First Machine Build

[jharvey407]

Here is a look at my first CNC machine. It is still a work in progress but it is coming along nicely. I am actually using it to build itself.

I'll start with a picture of the machine at it is now, and then start at the begining.

[bobsch]

Umm, what picture?

[Woodbutcher-59]

Whoaaa, it's invisible, too !!

[jharvey407]

Whoaaa, it's invisible, too !!

It's not invisible, I sprayed it with clear coat!

Let me see if I can re-post the picture. I'm new here and climbing up the learning curve.

[Woodbutcher-59]

Take your time...no big deal !!!

Just wanted to bust your chops a little...

Where can I get that clear coat....it works real good!

Jeff

[jharvey407]

Here is the concept drawing for the first prototype. I decided that I wanted a CNC router made of 8020 extrusions, but to keep the cost of mistakes to a minimum I decided to build the router out of MDF first as a prototype.

Here is the design I settled on. You will see ideas from an assortment of different machines, mostly gleaned from other builders websites.

The X and Y axis are driven by #25 roller chain. The Z axis is lead screw. The steppers are 475 oz. with matching drivers from Keling Inc.

Linear guides are V-bearings on aluminum angle.

[jharvey407]

Here is the first machine. It worked quite well.

The router is a Porter Cable 690. I was ale to cut MDF and plywood at 60 ipm and aluminum at 3 ipm.

The first machine worked well enough to help build the second.

[jharvey407]

Here is a look at the new machine as it was going together.

The gantry is 80/20 extrusion (40-8016 ) carried by legs cut from 1/2" 6061. The carriage and Z axis are guided by V-bearings on V-rails from Pacific Bearing. Their V-rails are hardened steel and are embedded in aluminum extrusions. The bolt right onto the 80/20 extrusion. The V-bearings are mounted on either concentric bushings or eccentric busings for preload adjustment. I tighten the eccentric bushings until I can just barely roll the V-bearing by hand. There is no play in the setup at all.

This table is made of MDF with the aluminum angle as bearing guides because I was not sure if the gantry legs would be stiff enough not to flex. Now that I know the legs are stiff enough to support the gantry with no flex I am going to build a new table out of 80/20.

I am considering filling the 80/20 table with epoxy granite to add weight, but I will wait until after the table is built to see if it is necessary.

[harryn]

Hi, I will be very interested to see how you like the V bearings. I am considering them for a project as well. What size did you end up using ?

[jharvey407]

Hi, I will be very interested to see how you like the V bearings. I am considering them for a project as well. What size did you end up using ?

So far I like the V-rails and bearing very much. They are less expensive than most linear rail and bearing combos. I paid $9.99 each on ebay for the bearings. The rail was about $60 for a 48" IVT from Pacific Bearing. The rail bolted directly to the 80/20 extrusion.

They are self centering, and the preload is very easy to adjust. They are also very easy to clean and lubricate.

I don't have the exact specs in front of me, but they are about 1" in diameter and are sized for a 3/8" shaft. The bushings are sized for a 6m bolt.

I have seen a few commercial machines that use them, including shopbot.

J

[gwsadair]

Even though I have been watching this site for about a year I am just now getting time to put together my first table. Your design looks like something that would not break the bank but be very functional for a first timer. The majority of my planned work is in wood so I do not think I would need something strong enough to handle metal. Biggst problem is where to start. Your unit looks great.

[ger21]

I don't have the exact specs in front of me, but they are about 1" in diameter and are sized for a 3/8" shaft. The bushings are sized for a 6m bolt.

Virtually all those bearings, regardless of the manufacturer, have the same specs. And the bushing have a 1/4" hole, which is larger than 6mm. You might want to check that, as using 6mm may allow the bushing to move a bit. Although, if they're eccentric, and you have them tight, I guess they can't.