First Design - C Beam Router

Hey guys:

This is my first kick at designing a router based on C-Beam linear actuators.

I designed a gantry plate which is basically an extended version of the standard C-Beam gantry plate but is larger and adds 4 more wheels on the outside tracks of the C-beam. I figure this will enhance the stability and stiffness of the C-Beam gantries. The same plate is used for both the X and Y gantries. It could also be used on the Z axis gantry plate if necessary. The Z gantry plate will have a router mount bolted to it.

The Y gantries are loosely based on the Routy gantry arrangement, with a single 80x20 upright. I'm a bit concerned about stiffness here, any ideas to reinforce the X gantry mounting would be welcome.

Keep in mind this is a rough draft, it's missing a lot of small detail like bolts, elbow brackets, and tee nuts, etc, but the major components are all there.

Please critique, let me know what you think.

 

Sorry, I just thought I'd supply a picture in case you don't want to load the .SKP file

 

Hey Justin:

Yeah, I thought about that too, but the limiting factor is the bottom end of the Z axis c-beam anyway. Unless, I could turn the Z axis around so that the X and Z gantry plates are facing each other and attached together, then the whole Z axis actuator would move up and down. Then simply bolt the router mount to the back of the Z axis c-beam. Hmmm.

The Z axis c-beam and the 40x20 are just held on with t-nuts anyway, it would be simple to loosen and slide them up for more table clearance anytime you need it. Maybe I could also just go with a 20x20 to give more clearance. I could also make the Y axis vertical 80x20's longer and move the whole x-z gantry up.

I think the 40x20 is needed to add stiffness to the gantry, I couldn't see any other way to stiffen the assembly.

I have to also figure out some kind of brackets to assist in mounting the X axis beam to the y gantry uprights. Do you know if the 2 holes on the front side of the end plates on the c-beam are threaded? It doesn't show them as being threaded in the drawings, but it makes no sense to put them there unless they are...

 

Update

I did a few mods like substituting the extended gantry plate on the z axis for the stock plate, and adding a router mount. As well, I moved the z axis c-beam and horizontal brace up a bit.

I now have about 60mm of maximum material thickness. I could make the 40x80 side pieces quite a bit longer. Steve, the side gantry plates on the Ox are quite high, so would allow more clearance.

However, with the c-beam z axis mounted like this, no matter how high the gantries are the bottom of the c-beam is your limiting factor. Since you can only get the router so low, and the bits and collet have a fixed length protruding down, you can't go much higher than this and still reach the table with the bit.

I think the answer is to connect the gantry plate on the z axis to the gantry plate on the x axis. That is, the z axis c-beam is 180 degrees from where it is now. This way the whole z axis c-beam moves up and down. In this way you can get 100-200 mm of z travel. The cross brace would have to go in this instance. I'll do up another mod to see how that works.

 

Here is a view with the z axis flipped, and the Y gantry uprights extended by 50 mm. I now have 125 mm of z travel and should be able to handle objects 125mm (5") high.

Just have to put some bolts and spacers between the x- and z- gantry plates. I could flip the bolts holding the wheels around so that the heads are in between the plates, then a 6mm spacer should be plenty between the gantry plates. 4-8 bolts is all that holds the z gantry on, easily accessible.

Router mount is approximately 35mm from the table at the bottom.

The nice thing about this is that you just slide the x-z gantry and the brace down and it should make the whole thing much stiffer for doing aluminum plates.

Oops, I just noticed I got the brace a bit too high. Its rubbing on the x gantry wheels. Not a big deal to move it down a few mm.

 

This does not give you any more clearance on the z axis. He says that he mounted the c-beam with its bottom even with the bottom of the x gantry plate, so they are the same height. The maximum his ox can do is about 2 1/2" z height on the work piece. Since the c beam is fixed, if you try to have a work piece higher than 2 1/2". the bottom of the c beam or the bottom of the x gantry plate will hit it when the y axis moves more than the distance from the collet to the c beam in the y- direction. You could do very small pieces that were a bit higher, but only 2" wide or so.

Granted he can raise the router higher using the 250mm c-beam, so as he says the tip of the bit can cut from just below the bottom of the end of the c-beam all the way till his collet touches the table. Just means he can use long or short bits without worrying about not having enough z axis travel.

My design can be adjusted the same way, you can lower the x axis beam way down, which should give a really stiff router mount, or you can slide it up to get 5" or more of work piece height. Not sure what I would be routing that's 5" high but its nice to know you can get there from here.

Let me know how your machine turns out.

 

Another iteration....

Flipped the y axis c-beams so that the lead screws are on the outside. This should prevent junk buildup in the c section and leadscrew. It also gives me a flat surface to put the scratch board against to help keep everything square.

