[contactirfu]

I have added some steel weights to the uprights as I have found that on the odd ocassion a resonant spot is hit which is enough to stall a motor. Had the weights on for months now and never missed a beat.

could you add a pic of what you are describing??

[Haydn]

could you add a pic of what you are describing??

Cant really do that as you can't see them. I clamped an additional 40kg of steel to the gantry to see how it performed and there was a vast improvement in the overall running of the machine. So i decided to add more mass permanently. The uprights of the gantry are hollow and basically filled with steel swarf/chippings from a local engineering firm. The new gantry weighs in at about 80kg, about the same as my current one with all the extra temporary steel strapped to it.

[hawkmoon77]

I appreciate the time you put into documenting your build and am using it as a guide for my own construction. I had two questions for you. The first is, how are the sides of your gantry (the gantry uprights) connected to the X rails? See attached picture. What are the dimensions of the steel you went with to replace the aluminum?

The second question is more theoretical. I like your "casting of a surface table" technique. I do not have access to such a table. I was wondering if you (or anyone else for that matter) could think of alternatives. For example, would thick glass work? What about granite countertops? I wonder if they have the required tolerances to cast a flat/smooth surface.

Also, I wonder if you (or anyone else) have ideas for adjustable feet that do not introduce wobble. I see (in the attached picture) the modification you made to the machine legs and the floor. In your experience, is there any chance of adjustable feet, or should I just give up on that idea completely?

Lastly, can you offer some advice on ballscrews. My machine will be similar in size and weight to yours. I have the choice between 16, 20 and 25mm diameter ballscrews, with either a 5mm or 10mm lead. I was thinking 16mm diam, 5mm lead on the z axis, and 25mm diam, 5mm lead on the x and y axis. I noticed that you did 10mm lead on your x and y. I just can't make up my mind and thought I'd ask for your advice.

Thanks.

[Benonymous]

I'd think a solid granite kitchen top might be flat enough. The best way to find out is with a decent straight-edge and a set of feeler gauges.

Fortunately I have access to a surface table and my friend who works at the engineering shop is checking some RHS steel for me to see if the cold formed section I want to use in my machine is flat enough without some sort of milling/grinding to do the job for my machine bed. He's gong to lay the steel on the surface table and check it with feelers.

I'll add the results of these experiments to my build log when I start it.

[hawkmoon77]

I'd think a solid granite kitchen top might be flat enough. The best way to find out is with a decent straight-edge and a set of feeler gauges.

Fortunately I have access to a surface table and my friend who works at the engineering shop is checking some RHS steel for me to see if the cold formed section I want to use in my machine is flat enough without some sort of milling/grinding to do the job for my machine bed. He's gong to lay the steel on the surface table and check it with feelers.

I'll add the results of these experiments to my build log when I start it.

I have a ground straight edge, and have been checking any surface I can find. Granite seems to bow a lot when installed on an uneven surface, so i've seen mixed results. I was hoping a Corian surface would be good, but too wavy. The best I've seen is a coffee table that had 1/2 inch thick glass on it. It was very flat. it had a small bow in the center but that is because it was unsopprted there. I am thinking of stopping by a glass shop and buying some 3/4 inch plate glass as a surface table. Certainly not appropriate for machine work, but seems like it would be great for the epoxy casting technique.

[harryn]

Hayden did an exceptional job using the casting technique, but there is also another path - self leveling epoxy. This is not just normal epoxy allowed to flow out, but in addition has special additives that make it really flow out flat.

I think you will be hard pressed to achieve a flatter surface in a DIY project than with self leveling epoxy.

There are several suppliers out there, but you can search on my posts or an on-line search engine and some suppliers will come up. It is often used in machine bases and to make very flat surface plates to set up race cars at specialty shops.