[JohnZ]

After reading hundreds of threads on CNCZone I figure that it is about time to post about my machine build. This will be my third machine build and hopefully not the last. I have plans to convert a Craftsman wood lathe to full CNC (It has nearly 200 lbs of cast iron in it's base), and to build a CNC mill completly from scratch. But first, I need to stiffen up and improve the accuracy of my CNC router so I can use it for all of the other projects I have in mind.

My workshop is in the corner of the garage. Or perhaps I should say, if I kept it clean and organized, I could get a car in there, but for now, it is taking up one of the bays in the garage, and sometimes we are lucky to have a pathway to get to the back door.

I got interested in CNC about 7 years ago when teaching telescope making classes. One of our students was the lead engineer at a local medical manufacturing plant. The plant was being shut down and he was being sent out of country to oversee the transfer of the manufacturing to the "Out Sourced" manufacturing. To make a long story short, before he moved, he said I could come over to his place and pick up all I wanted or he would just have to throw away all of his "Junk". In that junk was the start of a desktop CNC machine, and a bunch of components. I came away with the desktop components, some linear rails and other misc. parts that seemed too good to go to the land fill.

My first build was the desktop CNC machine. It had a cutting area around 15x15x6" or so and had ball screws on the x and y. I made the Z axis out of plywood, aluminum, and 3/4" round rails. To make the parts for the Z axis, I used a couple of shelf brackets, plywood and a router lift designed for a normal router table as a temporary setup. I rigged up a stepper motor to the lift screw and used that to mill out both plywood and aluminum parts for the Z axis. The y axis used 3/4" unsupported rails while the X axis was fully supported. There was a bit of flex in the unsupported rails, but I was able to cut aluminum pretty well. At one point I lost steps in the Z axis and cut 1/2" deep, 1/2" wide at about 20 ipm. I was surprised by the PC 7518 router. It bogged down a bit, but the speed control brought the speed right back up again. It plowed about an inch through the aluminum before I managed to hit the e-stop button. For controllers, I bought a linistepper kit and put together a 24v power supply. I was on a strict budget and had to use what I had on hand. But I learned a lot from that first project.

My second build is the router table shown in the first picture. I had a bunch of 1.5" x 2.5" x 0.093 wall rectangular steel tubing left over from another project laying around, so I welded up a steel table. The vertical uprights were cut from a 13" x 1.5" "C" channel. I cut it into triangles and welded the two halves back together to make a "T" shape that was about 11" deep at the bottom and 2" deep at the top of the uprights. I welded this to some 3/8" steel plate and used a second 3/8" steel plate on the other side of the table frame to bolt down the uprights. This allowed a little bit of left / right and front / back adjustment to square up the "X" axis.

The "X" axis was built with 3/8" plate as connectors to the uprights and rectangular tubing to support the profile rail. The "Y" axis uses some supported 1.5" round rails. I mounted the bearings at the center of the table. When tightened up, I could stand on the edge of the table with minimal deflection. The rails are mounted to 3/8" steel plate welded to the table frame. I bought some 3/4" x 5 TPI Acme screws for the X & Y drive screws and used some angle iron bolted to the frame to hold the bearing supports I got with the screws. The motors were mounted with carriage bolts as stand offs.

The "Z" axis is probably overbuilt. I found some 9/16" steel plate at a surplus store and proceeded to go through about a dozen sawzall blades trying to cut it to size. I ended up having to use a cutoff wheel on an angle grinder to cut through this stuff it was so hard. I have had it for a few years now and not a sign of rust or corrosion, so I think that it must have been some form of magnetic stainless steel. The rails on the Z axis are 1" round rail with 4 SPB 16 pillow block bearings. I bought a 1/2" x 10 TPI precision acme screw for the drive, and used smaller bits of the 9/16" steel to mount the drive screw bearings to. The aluminum router mount was taken from build #1. Overall, I think that my "Z" axis assembly is close to 100 lbs with near half of that being lifted by the drive screw. Even with the unsupported rails, it is very stiff, but I can move the axis up / down just by twisting the motor connector with my fingers.

My controller box is an old server case. Since I kept frying out the linistepper controllers, I mounted some drivers I got from Kelling and put together a hodge podge of power supplies, including a Linear, PC, and Laptop power supplies. (Talk about using what you've got). This gave me 5v, 12v, 38v, and 62v for everything. Then the breakout board I got had all kinds of problems so I ended up cutting the end off of a printer cable, identified and marked all of the wires and direct connected wires to the controllers as a "Temporary" fix that ended up lasting for a couple of years.

