Cnc Router It's Alive!!

JimDawson

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I've been a bit busy for the last couple of weeks, I've been working on 5 major projects all at the same time and haven't had as much time to spent on The Hobby Machinist as I would like. Here is one of the projects.

Some time ago I brought home a CNC router that a local company was retiring. I had previously done a controls retro fit on this machine so I really bought it just to strip the controls and other useful parts then was going to scrap the rest. The price of scrap is way down so I thought I would just sit on it for a while. I'm not sure I could have actually brought myself to actually scrap the aluminum. I use too much of it and the table alone is 48x96 by 1 inch thick, and it has a number of other heavy aluminum pieces on it also. This thing is 8 ft wide and about 14 feet long and weighs 5-6000#. Really too big for my shop.
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Last week a customer of mine asked me to bid on some plastic parts, a perfect job for a large router. I guess I was the low bidder, I got the job. So now I have to make the router go. First I had to find it under all of the stuff that had been stacked on top of it over several months. Any large flat surface becomes a junk collector.;)

The next few problems are how to run the thing. It is all 3 phase and I have single phase. The spindle motor is 12HP. I don't have enough power in my shop to run that. The 3 HP vacuum pump is also 3 phase of course.

It turns out the the bearings in the spindle were pretty tired and a bit loose (OK, a lot loose), and rebuilding the 18,000 RPM spindle is an expensive proposition. So killing two birds with one stone I decided to put a Porter-Cable 7518 3 1/4 HP router motor on it. So that solves the problem of the spindle power also. Then I used the 15HP VFD that was used to run the spindle to now run the vacuum pump from a single phase feed. Seems to work fine. I just converted the control panel over to a single phase panel, a little rewiring and done!

EDIT: I forgot to include these pictures when I posted this.
This the inside of the computer and the VFD when I opened them up. The were still working. Working around wood processing for years I have seen worse.

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Here is the new motor mount in process, milling the pockets for the motor brackets. I counter sunk two hold down bolt holes so I could bolt it down to the t-slot. I only held it on the centerline because almost all extruded aluminum is cupped a bit. So first I bolted it down on the table, convex side down so I could flatten the concave side, it took about 0.015 to clean it up. If you start with the concave side down, you will just flatten it out with the bolts and when you release it, it will still be concave. Then I flipped it over, and bolted it down with a piece of 3/4 MDF as a backer board. Then cleaned up the other side. I countersink the screws deep enough that there is no chance of hitting them with the cutter during the cleanup. The backer board allows through drilling with plenty of drill clearance above the table. I like MDF because it's generally flat, dense, and holds up well to coolant in the short term.
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And the finished motor mount. I already had the mounting clamps, so I just needed them to fit the new mount plate. The mount plate is 14 x 8 x 1 6061. What you can't see in this picture is that the mount plate is bolted to the Z ram, and aligned in the mill so I could drill & ream the dowel pin hole (under the top of the router)

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The motor installed on the Z ram. Note the dowel pin just in back of the little red dot (edge of the power switch) in the picture center. It's centered on the 4 mounting bolt pattern to allow some rotation but not horizontal or vertical movement. I drilled the bolt holes just a bit loose to allow some rotational movement for alignment.

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Here is a side by side comparison of the old motor and the new. The 7518 is a pretty big router motor, about 10 3/4 inches tall, and weighs about 15 #, the old motor weighs at least 50#, maybe more.

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How to tram your router head. This is just a piece of welding rod with a 0.500 plug attached to the router end and the other end just ground to a point. It's about 20 inches long. The paper is just there for contrast in the picture. To use, just sweep the table with it as you are inching the Z down. Once it touches somewhere then adjust just like you would with a dial indicator. In this case I really lucked out, in the ''nod'' direction it was better than about 0.003, using paper as a feeler gauge. 0.003 in 40 inches is good enough for a router, and my mill for that matter. In the rotation plane it was off about 0.010, so loosen the mount bolts a bit and smack it with a dead blow hammer to align. Worked out great.

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The next step is to take a skin cut on the table top, just to make sure it's flat, then I will make a vacuum plenum out of some 1/4 MDF. You waffle cut one side of the MDF, then take a light skin cut on the other side and the vacuum goes right through the MDF. Makes a nice flat surface, and protects the 3/4 inch Delrin cover plastic unless you forget to set your Z zero correctly. As you can see, there have been some less than careful operators running this machine. The Delrin has been patched a time or two. I'm glad (I hope) they never got down into the aluminum table.

