[skubajon]

Well after reading a ton of info on this site, I figured it was time to be a member here! Makes searching a little easier.

Im building a machine for my boss who builds guitars as a hobby and also is funding my experiment on building the mill. I currently design with Solidworks 2011 and I have been racking my brain on figuring out a secure, stable linear rail setup. Being that we are keeping the costs down on the first build I have been looking into angle iron and v-bearings. I have seen some other great and innovative setups people are using but I want to know if this setup is going to be a great starter.

I have also seen skate bearings used on square and round tubing before but in my eyes (correct me if Im wrong) it doesn't look near as stable as a v-bearing on angle iron.

Can you guys send me some links/pictures/info etc so that I can see what is working for you? And as always I will definitely be posting photos of the build and the design done up in solidworks.

Thank you guys in advance! Im excited to be part of this site....although it may cost me my job if I spend too much time viewing it!

[Drools]

Just my 2 cents, the products from cncrouterparts.com are top notch and makes for a great economical setup. To add they have top notch support.

[microcarve]

I'd agree with Drools. If I were using someone elses $$$,
I'd want something with a much closer guarantee of success than
trying to DIY from complete scratch.

DIY can get expensive and very time consuming before ya know it...


John

[skubajon]

Im looking at the carriages that are on the site. They do look like they are pretty sturdy. Anyone have experience with these?

[Drools]

I would say there are atleast a dozen builds of the CNCRP machines here on the zone and even more where people use the parts with their own designs.

[adprinter]

I have also seen skate bearings used on square and round tubing before but in my eyes (correct me if Im wrong) it doesn't look near as stable as a v-bearing on angle iron.

There is more than one way to skin a cat! The skate bearings can be used with great results, if properly designed. My thought, was a full wrap-around of steel square tubes used as the actual linear rails. So what I ended up doing, was to mount skate bearings onto threaded rod stock (which served as the axles for the bearings), and insert these into a large (4"x4") steel square tube section.

For the "Wrap-around": I mounted more skate bearings onto swing bolts, and onto a second piece of threaded rod stock, to "Grip" the other 3 sides of the square tube linear rail. Swing bolts are simply a type of eye bolts. Desired for this application, since they are machined from a single billet of steel, instead of just rings welded onto the end of a bolt.

By milling slots into the 4x4 tubes for mounting of the swing bolts, it is possible to load the skate bearings against all four side of the smaller (1.5"x1.5") square tube linear rails. Racking of the gantry can be adjusted out, by simply tightening, or loosening the nuts on the swing bolts, and tightening a bolt which is threaded into 2 pieces of angle mounted on the top side of the 4x4 tubes.

This allows for the swing bolts to be moved closer together (and properly load the skate bearings against the side surfaces of the linear rail tube) while raising the lower (threaded rod stock) axle up against the bottom surface of the linear rail. The top threaded rod stock is simply an axle, for the skate bearings which ride along the top of the linear rail tubes.

This design requires a bit of fine-tune adjustments, to set up the gantry for acurate travel. And a lot of patience. But the end result, is a heavier-duty all steel system which will stand up to just about anything you throw at it! Each of the 4x4 square tubes feature a pair of axles, and a pair of swing bolts mounted into Each End of the tubes.

As mentioned above, the top axle simply rides along the top surface of the linear rails (gravity-loaded bearings). The swing bolts are inserted through more bearings, and suspend the lower axle (which is inserted thru one swing bolt eye, two bearings, then the other swing bolt eye) and drawn upward against the bottom surface of the linear rail square tube by locking the nuts of the swing bolts on the top side of the 4x4 tubes.

The tedious part of adjusting this mechanism, is the fact that the swing bolts pass through a small piece of angle steel (one for each swing bolt). This angle piece features a thru-hole in the vertical plane of the angle on ONE of the swing bolts, while the other angle piece for the other swing bolt features a threaded hole.

A bolt is inserted thru the thru-hole of the angle piece of one swing bolt, and threaded into the threaded hole of the angle piece of the second swing bolt. This allows for drawing the 2 swing bolts closer together (and thereby loading the bearings mounted on them) against the 2 sides of the linear rail tubes. Add brush sweeps to the outer ends of these tubes, to keep the sawdust from getting caked up on the linear rail tubes, and it is a very durable system!

[skubajon]

Thank you for all your help.

Here is my idea that I have started to play with in Solidworks.

Using 80/20 brand 15 series 1.5x3 extrusion, and some angle iron bolted to the outside top slot about every 6 to 8 inches and a skate bearing carriage from that cncrouterparts site. Im really contemplating making solid aluminum sides to my gantry so that a....I can polish nicely, b.. I think its more rigid c.. form factor is a lot less and of course d.. I can project my gantry sides at an angle so that I have more workable room on my milling table (angle based on router used).

Is one carriage per side going to be sufficient or can I expect undesired wobble or play?

[adprinter]

Thank you for all your help.

Here is my idea that I have started to play with in Solidworks.

Using 80/20 brand 15 series 1.5x3 extrusion, and some angle iron bolted to the outside top slot about every 6 to 8 inches and a skate bearing carriage from that cncrouterparts site. Im really contemplating making solid aluminum sides to my gantry so that a....I can polish nicely, b.. I think its more rigid c.. form factor is a lot less and of course d.. I can project my gantry sides at an angle so that I have more workable room on my milling table (angle based on router used).

Is one carriage per side going to be sufficient or can I expect undesired wobble or play?