The table was made by welding some of the same rectangular tubing then bolting a 1" thick slab of HDPE to it. To get a flat surface (since neither the Welded steel table or the HDPE were flat) I used the router to surface the entire table top and mortise in some grooves where I screwed in some "T" slot guides I got from WoodCrafters to use as hold downs. Most of the time, i used a MDF sacrificial surface and clamped my work to that.

This machine worked fairly well, but had two major flaws. The table surface was constantly changing shape. I do not know if it was the HDPE surface or the welded steel frame underneath it, but I could end up with 1/8" or more difference in "Z" depth from one part of the table surface to another from month to month. The second flaw was in the welded steel table base. When the machine was in motion, the legs would flex and spring resulting in cuts being wiggly instead of straight. The end result was that I hardly ever used the machine, I was just simply frustrated with it and unhappy with the results.

The turning point was when I found a 3' x 4' optical breadboard on eBay. It was a local seller so i could pick it up instead of paying for freight. It has bolt holes on a 25mm grid over the entire surface and according to Newport Optical is flat to within .001" across the entire surface and can support a lot of weight without flexing. I think it was spec'd to flex less than .001" with 200 lbs in the middle of the table when supported out near the corners or something like that. In addition, and optical breadboard is designed to dampen vibrations between the top surface and the bottom. However, when I went to pick it up, I found out that it weighs over 260 lbs. O.K. that is good and bad. Like cast iron, weight helps to minimize vibrations in the machine, but my table base is springing around with my current table that probably weighs less than 40 lbs. It would be all over the place with a 260 lb table moving around.

So, last December, I tore apart the machine and started rebuilding it. I read through much of the epoxy granite threads and decided to stiffen up the table base by filling up the steel tubes. Since I was just filling the tubes, the EG was not going to be the only structural component, I use fiberglass resin as a binder instead of the more expensive epoxy. This worked fairly well until...

First lesson learned. If you are going to weld on a steel tube, do not fill it with concrete first. Weld it first as the heat from the welding boils the polymer concrete. I melted a hole in the rectangular tubing at one point and ended up with a blow torch blasting out of the hole where the super heated fiberglass resin out gassed and blew through the hole. I am just glad it did not explode.

But welding up all of the tubes first makes most of the tubes closed so I cannot get concrete inside any longer. So I thought about that for a bit and decided to just go ahead and weld up a bunch of triangular supports to stiffen up the frame as much as I could. I sort of designed with a cut off saw and welding rods. I would put in some angular supports, then step back and look at the frame for any weak points or points that could flex or had become weak points due to other supports I had welded in. By the time I was done it looks like I have gone totally overboard with angular supports and what not. My wife jokingly says that this is my "Leg Lamp" (from the movie "A Christmas Story" 1983) while I think it is looking like a work of art. I have finished up all of the welding, which takes me a while since I just bought a cheep harbor freight stick welder and taught myself to weld by reading a book, watching you tube instructional videos and just going out into the garage and doing it. My welds look horible. Thanks goodness for angle grinders so I can grind off some of my first, second, and third attempts before I get something that has a chance of holding the two parts together. Happily by the end of this project, I am finally able to produce some welds that could be passed off as "Presentable".

The next step will be to fill in the entire top of the table frame with concrete. While at the local Home Depot, I met the "Rapid Set" distributor stocking shelves. We had a long talk about the product and what I was going to use it for. He said that the Rapid Set concrete uses a different chemical process than portland cement in that the water is actually consumed by the setting process reducing or eliminating any water from seeping out of the concrete over the following days, week, months or even years. This means that the steel will not have such an issue with rusting from the inside out if I were to use normal concrete. The other thing I really likes is that this stuff sets up in 1 hour and is rated at over 3000 psi in one hour and over 6000 psi in 28 hours set time. They have a second product that reaches 12000 psi in 28 hours, but I went with the less expensive stuff since I am filling steel framing and am using the concrete for vibration dampening and as a solid mass to help counteract the movement of the 260 lb moving table this frame will be supporting.

Well, it is now 1am and I need to get some sleep before going to work in the morning. I will try to get some pictures of the frame and post them tomorrow.

This rebuild will probably take me a couple of months to complete along with the other chores and projects around the house, but I plan on documenting everything along the way. Especially since I just received in the mail a 55" THK C7 25mm ball screw with 4 start 25mm lead and a 43" long Kuroda C5 precision ground 15mm x 15mm lead ball screw with a 5 um accuracy along the entire screw length and 5 um backlash. I have designed a fairly simple rotating nut design I will be building with just a drill press, cross slide vice and home made jigs. I am very excited about this since those Acme drive screws I was previously using had about .015" backlash, but even worse had unpredictable travel along the entire length of the screw. I.E. .2" per rotation at one point, but .21"+ at another and .19"- at a third with anything in between along the length of the screw.

