Input on design

[PBillmann]

I got some free linear gantry’s (CBEAM, lead screw, end plates etc) wanted to make a machine with max volume.

I also already have various random stock of aluminum on hand to make gantry Arms/plates and any other mounting pieces. Take a look at the pictures and provide feedback. The RED pieces are those which i plan on making out of aluminum. Gantry Arms from 1/4in plate, end plates on Y Axis to connect to 2080 supports from 18mm aluminum, and 2080 extursion for support on the Y Axis.

For reference the X/Longer Axis is 620mm C BEAM with10mm end plates and the Y/Shorter Axis are 490mm with10mm end plates. The Z is 110mm of travel.

Concept below looking for thoughts.

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[peteeng]

Hi PB - The 1/4" columns will flex and vibrate, they will need webs or make them very thick. For the effort you are about to expend and the $$$ you are about to part with use round rails for your motion not wheels. The result will be 10x better at not much cost up. Peter

[phomann]

It depends on what you planning to cut.
It looks like some of the extremely popular diy kits. If you’re planning to cut wood, plastics and not metals it should be fine.
But, as Peter points out, the stiffer the machine, the happier you will be.

Cheers
Peter.

[routalot]

Peter is absolutely correct,as is quite normal.I would go further than he does and move the gantry uprights to the outside of the rails.Even if it means adding spacer blocks as it will then allow your spindle to traverse the whole of the table area instead of losing half the spindle size at either side (more or less-depends on tool dia.).You could then bolt on a section of 2"X2"X1/4" angle to the outer surface of the gantry plates to gain some stiffness.

[PBillmann]

Peter is absolutely correct,as is quite normal.I would go further than he does and move the gantry uprights to the outside of the rails.Even if it means adding spacer blocks as it will then allow your spindle to traverse the whole of the table area instead of losing half the spindle size at either side (more or less-depends on tool dia.).You could then bolt on a section of 2"X2"X1/4" angle to the outer surface of the gantry plates to gain some stiffness.

Thanks, part of this I was trying to do on budget, I was given for free everything only the red is what I’m designing. So yes rails better but wheel gantry’s for x/y free and rail z gantry was free

Trying to maximize volume, if I move arms/uprights outside the rails I need to increase their height or Z will hit the rails and 2 in on x axis is lost.

So I guess the specific question would be do I make the uprights 2 in taller (1/4 in plate) and move uprights outside or keep them inside and uprights as short as possible.


Would double up and use 2x 1/4 plates be advantageous.


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[peteeng]

Hi PB - 2x1/4" is better, but webs are probably even better. Budget is always an issue but in 3 months to a year when you decide that the wheels need upgrading (either you have just adjusted them for the 10th time and they are still not right or they have worn out for the 3rd time so now your at parity with buying rails) the initial extra cost will be insignificant. Seriously consider rails.... at least cost and design it out so you can make an informed decision vs a guess. The initial CAD work does not cost you $$$ only time. There's a lot of free cardboard around so make a cardboard machine? Consider using plywood for the columns. 16mm ply is considerably stiffer then 6mm aluminium, cheaper and easier to use. Peter

a quick calculation shows that 10mm plywood is the same stiffness as 6mm aluminium and 16mm ply is 4.6x stiffer then 6mm al....

[PBillmann]

Hi PB - 2x1/4" is better, but webs are probably even better. Budget is always an issue but in 3 months to a year when you decide that the wheels need upgrading (either you have just adjusted them for the 10th time and they are still not right or they have worn out for the 3rd time so now your at parity with buying rails) the initial extra cost will be insignificant. Seriously consider rails.... at least cost and design it out so you can make an informed decision vs a guess. The initial CAD work does not cost you $$$ only time. There's a lot of free cardboard around so make a cardboard machine? Consider using plywood for the columns. 16mm ply is considerably stiffer then 6mm aluminium, cheaper and easier to use. Peter

a quick calculation shows that 10mm plywood is the same stiffness as 6mm aluminium and 16mm ply is 4.6x stiffer then 6mm al....

Peteeng,

Thanks you make good points about plywood and I’ll look into it.

In terms of pricing out. I have all the wheel gantry’s. I was given them free and brand new. I also have the aluminum stock on hand in 1/4 in.

Only thing purchasing is the extrusion for for connecting front and rear of frame.


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[catahoula]

I would concur with the other posters here. My 3d printer has wheels like that for linear motion and they are barely functional but obnoxious to adjust, even on a machine with essentially zero load. I couldn't imagine using them on a cnc. solve the problem at just $50 per axis with something like this: https://www.amazon.com/CNCMANS-Beari...df_B09NBP15YW/

[peteeng]

Hi PB - I think you have two pathways:
1) Design everything down to the wheeled rails level in the knowledge that this will be the weakest link. So design a machine minimising everything. In this way when its time to get a new machine you effectively put this one in the bin or give it away. Those parts maybe free today but the consequences of using such a logic will cost you more in the medium term
2) Build a machine following some recommendations and get a better machine that won't go in the bin so fast. Design a great machine without considering cost and see how you go. You may surprise yourself, it maybe reasonable cost yet be a great machine. Wheels don't not take you down that path.

It seems to be a human condition that we place reasonable value on something that is given to us for free (except free advice Its effectively valueless yet we cling to the object. Salespeople have been using this phenomena since sales existed. I can hear the Egyptian 3T stone block sales man spruking now, buy 5 get one free!! Tutankhamun Finance available etc. Those free steak knive offers do work. But the free lunch does not exist to use those knives at Peter

[PBillmann]

Hi PB - I think you have two pathways:
1) Design everything down to the wheeled rails level in the knowledge that this will be the weakest link. So design a machine minimising everything. In this way when its time to get a new machine you effectively put this one in the bin or give it away. Those parts maybe free today but the consequences of using such a logic will cost you more in the medium term
2) Build a machine following some recommendations and get a better machine that won't go in the bin so fast. Design a great machine without considering cost and see how you go. You may surprise yourself, it maybe reasonable cost yet be a great machine. Wheels don't not take you down that path.

It seems to be a human condition that we place reasonable value on something that is given to us for free (except free advice Its effectively valueless yet we cling to the object. Salespeople have been using this phenomena since sales existed. I can hear the Egyptian 3T stone block sales man spruking now, buy 5 get one free!! Tutankhamun Finance available etc. Those free steak knive offers do work. But the free lunch does not exist to use those knives at Peter

Thanks Peteeng! I think I needed to hear that


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