Newbie- I made the plunge and finally started!

[RTamer]

First of all let me say hello to everyone. I've been doing all of the research that I could for the last two years... just enough to annoy the wife it seems, and finally started on my very first frame. I've never tried anything like this before, so be gentle with me. I've seen thousands of photos from homemade wood to profi expensive, and read hundreds of articles on building and software. In the photos, this is what I've started.

The frame is constructed from 30mm x 60mm steel with 30mm x 30mm cross members. It's 1226mm x 800mm outside and the cutting surface is 1200mm x 70mm. I'm still debating on removing the adjustable feet (input is welcome). No, the table is not the final resting place for my machine. I've decided to build a cabinet system under the machine for parts and electronics with a heavy duty table top.

The linear rails are ones that everyone knows, i think. 25mm for the x axis, 16mm for the y, and z axis. I bought a Kress router that turns 30,000 rpm at 650w (it was new and free... I won't complain). I also have the complete electronics and an old, but reliable laptop to run it. The funds got a bit short this time, so I was unable to purchase Trapez leads, and I have my own design for the anti-backlash (should be interesting at the least)

I ran into a dilema with the y axis now. I wanted to use 10mm aluminum for the side plates, but funds are too low (I'm at the €900 mark now, steam is risinig from the wife's head). Would it be just as sturdy to use 2 10mm hardwood sides bolted together, or does someone have a better idea before i cut them.

Will the 3Nm 3amp Step motors be adequate for my machine.

Here's the best part... I'm very good at mechanical drawing, but never used a CAD program. I did download a free program though, Draftsight (2D), and a free converter to g-code. A Mach 3 license came with my electronic package for the machine.

Did I miss anything? Oh yea, I design and build computer networks for small businesses, so I do have some ability.

I would greatly appreciate some help with my venture, and am very good at taking a critics point of view.

Thank you,
RTamer

[JohnZ]

Looks like a good start to your machine. Have you verified that your two linear rails are parallel to each other? If not, you will end up with a lot of binding. You may need to shim one or both rails, or rotate the rails to the top of the frame since that bearing type has about 50% load rating when turned on their sides like that.

That rectangular steel looks like the exact same profile I used to make the base table for my machine. After using it periodically for a year, I tore everything apart so I could stiffen up the base. In use the steel flexed and bounced all over the place, I could hardly cut a straight line. With my "upgrade", I welded in a lot of angular braces and even filled in the entire top surface with a polymer concrete mix. I still have a lot of work to do to finish it all off.

With regards to the leveling feet, you will want to keep those. I would even recommend placing some in the middle if you do not need the clearance for a moving gantry.

Thanks - John Z

[RTamer]

Good morning John,
Yesterday when I put them on I checked to make sure that everything was level in all directions, and was amazed to see the bubble from my level centered no matter where I put it, but I didn't even think about it being paralellel. I just ran out (before my coffee) and measured to see both ends and the middle at a very nice 71.15 cm.

Is that going to be a problem with the bearings? I didn't think too much about the loading because of so many with them mounted on the sides. I assume that even the THK rails would have somewhat the same problem then. I am going to build the y axis as light as possible, and also not too high to keep the center of gravity as low to the table as possible. I only need about 15cm of movement on the z axis.

Thanks,
Robert

[aarggh]

Robert,

Congrats on the build, you've done a great job so far!

I'd strongly recommend not using grain timber for any structural parts as it's almost impossible to seal it enough to stop warping and expansion/shrinkage.

If you absolutely have to use timber go for MDF or good quality plywood.

But as you doing such a fantastic job so far, it would be a real shame to use inferior parts, even if it does build the cost up :-)

Keep up the good work, and post lots of photos, apart from myself there would be many people very interested in following your build!

One thing you may find with the feet so high on the corners is that at higher speeds you may get a bit of a rocking action affecting joints and precision ultimately. Maybe add another two to the middle to more distribute the footprint of the machine? But I'd certainly lower them myself anyway to the lowest practical level to lower the centre of gravity of it.


One thing that is always good, is make the base as heavy as possible, this acts as a sound dampener, and limits flexing problems. I'd add some supports to not only strengthen it as John Z suggested, but also add mass to the lower centre of gravity.

cheers,
Ian

[RTamer]

@aarggh

I think I'm going to take your advice and go for the MDF for right now. I have some here that is 19mm thick. Should be sturdy enough to get it running. I can always accumulate some funds and purchase some 12mm aluminum later and change the parts out. If I'm lucky I can use this machine to cut and drill them also.

I did find out, or at least I think I did, that I'm building the machine backwards. I've found some posts that seemed easier to start with the z axis and work down to the table. I'm already a couple of miles in the woods, so I'll just have to find the way back without the breadcrumbs.

I'm seeing a problem measuring the cross-section on the y axis because I also need one under the frame for the spindle. Getting both sides at 90° and an accurate measurment. Should be interesting to see if I can get this one right.

My ears are open to any suggestions!

Plan for the day.... drawing and cutting.

Thanks,
Robert

[aarggh]

Hi Robert,

MDF doesn't have a large amount of lateral support for a gantry on it's own, so if your using 19mm sheets for now, I'd recommend to try and find a way to stiffen the sides, especially on the outside of the gantry where the bearings are fitted to the side rails.

Offcuts of steel plate while not great aesthetically, would be ideal for this, and would hold the MDF sheet rigid and at 90 degrees against the bearings, helping to minimise sideways flex. Same goes for the top, and back of the gantry, try to reinforce any spot you can to reduce flexing under load. Even doubling up the MDF can help, but rigid offcut material can be the best approach.

It can work really well and is more than do-able, but flexing is your enemy!

cheers,
Ian

[RTamer]

Hello aarggh,

Well, I took your advice and canned the MDF thoughts and went for the metal. This is the first prototype of my upright to the y axis. They are 30mm x 30mm x 3mm thick square, cut at 45cm sandwhiched between two 3mm steel plates. You were right though, this is definitely better than wood. I'm going to use 2 30mm x 20mm crossbeams with 100mm plating, also 3mm thick to mount the y axis rails. That will fit just between the uprights bolted with M8 x 90mm bolts.

Any criticism is more than welcome.

Thanks,
Robert

[RTamer]

Well, it's finally starting to get interesting. This is my first build, and the levels are showing me some real nice positions... all centered.

I'm getting ready to cut the cross-members and plates to mount the 800mm rails for the y axis. I've checked all of the measurements at least a hundred times, and the axis did not bind

I moved it into the house to get more done, but I don't recommend that anyone else do that... my wife is not happy.

Robert