design first.
There is no argument that steel will last longer and stay truer than wood will, but unless you are making tight tolerance parts, the typical hobbyist wont notice a difference when cutting plastics and wood.
One other consideration is that there were changes I wanted to make to my machine once I had finished it. Working in wood gave me the chance to build a machine and learn about the special needs of CNC without having it cast in steel. I will be much more "qualified" when I do the design and build of my steel machine.
co

[pminmo]

MDF actually is a relatively stable product. Not steal mind you, but much better than dimension lumber. MDF, not particle board. There not the same.

Phil

[vladdy]

The only time I've noticed any problems was in high humidity, as the MDF does seem to swell a bit...Actual prolonged moisture on the MDF itself will cause permanent swelling and deformation..
I coated all parts with a thinned shellac mixture, and then brush painted a hammertone medium grey paint over that when it was dry..[second time]
first experiment on a small piece I noticed that just the paint alone would cause some minor swelling, thus the quick dry shellac seal coat..
Standing water [from cutting lexan] doesn't bother it now...

enjoy..

[yukonho]

Another wood product people use with great success is Baltic Birch plywood. I may make my next router from it to see how it goes. Finish is nicer than MDF, and it should be more resistant to swelling from moisture and splitting from screws.
I like the idea of sealing and painting too, how does it look?
Colin

[2muchstuff]

If I was to build one out of wood, I would definitely use Baltic Birch veneer plywood over MDF. I have used birch plywood in my model boat construction for years now with no signs of warping. Yes it does cost a little more but it is definitely worth it in the long run, besides 3/4" -13 ply, is awsome stuff to work with. By the way, due to the size of my router, I'm having to build it out of steel.

[dave925]

Thanks for the good info. Steel was not an option I was considering. I do not have any welding equipment and it has been many many years since I have done any welding. I would not have any confidence that I could maintain the necessary accuracy or jount strength with my welding skills. I do have some experience with building out of MFD. I mostly biuld with Oak, Maple and plywood. The other option I was concidering was using the T slot aluminum extrusion. My other concern with using MFD or plywood is maintaining a rigid gantry with a y axis in the 18 to 24 inch range. Most of the plans I have seen for MFD have Y axis below 12". Has anyone made a MFD or baltic birch plywood router with a Y axis above 12"?

[joecnc2006]

Originally Posted by dave925 Thanks for the good info. Steel was not an option I was considering. I do not have any welding equipment and it has been many many years since I have done any welding. I would not have any confidence that I could maintain the necessary accuracy or jount strength with my welding skills. I do have some experience with building out of MFD. I mostly biuld with Oak, Maple and plywood. The other option I was concidering was using the T slot aluminum extrusion. My other concern with using MFD or plywood is maintaining a rigid gantry with a y axis in the 18 to 24 inch range. Most of the plans I have seen for MFD have Y axis below 12". Has anyone made a MFD or baltic birch plywood router with a Y axis above 12"?

Here is mine.

http://www.cnczone.com/forums/showthread.php?t=10067

[2muchstuff]

I can say this having used birch veneer plywood before, you won't have to worry about warping and flexing. I'm not refering to the junk you can find at Lowes and Home Depot, the good stuff can be found at hardwood specific lumberyards and usually comes in metric sizes. If you are concerened about it on the spreader piece between the two uprights on the y axis, double it up and use Gorrilla glue with some screws. Use biscuts and screws at all joints and stagger the joints. It sounds like you may be a woodworker, if so you shouldn't be a problem for you. You could go crazy and be the first to dovetail all your joints. The only thing I have read about in this forum regarding MDF is the stripping out of screw holes and the stability/ swelling due to changes in humidity. I know all woods will swell/ change due to humidity but a good coating of shellac will seal things up nice. Sealing up with just paint doesn't work because it is too porous to be effective.

[yukonho]

http://www.cnczone.com/forums/showthread.php?t=3059

This is a link to my build thread for my second router. Travel is 22 X 10 X 3. I know you want more, the reason I posted this is because of the rigidity of the design. I am certain it can be enlarged somewhat. Food for thought anyway.
co

[pen25]

I am thinking with the cost of 8020 it seems to be the best overall for stability and all. you can still use mdf or birch ply for some of the parts. I just bought 6 97" sticks of 1515 i plan on using in my router. I will be buying prob 6 more. all for the cheap cost of 187 shipped to the house.