I actually used a similar design on the Y axis of my machine. (The only difference being, that they ride on a 3/8" thick bar instead of the 1/4" bar in their design). They work, but are not very beefy. For this reason, I will probably end up utilizing the square tube design I am currently using on the X axis. With a pair of rails, instead of the current single bar design. The problem is with only a 3/8" thick bar, they just don't offer the stability of a 1.5" square tube rail design. Of course, this will add more weight to the gantry. Which is already pushing close to 200 lbs. Again, the full wrap-around design used on the X axis will offer much greater stability.

[skubajon]

That sounds pretty rigid. ON my first machine Im looking to mill light aluminum but mainly wood. Im also debating on making it a plasma table to cut the pieces I need to build a bigger table....to build a bigger table which builds a bigger table which then rules the world!(chair)

[skubajon]

You have a link to photos you can send to show your x axis? That would be helpful!

[adprinter]

You have a link to photos you can send to show your x axis? That would be helpful!

Sorry that I haven't gotten around to taking any photos (yet). Please see the attached Trucks.PDF file.

[skubajon]

That is pretty sweet. I was trying to wrap my brain around it but now I have a clear picture. I like that design a lot!

You said that this was pretty hard to adjust. What if you put a tab across the top of the outer rail so that you can attach a heavy pulling spring to that and the lower axle. That may make for easy adjustments to load. The you could remove the spring after all lock nuts are tight if you need the extra room

The idea sounds great in my head but I have NEVER even messed with mechanics of a CNC machine before so Im not sure if the springs is an dumb idea.

[adprinter]

That is pretty sweet. I was trying to wrap my brain around it but now I have a clear picture. I like that design a lot!

You said that this was pretty hard to adjust. What if you put a tab across the top of the outer rail so that you can attach a heavy pulling spring to that and the lower axle. That may make for easy adjustments to load. The you could remove the spring after all lock nuts are tight if you need the extra room

The idea sounds great in my head but I have NEVER even messed with mechanics of a CNC machine before so Im not sure if the springs is an dumb idea.

The PITA part of this adjustment process, is the locking of the nuts on the swing bolts. As this action pulls the lower axle UP (thereby increasing the load on the bearings of the lower axle). This was the reason that the second nut was added to the swing bolts (on the INSIDE of the 4x4 Truck tube assembly) - to LIMIT the distance that the swing bolts are pulled upward, when locking the nut on the top of the Truck tubes.

A special open-end wrench had to be ground down, thin enough to insert them inside the tube for gripping the nut. Add to this, adjusting the load on the side bearings of the swing bolts. And it becomes a real nightmare to properly adjust. As I said, it is do able. It's just a very tedious process.

Then jog the axis to the opposite end of the table, while watching all bearings to ensure they remain in contact with the linear rails from one end of travel to the other. And that the gantry does not "Rack" (one side getting ahead of the other in terms of distance traveled). Over, and over again, until as perfect as one can achieve.

The good news is that once this adjustment process has been completed (and all nuts are securely locked), the only need to revisit this adjustment process, is when any of the bearings become worn, (or if you have over-loaded any of the bearings, CUTS will appear along the affected surface of the linear rail tubes). Since the steel the bearings are made of, are harder than the hot roll steel the linear rails are made of.

[skubajon]

Well I worked more on my design with Solidworks over the weekend. I scrapped what I started which was from bottom up and re-started by designing the Gantry y and z axis first.

The reason I did this was so that I could get a pretty close idea on what my gantry will weigh in at. This way I can know which direction to go with my x axis.

I designed this with cold rolled steel and then 2 carriages from cncrouterparts. I also spent the time adding in all the hardware etc so that my weight will be close to exact. This will help me in stepper configuration.

Ill get some renderings here soon, just busy with moving into a new house

[skubajon]

Here is the start of my gantry. I still have a ways to go on the design but this gives you an idea on my design.

Im worried about the 2 bolts that hold the gantry sides to the center beam. Im going to add some bracing in there just to make it fully supported.

The sides are done in aluminum and behind the cold rolled 4 inch x.25 inch steel is 1530 80/20

I still have yet to decide on motion system. Its a toss up on lead screw or rack and pinion drive. My x axis is close to 4 feet so Im leaning more on rack and pinion. I have to do a little more research on both to see what is going to be the best and what motors I will need to run this thing.

Let me know your thoughts

[adprinter]

Here is the start of my gantry. I still have a ways to go on the design but this gives you an idea on my design.

Im worried about the 2 bolts that hold the gantry sides to the center beam. Im going to add some bracing in there just to make it fully supported.

The sides are done in aluminum and behind the cold rolled 4 inch x.25 inch steel is 1530 80/20

I still have yet to decide on motion system. Its a toss up on lead screw or rack and pinion drive. My x axis is close to 4 feet so Im leaning more on rack and pinion. I have to do a little more research on both to see what is going to be the best and what motors I will need to run this thing.

Let me know your thoughts

If you are planning on a lead screw installation on the front side of the cross bar (the side shown in your picture) it will be a very tight fit, since the lead screw nut assembly would have to be 1" or less in diameter. Of course, this distance could be easily increased, by mounting the Y axis trucks to a spacer plate, or blocks. As for the two-bolt mounting (as shown in your picture) of the cross bar, this could be reinforced with a 4" length of maybe 1.5"x1.5" angle steel at each end of the cross bar. (With 2 bolts inserted thru the cross bar, and 2 bolts inserted thru the gantry uprights in each plane of the angle piece). This arrangement would offer added stability in mounting the cross bar of the Y axis, as well as reinforce the stresses which will be introduced by the Y axis lead screw (or rack and pinion, should you decide instead on this).