[MattyJ4]

Hi, I'm Matt. I'm new here.

I want a VMC, but they're expensive. So, I decided to to see if I can build one, or something close. I have no practical use for a CNC machine but it seems like a fun challenge.

This all started a year ago when I discovered "This Old Tony" on YouTube. Fast forward 6 months and I had found myself a Bridgeport and was learning to make parts, or as my girlfriend calls it, a very big mess in the garage.
Then I discovered "NYCCNC" on YouTube and was hooked on the idea of owning a VMC.



I started out learning Fusion 360 about 2 months ago. Then bought an Arduino, some accessories and stepper motors. I wanted to make sure I could learn the CAD/CAM and electronics before I really began building. Loaded up the gcode with UGS. That test was a success. I then started to draw out some gantry style machines based on some builds here and other research. I was happy with my rudimentary plans and wanted to move onto building. I started shopping for material to build the structure. I had planned on using aluminium extrusions but soon realized I was never going to have VMC rigidity with that method. Then I modified my design to use steel plates. I found some MiSumi linear rails that met my needs and incorporated them into my newer design.





I wasn't thrilled with this design. It still lacked rigidity and would probably never be capable of cutting more than aluminum. Then I stumbled upon this contraption.

Parker M57-83 X-Y-Z Stepper Motor 3 Axis CNC Stepper Motor Ball Screw Stage | eBay

It is a 1,100 lb granite and steel machine used for precision measuring from the 80's. It had a small X, Y and Z axis but more importantly, an incredibly rigid structure of granite on top of a nice steel stand. The table is 36"x35"x5" of solid rock.

I picked it up for a fraction of the asking price and it was only 70 miles my house.

The seller loaded it into my truck with a fork lift and I headed home, with no clue how I was going to get it out of the bed. 8 hours later and I had cobbled together a sketchy chain hoist mounted to the ceiling of my garage with strut and I was unloading it piece by piece, as I feared putting too much weight on my hoist and having it tear the TJI joists from my ceiling and who knows what else. It worked.



I also picked up a fair amount of scrap aluminum and stainless steel from the seller, including some pretty cool machined parts to assist with the build.




I expect to do some layout of materials tomorrow. I'm not sure if I am going to model this in Fusion or just go for it. I am open to ideas and suggestions of any type. I have a lot of work and will take any help I can get.


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So, I have come here to share this build with you all. I hope to learn from others who are more experienced than I am and share what I learn along the way. Stay tuned.

-Matt

[MattyJ4]

Today I am working through layout options.



The linear guides I bought were used, but in like new condition. Misumi wide block, heavy duty, stainless and 27" long. I had previously purchased them from the same company that sold me the granite machine. These guys have so much cool stuff. No affiliation, but see the ebay link in the first post to check out their items for sale.

When I picked up the granite the guy mentioned they had the plates that the guides had been removed from. They are a machine dismantler. I bought them at scrap price and figured precision machined plates that were drilled and tapped specifically for my linear guides could be very helpful.



I think I like the width of the Y axis being 2 plates wide. I hope I am not making a mistake by not factoring in my ball screws (which are TBD) during this phase. I am assuming I can make them fit later on.



Now with another plate sitting on top, i have a place to set the X axis guides.



I have one set dimension for this project, the ability to cut a part for an equipment rack. A standard rack face is 19" wide, so I would like to get 20" out of my X axis. With a 27" rail, this may be hard.



Am I totally destroying my rigidity by placing the blocks so close together to accommodate this 20" travel? I can add more guides on the same axis but I don't really want to return these and start over with a new linear guide. I can also make the X axis double wide for stability like the Y but that would really limit my Y travel.

[MattyJ4]

I have also purchased this 3/4” plate to make the X and Y axis if the smaller pre tapped ones don’t work out.

One of my first challenges is going to be tapping the guide blocks. They are through holes and I really don’t want to run screws through the back side or use a nut, I need to get these threaded. My Dewalt M8 tap might as well be plastic as it can’t even scratch the surface of the hardened guide blocks.

Open to suggestions on that too.

[MattyJ4]

This is the tap I am considering for the guide block holes.

https://www.mscdirect.com/product/details/89348452

[skrubol]

If those are hardened through I'm not sure tapping is even possible. There are carbide taps, but I think even those have hardness limits and without finding out exactly how hard that steel is, you're pretty likely to have a very expensive broken tap. Thread milling might be an option, but you'll need a working CNC to interpolate. Would backer plates with tapped holes be a possibility? Assuming you can find a way to keep them loosely attached to the blocks when the screws aren't in them it would be much more convenient than nuts.

As far as your X axis having longer travels, you may want to start shopping for some similar linear rails in longer length. Even if they have to hang off of your saddle, as long as they have at least 3 blocks on each rail, very little force will be on the blocks that are on the rail that's hanging off.

[assink]

Maybe u can glue in some steel bushings with M6 Thread? Or glue in the bushing and then tap a thread.
Guess those blocks are hardened.
And why limit yourself to the existing plates? You can machine some new ones using your bridgeport mill?

[MattyJ4]

I bought that tap. It’s slightly harder than the blocks I believe so if I’m careful it may survive.

As for design layout, I can reach my X axis requirements if my blocks are placed as pictured.



If that layout sacrifices too much rigidity I will have to choose different rails.

[handlewanker]

Hi, I think you'll find most machine parts are case hardened steel......it's not often you'll find through hardened parts unless they are destined for press tool work....that's a whole different kettle of fish.

The case hardening is probably only .5mm deep.(.020").....it's purpose is to prevent the surface from getting damaged and burred from gripping in a vice and other handling etc.

You can burrow into the case surface with a carbide drill......(or use a pointy grinder stone in a die grinder or even a drill would do)......... to start with and then use an ordinary HSS drill to depth.......once drilled the tapping will be easy.....keep the tap square to the face or you'll break it.

In my opinion, the medium you've chosen to work with has to be about the most difficult way to build a CNC mill.

I think you'll find the table will be the most challenging part to get right.........it does need to have a fairly significant mass to ensure rigidity and integrity..........don't even think of having tee slots.....attempting to do that will make you cry.

Best of luck.
Ian.

[MattyJ4]

Here is it rendered. I really want to stick with the rails I have already purchased, but as I said previously, I am afraid mounting the X blocks so close together to achieve my desired travel is going to reduce the rigidity. I am only planning on cutting 6061 though. Thoughts? Fusion file attached.

[handlewanker]

Hi....this design is too unconventional for me to pass any valid criticism.

I think if you were only intending to cut some ally I would have stuck with the pic you showed earlier of the steel plate design........steel is so easy to attach and rework etc.

I'm a metal worker so I'm totally biased in that direction, mainly because an old dog needs more time to adapt to new tricks.....LOL.

I would base the design on conventional mill proportions as it works for them so if you adapt your materials and design in that direction it should work for you.

As I said, the table will be a challenge, but for the light usage you intend to put it to I think a 20mm thick solid slab of aluminium with tapped holes will be OK.
Ian.