CNC mill conversion ?s
 

Our team is considering purchasing a small mill with the intent to convert it to CNC in the (hopefully) not to distant future. Right now we are looking at the HF/Grizzly/Sieg X2 class of mills. They seem to be very popular to convert to CNC as there are many different sources of parts/plans/etc. to do the conversion.

For anyone here that has done one of the conversions, can you provide your input on some of the following questions?

Did you use some of the available plans (if so, which one), or did you roll your own conversion? I was looking at the conversion from cncfusion.com. It looks like a well designed kit and incorporates ball screw leads, but it is pricey and it's not very friendly for manual use because it has no provisions for the scales and moves the Z controls to the top of the machine. The scales being gone can be gotten around by adding DROs, but that just adds to the cost.

How accurate can you get with the factory screw leads? Is it worth it to go to the ball screws? From what I read, the Z axis is the worst one on the machine and seems that you would want to convert it to a ball lead if possible.

How big of an issue is the plastic intermediate gear? It would seem that since we will have some inexperienced students learning on the machine that this could be a weak point. It would seem that it could be a good idea to do the belt drive conversion.

Any suggestions on controllers? I was looking at the Xylotex controller. Comments? Any reason to try to go to microstep controller? I would assume no with factory screws? How about with a ball screw?

How much work are we realistically looking at here? It doesn't seem too bad, but given the reality that everything will take at least 3 times longer that expected, what's your experience with it?

Thanks,
Kenton

Re: CNC mill conversion ?s
 

I converted my Sieg X1 using the HobbyCNC kit and doing my own motor mounts. I put in the extended X and Y axis kits which are really nice to have. I use TurboCNC on DOS to run it. For what I spent on it (probably around $800), I'd say it's decent. However, it's far from a real precision work-horse. It's a hobby level machine, and will get you to within about .004. It would not be suitable for milling precision fits for bearing bores for example. So long as you work within it's capabilities it can be a really valuable tool in the middle of the night to do work such as milling a hole that is bigger than you have a drill for, or for doing cutouts and pockets. I've also done some engraving on mine. I've even done some 3D milling as shown below. The problem is on the Sieg mills there's a VERY fine line in the gib adjustment between tight enough to take out slop, and binding. Also, on these low-end machines there are often problems of dovetails not being entirely flat, causing binding in one spot. It's really difficult to get it dialed in. Also on my mill, I burned out the original motor speed controller. I've only broken one of the plastic gears once. To me, the plastic gear is not a big deal if you keep spares. If you're breaking it, you've either hit something or are working over the capability of the machine. It's saving other parts from damage. For milling, plastics such as LDPE the mill works great. In aluminum, you really have to know your limits and stick to them. With a 3/8" endmill we're talking maybe no more than .030 DOC and 4 IPM. Also, plunging down is VERY chattery on this machine. Nonetheless, I still really like having it around when I need it in a pinch.

For most FRC parts, I'd say you need a bigger mill than a Sieg X1 or X2. You're better off looking for a used real mill some place. However, any mill is better than no mill.

What's your budget?

Also, do you want a machine to make projects, or do you want the machine itself to be the project?

Re: CNC mill conversion ?s
 

I have been happy with Xylotex controllers. I currently have two. One I bought to retrofit a Phoenix cnc router. this one is running with a CandCNC break out board and TurboCNC. I just powered up the latest system and it is on an Enco x-y table that I converted to precision lead screws and has the latest CandCNC BOB and Mach3.

The router is very accurate but was designed for wood so I have limited my cutting to polycarbonate. I plan on using the x-y table on top of the table of my Bridgeport.

The little machine will get you started. If you can go to a larger size you will be happier.

Re: CNC mill conversion ?s
 

We want a machine to make projects.

Re: CNC mill conversion ?s
 

Truthfully, I see it as a project for me, a learning opportunity for the team, and hopefully filling a need that we have as a team since we don't currently have a relationship with a machine shop to help us with custom machining and are therefore stuck with whatever we can get off the shelf and/or improvise.

Thanks everyone for the info.

Kenton

Re: CNC mill conversion ?s
 

The Sieg machine will certainly be a project, both to build and to improve, adjust, and maintain. It's certainly a fun and rewarding project though, and to get into anything turn-key you're looking at thousands more. Again though I ask, is there a budget?

