Help designing t-track table for CNC

[Crusarius]

I am down to the final details on my CNC build. Right now I am working on the table. I happen to have some t-track pieces I was thinking I was going to use to make holding parts easier.

Does anyone have any good layout ideas? I keep thinking 12" between the rails and got the full length of the table. Should I add horizontals as well?

Not sure why I am having such a hard time just doing this. I think I have analysis paralysis

[Crusarius]

I just found this dovetail track and cam lock kit. I like the clamps alot but prefer to stick with standard t-track for its availability.

Woodworking Tools | In Line track Clamps, Dovetail aluminum Tracks, T-track accessories T-bolts, Star Knobs | Creating jigs and fixtures for Cutting, Routing, Drilling, sanding, Assembling (track Kit) - - Amazon.com

[Crusarius]

Since no one was able to help me out with a decent table design, I started doing a little freelancing. 

So, I started with a normal table using 2x4 construction with t-track screwed to a flat top. 



 

The plan was to fill in between the t-track with 3/4" MDF for my spoilboard.



 

I spent some time testing and working with the layout before I was ready to cut the overpriced MDF to fit. During my testing I found I did not like the layout at all.

My primary goal for the CNC is flattening slabs. The primary hold down on this table is designed to clamp from the top. Unfortunately, we all know clamping the top of a slab that is to get flattened is not going to work for very long  

Here was my solution for that. I made those spikey plates out of some 2.5" square stock I had laying around. They actually worked pretty well for holding it in place.  



 



 

With some more fine tuning I am sure those would have been fine. But I just was not happy having to constantly fight with all of it to get the slab to stay in place.

On to the next version of the table.

I used the same table, but I removed all of the t-track and the plywood. Now I just have a simple 2x4 framework with cross pieces at 16" O.C. and the first bay is odd spaced for the smaller items I have been dealing with. Both table designs are shorter than the travel of the CNC so I can machine the edges of panels. I spaced it so I can machine the end of a 6" leg or the center of a 6" panel edge.



 

Now the next innovative idea I came up with was adding 4" wide strips of MDF to the back side of the 2x4's. You can see those in the image above.

Once I had those on, I rabbeted the front edge of the 2x4 to accept the t-track. 



 

After this was all completed I made some custom hold downs that support the slab from the bottom and hold it down at the same time.



 

Both are made from 1/8" material the top is aluminum, and the bottom is steel. I am not sure how they will hold up, so I made a bunch of them and will be doing some pretty thorough testing. Right now, I am pretty happy with their holding ability.

The plates are designed to go 4 different directions. Originally, I did not have the small notch in the bottom corner. What I found out was that with 2 of those plates with the hooks holding the material down, the narrowest board I could clamp was 8". Typically, this probably would not have been an issue, but I like making fun little trinket things to. So, I added the little notch to make the plate reversible to hold smaller pieces.



 



 



 

All of the hold downs have support for the bottom of the slab along with clamping to keep it from lifting.

So far they have worked pretty well. Once that thumb screw is tightened, they do not move.

I will be adding some more triangulation to the table but for now it is working well and the hold down design is much nicer. I made the aluminum ones hoping they will last since they will be much more forgiving if I clip them with the cutter.

I guess I should have tried to get better pictures. Sorry about that.

[Crusarius]

oh yea, forgot to mention the reason I chose to use the MDF strips like that is because now when I use a fly cutter to flatten the table I will not burn up a set of inserts surfacing the table. Just a few thin strips and its all done.

I will write a program specific just for flattening the table.

[rusticretreater]

Hey, I guess I missed this thread earlier.  I remember seeing one setup that used pipe clamps to handle wide stuff and clamp from the side.  Your setup appears to work well with positive gripping ability and is able to conform to live edge pieces.  The open table surface also allows you to use quick clamps for those other projects that come along.

I think you would still want to have a conventional table surface to place on the machine as well.  Thanks for giving me something to consider when I go to upgrade my machine. The new shop is under construction.

[Crusarius]

yes, I did forget to mention that I actually have some 2x4 pieces of MDF that will get angle bolted to the bottom of them so I can just clamp them into the t-track.

The other option I also have is a plasma table since I can change the head on the CNC over to a plasma cutter. I can make this a downdraft table or a water table. I prefer downdraft table. I just don't like mixing steel being plasma cut and water. 

The other great thing about this table design is multiple fixture setup. If I am doing a repetitive task, I can setup fixed stops and quick clamps to get it right. 

I think I have way to much time and thought invested in this machine  so far though its super kool!!!!

[customsawyer]

Your set up is looking great.
I will share some lessons I have learned on the WM slabmizer. First off don't clamp to hold it down. If the piece is going to move, holding it down won't stop it. It will just pop up when you remove the clamps. If it does start to move, then you are going to need to make another pass. However your next pass should be on the opposite face first. If you continue to work on the same face most times it will just move more. Don't ask how I know. I remove about 3/32 per pass so if a corner raises up don't think by going down another 3/32 on the same face is going to fix it. The wood is reacting to what you are removing from it. You have to relieve some of the stress from the other face to balance the stress out. Might have to take more than one pass. This can be caused by the location of the juvenile core, other stress in the piece or something in the drying. My clamps now just barely touch the piece to keep it from moving side to side or front to back. If it is a large heavy piece I never engage the clamps as the weight is enough to hold it down. Keep some small felling wedges close by. When you first start on a piece there will likely be some raised up parts or corners. Sliding a wedge under these points just lightly touching the material. Not enough to make it rise up higher. You just want to keep the slab from rocking. I'm sure there are other things I have learned (or messed up on) but I can't think of them right now. Hope this helps.