There is nothing proprietary about the job I'm going to run on it, so I'll post pictures and process of that one when I run it in the next week or so.
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Wow Jim, makes the little 36"x48" I am working on look like a toy. You are certainly inspirational with your skill set. I look forward to seeing more on this project.
 
Hey Jim: Gnarly Machine! How about a pic of the waffle cut MDF. The vacuum pulls right through the MDF. I'd like to see that in action.
 
The new dust collector. This is a case of ''use what ya got'' to do the job. A couple of years ago I bought a large central vac unit for a project and that project ended so I have had this unit hanging on the rack ever since. This is a shop vac on steroids, 240 volt, twin dual stage blower motors. It will suck the chrome off of a trailer hitch ball. The only real problem is the limited capacity of the collection canister, only about 10 gallons. Due to the design of the vac, the collection canister is under vacuum so I can't put a bag on it. If it becomes an issue, I'll make an intermediate collection stage out of a 55 gal barrel.

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So over to the mill and make a chip management adapter to fit the router motor and the suction hose. A chunk of 3/4 inch UHMW will work fine. That's a 0.500, straight flute router bit. I didn't have a sharp spiral bit which would have been better suited for this job. The part is screwed down to a piece of particle board that I had used for a backer on another project, so it already had the countersunk holes for the t-slot bolts.

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And the finish pass. I just drilled the bolt hole with a hand drill and slotted the clamp end on the table saw.

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I couldn't find a brush for it on a Sunday, so I used some thin conveyor belting and screwed it to the shoe. I slit the belt about every 3/4 inch to get the flexibility needed.

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And the system overview. The vac is controlled by the computer and comes on when the head comes down to start cutting. I'm using M7, M9 codes (Mist Coolant, and Coolant Off) in the G-code to control it. I'm waiting for some tooling so I haven't had a chance to actually make chips and try it out yet.

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That is sweet, what a monster.
Quick question; what would one search for to find that bada$$ shopvac?


Stan,
Sent from my iPhone using Tapatalk
 
Google Central Vacuum Systems. This one is a Vacuflo FC1550 I think. One warning! These things are expensive, I think I paid about $1100 for that one. I would not have bought it for shopvac service. I needed a high powered vacuum source for a specific use, and the specs on this worked for that project and I had an almost unlimited budget for that project. For that project I tried using 2 shopvacs and they weren't quite enough, so I went searching for something bigger & badder.
 
Great, thanks Jim for the info! Though my shop is not big, I thought it would be nice to have a central type vac with a portable intermediate stage collector.


Stan,
Sent from my iPhone using Tapatalk
 
I got to make my first chips today with the poor old router!!!!! It seems to work fine, but a bit slow for a CNC router. I'm limited by the spindle HP, only 3.25 HP, vs, the original 12HP. The first order of business was to skin cut the table 0.005 just to make sure it was flat. It wasn't.... Up to 0.010 variation. Let's just say the previous operators were less than experienced. The power consumption is not too bad, about 5KW with everything running.

Below is the waffle cut MDF backer that I referenced above. Cut like this, it distributes the weight and provides a solid base for the work. It also provides vacuum channels for the hold down system. You waffle cut one side and take a skin cut on the other and the vacuum pulls right through the MDF. I found that the MDF that I'm using is not very consistent in the thickness. I'm down 0.035 (third pass) trying to clean it up. It started out as 1/4 thick, which turned out to be 0.214 actual. If I have to take any more I may run out of material in the channels. It's down to about 0.055 web thickness now. I have three zones corresponding to the vacuum control valves on the table and a 1.25 inch border around the edge.. This allows turning off the zones you are not using. This method will securely hold almost all flat materials.

You can also cover the unused area with just about anything, stretch wrap works great, or another piece of plywood or whatever. The edges are taped with some vinyl tape to seal them. I'm using a 1.25 bowl carving bit for these operations. 13,000 RPM, 100 IPM cutting speed, 0.120 DOC.
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The vacuum zone control valves

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I also learned something about why the dust control shoes all have an inner chamber. That is all but mine...yet, that's the next project. Once the tool moves over to the edge of the work, you lose the suction and get sawdust all over. So I'll be redesigning my dust control shoe.

Here's what a real one looks like. I would use this one, but it is way too big for this spindle.

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I also found out that a 6 gallon dust collection canister is way too small, so pretty quick I need to build a 55 gal intermediate collection canister. I'll post pictures of that build when I do it.
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