[ger21]

Actually, I was thinking about 3 pieces of plywood laminated together. If I took the inside layer and cut a bunch of holes in it, would that be the same thing as a torsion box?
Mike...

Use something like a 1" thick center, and drill maybe 1-1/2" holes @ 2" OC. Then use maybe 1/2" skins. I'd make the uprights the same way. Try it on one of the smaller parts first, and see how it works.

[jeffs555]

I wouldn't waste time drilling holes in the inner layer. The only reason for the air space in a torsion box is weight and material savings, it would be slightly more rigid with a solid core. Cutting holes in the inner layer would not save material, and weight usually helps to reduce vibrations.

[buscht]

Mike, here's my 2 cents.

1. gantry stiffness. You would gain more stiffness in the gantry if you could increase the height of the Y axis mounting plate. I don't mean make it taller overall, but draw a side section of the gantry. Figure out where the bottom tip of your router bit will be when the Z axis is fully retracted. Extend your mounting plate down to this dimension. You might gain a couple of inches here and that will dramatically increase the strength of the gantry.

2. IGUS slides. I see nothing but trouble with the way that you are trying to use the slides. I agree 100% with your friend who said that you need 2 bearing blocks per slide. Another issue, I talked to IGUS about some slides, not these particular ones though. I've attached a picture of their recommendations.

[fyffe555]

If possible Mount the bottom Y rail up the other way. Best load capacity and least binding risk is with the load through the bearing with greatest contact area. The mounting flange directions are the direction of least capacity. Again the Igus site shows this.

Try and brace the joins in more than one plane. Increasing the x section does little is the joint is weak.

If you're going to spend that much on Igus rails then consider something more for the leadscrew. 1/4-20 is slow and too whippy for a leadscrew imho. Vibration of undue forces due to ship will cause other problems later, incuding increasing the probability of binding. Cheap Enco 1/2"-10 Acme is only 4.59 for 3'

I know this is repretitive but once you've got the dimensions and loads put them through the Igus tools and see what they say for spacing and binding before you spend the money.

Andrew

[mikeschn]

Okay, I flipped over the bottom rail, and added the 1/2"-10 Acme screw. Can you still use that cutting board stuff to make anti-backlash nuts at that size?

I put a VRML file here, if anyone wants to view it in Cortona.
http://www.mikenchell.com/cnc/2nd_try_cnc.wrl

Cortona VRML Client 4.2 is a free plugin for I.E. which you can get here:
http://www.parallelgraphics.com/products/cortona/

If you'd rather import the solid into your Cad/CAM package and play with it, or redesign it for me :banana: ,
the parasolid is here:
http://www.mikenchell.com/cnc/2nd_try_cnc.x_t

and the acis solid is here:
http://www.mikenchell.com/cnc/2nd_try_cnc.sat

Mike...

[strat]

yeppers you sure can ..... and it works fine you just need to make a tap from your acme rod you get

[ger21]

Okay, I flipped over the bottom rail, and added the 1/2"-10 Acme screw. Can you still use that cutting board stuff to make anti-backlash nuts at that size?

If you're using an actual cutting board, it's probably too thin. Get a thicker piece of Delrin from Ebay or Mcmaster-Carr for $10

[ger21]

Mike, what I'd recommend when you start building this router, is to try to allow for things to be easily changed if they don't work to your expectations. Ideally, you don't want anything to be able to flex at all. If you find they do, make it as easy as possible to be able to upgrade the machine rather than have to build another one.

[strat]

"make it as easy as possible to be able to upgrade the machine rather than have to build another one"

gotta agree with that one my machine is a couple years old now but still runs fine when i was laying mine out i did try to keep it "open" for changes
the main change i have done is removed the rails for the x axis and replaced with igus w my rails were joined together when i got them and no band saw my z axis was done with a dolphin slide so it bolted right to the igus slides need to get some new pics up

[mikeschn]

Agreed! Everything will be bolted together with socket head cap screws this time, instead of drywall screws. I should be able to swap out most major components if something has too much flex.

The first machine would need a major rebuilding if I wanted to salvage it. Instead of 3/4" x rod, I would need 1" or 1 1/4". The Y axis would need 3/4" instead of 1/2". and a lot of the MDF needs to be doubled up. That's why I opted to start with a clean sheet of paper.

Question: you are using a lot of plywood on your machine instead of mdf or aluminum. What's your logic behind that? Just wondering...