[rusticretreater]

An old trick woodworkers use with a planer and crooked wood is to make a sled and use hot glue to support the wood so it doesn't rock.  The cool thing about hot glue is that it is self adjusting when the board surface touches and it also doesn't move from vibration.  A replaceable, moveable pad locked to the T-track on both sides of each crossmember would be workable.  You could choose to use between metal/quick clamp or glue methods or mix and match.

[Crusarius]

Customsawyer, thanks a ton for the advice, I think I have begun learning just what you said. The clamps can be tapped with a hammer and embedded into the edge of the board to lock them down but now I see that is probably not necessary. The other nice thing about my clamp design is the radius ramp that actually supports the slab from underneath. So, if I use your technique, it would be set the slab, level it, and then slide the clamp in place and just make it snug. I may need to make some end stops to keep the slab from moving since that is the direction I will be cutting.

Rustic, I have thought about the hot glue trick but didn't really want to fight with it. Especially since the wife would be less than pleased if her hot glue gun ended up in the shop

Thanks for the help guys. I am really happy how everything is turning out on the entire project.

I am currently working on a quick change tool plate so I can take the spindle off and replace it with a random orbital sander, or when the time is right my plasma cutter  stay tuned

[customsawyer]

Each log is different. If you slab an entire log then start on your least valuable slabs first. See how they move first. They can give you an idea of what the high value slabs are going to do. Sometimes if the slabs are moving a lot I will flip the slab after each pass. It's a pain but it keeps the slabs more stable. I've only had to do this on one log. Most are just well behaved little angles. ;D

[Crusarius]

Most are just well behaved little angles.

Hehe, I know this was not intentional, but it is funny


I have surfaced more than a dozen different size and shape slabs. The first ones I did were junk punky pine just to get a feel for it. the rest have been walnut. It is what I have the most of.

Before and after with quick Danish oil rub and about 30 seconds with 80 grit sandpaper on RO sander.
 
 


More before, during, and after with Danish oil and about 30 seconds with 80 grit sandpaper on RO sander.

   
 

Keep in mind these were very early test pieces. If you notice the swirl marks it is from the 2.5" cutter not being true to the table.

If you notice, my before pictures are usually a little late Hence the single strip of fresh wood

Thanks for the advice and assistance. My product only gets better each time I play with it.

[Crusarius]

Those pictures show the early table and hold downs very well. I had a hard time keeping them from sliding and letting the slab move. I feel the new setup is going to be much better.

[Walnut Beast]

Looking great 👍 

[Crusarius]

Thanks, I will take all the encouragement and compliments I can

[aigheadish]

Your little holder plates look pretty slick. 

Some of you guys are able to come up with way neater jigs and tables than I could possibly imagine. Good work!

[Crusarius]

Thanks, it took me a while to get to this point. But so far things seem to be going pretty well.

[Hilltop366]

Nice work on the build and progression.

By the sounds of it you really need more of a bumper and wedges than a hold down, could be made of wood for the "just incase" fear of hitting them with the bit. Some cam locks on the bolt for quick adjust.

[blackhawk]

I've had my CNC for about 13 years,  I've always just screwed down everything into my spoilboard.  My spoilboard is 3/4" plywood with a 3/4" thick MDF top.  Once the MDF gets down to about 3/8" thick, I just mill it off and glue down a new 3/4" thick sheet.  

Now for slabs, I don't put screws through the slabs.  As someone else mentioned, for big slabs they are heavy enough just to lay there.  For smaller slabs, I just use blocks of wood screwed into my table pushed tightly against the slab to keep it from moving horizontally in any direction.  

[Crusarius]

Hilltop, the first ones I made were steel because I had it in stock. I have since made some out of aluminum. These ones are much nicer to the cutter if I slip. I also made sure they cannot stick up more than 1/2" above the bottom of the slab. so as long as I am not going to thin, I should never have an issue.

Blackhawk, I did that on a few of the slabs I was working on, and I ended up shaving the top of the screw with my brand-new cutter. That was the end of that

[blackhawk]

Blackhawk, I did that on a few of the slabs I was working on, and I ended up shaving the top of the screw with my brand-new cutter. That was the end of that

I countersink my screws and keep them at least an inch away from the cutting path.

[Crusarius]

yea, they were countersunk a good bit but I was surfacing the entire slab. so there was no uncut edge. This was also during one of my small test runs.

If I am making carvings, signs, or anything else like that where I cut the perimeter off the face screws are the easiest way to go.

[blackhawk]

Crusarius - I don't put my screws through the slab.  I use separate scrap blocks and butt them tightly against the slab.  I always make the scrap blocks thinner than the finished slab thickness.  The screws are in the scrap blocks so they stay entirely out of the cutting zone.

[Crusarius]

ahhh, that makes more sense. I tried something like that and was not overly happy with the results. Seemed like no matter how hard I tried the slab would move on me.

Once I get the full length table put together it will be time to test on a full 12' slab. To bad all I have to test on is walnut