My First CNC Design

**trmpyro** · 12-22-2008, 02:27 PM

I have been working on this Autocad drawing since I purchased my Thomson rails and pillow blocks on Ebay a while back and thought now is as good a time as any to get comments and help. I am new to CNC design and am looking to build a machine to make fireworks plugs and firing system front panels as well as anything else that may come along. The plugs are made from 2x dimension lumber and the front panels will be made of Lexan or Aluminum. The size of the machine was mainly dictated by the rails I purchased but I am open to changing the Y and Z if necessary. I have 39" fully supported 1" diameter Thomson rails for the X axis that I plan to keep. The Y and Z axis are currently designed around 1/2" diameter rails but I am concerned about the flex in the Y axis and may change my approach. I plan to use a Dewalt 618 or equivelant for my router. I am planning on NEMA 23 Steppers to keep within the specs of the Gecko G540 and plan to drive the X Axis with 2 steppers. I am planning on 1/2" ACME Screws with 5 starts on X and Y and 2 Starts on the Z (not sure why I chose that setup, no real cost savings in it) So here are a few of my questions for now.

1. What are the thoughts on the 1/2" diameter Y Axis rails? Would I be better off designing around the cncrouterparts.com Linear Carriage or THK rails if I can find them on Ebay?
2. Is there any reason why I can't use 5 Start screws all around?
3. Is my Motor Detail correct with regards to Thrust Washers, Thrust Bearings, and Couplers?

**CarveOne** · 12-22-2008, 06:53 PM

I would recommend 3/4" to 1" supported rails on the Y axis and 1/2" to 5/8" rails on the Z axis (with 5/8" being preferred).

If you have enough 5 start acme rod left from cutting the x and y axis acme rods it makes sense to use it for the z axis as well. I personally would rather not sacrifice the speed of 5 start screws for a slightly lower priced 2 start screw.

I'll defer to others for answers to your third question.

CarveOne

**TOTALLYRC** · 12-23-2008, 03:21 AM

The radial bearings and thrust bearings should work well for you. Many people use angular contact bearings to get axial and radial loads all in one bearing, but there is not any reason why you can't do it your way.

Nice drawings.

Mike.

P.S. I can't stand black backrounds with white lines, doesn't work well for my eyes. Just me I guess

**trmpyro** · 12-23-2008, 10:17 AM

Thanks for the input, I will be looking for a rail system on Ebay for the Y axis or most likely go with the Linear Carriage setup from cncrouterparts.com with a flat plate on each 8020 extrusion on the Gantry extending above and below for bearing; I wll update the drawings and post when I have something different; sorry for the black background but I can't look at the white while I am drawing, I can select white background in my PDF generator if that is easier to look at. One other question I do have, can all of the THK or similar rail and bearing blocks be used in the Y Axis position? I have seen several on Ebay but not sure if they can all be oriented for Y Axis Loads. Thanks Again and Happy Holidays to everyone.

I am going to be in withdrawl for the next couple of weeks without access to the internet but I should have a new set of drawings after January 5th when I get back to civilization.

**TOTALLYRC** · 12-23-2008, 06:45 PM

Originally Posted by trmpyro

Thanks for the input, I will be looking for a rail system on Ebay for the Y axis or most likely go with the Linear Carriage setup from cncrouterparts.com with a flat plate on each 8020 extrusion on the Gantry extending above and below for bearing; I wll update the drawings and post when I have something different; sorry for the black background but I can't look at the white while I am drawing, I can select white background in my PDF generator if that is easier to look at. One other question I do have, can all of the THK or similar rail and bearing blocks be used in the Y Axis position? I have seen several on Ebay but not sure if they can all be oriented for Y Axis Loads. Thanks Again and Happy Holidays to everyone.

I am going to be in withdrawl for the next couple of weeks without access to the internet but I should have a new set of drawings after January 5th when I get back to civilization.

Don't change the drawings on my account. I will be OK if I look at a few in white on black.
Not sure on the rails but I can't see why not.

No internet, SAY IT ISN'T SO!!!!!!!!!!!!!!!!!!!!!!!!!!
That is like saying, time to go on a diet, very scary. LOL.

Mike

**zyh12398** · 12-26-2008, 03:47 AM

good

**trmpyro** · 01-02-2009, 11:48 AM

Back to civilization for a day and thought I would post a new set of drawings. I finally saw the light on the linear carriage usage thanks to Glacial Wanderer's website and reworked my Y and Z axis to get rid of the 1/2" diameter Thomson rails. I am still looking for a few dimensions on the Linear Carriages like distance from each edge to the center bearing and bearing sizes or if anyone has an accurate dxf or dwg file of the carriages I would love to have it. I am showing the Gantry made of 2 pieces of 1/2" Aluminum in an effort to minimize outsourced machine shop work but not sure if it is really worth it. Hopefully I can get some funding together and start making some progress and stop obsessing about the drawings. If anything seems out of place please let me know.