Hey everyone,

This might be a few days early to start this, but I figured I would get it going and post some initial thoughts/questions and see if anyone has anything to suggest or add.

I ordered the machine on Friday, and should be getting it middle of the week this week. I will snap plenty of pics and document this entire build.

Some background first. My name is Erik and my entry into machining and CNC has been robotics.

I started out with a 3D printer to be able to make parts for robots and other things, built a RepRap MendelMax, and was instantly hooked on cartesian robotics.

3D printing is really cool, and I still do a lot of it, but sometimes you just need more strength than plastic can provide.

So I pretty quickly knew I needed to do a CNC conversion. I started with a LMS 3960 SX2L and bought a CNCFusion kit, and a pretty straight forward G540 and 3 Nema 23 steppers.

Overall it has been a good machine, but I need more workspace and more precision. After a lot of fiddling, the absolute best I can do for backlash is 0.0025" X, 0.002" Y and 0.004" Z.

I know if I wanted to, I could get it down further than that by replacing the balls in the ball nuts, and scraping the ways, but I want more rigidity and more space, hence the PM-30MV-L.

99% of my cuts are aluminum.

I want 0.0005" backlash or better on at least my X and Y, and would love it on my Z.



OK, so now for my thoughts/plans so far:

I have read a lot of conversion threads and bought Hoss's G0704 DVD.

Other than the Mill, I have not bought anything yet. Figured I would post my thoughts first to see if anyone has any feedback.


First off, in order to achieve the low backlash, I am thinking about using a double nut system on at least the X and Y axis with a spring separating the two. I plan on using Roton per Hoss's DVD, and I also plan on replacing the balls with oversized ones as Hoss does. I am wondering if the oversized balls AND the spring separated double nut system is overkill and will provide more friction than good, as it seems like one or the other may be sufficient. Would love to get anyones thoughts on this.

I plan on using Hoss's plans for the AC bearings and the mounting systems for each axis. I may need to use some different sizes depending on my mill's measurements when I get it.

I am also planning on using steppers instead of servos. From what I have read the accuracy is the same either way, and it seems like the tuning of the servos may be a pain in the neck. If anyone has reasons I should definitely use servos, I am open.

I am thinking that 570oz steppers should be good for the X and Y, and 906 or possibly 1200 Nema 34 for the Z should be good. Gecko has worked well for me, so I am inclined to go with Gecko just based on familiarity, but again I am open to change and suggestions.

The next thing I am up in the air about is to build a stand/bench or use the stock one. I have never ventured into coolant before, and have always used air to blow chips away which has been fine to date for aluminum. I know eventually I will have to go to coolant, so I want to make sure that whatever I use for a stand will be OK.

Either with or without coolant, I really want to build an enclosure as I have for my SX2L, just to keep chips under control. My shop is in my garage and my wife is not fond of me tracking chips through the house.

If I use the stock stand, I am not sure how I would be able to build an enclosure, I suppose I could lay down a 5 foot piece of plywood and laminate it, and build some supports from the stand to hold it, but that seems clunkier to me than just building a stand.

If I do build a stand my plan was to build a wooden stand which should help reduce vibration as well, and use a laminated surface as a bench top. Having never used coolant, I do want to make sure when I do go to a coolant system, that my stand can handle it. I am a bit unsure on how that works and how far down the coolant can wander. So if anyone has any thoughts on this I would love to hear them as well.

I plan on eventually switching to belt drive, but that will be a bit down the road. I plan on buying Hoss's belt drive DVD again as a guide since I will have a different machine.

Looking forward to getting the machine in and tearing it apart.