Later - John Z

[Mountaincraft]

First of all, I like your shop.. Definitely looks more organized than mine... Yours is way more inviting....

I think that if I were going to use concrete, I'd just go ahead and form the thing and pour high strength concrete as the structural base itself.. Just put a lot of rebar, and pour it with the required fasteners and what not in place... The great thing about concrete is that if you use the right slump, it levels itself..

I thought about this approach for a bit, pouring massive sides that went right down into the ground into a foundation, and a massive table poured between them all as one unit... then building a mechmate style system on top... but in the end decided to go with a faster/easier approach with ready made off the shelf stuff and a welded steel base... gonna make the base all out of 2x2 tubing, 0.25" thick...

Anyways, I'll be checking out your build...

[JohnZ]

First of all, I like your shop.. Definitely looks more organized than mine... Yours is way more inviting....

I think that if I were going to use concrete, I'd just go ahead and form the thing and pour high strength concrete as the structural base itself..

but in the end decided to go with a faster/easier approach with ready made off the shelf stuff and a welded steel base... gonna make the base all out of 2x2 tubing, 0.25" thick...

Anyways, I'll be checking out your build...

Thanks for the compliments. This last weekend, much to SWMBO's delight, I cleaned up the shop space. It had gotten much more cluttered than in the picture posted above.

I had considered building a base out of concrete cinder blocks and pouring concrete / rebar etc. but two things keep me from that.
1 - I have to be able to move the machine if needed, and
2 - most importantly I was told that I was not allowed to bring cinder blocks into the garage as a permanent... Apparently her dad did a bunch of projects leaving everything unfinished. He even made kitchen cabinets out of 2x4's and CDX plywood. The way it was put ... "Not in my house ... If you do it, you are going to do it right and make it look good"

So the main structural component will be welded steel with concrete poured into the steel for vibration dampening etc. I will even be sealing the visible surfaces of the concrete and painting it.

When I get home tonight I will take some pictures of the table frame with the welding finished and a few other items and get those posted.

Thanks - John Z

[Mountaincraft]

yeah, I have a little property, so my version would have entailed pouring the table (no cinder blocks.. just forms and rebar and 5000 PSI concrete), then pouring a slab around it, and building a small shop building over it...

Eventually, the table I am building now will have it's own little building... with an attached control room (probably 5' x 6') and window in between... This will make it easier to control dust and fumes (from the plasma), and also cheaper to heat and cool... a small plug in ceramic heater and tiny window box AC to control the control room temp...

[JohnZ]

Wow, that would be nice to have enough land to build a dedicate shop just for a machine.

Here are some pictures of the beefed up welded steel frame.

TableBack.jpg - This picture shows the back side of the table frame. Initially the only steel I had in the frame were the legs, the outer rectangle for the top of the table, the flat steel plate where the Y axis linear rails are mounted and the small angular supports going from the legs to the top. The problem I had was with the legs flexing back and forth when the machine was in motion. To stiffen everything up, I added a rectangular tube between the legs at the bottom, then realized that I had just the flat side of the rectangular tubing to keep the table top from flexing so I added the longer angular supports and a vertical support going down to the bottom cross brace. That square tube sticking out the back is there to support the longer ball screw I got to replace the acme screws previously used. I still need to add some of the rectangular tubing to fill in the gap between the top of the frame and the square tube. This also ties the front and rear of the frame where the ball screw ends will be mounted making those connections stiffer.

TableSide.jpg - This picture shows the new bracing on the sides of the frame. Originally I did not have ANY additional supports on the sides, just the legs going down. To stiffen the frame I stuck in the cross brace near the bottom of the legs, a vertical support and two angular supports. I was also able to weld on some angle iron on the lower cross brace and bolt on some casters I had sitting in the junk drawer. The machine will NOT be on the casters when in use. I have some 3/8" steel plate welded on the bottom of each leg and have some leveling feet scrounged from some industrial equipment that will support the table. But when I need to move it, I can raise up the feet and roll the table around as needed, then drop the feet again once done.

TableTop.jpg - This picture shows all of the bracing put in the top of the frame. Initially all I had in the top were the outer edges connecting the legs and the flat steel plate for mounting the Y axis linear rail. First I added the angular braces across each corner, then the braces front to rear, then the square tube under the top to tie in the front / back where the Y axis ball screw will be mounted. Since I will be filling the entire top of the frame with RapidSet concrete, I welded in a munch of thin "C" channel along the bottom of each chamber to help support the concrete. Additionally I am welding in a bunch of bolts around the edges of the chambers and putting weld beads on the steel where the concrete will be contained to give a rough surface for the concrete to grab onto. The RapidSet concrete is supposed to be non-shrinking and have a strong bond to steel if allowed to set in contact with the steel, so this will hopefully add mass and vibration dampening to the frame.

