My 1st Router - PEU

[PEU]

You're right, thats my boldest compromise in this design, because I only have 8 rails, can I live with it or it can damage the ballscrew ?

Second compromise is that Im only using 2 blocks for the Y bridge, but the loads are somewhat more balanced.

I think in the future will look for some longer rails, but in the meantime I need to deal with what I have, yesterday I asked a local THK dealer and they quoted $600 for a single shs15 rail... maybe some appear in ebay

Thanks


Pablo

[JRoque]

Hey Pablo.

Not sure what you will be cutting but you certainly don't want to put any kind of radial load on the ballscrew. It might be able to take it for lighter stuff like PCBs but that's what the rails/blocks do. What size THK rails are those? You can find lots of smaller HSR type rails and blocks on eBay (easy for me to say that)

I can't tell from the last drawing but, do you still have two blocks on the top Y rail and one on the bottom? I assume that's because you only have 3. If so, I'd put the 2 blocks on the lower rail closer to where the action will be.

On the frame, won't the Z plate hit the Y column support? If so, trimming the plate a little might give you extra Y movements. Hard to tell from the graph. You might also want to replace the column supports with a couple of corner plates that you can hold on the outside of the frame. Depending on the size, these plates will have much more contact surface to the bottom frame and Y column.

If possible, I would attach the Z rails directly to the Y plate rather than through the aluminum extrusion. That's so your stress points (Y and Z rails) are as close together as possible. Put as close as the ballscrew will let you.

Dude, excellent work with Solidworks - keep it coming.

JR

[buscht]

peu, I disagree that you will have twisting problems with the Z axis. Those THK rails are amazingly rigid in all directions. I would move the spindle over so it sits in line with the rails. If this hampers your table coverage, I'd leave it just like it is.

You may get some racking on the Y frame. I've seem some people built similar designs and they say that cross bracing solves the problem.

As a compromise, you might think about 3 blocks and rails on the Y and 3 blocks and rails on the X.

Either way, I'm sure that this design will work just fine.
Trent

[acondit]

Pablo,

I personally would go back to the moving table like you had it in router3.zip.

Like JRoque said, "If possible, I would attach the Z rails directly to the Y plate rather than through the aluminum extrusion. That's so your stress points (Y and Z rails) are as close together as possible. Put as close as the ballscrew will let you." If you need a little extra separation between the two plates for the ballscrew, you could use some solid aluminum of the appropriate thickness to mount the bearings on. I also would advocate getting another rail for the z-axis (I'm no engineer but it just seems better to me).

Peace,
Alan

[PEU]

Thanks for the comments, here we go:

JRoque: the complete ballscrew assembly is high from its bottom, so if I put the rail in the base aligned with the ballscrew support bases I will need to put some spacers from the blocks to the table, thus inserting more custom parts and possibly more problems. The rails are caged balls THK SHS15mm. A more detailed view can be seen in the eDrawing file using the free SW edrawings viewer (from their site).

I may draw a new Z movement using this example: http://www.pro.com.sg/CNC-PARTS/Z-AXIS/z120/Z120.jpg

No it wont touch the frame, but I agree that from the pic it appears to.

I used that long Z extrusion to avoid the torque problem explained some posts back.

Thanks on the SW compliments

Buscht: I dont quite understand the term crossbracing (English is not my main language ) I agree these caged balls blocks are pretty stiff, but as Im not sure how stiff they are, I ask...
I tough of removing one rail from the X axis and have a kind of triangle support, but wasnt very convinced of the idea and I left four rails there.

acondit: will redraw the Z axis based on the previous link. What I don't like about that setup is that I will need to order more custom parts, I mean that setup requires 2 perfectly square solid parts of aluminium against the base, but I agree the width and stiffness if done properly will improve.

I plan to use the router to machine from aluminium/brass to wood/plastics.

And when I tought the drawing was final... baaack to drawing


Thanks for the comments, keep them coming.


Pablo

[buscht]

Here's a poor drawing of cross bracing. It would be on the back side of your gantry of course.

[PEU]

Now I understand

A backplate can do the same trick? Is difficult to make a cross with extrusions, maybe just one side of the cross is enough?

Thanks


Pablo

[buscht]

Pablo, here's the thread where Balsaman used cross bracing. They are not made out of extrusions. Yes, a back plate would do the same thing.
http://www.cnczone.com/forums/showth...&page=12&pp=10
Trent

[PEU]

Wow, thats simple AND cheap. Thanks for the advice!


Pablo

[PEU]

I have time available today...

Here is the preliminary view of the new Z axis in the router, I need to adapt some lenghts due to various modifications and add the spindle, but before continuing, I want to read some feedback



Attached new eDrawing


Thanks


Pablo

[buscht]

How are you going to attach the Y and X axis motor mounts. It looks like they are suspended in mid air.

Seu projeto trabalhará bem.

[PEU]

These are part of the adjustments I did nod made yet, if you look at the previous drawing you sill see them

BTW, I understand brazilian very well because I worked there for some years, but here we speak spanish muchas gracias (muito obrigado)


Pablo