My DIY Build Bosch/Rexroth and 8020

[JC1]

I decided to post my build log to this site, it's still in process but near completion and I wanted to share my progress. I'll be uploading in sections tonight.

I have a very restricted workshop and limited tools, so this has been a bit of a challenge to put together. A wobbly drill press, a Dremel and a carbide tipped blade on my miter saw.

I started off by doing a lot of reading on CNCZone and other places to decide on what I wanted for a machine.

I decided to go with an 8020 build as it seemed like it would be fast to fabricate and build, but after pricing the 8020 out and coming up around $1600 with some parts still missing from the price list I realized I'd need to look into some other options. I ended up going with used Bosch/Rexroth extrusions from eBay and also ordered some parts from Bosch directly.

In the attached two photos you'll see my original designs and the 8020 price list, my how things change over time. The end product looks not too much like either of my original concepts below, one which was a moving table design.

[JC1]

I decided not to build a moving table design, but go for a moving gantry design instead, I also went for the maximum dimensions I could achieve with the quantity of Bosch/Rexroth extrusion I had ordered (something like 56 linear feet).

Once the corner parts arrived from Bosch I laid out the table frame (first picture) and then adjusted and repositioned things. I wanted this construction to be extra sturdy so I bolted through the extrusions as well as implementing the 90 degree angle braces from Bosch.

Tapping the 45mm x 90mm extrusions with the M12x1.75 tap was quite a bit of work to do by hand, it also taps oddly as the 'vanes' in the extrusion cause the tap to repeatedly slip/grab which is more abusive on the arms and hands.

[JC1]

At this stage, end of April, I changed things a little. Originally the Bosch extrusions in the center section of the table were installed on their edges but due to budget restrictions on doing a dual lead screw drive I decided to run a single lead screw through the center of the table.

I laid the extrusions flat between the left and right sides of the table, and installed aluminum plate ends as I had seen on another project on the CNCZone.

The hole for the stepper motor in the end plate was drilled with a cheap hole saw. The hole saw will never drill another hole again, but it did make a nice hole.

This is also the point where I had decided on some of the hardware and software I was going to use to run the machine.

I ended up ordering 4 NSK LY20 rails from automation overstock. They're preloaded and are have pretty tight tolerances. I was originally looking at their THK stock but it seemed none of the rails were drilled through which I needed to accurately drill the mounting plates.

I bought a Gecko 540 and 3 stepper motors from Keling tech and bought some spring style motor couplers on eBay.

I also decided to use a DCI linear stage for the Z-axis as I had picked it up a while ago at a surplus shop. I'm not sure how well this will work out for a Z, but the price was low and it's worth a shot at any rate.

I went with Mach3 for the software.

I hadn't decided on lead screws or ball screws at this point.

[JC1]

With the basic table assembly complete I moved onto installing the NSK linear rails on the extrusion. I used a 3/4" wide x 3/16ths thick strip of steel. I laid the rail onto the steel strip and then used a center punch to mark the hole centers for each hole. I then drill the strip, along with a second for the holes and tapped all 36 holes for 5mmx 0.8m pitch while watching TV.

The rails fit in well to the 45mm x 90mm Bosch/Rexroth 10mm slot and allows for a little adjust-ability up and down which would come in handy for alignment.

[cornbinder23]

Tapping the 45mm x 90mm extrusions with the M12x1.75 tap was quite a bit of work to do by hand, it also taps oddly as the 'vanes' in the extrusion cause the tap to repeatedly slip/grab which is more abusive on the arms and hands.

Spiral flute taps are your friend!!!
Looking good so far!!

JTCUSTOMS

[JC1]

Thanks cornbinder!

The next stage was to build the linear rail interface plates for the table axis. These plates interface the rail trucks to the 45x90mm bosch uprights. I'm sure not still if I have them named right but for the sake of my sanity I've been calling it the X-axis.

The plates were cut from a piece of 4" x .75" x 8' aluminum bar stock I bought from 8020's eBay store along with some angle extrusions and one 8020 extrusion which I planned to use as the draw-bar for the X-axis.

The bar stock was extruded and I had originally drilled the holes for the NSK trucks and mounted the plates, but they were so uneven that tightening the screws caused the trucks to begin binding so I began to sand them down.

Sanding the plates took about a week of evening sanding off and on when I felt like it(I have RA so it's a bit of a hassle to do repeated motions like sanding). It was a slow process for sure, but with worthwhile results. Once the plates were sanded flat(at least around the truck areas) I remounted them. I turned the 5mm screws in finger tight and then tightened with a wrench, they all tightened in less than a 1/2 turn.

[JC1]

A little bit gets lost at this point because I was busy building and didn't take as many step photos as I could have.

I finished the drilling of the rail interface blocks. I counter-sunk the rail truck screws into the plates and then drilled the plates to mount more 45x90mm bosch extrusion to them. There is a vertical upright and a horizontal to mount angle bracing on.

I temporarily mounted some horizontal pieces across the uprights and tested the glide. There was some binding in the linear rails but with some minor adjustments they were gliding as smooth as they would if it was just the trucks themselves. These trucks aren't glass smooth, there is some resistance in them even when unloaded due to the preloading.

I also added on some legs and mounted some small corner braces as end stops to both sides.

The extrusion at 45 degrees pictured below seemed like a good idea, but I realized the cut was not 'precise' from my miter saw, and I do not believe that the Forstner bits I was using to countersink the 12mm bolts I have been using would do me well at that angle.

I had decided to go with 1/2-10 ACME 5-start screws for the X and Y axis. I had been looking for ball screws and it seemed like the only thing in my price range was cheap screws that I wouldn't be happy with so I decided t go for ACME screws for now and see how they do until budget is better.

