Grizzly G0704 Cnc Conversion

At this point I wish I could just pay someone else to make these parts for me. I'm probably not going to get to it until winter at this rate.

Yeah, I get the same feeling. I think Hoss could add to his business if he did that. Even if he had someone from China.com make the parts and he just sold them. I'd be curious just how big the market is. I mean, how many of these does Grizzly sell in a year, and how many get converted to CNC? If you had a machine shop make 20 sets of the parts that you sold, how long would it take to sell them?

Automation technologies sells a kit for BF20L mills -
http://www.automationtechnologiesinc.com/products-page/g0704-kit/bf20-cnc-conversion-kit-set

There are others, too. Just Google G0704 CNC Conversion or BF20L CNC Conversion.

I'm not out of the woods on this job. I don't think I even get into the woods until I take the G0704 apart. I have no clear picture in my mind of how this all goes together, or how I'm going to get to the finish line. Right now, I'm drilling holes and using the G0704 itself to cut the big ones. Once it's apart, and I'm back to handheld tools, along with my Grizzly drill press with terrible run out at the bit, and my small Sherline/A2ZCNC mill, it's going to be like walking a tightrope for the first time - without a net.

Meanwhile, I finished one more part, the Y-axis extension. I didn't chamfer the corners. I might do that and might not.
Y-Spacer.JPG

Down to the two motor mounts (X and Y - the Z-axis motor mount I made for Phase 1 is still usable), and the X-axis end cap.
 
For somebody without any machining experience you're doing pretty good- looks like fun too I'm jealous :D
Mark S.
 
For somebody without any machining experience you're doing pretty good- looks like fun too I'm jealous :D
Mark S.

Thanks, Mark.

Yeah, I'm having fun. Spent a few hours drilling some holes in those motor mounts. Well, spent a good chunk of the time figuring out how to fixture the first piece. They're an odd shape, really an irregular pentagon, and nothing I had with my small CNC setup looked like it was going to work. Finally figured out an approach that's working.

Should have them done in a couple of hours.


Bob
 
Work holding is half of the machining process. Back when I was working in an R&D shop we regularly had to make half a dozen or more fixtures to completely machine a part. I enjoy the challenge though it can be frustrating when making one-off parts.

The thing I found invaluable when I did my mill conversion was making all the parts in Solidworks before I ever cut metal. It required that I mostly disassemble the machine to measure all the parts to model but that really helps you understand the machine. Also the great thing about modeling in 3D is the ability to make different iterations to see which works best for your own requirements. If Solidworks had not been available to me I would have used AutoCad Fusion 360.

The whole conversion process is a huge amount of work but very rewarding when done.
 
Work holding is half of the machining process. Back when I was working in an R&D shop we regularly had to make half a dozen or more fixtures to completely machine a part. I enjoy the challenge though it can be frustrating when making one-off parts.

Oh, absolutely! I haven't been making metal things for very long, but I've had that rammed into my brain often enough that it stuck. Like you say, with these one-off parts, it's pretty tempting to do it all with one fixture, and I generally have been able to. With these mounts, I used a clamping kit with the clamps just "above" (toward the top in this view) the two holes at the widest point.

G0704_stepper_mount.jpg

The thing I found invaluable when I did my mill conversion was making all the parts in Solidworks before I ever cut metal. It required that I mostly disassemble the machine to measure all the parts to model but that really helps you understand the machine. Also the great thing about modeling in 3D is the ability to make different iterations to see which works best for your own requirements. If Solidworks had not been available to me I would have used AutoCad Fusion 360.

The whole conversion process is a huge amount of work but very rewarding when done.

Likewise, I've put everything into Rhino 3D, my 3D CAD program. Now, I bought Hoss' DVD and he supplied .DXF files of all the parts and that helped a lot, but I've used those files to create a datum, add dimensions that aren't immediately obvious to me, and a bunch of other things. Some parts have been made by CNC on my modified Sherline mill, but most have been made on the G0704 itself, using those drawings and "old school" layout techniques.
 
I'm back here after a rude interruption, and still working the CNC conversion. I think I've decided I need to redesign one of Hoss' parts.

