turning a manual mill in to a CNC mill

[garyshipwright]

Hello everyone. I am planning on changing my Sherline manual mill over to a CNC mill and looking for the good and bad in doing this. Its a little on the costly side I know but would like your insight in to what you guys think and what you guys did or didn't do.  Of course I might just be tired of turn the hand wheel. ;o) Thanks.  Gary 

Edited February 3, 2020 by garyshipwright

[mtaylor]

I can't speak for Sherline, but one disadvantage on many mills is that you lose that capability to use the hand wheels.  

[garyshipwright]

8 hours ago, mtaylor said:

I can't speak for Sherline, but one disadvantage on many mills is that you lose that capability to use the hand wheels.  

Hi Mark and thank you. That was one of the items that I was most concerned about, taken away the capability of the hand wheels and its manually use. Am not sure about other ones but you can still use the hand wheels by just unpluging the steeper motor from the drive box and now you don't have a feed back ,in to the drive box unlocking the handwheels for manually turning. Some say if your not going to use it for cnc why have it.  Seems one now has a choice to use either manually or cnc. I also found that you can reuse your dro and handwheels to keep track of where things are out so you don't have to count turn's, which suck when its a long or deep part. Being able to still use the DRO with out the computer hooked up gives you all the capabilitys you had before adding steeper's. Because learning how to use cnc takes a bit, its nice to still have the manually part. Gary

Edited February 4, 2020 by garyshipwright

[mtaylor]

Ah... thanks for filling me in the Sherline,  Gary.   In that case, I can't see how you can go wrong.  

[garyshipwright]

Thanks Mark

[zhuying1317]

The first question is, what are you planning to do with this CNC machine, and then how much will you be pleased to pay for the conversion.

 

In my opinion, 4 axis engraving is utterly useful in ship making, so adding a forth axle is highly recommended. It wont cost you much if you dont ask for too much accuracy and robustness, I think ive seen kits down to 60 dollars on taobao. If you are not currently planning for using the 4th axle, at least buy a controller that supports it, so later you wont have to change the whole set when you need it.

 

The controlling system I personally prefer PC-MACH3 system, using USB control board or serial port. But be ware, serial port is hard to find on current PCs. Industrial-level CNC systems are way too strong for personal usage, and it consumes so much budget that you can use that money to upgrade all your steppers to servo motors. SCP based systems, like Arduino systems, are too cheap for a decent milling machine, it lacks a lot of functions, and not accurate on circles.

 

Are steppers good enough for normal CNCs? Yes. But if you have the budget to use servo motors, please do, it is so much human-friendlier than steppers, make your working place a better place for human beings, and provide better accuracy for the machine.  "Close circut steppers" are simply junk, they work as loud and vibrate as steppers, but even more fragile than a servo motor.

 

You may want to change all the screw bars to ball-screw shaft for less friction and less backlash. The latter is very important in transforming machinetools.

 

The rails, if you were using dovetail guide or other means of heavy guides like normal milling machines, you can try "Plastic-adapting"the rails(Im not quite sure on how this spells in english). By sticking a PTFE "tape" kind of thing to the rail, it can highly reduce the friction and thus the driving power, so as to make the machine faster, more stable, quieter, and accurater.

 

Finally, you can consider using a second spindle for engraving. One can get a 30K rpm water cooling engraving spindle for like 200 dollars. If you are more dealing with wood, a faster spindle can offer a much less cut-per-rotate, thus protects the wood structure.

 

 

 

 

[zhuying1317]

NC milling tools are just sth different. Once you have one, a lot of things that you have been used to will no longer be tolerated.

 

It can be used on almost anything. I use mine on wood, copper, aluminium, steel, leather, carbon fiber, everything.

 

Keeping the hand wheel is an important thing, quite useful in some occasions.

 

 

[thibaultron]

One suggestion. If you are going to spend all that money to do a CNC conversion, why not get a larger mill to do it on. You may find other interesting projects, that a larger mill would be nice for.

[Thistle17]

At the outset let me say I am not trained as a machinist. Having said that I did invest in the Sherline Mill with DRO capability. I love the machine! I also invested in a Sainsmart 3018 Pro to try to teach myself and my grandson who is in college studying Mechanical Engineering to give him some early hands on exposure to this type of tooling. Firstly let me say I do not recommend that CNC system. It is a learning tool. What I would offer is that we had such a disappointing entry into the CNC world via this product. However as painful a startup as it was, we learned quite a bit about the entire environment.

 

Here are my thoughts: invest in  a turn key system of both hardware and software (CAD/CAM) if you don't want to spend all your energy and time stitching together a system. From the standpoint of a machine paying for itself one should have other projects other than ship modeling as Ron suggests. Depending on what software front end (CAD software) you choose, and there are plenty, there can be a steep learning curve for the more powerful/useful ones. Even some of the better ones are freeware to the home user. The more powerful systems (CAD/CAM) allow one to even scan in images, import certain types of files, like DXF files and even with conversion JPEG images. But you may have to learn how to debug and edit 'g code' to have it produce what you want. There is a caution on the import of the more common DXF files. Certain DXF files that were meant for a laser system may need significant editing to have them run a router based system. Node discontinuities are the problem for the most part.

 

These are just a few thoughts that I/we had to learn the hard way' We did this over 2 months of summer trail and error. What made it fun I was spending quality time with my grandson!

 

If all this doesn't deter you please keep this thread alive and we all can learn and contribute with you.

 

Joe

[Thistle17]

I forgot to mention that you can get a healthy dose of knowledge from this individual's email and postings. He is quite the CNC enthusiast. Bob Warfield from CNCCookbook <bob@cnccookbook.com>

Joe

[garyshipwright]

Hi Joe, Ron and Zhuying and thank you for your thoughts about this and may take me some time to figure this out. Am very much a newbe at this and has given me a lot to think about.  Might take me a little time but seems I have a little of that now. Thank you good sirs. Gary