Designed a plate to mount the x-z gantry to the uprights, this seems to work good although in combination with the flipped y axis c-beams it does reduce my x axis travel by 50 mm or so.

I WISH YOU COULD GET 750MM C-BEAM LINEAR ACTUATORS FROM THE STORE, HINT HINT!!! This thing would be about perfect with 750mm x and y axes.

The x-axis slide and the gantry stiffener can both be moved up and down the y axis uprights. This allows the z gantry assembly to be lowered down close to the table for cutting aluminum and thin materials, which should make the whole assembly much stiffer. It can be raised up for doing thicker pieces or for wood carving.

The whole router only uses 2 plates, one for all the gantries with both inner and outer wheels, and one for the x-axis c-beam mounts.

Take a look, give me some feedback guys!

Metalguru

 

Hey Mark, Justin, thanks for the feedback. All great ideas.

Mark, the "lowrider version" would be good for plates and signs. My design allows one to adjust the x-z gantry to whatever height is needed for the job at hand. I originally was going to go with the stock universal plates as you've done, Mark, but wanted something a bit beefier. Using the 6mm material should add a great deal of strength and minimize any flexing. The 20x80 uprights should also be a lot stiffer than just a 3mm or 6mm plate. I like the corner brackets holding the x-axis on, with the y axis reversed there is lots of room for those without limiting x travel.

My original design had the y gantry plates on the inside, but I thought that that would just make a huge trap for dust and debris under the table. I like the arrangement with the gantry plates on the outside, as I said it makes the bottom sealed better for easier cleanup. I also thought of using a piece of pipe across the front of the table with small holes drilled connected to an air compressor. This would direct air across the table front to back. I am a woodworker, and I have a 4" dust collection system for which I have a huge 18" wide scoop pickup. If this was placed at the back of the table, almost all the debris generated would get blown to the back of the table and sucked into the scoop.

Justin, I like the c-beam uprights, I also thought of this, but that will lose another 50 or 60 mm of x axis travel. I think they might be a bit overkill. I like most of your other ideas as well.

Mark, I have attached the design for the gantry plate here as a SKP file. Check it over carefully, I am a beginning sketchup user and there might be some boo-boo's.

 

oops forgot the attachment

 

Hey PuntoMX. Not sure exactly what you mean about the washers? And the second plate, any chance you could do a quick sketch to illustrate?

I like the idea of using tapped holes on the gantry plates for the wheels. As you say, it would make a clean installation. However, you could only do this for the fixed (without the offset bushing) wheels. With the offset bushing, the bolt hole moves around with the bushing, and does not end up in the center of the wheel. However, you could put the adjustable wheels on the bottom where you can't see them.

 

Yeah, I'm kind of a beginner with SketchUp, so I'm not surprised. If you can let me know what is out of spec, I'll try to fix it.

Thanks.

 

Ronald:

Ahhhh, I get it now. Use the extra plate with clearance holes for the wheel and acme block screw heads to eliminate the washers. Cool, that looks good.

The wheels and Acme block can be adjusted before you slide on the 20x80 V-slot anyway. You'll have to be careful adjusting the wheels, if you get them too tight you might bow the plate that the wheels are mounted on slightly. Then when you add the v-slot and tighten it up, it will cause the plate to straighten out and may put too much force on the wheels and bend the bolts. That's why it would pay to just leave the bottom wheel bolts uncovered as you say, and adjust the wheels after it was all assembled and tightened up.

I did look at using the universal plate initially, but I was worried it would bow out at the top and bottom if the wheels were too tight. This is why I decided to use a 6mm plate, it would be much less subject to bowing when the wheels were adjusted. What do you think of the gantry plate I designed with the inside/outside wheels?

 

Hey Guys:

So, I've done a few more mods on the c-beam unit, and I think I'm about where I want to be.

I added another pair of outside wheels to the gantry plates. This now has 6 outside wheels and 4 inside wheels. I made recesses for all of the bolt heads so the plates can be joined together back to back without spacers. The plates are 6mm thick and quite a bit wider than the Universal Plates, with a wider "wheelbase", so should be bulletproof. The 20x80 uprights should also make the gantry a lot stiffer.

Also added a couple of threaded holes to allow the plates to be fastened together for the X-Z axis without tee nuts. This allows the z axis to be easily removed with just 8 easily accessible screws if needed. Same gantry plates are used for all 3 axes.

The X-axis c-beam can be high mounted as shown to get maximum clearance for doing thick pieces. It can be swapped with the 40x20 cross brace to bring the axis lower to make the z-axis mounting stiffer for cutting aluminum and thin plates.

Added a 20x80 extrusion connecting the two gantries underneath the table. This should stiffen things up nicely.

With the Y gantries on the outside, this keeps junk out of the y-axis leadscrews, and allows the spoiler board to fit snugly between the two c-beams, helping to keep the table square.

