Hardware Store CNC Router Design #2

[datacop]

I was wandering through Menards yesterday trying to get some inspriation for a hardware store designed router...

I wandered over to the cabinate section and started looking at drawer slides and thought about what was good and bad about them. The good that I saw was the fact that the higher quality ones were fairly ridged with ball bering action. The bad things that I saw about them were when the slides were extended, there was little to no support for the rails.

My thought was to use two slides of equal length, facing the opposite of each other.

The gantry would be bolted to both of the rails for action. In this respect, when the left slide is fully extended and unsupported, the right slide would be fully retracted and totally supported.

The box design would have to be split so that the gantry would be able to be bolted to the rails. Using this design, the gantry rides on the outside of the work area.

Please forgive my crude sketch... I've not yet figured out how to use this damn CAD software yet. Hopefully this will explain the basic concept.

[txcowdog]

I don't understand why the box design is split. Don't you need a solid box for the slides to bolt to? I like the idea of one fully retracted and the other fully extended. I guess the big question is how stable the gantry will be. That question will only be answered when the first one is built.

[datacop]

My thinking was, you would need to split the box to allow for the attachment of the gantry to the rails since the gantry rides on the outside...

I suppose in retrospect, all you would need to do us cut a U channel out of the top of the box to allow for the screwdriver to pass through..

The only drawback that I see from this design, is the machine footprint is going to be twice as large as the usable cutting area. That being the case, the gantry sould be rock solid depending on the quality of slides used.

[datacop]

still working with autocad.. this took me a dang hour to do

[phillby]

I think that less space could be takenup it the two slides are offset vertically so that they can truely overlap. I also think with this design that if the closed length of the slide should be the same width as the gantry needs to be to optimise dimensions.
I also think that if you use slides with three sections then the travel can be two times the gantry dimension but with two section slides it will be only one times the gantry side length. This prediction is is as above the width matches the closed slide length.

Cheers

[datacop]

I see what you are saying, and it makes sense... Basically the open channels of the slides would line up vertically.

The question I have, how would you attach the gantry sides to the slide rails?

I suppose it would be easy enough to bore through holes in the box...

I'll work on the design more and post a follow up.

[datacop]

So, I modified the design a bit...

This is what the side view of the box would look like with the gantry slides..

[phillby]

That's exactly what I was saying. If you have three sections in the sliders rather than two as shown you will get twice the travel.

The attaching of the sliders is as designed The sliding bit attaches to the gantry and the stationary part attaches to the base, just like a draw, the mounting screws or bolts go in oposite directiona.

Cheers

[Colin31]

Hi, if you take a careful look at the slides you will normally find that the bearings in the rear part are housed in plastic holders and are much further apart in the holder than in the front slide. This normally makes for a much "rougher" traverse than the front slide. I have a set of these in my workshop and the best, well supported, movement I can get from a 24" slide is about 12". (using only the front slide and trimming the carrier so that it is well supported through it's travel).
You will also find that the slides have a near perfect slop free action in their vertical plane (ie. with the bearings aligned as if they were drawer mounted), but they have lots of slop in the horizontal plane. The answer to this problem is to preload the carrier either towards or away from the slide frame.
Some-one has already used these on a cnc machine, successfully, but how long they would last under heavy load is unknown.
I am tempted to give them a try on a small router for making foam masters for lost wax ally casting, but can't elaborate any more than that.

All the best, Colin31.

[Milton]

Use pockit door guides, They have same support through out travel

Milton

Originally Posted by datacop I was wandering through Menards yesterday trying to get some inspriation for a hardware store designed router... I wandered over to the cabinate section and started looking at drawer slides and thought about what was good and bad about them. The good that I saw was the fact that the higher quality ones were fairly ridged with ball bering action. The bad things that I saw about them were when the slides were extended, there was little to no support for the rails. My thought was to use two slides of equal length, facing the opposite of each other. The gantry would be bolted to both of the rails for action. In this respect, when the left slide is fully extended and unsupported, the right slide would be fully retracted and totally supported. The box design would have to be split so that the gantry would be able to be bolted to the rails. Using this design, the gantry rides on the outside of the work area. Please forgive my crude sketch... I've not yet figured out how to use this damn CAD software yet. Hopefully this will explain the basic concept.

[erlyrisa]

Have you considered the slides used in Large Metal Drawer cabinets - they are n't available off the shelf , but if you go to your metal recyclers you will often see these cabinets being thrown out - they have really large industrial type drawer slides. - not only are they really strong, but you can pull them apart fairly easily for modifications and they 're usually longer than the average slide.