would like imput on my machine

[cncfoam]

Hi everyone.

I would like imput on my design, I will post a few posts with pictures to get started. then I would like comments from every one. this picture is of the end plate. the next post will be of the second end plate, then how that assembly goes together.

thanks.

Eric

is there a way to put multiple pictures on one post?

[cncfoam]

2nd pic

[cncfoam]

here is more of the base assembled

[cncfoam]

here is the gantry that will cross over the frame pieces.

I will post more later. I have to run.

all the flat stock in all the pictures are 1/4" x 4" aluminum.

slides will be 8020 extrusions and 8020 linear bearings through out.

I have most of the design worked out, would like any and all imput, to better the design

EZ

[buscht]

cncfoam, It looks pretty neat.

I have used the 8020 linear slide and I think that its kind of sloppy. They give you shims to adjust it, but if you go that route, I would not count on it being very accurate.

Your Z axis looks pretty good, because the slides are far apart and narrow.

The axis on your gantry and your base will give you trouble because you have two small slides and a large width between them. This will be very difficult to get to move without cocking and binding. Especially with sloppy bearings

I'm worried about your end plates flexing. It would be better if they had a bend in them to stiffen them up, similar to the blue parts in your gantry.

It looks like you are making the endplate in multiple pieces to give you adjustabiliy for aligning the rails. If that is so, I don't think you need that much. Make the end plates out of one piece and slot the holes where the 8020 mounts. This should be plenty.

If its because you can't get material long enough, then your idea is fine.

It looks like both ends are machined for a motor mount. One end should be made for your bearings. I guess you could have a bearing mount that fits this pattern easy enough.

Keep posting, this is very interesting.

Thanks
T

[cncfoam]

I have only touched the 8020 bearing matereial and run it down the extrusion by hand, didnt actually run a bearing assembly down the extrusion, are they that sloppy on a machine?

That is why I have multiply bearing points, I tried to spread out the bearings to take some slop out, if there is any. I may change the gantry bearings to a longer set,(twice as long)

The reason, so far, that I am going with 8020 and this design, is that I dont have machining capabilities, and Im trying to eliminate as much machining as possible. I can redesign if 8020 is a bad choice. I have all the aluminum cut, will post a picture later. Also, I designed everything so that it has adjustments in all directions.

I am going to run ball screws down the outsides, you can see the holes in the end plates where the 2 ball screws will run. (outside of the 2 linear slides(red)) I will use timing belts on the end where the motor is, will post pics later.

this picture is a different angle to see the adjustments of the end plates.

thanks,

EZ
keep the ideas coming.

got to go,
later

[cncfoam]

Here is some more of the whole assembly.

Please feel free to comment, I would like to find the mistakes before I actually build.

At this point, I do have all the flat plates cut as shown in all the drawings. Otherwise, the design can change, if there are any good ideas. Im not totally sold on 8020.

the X axis ball screws are in. (qty 2, blue) 1 per side. will have belts on the one end to tie the ball screws together.

as it stands, Im trying to achieve X=60" Y=36" Z=4-6"

EZ

please comment, everyone. You wont hurt my feelings

[yukonho]

I have to agree that your Y axis is going to give you problems. It is too long and skinny. If you were to double the width of it and add another set of slides, that would help out tremendously.
co

[cncfoam]

yukon

Is this what you are talking about, right now the bearings(yellow) are 3" wide, same as the extrusions, are you saying that I should lengthen the bearings, 8020 does have a 6" bearing. Also, I was planning on putting the ball screw in the middle of the Y axis, as shown. If I put a vertical bracket that would hit the top and bottom of the Z axis, This would be simular to the design where the table moves, they use only a single screw. the Y axis slides are currently 13" apart.


buscht
are you talking about the "X axis plates" bending? I will probably make a table that goes underneith this, where I could mount the long sides to take the flexing out.

thanks, keep it coming
EZ

[buscht]

cncfoam, Great pictures. They really help to understand what you are trying to do.

What are you trying to cut and what are the tolerances? That will help any suggestions about the bearings and slides.

I have never used the 8020 bearings on a CNC, just another application. I agree that they slide well, but I know from my CNC that any slop in the carriage causes inaccuracies in your finished milled product.

THe Y axis will need a bearing structure similar to your X. Two bearings spread farther apart. It you were using THK ways, you might get away with your design, but I wouldn't try it.

Keep in mind, if you spread the bearings out in the Y, it means that you either lose distance in the Y or you have to spread the base out to compensate.

Your plan on the X with the two lead screws and timing belt should solve that racking problem. What kind of bearings are you going to use on the screws? I don't think that having the steel screw turning on the aluminum plate as shown will last very long.

Post how you are driving the Z axis when you can. I'd like to see that mechanism.

FYI, even if you used THK ways for the slides, you wouldn't have to do any more machining than you are doing now. The rails can mount right on the 8020 with Tee nuts. You might have to drill for mounting the bearings depending upon size, but that is easy.

Cost is the real issue.

[cncfoam]

>>>>>my answers are followed by these ">>>>>"


cncfoam, Great pictures. They really help to understand what you are trying to do.

What are you trying to cut and what are the tolerances? That will help any suggestions about the bearings and slides.

>>>>I will be cutting light ply, and what Im shooting for is 3D MDF board. maybe...possibly... aluminum.

I have never used the 8020 bearings on a CNC, just another application. I agree that they slide well, but I know from my CNC that any slop in the carriage causes inaccuracies in your finished milled product.

>>>>Im leaning more and more against 8020. I am going to stop down at the distributor, and see if they have a bearing I can play with.

THe Y axis will need a bearing structure similar to your X. Two bearings spread farther apart. It you were using THK ways, you might get away with your design, but I wouldn't try it.

>>>>>OK

Keep in mind, if you spread the bearings out in the Y, it means that you either lose distance in the Y or you have to spread the base out to compensate.

>>>>>Yep

Your plan on the X with the two lead screws and timing belt should solve that racking problem. What kind of bearings are you going to use on the screws? I don't think that having the steel screw turning on the aluminum plate as shown will last very long.

>>>>>>For simplicity, I put that in there, Im planning on ball screws and a ball nut.

Post how you are driving the Z axis when you can. I'd like to see that mechanism.

>>>>>dont have a drawing yet, the drawing might not be proportional, but there would be a plate mounted to the top of the light blue extrusion and ball screw mounted to side of red extrusion. motor on the other side of gantry. with belts.

FYI, even if you used THK ways for the slides, you wouldn't have to do any more machining than you are doing now. The rails can mount right on the 8020 with Tee nuts. You might have to drill for mounting the bearings depending upon size, but that is easy.

>>>>>> If I was to go with THK, I would eliminate the 8020, I dont think its needed.

Cost is the real issue.[COLOR=blue][COLOR=blue][SIZE=3][FONT=century gothic][COLOR=blue][COLOR=blue]

>>>>whats a good source for the THK ways.

EZ

[cncfoam]

buscht


send me a personal email

I want to show you something

Eric

jjme @ comcast . net (put together)