# CNC Conversion Anyone?



## modamag (Dec 25, 2005)

As a few of you might have known. I'm now trapped at home for the near foreseeable future due to little mischievous Andrew and newborn Julia.

In the past I have been spoiled by my friend’s machine shop which includes YCM/YCI  XV-1020A VMC, TC-36W and HAAS CNC Lathe and several manual one such as Bridgeport Mill & SB Lathe. Now it’s very hard for me to make the 45 minutes drive to Gilroy to access the shop. It’s so easy to make stuff with 0.001” tolerance (±0.00008" (0.002mm) tool repeatability). I was able to go from ProCAM to prototype piece within couple hours.

As a Christmas wish, I asked for an in home “hobbyist” machine shop. So my wife got for me a Sieg X2 Mini-Mill from Harbor Freight (44991-1VGA). As a present for myself I got a Sieg C6B 10x22 bench lathe. My father and I built a 32”x72” bench made of MDF to support the machines.






Seig C6B-550 lathe
- Option "A" includes a DRDC
- Option "B" is the variable drive speed 





Seig X2 Mini-Mill
Commonly sold as HF44991 / Grizzly G8689 / Homier 3947 / MicroMark 82573

The mini-mill arrived home couple days ago, while the C6B is still on a freight ship originated from Shanghai, China. My father and uncle got a chance to clean off the red grease on the mini-mill with WD40 and leveled it on the white bench. Today (Xmas), I got a chance to make a chance to make a few cuts. It’s not too bad but leaves me much to desire. I got most of the basic cutters, end mill adapter, boring head, clamping kit and the invaluable rotary table. What I desire now is more precision and CNC.

So now I’m on a quest to build my own home CNC shop. This will probably take me ~40-120 man hours (2-4 months) and $2-5K to perform the conversion.

Some of you may question “why bother with those bench top units that have 0.005” backlash, with that amount of money you can probably get a used Bridgeport and convert them”. Well the reason is fairly simple housing cost in the California Bay Area is ~$400/sqft ($4500/m2). My wife is not allowing me to build another shed in our tiny backyard. The total space she allocated for my so call “shop” is 32”x76” (basically one side of our garage). So I don’t have much choice but a bench top. Similar to flashlight, if you want things to be “perfect” you have to throw more $$$ and passion into the project to bring it to life. Who could imagine a flashlight that can roast marshmallow, right!

I plan to improve the precision by upgrading all axis with ballscrews. Some software backlash compensation will also help.

I will start out with the X2 Mini-Mill for CNC conversion due to several reason. I already have the unit in-house. There is more need of a CNC mill than a CNC lathe, however with that said I plan to convert both. It’s the harder of the two machine to convert and I like the challenge of an uphill battle, because the second half is all down hill 

*=== Sieg X2 Mini-Mill CNC Conversion ===*
3x NEMA 23 260 oz-in / dual-shaft stepper motor … $128
- from homeshopcnc.com
3x Gecko 201 stepper motor driver … $321
- from homeshopcnc.com
3-Axis CNC Retrofit Kit … $0-$1000
- from KDN Tools … ~$1000
- from CNC Fusion … $365
- DYI then it’s “FREE!”
1x Parallel Port Interface Card … $25 (due to IBM T40 Laptop)
1x IBM T40 Laptop & Samsung 19” LCD
- Bluetooth Mouse/Keyboard interface
- future upgrade will include EloTouch Touchscreen interface
Controller Software: Mach 2/3 or TurboCNC
CAM Software: MasterCAM
CAD Software: Solidworks
~40 hours of luvin labor for the conversion.

I can’t wait till this project completes. I know it’s no Fadal but hey it’ll fit in that tight 32”x76” space and do most of the stuff I need for RC, wood, and flashlight.


I hope to keep this thread as an update and share the experience with any members who would also like to pursue this great endeavor.

If any member have already performed the conversion, your tips/insight will be greatly appreciated.


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## AdamW (Dec 25, 2005)

Cost and complexity are keeping me from converting a mini-mill to CNC. I wish one of the Chinese manufacturers would sell a CNC mini-mill that is ready to go, with stepper motors and a controller included. Just add a computer, software, and cutters.

Is your mini-mill 4th axis capable? The 4th axis allows for some really trick machining.

Good luck with this, and please keep us posted on your progress!

Adam


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## modamag (Dec 26, 2005)

The Mach 3 software is capable of handling up to 6 axis, so the A-Axis (rotary table) should not be a problem.

If you're looking for ready to run units check out the Taig or Sherline. With one of these you're gonna be shelling out $2K+.

The problem I face is they're not large enough for me to do 1/8th or even 1/10th scale RC. 

As far as a chinese manufacturer. I've got a chance to chat with one of their rep, and they indicate that they're not interested in such due to low demand and significant cost increase to the product line.


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## pbarrette (Dec 26, 2005)

Hi Modamag,

This summer I completed a CNC retrofit to my Sherline 4000 lathe. The Sherline is much smaller, but my space is extremely limited and the Sherline is still a very capable little machine.