The last part to build is the X-Axis endcap, which is a large part. It's about 7.1 x 2.2 and the motor mount area is left 1" thick. The rest of the cap is thinned to 0.5" thick. That's a lot of stock to remove, and made me wonder what the best way to do that is. On Hoss' DVD, he makes that part on his "phase 2" CNC G0704, and it's a workout for a machine with flood cooling and pretty fast motion. Since I don't have flood cooling or CNC control, it would be manual and take quite a while.
X-axis-endcap.jpg

I think the way to do this part is to make it out of two 0.5" thick sections screwed together at the middle. There are already three tapped holes for the motor mount, and room for me to add a couple of tapped holes to attach my two pieces together. That turns it into one big (X/Y) piece and another, smaller piece that's almost a copy of the motor mounts I've already made. It adds the chance for tolerance stack-up and design-type issues, which is most of what I'm thinking about. Now I'm stacking a motor mount on top of two parts instead of just one.

Sure would love some comments and sanity checking.

Bob
 
It's 10 days later and time for an update. I have what appears to be a usable Rev 1 of the two piece X-axis end cap.

X-endcap-Rev1.JPG

This is a half inch thick piece mounted on top of another half inch piece, and held together by the two black SHCS screws at the 2 and 10 o'clock positions of the big bearings. It's an easy mod to do in any CAD program to copy the hole pattern and then flip it; when you do so, the top hole overlaps the bottom edge, so I deleted it. Of course that leaves only two screws to hold the parts together. The stack-up of two bearings with a shim between them fits perfectly, and stand slightly proud of the top surface (didn't measure). The next part is a motor mount and stepper motor support that mounts on top of this. The motor mount's bore is considerably smaller than the bearings, sized 0.800" while the outer bore at the bearings here is 1.024". The motor mount compresses the bearings to help control backlash.

I started with the Hoss DVD drawings that I purchased for the end cap, and then split them in two. One became the small top piece while the other became the 7x2 (-ish) bottom. I partitioned features between them so that when the two pieces are joined, the result should be the same as the one piece end cap. For example the original part had a dual diameter bore for the bearings: 1.024" that went down 0.638" and the rest of the hole is 0.875". I split that into the top and bottom pieces, so the top is all 1.024 diameter and the bottom piece has 1.024 for 0.138" depth and 0.875" the rest of the way through.

There's a goof up here - in those three holes around the bearings you can see in the top piece. Those are not threaded and are sized to clear an 8-32 screw. The base of the end cap has those holes threaded. That's wrong. The top piece should be threaded. I moved the threaded portion down from the top piece without it registering in my mind that the screws need to thread into the bottom piece but can't because they're not long enough to make it to the bottom piece. What I missed is that motor mount I mentioned that goes on top of this piece. The stack up looks like this (the parts are just stacked - no fasteners - just sitting on the Grizzly with my boring head still mounted.
X-axis-full-assy.JPG

The motor mount is 3/8" thick, the top of the end cap is 1/2", so a screw has to go through 7/8" of metal before it gets to the threaded holes, and you'd want some engagement there, like another quarter inch (1 1/8). So instead of 3/4" screws, I need three longer screws. No big deal, but if I was starting again, I'd just thread the holes in the top piece and not drill them into the bottom piece at all.

There's another problem lurking in this piece, which is that when I transferred the base (7x2 piece) from the Sherline, where I drilled all the holes, onto the big mill for boring the holes, I flipped it upside down! So the "top view" you're seeing has the two mounting holes left and right of the 1" thick area counterbored on the bottom - backwards. I think that's also going to be fixed by two new screws.

This part doesn't have the stylish tapers that Hoss' part has. I'll have to see if I can figure out how to add those without barfing anything up.

Getting close to time to take the Grizzly apart and add all this stuff.


Bob
 
I think I see how to cut the tapers.

Kind of a DIY sine vise. Make the 16 degree cut into a straight horizontal cut.
(The black plastic clamp is just there to keep the angle indicator from sliding off, and won't be there during cutting).
CuttingTheTapers.JPG

I'm pondering whether I have a good way to add a clamp in the bored hole. Or if I need to, since all the cutting is in that roughly two inches over the center of the vise.

Two 16 degree cuts, then two 45 degree cuts to clean it up near the bearing holder.
 
I'm pondering whether I have a good way to add a clamp in the bored hole. Or if I need to, since all the cutting is in that roughly two inches over the center of the vise.

If your purpose is to reduce chatter, then this is the way I do it. Just clamp a piece of something heavy to the work. There is a lot of material sticking out of the vice in your picture above, so yes, I would add some mass.

upload_2016-7-16_11-24-8.png
 
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