[CtrlZ]

This is my second attempt at this design per everyone's advice. Thanks to everyone who helped and I appreciate any further comments.

I pretty much started over and tried to make this design more substantial. The table is 56" X 96" made from 4" square tube stock. The gantry clearance is about 13 1/8" so I can mill a 12" part easily. I intended to make a removable bed for milling thinner parts but now I don't think it's necessary. (I could be wrong) The Z travel is a little over 13".

I'm not showing the drive components, but intend to use AC servos and ball screws with direct drive couplings. Probably 1 1/2" drive for the X axis, 1" for the Y axis and 5/8" for the z axis.I may add a fourth axis later.

Thanks for your thought, don't hold back.

[eloid]

Looks abit like the Arty
http://www.legacycncwoodworking.com/arty-cnc/

If i was design a steel fram cnc I would not use ball screw for your y axis
use rack and pinion and save your self a future upgrade also you dont need
the bottom ballscrew brace on your gantry making it lighter if you go R/P

look good so far

[CtrlZ]

Eloid, thanks for the comments!

If I use rack and pinion for the X axis, does it have to be driven from both sides, or can I get away with just one side? One of our copy lathes has R/P for the X and is only driven from one side but the rails are only about 8" apart. It seems the wider span would require driving from both sides to prevent chatter, and every R/P table I've seen are driven from both sides.

I like the idea of using R/P for the X, but if it will require two drives, I'm a little intimidated by the prospect since I don't have any experience or knowledge of doing anything like that. I will be using AC servos we already have, and I have enough matching servos to do the job, but I don't have a clue how to sync them together. Does it require special wiring, hardware, software, etc?

[Phife]

Looks good!, my only concerns would be where the Y/Z gantry meets the X rails, it looks like that big heavy gantry is supported by those thin plates that the bearings get attached to, I think some sort of beefing up there would help. Also that gantry is heavy, your going to have alot of mass to accelerate and decelerate, perhaps you could make that out of 2.5" - 3" square tube? try to save weight on the moving parts, having a heavy gantry will only slow you down.

Also, I would try to get my Z axis thinner, it looks like it hangs out quite far, any chance you could move the Y rails to the back so your router is closer to the Y beam?

As for adding a second motor to the X, its really not hard to do, Mach3 does all the work (slaving the second X motor), all you need to do is have an additional servo driver and wiring. And 2 limit switches on the X helps keep everything lined up and square.

Those are my suggestions, Good job so far!

[CtrlZ]

Thanks for the comments Phife! I feel like I'm getting close to a final design.

I made the gantry heavy to accomadate the extra Z travel, but maybe I could lighten it up a bit and still be ok. I was planning on using Mach3 so I think I'm going to go ahead and plan on R/P for the X axis since you told me I can easily set up the second servo as a slave. That will also eliminate a lot of weight. When I redo the gantry, I'll also see what I can do about the Z axis hanging out so far.

I'm off to make some modifications, will update.

[eloid]

[QUOTE=CtrlZ;803370]Eloid, thanks for the comments!

If I use rack and pinion for the X axis, does it have to be driven from both sides, ( yes I recommend)

or can I get away with just one side? One of our copy lathes has R/P for the X and is only driven from one side but the rails are only about 8" apart. It seems the wider span would require driving from both sides to prevent chatter, and every R/P table I've seen are driven from both sides.

I like the idea of using R/P for the X, but if it will require two drives, I'm a little intimidated by the prospect since I don't have any experience or knowledge of doing anything like that. all done in mach just requires some
configure mach to see other motor as a slave.

I will be using AC servos we already have, and I have enough matching servos to do the job, but I don't have a clue how to sync them together. Does it require special wiring, hardware, software, etc?

nothing special software just mach...

Looking at your design i would may add a addtional support like you have in the mid spam of your y axis having 2 mid span support per y axis would be ideal..

[HereinCS]

Looks abit like the Arty
http://www.legacycncwoodworking.com/arty-cnc/

That's an interesting looking machine. Is the rotary axis a direct mount servo motor?