About this time I ordered up some precision ACME rod from McMaster, bought some anti-backlash leadnuts, 1/4 to 1/2-10 ACME and shaft collars from dumpstercnc and some bearing blocks and thrusts bearings from CNCrouterparts.

[JC1]

With the parts arrived from various sources I stared working on the X-axis/table-axis drive for the gantry. The pre-made parts such as the bearing blocks and 1/4-Acme 1/2-10 adapter made this part pretty easy. The anti-backlash lead-nuts seem really small to me but I went ahead and installed them.

The photo's below show how the axis went in. The connection of the draw-bar to the lead-nut was a bit of work. I ended up slotting a piece of 3/8th's x 4" L extrusions with my miter saw to provide some up and down positioning of the lead nut. It's not beautiful but it is functional. Perhaps when I get this machine running it will be sturdy enough to re-make a couple of the parts I've not been so happy with.

The connection from the stepper is straight forward. It's the stepper with a 1/4 drive connected to a 1/4->1/4 spring motor coupler which is connected with a piece of 1/4 rod to the 1/4 -> 1/2-10 5-start acme coupler. Then a thrust bearing, the CNC Router Parts bearing block, another thrust bearing and then a threaded shaft clamp against the second thrust bearing.

[JC1]

And again I forgot to take 'progress' photos but the ones below show the assembly of the Y-axis/Gantry. I had some ground aluminum plates left over from some ball screw mounts I had so I used that to make end plates for the Gantry.

The plates are connected to the gantry uprights with 6 carriage bolts which allows me to adjust the gantry up and down if needed. The original plan was to adjust it down to the right height then chop the uprights down to size, but I decided to leave them at their current length in case I need to ever machine a tall object/surface.

The gantry horizontals are mounted to these black end plates with 4 12mm x 50mm bolts on each side and will have additional corner braces in the back once final alignment is done.

I had struggled with the thought of mounting the horizontal rails to the back of the uprights, but it would have meant cutting down the linear rails and I didn't want to do that. Also it would have reduced my gantry travel by about 2 inches. I decided to sacrifice travel on the table front-to-back axis than on the gantry axis.

Mounting the ACME screw into the gantry was a lot more work than the table. As you can see I had to mangle one of the nice Al bearing blocks to fit around the bolts on the left side. On the right side I took the bearing out of the bearing block and mounted it in a blind hole I drilled with a Forstner bit on the right-side black plate.

I also mounted the linear drive I want to try for the Z-axis and temporarily connected electronics to test out the movement. Everything moves smoothly after a little bit of shimming with aluminum flashing and some adjustment.

[JC1]

As of Today, May 21, I don't have a router mount for my Dewalt DW618 at the moment so I taped a pen onto the Z-axis to test out the router (probably safer anyway) and ran a spiral program from one of Mach3's wizards.

The results look pretty good to me, but you might notice some up and downticks of the circles at the top and bottom of the picture. I tracked this back to ACME collar which was supposed to be pressing against the thrust bearing on the table axis. I had forgot to tighten it down completely, but once done it eliminated slop in the axis (at this low of load anyways).

While I'm saving up to buy the mount for the Dewalt router I'm going to spend some time on the electronics cabinet and support table for the machine.

I have some N.O. magnetic reed switches I'm going to try for the homing switches and failing that I have some hall effect switches I can try if those don't offer repeatability.

Also here's a video I took yesterday of motion before I did some more work on it today [nomedia="http://www.youtube.com/watch?v=HI9g-SLdFCU"]YouTube - ‪My DIY CNC Router - Test Run on 3 Axis no Spindle‬‏[/nomedia]

[JC1]

I shot another video, this time doing a repeated pattern to see how well it could replicate a 'cut' to check accuracy. I think it could have been better. I'm waiting to do final alignment on the gantry until I have the router on the new table. It's amazing how much clearer the high frequency sounds are in the video than with my own ears. [nomedia="http://www.youtube.com/watch?v=H2P_PS80gZs"]YouTube - ‪DIY CNC Router Pen Drawing Circular Pocket‬‏[/nomedia]

I snapped the collet in my DeWalt DW618 router on a non CNC project so I had to order a new one which will delay the mounting of a router for a little bit. I may try to mount my Dremel clone instead and try some light cuts before then. I am also thinking of building a pair of mounts that CNC Lurker posted the drawings for on this site, but I'll need to rescale them slightly for the 3.5 inch body of the DW618.

I did get the table built on Sunday with 2x6 and 2x4 construction with an MDF table top. Another MDF shelf will go underneath for the computer, vacuum pump and control electronics. It's a bit larger than I expected, but it will squeeze in next to the breaker panel which will make it much easier to wire the outlets for the machine. I've been thinking of bolting the table to the floor and mounting the machine on some kind of slider rail to make maintenance easier since I won't have easy access to the back.

I coated the top of the table in a layer of epoxy to try and protect it from any dripped oil, etc. It's also by a window so I plan on installing an outside venting system of some sort to provide negative pressure in the room and hopefully pull dust out of the room. I'll build a windowed box around the table if I need to to help contain dust.

One of the things I'm hoping to be able to do is build molds for R/C aircraft using methods similar to these guys DLG Molded Project - RC Groups so I'd like to get the accuracy and precision pretty good.

[Bear5k]

It's also by a window so I plan on installing an outside venting system of some sort to provide negative pressure in the room and hopefully pull dust out of the room. I'll build a windowed box around the table if I need to to help contain dust.

One thing to note - negative pressure in a room will attract air from the positive side. In other words, the dust won't go anywhere. You really need a dust shoe and a dust collector or a shop vac.