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DIY CNC Machine Base Design & Fabrication Part 2

DIY CNC Machine Base Design & Fabrication Part 2

Posted by Jonathan Gee on Mar 19, 2022

NO BIRD POO WELDING ALLOWED!!!

Machine Base Design & Fabrication Part 2

Posted by Jonathan Gee,

19 Mar 2022


This is a privately funded project that frequently sees shortage of funds delaying progress, If you are enjoying this build diary and would like to contribute to the completion of this project and all the future guides and video journeys it would be gratefully received and spent directly on this project. Donate through PayPalMe Here...

Machine Base Design & Fabrication Part 2

Basic Base Design for mounting the granite on.

The design above is one of the early iterations without a slide in coolant tank and an older design of granite skid. In any case, it shows the principle of how the granite will be mounted above, and in the centre of the drain tray. The granite will sit on what I will continue to refer to it as, the granite 'skid', or 'sled'. This was a first version and the design improved to lower the centre of gravity and to provide functionality to raise and lower the granite. Raising and lowering the whole granite assembly is intended to be used for the installation and removal of the granite assembly, access and future maintenance and calibration of the surface plate. I will go into this design in more detail as this series of articles goes on.

Cross Sectional view of the basic base design.

Cross Sectional view of the basic base design.

Above you can see a cross sectional view of the base design which helps to show the design and how the drainage will work. As I have previously mentioned, I am using fairly basic tools and equipment to achieve a functional design, so the solutions are very considered, and simple in its nature. There will be no custom profiles, mould tools or extrusions for creating runners or seals or cast parts etc. In my experience, it is easy to design any sort of mechanism to achieve the desired effect, but it takes a lot of discipline to bring your ideas back to the very basics of creativity to achieve similar results. For anyone who considers designing their own machine like this, my advice would be that if you feel that the design is getting complicated, or more so that the process you are going to have to go through to make the components is becoming increasingly difficult, it’s probably time to click File New and look at it from a fresh perspective. A good way to look at it is to use the minimum number of parts possible to achieve what you need to do.

Preparing cut pieces of steel ready for welding.

Preparing cut pieces of steel ready for welding.

So this brings me on to prepping some parts. I had a pretty clear idea about what the plan was, and I had modelled it thoroughly in CAD now including all the coolant tank assembly. I was basically learning to weld and fabricate steel from scratch, so I took it steady, taking care to not end up with a welded mess of twisted metal. The metal cut-off saw was well worth the investment. I would recommend that you make sure you have spare cutting discs and don't buy cheap and nasty stuff as they won't last very long. The one that came with the saw didn't last very long at all, but the Makita branded ones I bought subsequently lasted much longer. If your disc becomes worn down too much, you will be unable to make full through cuts when set at 45 degrees.

Setting out the fabrication for taking measurements and making cuts.

Setting out the fabrication for taking measurements and making cuts.

I would recommend that you take care when making cuts in order to get the sizes correct. There is no need to get everything tight and clamped together before welding. You will find that it is much easier to cut slightly short and give yourself the freedom to make slight adjustments. If you can cutting equal lengths to fab up in a panel and one is too long, you will end you having to clamp up and your assembly will become skewed. The biggest benefit with welding though is that you can tack assemble everything together before committing. Without doubt you should do this. It is strong enough to hold everything together, but easy enough to grind off cleanly if you have made a mistake or need to make a slight adjustment. In the beginning I don't think I tacked things up as much as I should have done, but I was fighting with working in a cramped space inside or battling with sporadic rain and high winds outside. All in all though it went OK although the quality of my welds from the first panels to the last was like chalk and cheese. It makes you want to start the first parts again. A good tip is to use a bench or setup whereby you can secure the elements with quick or g-clamps to help the steel not move when you impart lots of heat into the metal when welding. Welding can cause a lot of distortion and movement.

Some early welding work for the new granite CNC base.

Some early welding work for the new granite CNC base.

Above you can see the first two panels that I fabricated together. The bottom one is complete but the top one just needs some angled braces cutting and welding in. In the centre of the top panel you can see a gap open at the bottom. This is for the clearance of the coolant tank to slide in and out. I made a bit of a mistake here on this part. before I welded everything up, I should have placed a temporary piece tacked in this gap to prevent it from pinching together. I had to work quite hard with clamps to hold this frame true, but I managed it in the end. This was the weakest element of the design, but it was necessary to allow the clearance height for the coolant tank whilst keeping the whole assembly at a comfortable working height when the granite base was mounted on it.

Close up of the internal design of the framework.

Close up of the internal design of the framework.

In order to strengthen this point of weakness I added the panel frame highlighted in blue to brace this section from spreading apart under load. I also doubled up of the vertical uprights of the centre sections of the front and back panel of the assembly as this would be where the load points of the granite base would be. The gap in the centre is where the coolant and chips would be funnelled down into the filter tray before draining into the tank.

A dry run of assembling the outer panels of the base using only g-clamps to secure.

A dry run of assembling the outer panels of the base using only g-clamps to secure.

I plan to use a load of M10 Stainless Steel bolts to tie all the panels together. I want the panels to be collapsible if it becomes necessary to dismantle and move the machine in the future, or for ease of modifying parts in the future. I plan to manufacture the fitment of all the panels so that every part is under a high level of tension for maximum rigidity.

It was at this point that the heavy panel at this stage (the one at the back in the photo above) toppled over from stood up and landed on my right foot breaking a metatarsal. Stupidly I thought I could walk it off, so I went running up and down my long drive for a few laps trying to stretch off the pain. Luckily my sister was visiting, and she got hold of me before I passed out.

 

Broken metarsal had caused some quite painful swelling.

Broken metarsal had caused some quite painful swelling.

Training show it is then for a few weeks!

Training show it is then for a few weeks!

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Originally Uploaded On: 19/03/2022

Last Updated On: 19/03/2022

Estimated Date Period: : 25/02/2022

This is a privately funded project that frequently sees shortage of funds delaying progress, If you are enjoying this build diary and would like to contribute to the completion of this project and all the future guides and video journeys it would be gratefully received and spent directly on this project. Donate through PayPalMe Here...

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