VerticalSupport.jpg - I stuck one of the vertical supports where it gets bolted on. These look like they are really tall, but the X axis beam gets bolted to two colums of four bolt holes on each vertical support. The supports have six bolt holes vertically so I could remove the X axis beam and lift it up an additional 8 inches for milling very thick stock if ever needed. At the bottom position, I have around 7 inches of clearance between the moving table surface and the bottom of the X axis beam.

[giz]

Cool build - I'll be watching.

[JohnZ]

Here is a shot of what I call my "Poor Man's Lathe". This is my drill press with a cross slide vise bolted to the table. In the vise I have clamped a lathe cutting tool. The cutting tools position is moved in / out by the cross slide vise, and by pulling down on the drill press handle, the item being turned goes past the lathe tool and gets turned down.

This was built by using an arbor from a hole saw. The arbor had 5/8" x 16 tpi, so I drilled and tapped a hole in a piece of 3/4" aluminum plate. That plate was then turned down and faced off. There are a bunch of holes in the plate where I bolt on what ever I am turning. In this case, it is a chunk of 4" diameter plastic. I thought it was delrin when I bought it, but it turns a translucent yellow or brown color when machined down to about 1/4" thick. It is about as strong as delrin too. This is the beginning of some bearing supports for the rotating nut design I have come up with.

The largest project I have spun in my "Poor Mans Lathe" was a 14" diameter aluminum plate to mount a diamond cup grinding wheel which got mounted to a MT3 spindle and used in this same drill press for diamond curve generating mirror blanks for amateur telescope making. I pretty much go by the concept of "I don't care what it was designed to do, only what I can make it do", and I have tortured this drill press and it just keeps on going.

I have also included a picture of the new ball screws, bearings, and timing belt pullies I picked up off eBay for my new drive screws for the X and Y axis.

[Mountaincraft]

Great idea with the cross slide and drill press.. I'm filing that one away in one of the piles of paper in my mind.....
:cheers:

[JohnZ]

A quick update. I turned the outside of the body for the rotating nut for the X axis ball screw tonight. The surface finish is nothing to write home about, but this is turned on my drill press, and the cutting bit came loose from the lathe tool while I was doing the final finish pass. Oh well, such is life. The body is still attached to the hole saw arbor and aluminum chuck.

Step 1 - I turned down the body until I could just slip the bearings on.

Step 2 - I turned down the end until it was the large diameter of the QC timing belt pulley, and the far end the small diameter. Making a mental note of the total amount I turned the handle on the cross vise, I then turned down the body in a stair step turning the handle 1/8 of the distance every 1/8" on the depth indicator on the drill press for the 1" needed for the pulley. Then I clamped the pulley in the vise and spun the body into the pulley using the sharp edges of the bolt holes used on this type of QC bushing to turn down the last little bit of the body for an exact match of the pulleys taper.

Step 3 - Bearings and timing belt pulley positioned as they will be in the final assembly. The gap between the two bearings is there on purpose. I will be turning down two aluminum disks, one to house each bearing. One disk will have a lip captured between the two bearings. I still need to bore out the center of the body to fit the nut on the ball screw.

That's it for tonight.

[Mountaincraft]

I am really liking your poor mans lathe...

I've wanted a lathe for a long time, but other things have always demanded my moola..

at least now I know that when in a pinch there is a way to get it done with what I have... I may have to go to harbor freight and buy one of their mini lathe chucks... combined with a shaft to fit the drill press, my cross slide and a pair of calipers (which I will need to buy soon anyways), I too will have a poor mans drill press lathe/mill

[JohnZ]

I do have the machine functional again, but with a few temporary parts. Since my last post here, I picked up a precision spindle and a 2.5 kw servo motor and controller. I have built this so I can put on a 5C chuck and mount it on the z axis for milling, or put on a 5" lathe chuck and mount it on the milling table as a 4th axis or lathe spindle. That is once I finish the axis upgrades. Pretty much whenever I think I will have time to work on the machine, honey do lists get assigned or other commitments show up consuming all my time. This will end up being a lengthy build.

Current capabilities. I can machine aluminum with my pc router. Typically I run at 10,000 rpm, 45 ipm and .025 depth easily. When complete, I should be able to have similar material removal rates on steel. When I get back home in two weeks, ill take some pics and post more of an update.

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