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CNC router build #1: CNC router plans and back story

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Blog entry by Mainiac Matt posted 11-29-2017 09:14 PM 435 reads 0 times favorited 7 comments Add to Favorites Watch
no previous part Part 1 of CNC router build series Part 2: Z-axis motor mount fabricated and installed. »

Hi all,

After years of planning and several different design variations… all with a tight budget in mind, I am finally building a CNC gantry robot. I have been an active dumpster diver at work for linear motion and electrical components replaced on existing machinery, or salvaged off of scrapped machinery. But I could never get to the point where I could build the machine I wanted within the puny budget I had.

However, I finally pitched this project successfully to my boss at work and received the go ahead with a decent budget. We’re actually going to use this small machine as a prototype build for a robotic hot melt glue applicator, so we can figure out the user interface and glue controls. Once we have that figured out, we’ll build a larger gantry robot for the auto-gluer and convert this little boy into a router for use in my proto-type machine shop.

We already have a large CNC router in our wood department, but it is a PITA working around the shop schedule and since the machine is set up to run sheet stock with a vacuum table, we can’t take the machine down to fixture any different materials.

So we have the operating and programming expertise… and since I’ve converted a bench top hobby milling machine to CNC control, I felt I could pull off designing a proto-type router. Let the fun begin!

Here are my solid model screen shots….



The linear bearings were all salvaged, and the Thomas linear rails purchased from McMaster. We are machining all the custom components from aluminum bar stock in house, and the frame and gantry are all 80/20 extrusions cut to size. For a wood router this small, the machine is stoutly constructed…. much more so than your typical hobby machine.

But my design criteria is a little more challenging that your average hobby machine.

1. Rigidity suitable to hold +/- 0.005” making light passes in Aluminum.
2. Min. operating envelope of 40” x 24” x 4.5” which will allow through cutting 2” stock.
3. Easily upgraded with a 4th axis (rotary indexer)
4. MDF spoil board with integrated T-track for flexible and easy work holding.
5. Minimum 2 HP router or spindle.
6. Able to chuck up to 1/2” bits (with 1/4” and 3/8” collet adapters).
7. Quiet operation
8. Able to run long programs without overheating.
9. Cost efficient design that uses salvaged items.

-- Pine is fine, but Oak's no joke!



7 comments so far

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Mainiac Matt

7447 posts in 2161 days


#1 posted 11-29-2017 09:25 PM

We have a part time semi-retired machinist working for me in our one man proto-type shop (a converted 2-car garage). so I have to do a complete print for each of the 12 unique custom fabricated parts. None of these are overly complicated… most of the work consist of finishing the stock to size and drilling and tapping holes.

I’ve posted a couple times before about how much I enjoy working with Dave (our machinist), and how much I’ve learned from him the last 1.5 years. I manage to sneak out to the shop and cut a few parts myself every once and a while, but mostly I’m a slave to my day job. The prototype shop is a side gig, and when we don’t have a project going, Dave plays golf.

-- Pine is fine, but Oak's no joke!

View Mainiac Matt 's profile

Mainiac Matt

7447 posts in 2161 days


#2 posted 11-29-2017 09:49 PM

The gantry apparatus is done accept for the motor mounts…



The ball screws, ball nuts, bearing blocks and motor couplers were all purchased from a Chinese vendor on e-bay for a screaming low price. They don’t have the level of quality needed for a production cutting machine, but in our little proto-type shop, this router will probably get used once or twice a month and I wanted to see how these compare to American or Japanese premium hardware (Thomson, NGK, Nook, etc…). You definitely get what you pay for with premium hardware…. but for a hobby machine or a light use machine like we’re building, I think they will be suitable.

On the large glue robot, there will be zero cutting forces, and we don’t need uber accurate positioning, so I’m not quite sure if I’ll go with this China stuff or not.

The linear rails and linear bearings are all top shelf Thomson products. They are replaced as part of the annual PM on a CNC knife cutter we use, and with only 1 year of service, they are still in pretty darn good shape.

-- Pine is fine, but Oak's no joke!

View SteveMI's profile

SteveMI

1058 posts in 3127 days


#3 posted 11-29-2017 10:05 PM

The linear rails and linear bearings are all top shelf Thomson products. They are replaced as part of the annual PM on a CNC knife cutter we use, and with only 1 year of service, they are still in pretty darn good shape.

“Darn good shape” is an understatement. Design looks traditional and should perform.
What diameter are the rails?
Steve.

View DS's profile

DS

2819 posts in 2253 days


#4 posted 11-29-2017 10:30 PM

Way to go Matt!

I am eager to follow your progress!
This looks like good practice for building a version that might make it to YOUR house!

-- "Hard work is not defined by the difficulty of the task as much as a person's desire to perform it.", DS251

View Mainiac Matt 's profile

Mainiac Matt

7447 posts in 2161 days


#5 posted 11-30-2017 12:42 AM


What diameter are the rails?
Steve.
- SteveMI

On the base, the rails are 1” and they are quite heavy. They are mated to the 1”x2” 8020 via. 3 “pillars” and the two end caps.

On the gantry, the rails are 5/8” and are mated to the 2”x4” 8020 via. 4 “pillars”.

The pillars are 2”x2” and attach to both the rail and the t-track with two cap screws each. This transfers quite a bit of rigidity from the rails to the aluminum, creating a truss action. I can’t flex the base with ~50 lbs of force, and the gantry ways a lot less than that.


This looks like good practice for building a version that might make it to YOUR house!
- DS

Ulterior motives? Me? I have enough of the 5/8” linear bearings to make two more builds, and the 5/8” rail is pretty modestly priced @ McMaster. The 48” 1” diameter rails on the other hand, were somewhat pricey.

We trashed a couple carbide center drills before we figured out the right rpm and feed speed to cut through the case hardening on the rails…. they were really hard and the case was quite deep. The key turned out to be cutting them dry with no cutting oil. Go figure.

For now the vertical plates that support the gantry are going to have to be made out of 3/4” baltic birch, as I don’t want to buy Mic 6 plate and pay Dave a weeks labor to manually mill the profile.

-- Pine is fine, but Oak's no joke!

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MrRon

4487 posts in 3076 days


#6 posted 11-30-2017 07:14 PM

Why would you need to use Mic 6 for the side plates? It would seem that ordinary 6061 or 5052 would work as well and cost a lot less. Although Baltic ply will work, it would be a shame that the CNC won’t be 100% metal. I am building a CNC router of my own design. I would prefer all metal, but it’s overall large size dictates more economic materials. The material I used is 3/4” MDO and I have reinforced it as needed. I’m hoping to machine aluminum with it. So far, I have about $200 invested. The structure is complete and the remaining electronics will be the greatest cost to me. I have been working off and on, redesigning/refining as needed. Once complete, I want to use it in support of my large scale train building. Overall size of the CNC is 36×72.

View Mainiac Matt 's profile

Mainiac Matt

7447 posts in 2161 days


#7 posted 12-01-2017 07:08 PM


Why would you need to use Mic 6 for the side plates? It would seem that ordinary 6061 or 5052 would work as well and cost a lot less.
- MrRon

A good question… the jig plate is actually only about $20 more than the 6061.

But either way, it’s really inefficient to fab large items on our small knee mill, and I don’t want to pay a weeks labor to make these, when I can set up and cut the plywood on the CNC in a half hour. It’s not my money, but I try handle it as if it were.

-- Pine is fine, but Oak's no joke!

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