For my CNC lathe conversion, I used:
---=== Lathe End ===---
2x Sherline CNC motor mounts. (Ebay *)
2x NEMA-23 269oz/in stepper motors. ($100)
1x Xylotex, 3-Axis controller. ($145)
1x 24V, 5A voltage regulated, linear power supply. (Locally purchased, 50 Euros)
3x 4-pin full sized DIN connectors (male and female, 10 Euros total).

---=== Computer End ===---
1x EPIA M10k Mini-ITX computer
1x Casetronic, Cubid 2699 case.
Solidworks (for part modeling)
OneCNC 2000 Lathe (for CAM)
TurboCNC (for part creation)

The motors are significantly larger than I need to run the tiny Sherline, but I had heard some bad stories from people using underpowered motors and having horrible results. I decided, better safe than sorry, and opted for the larger motors.

I also went with a 3 axis controller even though my lathe only requires 2. I disabled the third axis on the Xylotex controller (via an on-board jumper) and only use X and Z. Going with the 3 axis Xylotex saved a lot of money over the Gecko drivers and I have the room to expand to a 3rd axis if I ever need it.

Both the Mini-ITX motherboard and the Xylotex driver fit in the Cubid case. The case is rougly the size of 2 laptops stacked on top of each other, which conserves a lot of space. I'm using a 2.5", 6GB laptop HD which also resides in the case and is loaded with DOS 6.22, LAN drivers and TurboCNC. I have a boot menu set up so I can select whether or not to load the LAN drivers, boot directly into the TurboCNC application, or go straight to DOS.

I am currently using a PS2 keyboard. I was originally using a wireless Gyration Ultra keyboard and mouse (now obsolete apparently), and I was booting from an external, USB HD. Unfortunately, even though the Mini-ITX had no trouble booting from the HD, or detecting the keyboard and allowing its use, TurboCNC got real jittery whenever the system got an interrupt from the USB port. I switched to the PS2 keyboard and wired the same HD as IDE and all the noise went away. Some people have had timing issues with DOS LAN drivers in conjuction with TurboCNC, but I haven't noticed any problems yet.

I currently do my modeling in Solidworks, then CAM in OneCNC-2000-Lathe. It's a real chore. First, I draw the profile and an "invisible" centerline, then revolve it to see what the finished piece should look like. But OneCNC is a bit finicky with 3D model imports. So I then hide the revolve and show the profile. Then I make a Solidworks Drawing of the X-Z plane of the profile and export that as an Autocad v10 DXF file. Then I import that into OneCNC, reposition it to the right coordinates using the centerline, then delete the centerline. Then I run the CAM operations to generate the G-code, export the code to a file, clean up the code (since there doesn't seem to be a good TurboCNC post processor) and copy it over to the Mini-ITX via the LAN.

Then I get to try machining it.. If it's wrong, and I need to tweak it? Repeat all of the above.

The Sherline CNC motor mounts I picked up on ebay for ~$300. It worked out very well, since those motor mounts were already attached to a new lathe bed, crosslide, leadscrews, spindle and tailstock. The only things missing from that ebay purchase were a motor and the lathe mounting base. The newer Sherlines come pre-drilled to accept the Sherline CNC motor mounts, but mine wasn't pre-drilled and I don't have a drill press large enough to handle the lathe bed, so I was worried about buying the mounts from Sherline and not having a way to properly attach them. The ebay deal really saved my bacon and left me with lots of spare parts at a price that I couldn't pass up.

Since the Sherline doesn't have built-in threading capability, this is one of the reasons I converted the lathe. CNC threading with TurboCNC requires a pulse sensor to determine the spindle speed. I used a Sharp IS471F IR sensor, an IR LED and a trim pot to create my spindle sensor. The Sharp sensor IC uses a pulse modulation system to drive the LED which it then decodes via the built-in IR sensor. This allows it to ignore background light sources and makes the spindle pulses quite accurate. I had trouble getting the distance sensitivity set correctly, so I added a small trim pot in line with the LED to adjust the LED's output, and thus the sensitivity. I cut a strip of glossy black duct tape and placed it on the spindle pully to test the setup with the intention of painting the pully later. It worked so well that the tape is still in place and I never bothered with the paint.

At some point, I plan on getting the DigiSpeed Controller from Homann Designs. This controller allows you to set the spindle speed via CNC for spindle motors which use the KBIC DC motor controller. The Sherline lathes and mills use this controller, as do some of the mini-lathes / mini-mills. Since you got the variable speed lathe, I wouldn't be suprised if it used the KBIC controller as well.

Anyway, I should probably post some pictures of my setup.

Here's the lathe sitting in a cabinet from Ikea. The lighting is actually a lot better than this picture would lead you to think.




Again, the lathe:




Here's a close-up shot of the spindle sensor with it's shoddy mounting and the duct tape:




Did I mention that the cabinet is a roll-top, so I can close it off completely when I'm not using it?




Finally, here's a (very large) picture of my old setup on my desk with the box I originally used for the Xylotex controller. It also shows the power supply and the keyboard I currently use:




pb


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