Sherline mill/CNC conversion

[kellogs72]

I have a Sherline mill model 5000 and I have been toying with the idea of converting it to CNC mill. I am wondering if anyone has done this with this model or similar and what stepper motors you used.

Sherline says that this mill is not designed for production work (only finishing) but do not know how true that statement really is. I have used it for production work for my business and find myself having to adjust it often to remove runout and other tweaks here and there. Plus the vise that comes with the mill is much to be desired. Trying to decide if I should spend the money to convert it to CNC or to upgrade to more of a midrange mill that could possibly handle more wear and tear and then do the CNC conversion.

Any thoughts or input are welcomed.

[fpworks]

CNC will put a lot more wear and tear on the mill.

It really isn't appropriate to use for production. I suggest you keep your current Sherline for prototype work, then buy something a bit beefier for production.

I tried using a Sherline CNC mill for production, and here were my problems:

- backlash increased to unacceptable levels very quickly

- repeatability is not good enough, especially when you are using the extents of the travel to make a lot of parts. For instance, I used a spot drilling cycle, then two drilling cycles, and then two milling cycles for a single lot of twelve parts. The lead screws' relatively low quality/accuracy/repeatability was not good enough to use the entire table, and the finished parts were unacceptable. I can only effectively use 1/4 to 1/3 of the table for production type work.

- You will find yourself increasing spindle speed so you can increase feeds. The leadscrew pitch is very low, and steppers will run out of speed very quickly. My metric Sherline mill is maxed out at ~18 inches/minute, and I dare not go faster in fear of lost steps. I am using 3/16" 4 flute endmills in tempered aluminum, and it needs to feed faster (with 5500 rpm pulleys).

Justin

[Swami]

fpworks, do you have any idea what the "next step up" in terms of a more production capable machine is? I just got a CNC Sherline 5400, and I do plan to make production parts on it. I only need to make maybe a dozen parts a week, each about a square inch. At least thats whats going on currently.

I have only been using it for a few days, but I can't imagine doing this without CNC now.

Swami

[fpworks]

Swami,
I am hoping the next step up would be the mills from Minitech, because I have one on order now. I ordered a "frame" from them in which I can install my existing Sherline spindle/motor.

I think you'll be fine with the Sherline, as long as you don't get greedy with production. Don't make a fixture so you can cut 30 of your parts in one cycle, even if it fits on the table and travel limits.

Keep the leadscrews clean and lubricated, and measure/confirm your backlash before every production run, or you'll end up with some ruined parts.

Just for comparison, I was doing 12 parts at a time that used up nearly all x and y travel, with the milling programs taking 40 minutes. I hoped to make 2-3 runs per day. The Sherline was not designed for this type of work. I don't need a bigger mill to make my parts, I just need something that can maintain accuracy over long distances and long programs, and is capable of slightly faster feed rates.

[kellogs72]

I know what you mean fpworks. Backlash has become a big problem with my Sherline and I have ruined many pieces because of this. Its great for doing fine detailing and prototyping but designed for more than 3 parts with 30+ cycle times consecutively it is not.

I purchased the Sherline mill vise with rotating base and it was wonderfull for about 2 months. Soon after that the machine screws that secure the rotation on the vise stripped out and I had to remove the disk shape plate from under it, drill out the stripped holes, retap them, enlarge the machine screw holes on the vise and get bigger screws. I was dead in the water for a few days as the vise became useless because I could not stop it from twisting.

I've had other minor issues with the mill here and there but it still was a good purchase. I decided that I will be updgrading to a larger mill in the near future. Thinking of going maybe with a Grizzly or Homier and then doing a CNC conversion. Will still keep the Sherline for proto work.

[fpworks]

I'm doing the same thing...my Sherline is perfect for prototype work, light jobs, and maybe some engraving (havent tried this yet)...and it won't tie up the other mill that is doing production.

Good luck