Mike...

Mike, what I'd recommend when you start building this router, is to try to allow for things to be easily changed if they don't work to your expectations. Ideally, you don't want anything to be able to flex at all. If you find they do, make it as easy as possible to be able to upgrade the machine rather than have to build another one.

[mikeschn]

Do you have a before and after photo of your x axis?

Mike...

gotta agree with that one my machine is a couple years old now but still runs fine when i was laying mine out i did try to keep it "open" for changes
the main change i have done is removed the rails for the x axis and replaced with igus w my rails were joined together when i got them and no band saw my z axis was done with a dolphin slide so it bolted right to the igus slides need to get some new pics up

[ger21]

I'm using Baltic Birch. It's lighter and stronger (and costs twice as much) as MDF. A good place to get it is Pontiac Plywood. About 2 miles south of Great Lakes Crossing.

[mikeschn]

I've been there before!!! They've got the Baltic Birch in 4x4 and 5x5 sheets.

So it's lighter and stronger. Are you concerned at all about the effects of humidity, or contraction & expansion?

Mike...

I'm using Baltic Birch. It's lighter and stronger (and costs twice as much) as MDF. A good place to get it is Pontiac Plywood. About 2 miles south of Great Lakes Crossing.

[ger21]

I've had some parts I cut 2-3 years ago sitting in my garage, and they stayed perfectly flat. I've had MDF warp overnight. I'd paint it with a good primer and exterior latex, or the always popular hammer paint. If using the hammer paint, get the quart can and roll it on. Use 2 coats, too. Lowes sells the quarts, Home Depot has spray cans only.

Are you sure they have 4x4? Last time I was there they only had 5x5. I bought mine at Public Lumber, 7 mile and I-75. They'll cut it down for you. The 5x5 wouldn't fit in my truck.

[fyffe555]

A thought on the existing machine. Your rod end support isn't stiff enough. Put a second set of rod supports a few inches in from the existing ones. Two supports at both ends would be significantly stiffer and so reduce the defelction. It would reduce the travel of the aix though..

Andrew

[Halfnutz]

I still dont understand why you dont just use aluminum for the entire construction. 80/20 will cut and tap the two main supports, and the rest can be made of 1/2 precision plate that you can cut with a regular wood table saw (with the right blade) or even a cheap jig saw. Otherwise build it just like you would with MDF, except forget about extra support, you wont need it.

[ger21]

I still dont understand why you dont just use aluminum for the entire construction. 80/20 will cut and tap the two main supports, and the rest can be made of 1/2 precision plate that you can cut with a regular wood table saw (with the right blade) or even a cheap jig saw. Otherwise build it just like you would with MDF, except forget about extra support, you wont need it.

Probably because aluminum will cost 4-5x as much.

[strat]

just do a search my photos from when i first built it are on here need to get some pics of the change ...... as far as the mdf i used it for my gantry and my cut table i just painted the gantry and for the cut area i used plastidip its a rubber for dipping your tools in less slippery and made the wood air tight also on my cut area i routed channels that i put neoprene in in the center a hole is for a vac that holds the work down (no clamps)

[mikeschn]

Probably because aluminum will cost 4-5x as much.

And because I already have lots of good plywood sitting in the garage!!!

Mike...

[Halfnutz]

Theres nothing wrong with wood or MDF, but aluminum of course is far superior. If you have the lumber and dont have cash, well, thats a no brainer. But if your spending a bunch of cash anyway, and your experiencing problems with flexing, then it starts to make less sense sticking with the wood, especially when mixing it with other structural aluminum components. My feelings are go with one or the other, a low cost JGRO style MDF frame, or an all aluminum frame that costs more and doesent compromise. I was just trying to get you to consider the all aluminum approach, and wanted to assure you that it's something you could do with out too much added effort or cost.

Ive got a MDF table on my router and I'm replacing it because of the sagging, warping and flexing. I spent alot of time trying to strengthen underneath it, and I've concluded its not worth the hassle and frustration trying to make it sit flat and true, so I'll replace it soon with a 30.00 piece of 1/4 in. aluminum plate.

Just my two cents, the fun of this is doing it the way you want to, so dont mind me, I'm just sharing my experiences with you on MDF. Plywood may end up being completely fine, try it out, you could allways replace the wood panels with aluminum later if they dont hold up or start flexing.

(The above comments are the author's, and do not represent those of CNCZone or its management.)