[eloid]

Thanks for the comments Phife! I feel like I'm getting close to a final design.

I made the gantry heavy to accomadate the extra Z travel, but maybe I could lighten it up a bit and still be ok. I was planning on using Mach3 so I think I'm going to go ahead and plan on R/P for the X axis since you told me I can easily set up the second servo as a slave. That will also eliminate a lot of weight. When I redo the gantry, I'll also see what I can do about the Z axis hanging out so far.

I'm off to make some modifications, will update.

why not do x and y r/p? and z axis ballscrew

[Phife]

Looking at your design i would may add a addtional support like you have in the mid spam of your y axis having 2 mid span support per y axis would be ideal..

I dont agree here, He already has a aluminum plate running the entire Y axis, surely that is enough support between the 2 Y beams.

Adding a midspan support just adds more weight to the moving gantry.

[eloid]

I dont agree here, He already has a aluminum plate running the entire Y axis, surely that is enough support between the 2 Y beams.

Adding a midspan support just adds more weight to the moving gantry.

Not to the "gantry ( gantry is fine )" but the long axis Y it only 6" worth of tubing
it does weigh much.... when you start welding , you find you tubing is not
the same any more... this 6 tall tubing will help with high freq....resonance vib in this rail


If you do any cabinet work or drawers... etc you may want to make a cantilevered front so you can dovetail / dowel pin work..
see attached picture.. and videos

[nomedia="http://www.youtube.com/watch?v=4Aw4lElTecg&feature=related"]YouTube- ShopBot Cutting Dovetails[/nomedia]
[nomedia="http://www.youtube.com/watch?v=4yX-ZrDt2sM&feature=related"]YouTube- Dowel and Assembly Test[/nomedia]

[CtrlZ]

Eloid, I think the extra support is a great idea. I also like the R/P idea for the Y axis.

For milling the edge of parts, couldn't I just clamp the work piece in the center of the table and cantilever it over one of the middle supports? I may also use a sacrificial piece of plywood for some work.

[Phife]

Ahh, I see where the problem is Eloid, what you call the Y, I call the X.. sorry for the mis understanding, I agree with you.


CtrlZ,

You will want to have a permanent table on your machine, you will have to machine it flat with your spindle, and it will probably be a pain to remove. So if you plan on doing any panel edge work like the videos eloid posted, you will want to have an overhang off the end, or a table designed with this in mind.

I have used various beds on my machine, and I have settled on 2" MDF with a 1" HDPE Vacuum table top, 1/4"-20 holes spaced 2" apart on the "islands" of the vacuum grid. I find this works best for me as I do alot of carvings, signs and panel work.

[CtrlZ]

Thanks for the clarification Phife. We won't be doing a lot of panel work but we will be occasionally cutting small parts out of sheets of plywood so I guess I can use a piece of sacrificial plywood on top the permanent table right? I will probably still add the cantilever idea, but I haven't done it yet. I'll do that when I know for sure where the travel will be.

Here's some quick renders of what I have so far. I haven't added the drives yet, but I now plan on using R/P for the X and Y axis, and ball screw for the Z. The gantry is now 3" square stock instead of 4" and I added some support near the X bearings. I also added the extra supports along the X axis.

[eloid]

Eloid, I think the extra support is a great idea. I also like the R/P idea for the Y axis.

For milling the edge of parts, couldn't I just clamp the work piece in the center of the table and cantilever it over one of the middle supports? I may also use a sacrificial piece of plywood for some work.

you need allow enough room for your spindle to reach the end of the table
problem 1( see secound picture... your spindle will never reach the front of the table)
problem 2 for machine ie if your pockecting 3" thick soild peice hard wood your gantery would max out and hit the end stops limts ( as phife point out this your x axis I was look at wrong picture when i wrote the above) is why you need some
cantilever ... it could 2"-8" what ever your needs are

question? the end stop on your x axis are for... safty? or wiper system for linear rails?
with your gantry bracing in the forward postion your spindle will never reach the end of table... maybe place the bracing to the rear of the gantry... the spindle thus can over hange the front edge not hitting your end stop?

also your x axis linear bearing could be placed right under the verictal gantry support this clean up you design for building but keep the plate just move support direct on linear rail?

this will buy you more room for r/p setup other wise i can see issues here when you do the r/p tension and gearing.... your gearing needs to be close to the rack....for good insertion of the pinion and tension.

