Drawer slide design

[mikeschn]

Drawer slide design...

We've got several CAD users that are willing to work on some open source designs for us. I need someone to pursue the drawer slide design. Who would like to work on that?

jpot?
chronon1?
phillby?
someone else?

Mike...

[triticale]

I'll be concentrating on this thread, but CAD is one of the things I aim to learn from this project. Right now I have some pen on graph pad sketchs exploring my angled slide notion. Should I post cleaned-up scans here, or forward to whomsoever picks up the task here?

[mikeschn]

Originally Posted by triticale I'll be concentrating on this thread, but CAD is one of the things I aim to learn from this project. Right now I have some pen on graph pad sketchs exploring my angled slide notion. Should I post cleaned-up scans here, or forward to whomsoever picks up the task here?

Definitely post them here... we'll look at them and try to convert them into CAD.

Mike...

[triticale]

It cleaned up fairly well. Paint Shop Pro knocked out the red graph guide lines with just a few clicks. The two lines across the top which I left freehand are the shafting for the Y axis. I designed industrial equipment for close to 20 years using pencil and paper, and changed my direction as my employer was implementing CAD.

The main premise I'm trying to raise here is the notion that angling the slides should increase stability and rigidity. With a fixed table and moving gantry, the angle would go the other way. I expect to have access to a precision cabinet shop when I'm ready to start construction, but consistant angled wedges could be cut with a miter saw.

[ger21]

You'd be better off using 2 pairs of slides at 90° to each other. With your method you will still get a little play in the movement.

[triticale]

Originally posted by GER21 You'd be better off using 2 pairs of slides at 90° to each other. With your method you will still get a little play in the movement.

Believe me, if there'd been two pair in that dumpster I'd have grabbed them both.

We know that one pair of good slides, installed in the standard manner, does a minimally sufficient job. If my idea is valid, it would cut the investment, for anyone shopping from the plans, in half while still yielding some improvement. McMaster (never the lowest price, but cheaper for industry than chasing down the deal) wants $64 a pair for their closest equivalent.

[fyffe555]

I'm with Ger on this one.

Draw slides take loads in one plane only. Sit at your desk and half open a draw, lift it up and down and it shouldn't move, move it side to side and it will move a long way, wrack it diagonally and it will move about the same.

A gantry cnc will load its bearings in two dimensions and try to wrack the gantry in the same way as the draw test above. Add the leverage and distance of the cutter from the bearing and you've got problems.

I don't know what brand the slides are that were proposed for a diagonal mount but I've got some Home depot full extension high capacity slides here and trying it (before posting) they bind quite badly on a 45%.

Reading this post and the other recent posts about the new designs it strikes me there's little talk of the loads the machines have to be built for and how the different materials and bearings will need different design points in the construction of the machine.

For example given the draw slide option and the loads a cnc machine imposes the slides has to suport two planes of load and so in the ideal solution you'd need two sets one 90% to the other as Ger suggested.

Similarly the black iron pipe skate bearing arrangement has limits and challenges on the span a pipe of a given size can support, the need for support and the need for adjustment. It's not practical to significantly increase the dimensions of the JGRO router and expect it not to deflect big time.

In the same vein a lot of the gantry designs have simple uprights and back plates with no triangulation or support while the tube/rod is supported at the ends only by the thickness of MDF or the ends of bolt heads. They need way more support than that.

Some thought needs to go into the manufacture of the parts for alignment too. Since most of us ( except Ger apparently ! ) can't get our parts cut on a cnc machine first, then the design should avoid excessive number of joins or hole alignments, use techniques like cutting parallel dado's in one go on one board and then cutting the parts from that, bolting together enda and bdrilling all as one part to approximately line up holes, that sort of stuff.

It strikes me that there's a lot of enthusiasm ( which is great) to develop the machines but the engineering of each option has yet to catch up.

Andrew

[vladdy]

Is this the kind of critter you are looking for??
don't have any cad [or any other, for that matter] drawing for, pretty simple to put together..
a good square, tape measure, and a saw..

[mikeschn]

Originally Posted by fyffe555 It strikes me that there's a lot of enthusiasm ( which is great) to develop the machines but the engineering of each option has yet to catch up. Andrew

Do we have any engineering types here? Or are we all machinists and cad users?

Mike...

[mikeschn]

Okay, let me just throw out a quick idea for the drawer slide design...

Both x and y have the drawer slides mounted at 90* to each other to keep things from shifting.

This is really going to be a simple thing. The table moves, and the gantry is fixed.

Is this the direction we should be taking?

Mike...

P.S. Are drawer slides in Europe metric? Can someone point me to a URL for metric drawer glides?

[Evodyne]

Originally Posted by mikeschn Okay, let me just throw out a quick idea for the drawer slide design...Is this the direction we should be taking? Mike...

Mike,

Hi. My concern would be that the width of the table might work against you-see the attached pic. What about using the slides as they would normally be and use another method to limit movement in the unwanted directions? Something like delrin guides to contain the slop?

Lance

[jerber]

Originally Posted by mikeschn Okay, let me just throw out a quick idea for the drawer slide design... .... Is this the direction we should be taking? Mike... P.S. Are drawer slides in Europe metric? Can someone point me to a URL for metric drawer glides?

As far as I know they are metric, but only on this side of the tunnel.

http://www.chambrelan.fr/en/pages/interface/iframe.htm

or www.chambrelan.com with intro.

Is it an idea to use more then two slides per axis ?
It's harder to line them out and there will be more friction but "accuracy" and the load will inprove.