Grizzly G0704 Cnc Conversion

The backtracking you are going through isn't anything we haven't experienced during our builds. Consider it a learning experience. I lost count of the number of times I assembled, then had to disassemble my mill because parts didn't fit right or I left something on the bench that needed to be installed three steps prior. When you have it done and up and running you will know your mill inside and out.

Keep the faith. You are almost there.

Tom S.
 
Thanks for the encouragement.

A couple of days ago, I had a private message from a guy who said he had bought a ready made CNC mill because he'd rather make parts than make a CNC mill. I understand. It's a long project, and to be honest, I'd rather be working on the kinds of things I want the mill for, but I really see the benefits of doing this. I've learned a lot and had to solve a lot of puzzles - almost every step of the way.

Again being completely honest, I can use to learn as much as I can.
 
And you have the benefit of knowing the machine inside and out so if anything fails or needs adjustment you'll know where to look and how to fix it.

I found building my machine very rewarding and educational. I would rather build machines and make parts. :grin:
 
Not to put any pressure on you or anything like that, but right now there is over 25 thousand people watching this thread that are looking forward to seeing you complete it... No pressure :)
Loved the 3d printed mounts btw.
 
Not to put any pressure on you or anything like that, but right now there is over 25 thousand people watching this thread that are looking forward to seeing you complete it... No pressure :)
Loved the 3d printed mounts btw.

LOL.

So yesterday I had an idea for a last ditch attempt to prevent having to take everything apart.

I pulled the new bent tube and made a new one so I'd have more tube to play with. After I heated the tube and flared it so it fits the oil fitting, I stuck the plastic tube from a spray can of air in it, held it over a heat gun and bent it a little past a right angle (plastic tube to emulate something like putting sand in a metal tube before you bend it - to keep the walls from collapsing/kinking). This was definitely a lower profile bend. I put that in place, but a straight edge sliding over it still rubbed on the tube. If I held the tube down with a finger tip, it seemed to clear, so I put a spot of RTV there and then taped it down with duct tape. It was still too high, so I stacked about 15 pounds of weights on top of it to clamp it as low as it gets. The tube said RTV takes a full 24 hours to cure, but after about 18, I took off the weights and tape to look at it.

BentTube-2.JPG

It worked. You can see the gap between the tube and slide in this picture. The white thing is a scrap of business card that I measure at .010". It's a bit loose in there, but a .025 feeler gage doesn't fit. I'd guess .012 to .015 or so, but haven't spent time trying to measure it. I think that if it doesn't rub, that's all I care about.

Onward!
 
I'm going to revise this post. I decided not to go with the way it was. I know I measured about .012 clearance, but I wasn't completely sure the table was sitting as close to that tube as it ever gets. So I decided to machine away the part of the table that crosses and could rub on the tube. I mentioned this yesterday and said I'd need a mill at least the size of the G0704 to do it, and a friend suggested an angle grinder. I had simply not thought of it because I just don't have experience with using one. I bought one months ago for this project and then used my Sherline mill to do the cutting the grinder was intended for.

It ended up going very quickly and came out remarkably smooth. Now I have plenty of clearance over that tube.
CutAway1.JPG

Yeah, this is a bit of "belt and suspenders" approach, but I see it more like, "I've spent so much time and money on this project, I don't want to screw it up by doing something stupid, or not doing something I should do".

EDIT 1/29 1942 EST - I left out a word; changed "I had simply not thought of it because I just don't experience with using one" to "I had simply not thought of it because I just don't have experience with using one"
 
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The conversion is complete. My mill moves on all three axes and is ready to start making chips.


It's not Done done, but I think it's fully usable. As I say in the video description, it's time to move from construction to optimization; building to tweaking. I've run all three axes for only a few minutes, and haven't cut any metal yet, but I think I could. I debated doing some engraving or something today to record, but instead just recorded about five minutes of a machine warmup routine I wrote. Even I found that too boring to watch, so I cut it down to about a minute and a half. Heck, just watch the last 30 seconds.

On the plus side, I checked accuracy this afternoon, at least on the small scale. When I tell the mill to move 0.100", it goes .100. When I tell it to go 0.500, it goes 0.500. Well, I can see what the QC guys call “ballscrew drunkenness” - a tendency for each turn to not be exactly the same length. Mechanical engineering classes teach that a screw is an inclined plane, so think of it as lumpiness in that inclined plane. Being accurate over half an inch means I swagged the scale for the machine sufficiently accurately for it to be OK for things smaller than an inch. I will recheck that with a longer scale by using 6" calipers.

Done.JPG

The mill's corner of the shop.

On the negative side, it has too much backlash. The whole purpose of changing from the leadscrews in the mill to ballscrews was to reduce backlash to the smallest amounts I could get. I measured over .010 on X and Y, with Z coming in at a more respectable .004. I was hoping for .001 or .002 on all three. Frankly, I'm kinda ****** at that. I'm not exactly sure where to start looking for the cause. It has the potential of making me pull things apart again. (Do your best Sam Kinison voice and scream, “No!, NO!!, NOOOOOOO!!!!”). Also on the negative side, I don't think I'm getting rapids as fast as Hoss says he gets. Rapid movements aren't terribly important because you can't do any cutting at those speeds, but they cut your production time if you need to go back and forth a lot to make something. The last moves in that video are done with a feed rate of 100 IPM, and while the LinuxCNC software interpolation partitions that speed between all the axes somehow, it's quite a bit faster than anything I can get on my A2ZCNC/Sherline mill.

Of course, in the total sense this is far from done. The advantage is that for everything I do from now on, I have the big mill for help if I need to make parts and not just the smaller mill. Things to work on are to hook up the oiling harness (I have everything except the oil), build the enclosure and the cooling system. I had been considering flood coolant all along for this, but need to consider misting or other alternatives, before I go buy parts.

As for now, I'm just going to enjoy completing a long, long project. Tomorrow's my birthday, so it's good day to celebrate.
 
Tweaking is a normal sequence of events after completing assembly. Heck, I've had my machine running for almost two years and it's been apart many times to correct those nagging little things that drive me nuts. As a matter of fact it's apart now because I'm trying to get the backlash down to a respectable number.

And by the way, nice job!

Tom S.
 
Tweaking is a normal sequence of events after completing assembly. Heck, I've had my machine running for almost two years and it's been apart many times to correct those nagging little things that drive me nuts. As a matter of fact it's apart now because I'm trying to get the backlash down to a respectable number.

And by the way, nice job!

Tom S.
Thanks, Tom,

If I may ask, what kind of backlash are you looking at? Is it around .010 like mine, or are you going between .003 and .001?

I'm going to spend some time with it and make sure it holds up to the stresses of cutting something, and then go look at motor tuning. I'm using LinuxCNC, which I still haven't decided if I'm going to stay with. I know motor tuning has a lot to do with what kind of speeds I can get, and the way LinuxCNC does that has me scratching my head. That latency testing aspect just hasn't sunk in.


Bob
 
Thanks, Tom,

If I may ask, what kind of backlash are you looking at? Is it around .010 like mine, or are you going between .003 and .001?

I'm going to spend some time with it and make sure it holds up to the stresses of cutting something, and then go look at motor tuning. I'm using LinuxCNC, which I still haven't decided if I'm going to stay with. I know motor tuning has a lot to do with what kind of speeds I can get, and the way LinuxCNC does that has me scratching my head. That latency testing aspect just hasn't sunk in.


Bob

I'm chasing about .007" in the X axis. Haven't checked Y yet. Here's the link to my thread. It's been a challenge. http://www.hobby-machinist.com/threads/chasing-backlash.55182/#post-456709

Tom S.
 
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