In the 3 picture your working "foot print" has enlarged with out change the size of the table.. and your spindle now over hangs the front edge?... you can mod the design as it suit your needs just... a friendly observation

[CtrlZ]

Some more good advice eloid!

The end stops are just for safety. I like the idea of moving the gantry supports to the rear to allow the spindle to reach the end of the table. I will plan on doing that.

The gantry uprights where offset from the bearings as part of the original design to allow a place to attach the brace for the ballscrew, so I can change that as well.

I'm now thinking I need to make some other changes as well. I originally planned on making a removable table for cutting thin materials but I decided it wouldn't be necessary. Now the problem is the spindle assembly will hit the table before reaching the edge, so I won't be able to cut a 4 X 8 sheet. I need the travel in the Z axis for doing thick parts, so I either need to make the table about 8" wider, or I need to make the gantry taller and move the bed of the table back up to be flush at the top. What do you think is the best option?

I also think I need to make the table longer so I have a full 96" of travel.

[eloid]

Some more good advice eloid!

The end stops are just for safety. I like the idea of moving the gantry supports to the rear to allow the spindle to reach the end of the table. I will plan on doing that.

The gantry uprights where offset from the bearings as part of the original design to allow a place to attach the brace for the ballscrew, so I can change that as well.

I'm now thinking I need to make some other changes as well. I originally planned on making a removable table for cutting thin materials but I decided it wouldn't be necessary. Now the problem is the spindle assembly will hit the table before reaching the edge, so I won't be able to cut a 4 X 8 sheet. I need the travel in the Z axis for doing thick parts, so I either need to make the table about 8" wider, or I need to make the gantry taller and move the bed of the table back up to be flush at the top. What do you think is the best option?

I also think I need to make the table longer so I have a full 96" of travel.

I would design the foot print of the machine such that you resurface the table as needed to make it co planer ie the center of your spidle is serval inches away from your table edge ie xaxis will be difficult to resurface it
so if you need wider i make it wider... but keep in mind the standard width of linear rail you can get try and stay under on full length on the y axis to give a full 4'-6" cutting area 8'-6".

[Phife]

Some more good advice eloid!

The end stops are just for safety. I like the idea of moving the gantry supports to the rear to allow the spindle to reach the end of the table. I will plan on doing that.

The gantry uprights where offset from the bearings as part of the original design to allow a place to attach the brace for the ballscrew, so I can change that as well.

I'm now thinking I need to make some other changes as well. I originally planned on making a removable table for cutting thin materials but I decided it wouldn't be necessary. Now the problem is the spindle assembly will hit the table before reaching the edge, so I won't be able to cut a 4 X 8 sheet. I need the travel in the Z axis for doing thick parts, so I either need to make the table about 8" wider, or I need to make the gantry taller and move the bed of the table back up to be flush at the top. What do you think is the best option?

I also think I need to make the table longer so I have a full 96" of travel.

You should widen the bed instead of raising the Z, you already have a high Z, raising it will make things less ridged.

Also definatly make the travel on the X longer, Most sheets come in 97"x49" size, so id allow atleast that, if not a little more so you can actually cut a full sheet edge to edge.

[CtrlZ]

Thanks guys, I think I have some direction for the next set of changes. I will update again.

[eloid]

Thanks guys, I think I have some direction for the next set of changes. I will update again.

will you be doing much of the welding for this build or will you outsource it?

[CtrlZ]

Our maintenance person will probably do the welding. I'm afraid it might break the budget if we had to have it outsourced.

By the way, here is what I have so far. I still need to do some tweaking but if you have any comments please feel free. It's getting late hear, so I will work on it some more tomorrow.