Did a quick sketch of different sizes for this machine. Easily converted to use 500mm, 750mm, or 1000mm for the x and y axes to make 3 different sized machines with all parts exactly the same except for the c-beam axes and the length of the base extrusions. Or you could mix and match, say 1000mm y axes and a 500mm X axis.

Now I just have to do the g-code to make the plates on my C-Beam Machine, and I'm set to go. The 750mm axis version is shown.

 

Hey Ronald:

The inner wheels are a holdover from the original design with only 4 outer wheels. I figured I'd leave them in, can't hurt. They come with the C-beam actuator kit anyway...

Not sure why you feel that the adjusters need to be on the bottom. I don't see where it would make any difference. Especially on the outside wheels, I'd rather have them on top where they are accessible than have to stand on my head to adjust them. I'll defer if you come up with a good reason for your suggestion...

Yeah, I agree with your assessment on the c-beam y-axis mounting. I have to figure out a better way to mount the feet and the bed stiffeners.

I assume you mean the 40mm spacers on the motors. That is the way the kit comes from OpenBuilds, and there is no clearance issue with the bolt heads. I was a bit uneasy about using only 2 motor mount screws but I could see no other way to do it. Shortening them to 30mm would be better both from a stiffness and strength point of view, and there should be enough space in the flexible coupling to bury another 10mm of motor shaft. Good idea!

Thanks Ronald.

 

Rick, Ronald:

Not seeing what the issue is here, guys. Using the models done by OpenBuilds, it seems to me that within a tolerance of .2mm or so, the offset on the mini wheels and the standard wheels is exactly the same. Now this is using models you guys made, so if I can't trust those what am I supposed to do? I measured several of the wheel assemblies in my model from the plate to the center of the wheel, and regardless of whether they were full sized wheels or mini wheels, the distance was 12.5mm +/- .2mm. This is close enough for the girls I go out with...

The only difference is that the mini wheels have 2 x 1mm precision shims instead of 1 on the regular wheels. This makes sense, since the standard wheels are 11mm wide from bearing face to bearing face, while the mini wheels are 9mm wide. This would mean to get the same center, the mini wheels would require one more 1mm shim than the standard wheels. This standoff/shim combination is not really "nonstandard".

Looking at the plates I built using parts from the OpenBuilds models, there ain't enough difference by eyeball that it would bind.

As far as the offset adjusters, can't really agree there either. The load bearing strength of the wheel comes from the bolt, not the spacer, and regardless of whether there is a solid spacer or an eccentric spacer, the bolt is the same. The bolt is supported inside the spacer in either setup, the only difference is a few mm of smaller hole in the plate with the solid spacer. This would be offset by the better strength of the offset spacer because it has a longer path where the bolt is supported inside the spacer. I can't see that there would be any significant difference in strength between the two setups, especially with 3mm universal plates. With thicker 6mm plates, there might be a bit of difference, but IMHO not enough to worry about.

Ronald, I'm also not getting your comments about putting the 8mm shim on the coupling side of the plate. I built my C-Beam machine by putting the lock collars on the 8mm lead screw with one of the end plate's screws loosened off a bit. Once the lock collars were tightened down, I tightened up the screws on the end plate. This puts a preload on the lead screw so that it can't move end to end and so maintains maximum accuracy. The shim is needed between the locking collar and the bearing so that the outside diameter of the locking collar (which turns) does not rub on the outer bearing race (which does not turn).

Your method of putting the shim on the other side of the plate and using the coupling to put some preload on the lead screw would work, but is much harder to do. The grease doesn't help here either, since the lead screw, shim, bearing and coupling all rotate at the same time, so there is no need for grease since there is no sliding friction... You are essentially using the shim as a spacer to keep the flex coupling from rubbing on the end plate, which is OK, but I don't think leaving out the shim on the locking collar side is a good idea.

 

OK. when you put it that way, it makes total sense. Since I don't actually have any mini wheels to measure, all I could do is go off the model... Can you get a .5mm shim? If you used that inside the mini wheel between the bearings, you would only be 0.1mm out, maybe acceptable tolerance? That's only 4 thou...

Point taken about the non-eccentric spacers. Makes perfect sense to use the upper wheels as fixed reference points. I was assuming you meant the strength of the assembly, when you meant the position...

As far as the lock collar, I was also making an assumption, since none of the models of the C-beam actuators have those shims. I didn't want to tear my machine apart to see, either. Again, I defer to your extensive experience. If the lock collar OD does not contact the outer bearing race, then they are redundant.

PS: Check Aspen Fasteners LLC on Amazon.com, they have 0.1, 0.2, 0.3, 0.5, and 1mm M5 x10 shim washers for approx 0.1 cents each (4800 pcs for $480.00)

 

Cool man. Get some sleep! And thanks for sharing your expertise.