Re: CNC mill conversion ?s
 

No budget yet. That will be discussed Wed. night. At this point, I'm trying to put together what the price ranges would be and then we'll see what we can allocate. If I had to guess, right now I'd say <$3K.

Do you have any recommendations on systems to look at if we were to consider stepping up to a larger system?

Re: CNC mill conversion ?s
 

Personally I was in a similar situation to you(though I'm staying with manual milling for a while) and I decided to go for the Grizzly G0704 Mill instead. The cost isn't much more than the SIEG machines, but it has a lot more capabilities and is much more rigid. http://grizzly.com/products/G0704 Just something to consider. There's also plenty of info on the web for converting these over to CNC. Also look out for a few other companies that also make this machine such as precision matthews.

Re: CNC mill conversion ?s
 

My personal opinion is to shy away from the CNC portion and buy the better mill. While CNC is indeed a valuable learning experience, a manual mill is just as capable and you get to learn how to run a mill as well.

CNC conversion takes away some of that learning, replacing it with a "Multi-Purpose Magic Replicator" instead - make it in software and let the MPMR pop it out.

The small mill you mentioned is moderately capable, but that's the best that can be said about it. Look at the reviews at Grizzly.com for more info. Replacing the nylon gear with the belt system, and the torsion spring for Z, are both good ideas - there are a few conversions around.

The next size up (or two) will be a far better machine. None of these is turn-key, you'll need/want to take the machine apart, adjust and polish and lubricate everything properly, to produce good work. That will also teach you what is important and what isn't, plus you'll really know the machine.

Tooling can cost as much as the machine, so research that as you make your decisions. A quite beefy vertical mill without DRO or CNC can be had for $2.5k, and later converted to CNC and/or DRO. See this thread, especially starting at Post #27.

Re: CNC mill conversion ?s
 

This is VERY true. I've spent as much on tooling(and measuring instruments) as I did on my mill, and I still have a wish list a mile long.

Also do you have a lathe? I would(and did) go for manual mill + manual lathe over just a CNC mill.

Re: CNC mill conversion ?s
 

We picked up one of the Harbor Freight 7 X 10" lathes earlier in the year that we are starting to set up. There was some debate on how much we would use it (I know there are folks that think they can't survive without a lathe) but we finally decided to move forward with it.

Re: CNC mill conversion ?s
 

Thanks for the info. I'll definitely read that thread as soon as I get time. I searched before starting this thread, but for some reason it didn't show up for me...

Part of the idea was that we don't have a lot of experience with machining on the team (though we just picked up a new mentor that did some experience), so we were hoping to overcome some of our lack of knowledge with technology. I agree that in the long run, we'll be better off by learning basics, but thought we'd get more short term benefits from CNC. We were being kind of intimidated with our lack of experience and finding some comfort in technology (and seeing all of the cool machine work on many of the robots in St. Louis made us want some of that too)...

After putting together a spread sheet estimating the costs, I'm starting to get it. Starting to question the wisdom of throwing 2-3 times the cost of the mill at it to convert it to CNC and in the end having a low end ($600) mill with a small table with relatively limited usefulness...

Re: CNC mill conversion ?s
 

You'll find uses for the lathe. Just need to look for them.

It would be great if you can find someone who really knows lathes to help set up and adjust it, teaching a mentor to keep it running right. If you want it to turn out good work, it must be set up properly, and that takes some effort. It is not ever plug-n-play. (Find a local machinist who can stop by for 2-3 hours to talk about it)

At 1676, we teach 2 or 3 kids each year how to run a lathe. It can be quite dangerous if you're not paying attention, so only serious users are accommodated.

CNC stuff is really cool, but overrated in a non-production environment. The kids certainly lose a lot of potential hands-on knowledge that way.

Re: CNC mill conversion ?s
 

We bought last season a Grizzly X3 mill and this season we decided to CNC it. We bough the cncfusion standard kit with preloaded bearings and it fit perfectly. We have just adjusted the mill with Mach3 using backlash compensation (.001 in) and we are able to see no error down to the thousandth of an inch over a one inch domain.