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View Full Version : Ok, lets get things rolling...



Liger Zero
01-21-2009, 04:10 PM
Considering a CNC mill. Got two choices as far as I can see for what we want to accomplish here:

The Sherline and the KX1 from Made In China Inc.

Pros and cons of each based on actual experience?

I forsee this thread becoming a FAQ/Sticky for nOObs such as myself who are looking to get our toes wet in home CNC milling...

That said (puts machine in each corner) REEEAAAADY..... FIGHT! *GONG*

John Stevenson
01-21-2009, 04:18 PM
What about the Taig ?
I believe MaxNC is also going but I haven't heard a lot about them lately.

.

Teenage_Machinist
01-21-2009, 08:25 PM
Also possible to get a Mini Mill, buy everything needed. I believe you can buy everything needed to make a mini mill CNC with no machining.

S_J_H
01-21-2009, 09:20 PM
I started out with a x2 mini mill and did the cnc conversion myself. Knew nothing about cnc at the time but it sure looked like fun! Just dove head first and read, read and read some more. Played with MACH and learned as I went.
The Sieg mini mills make a pretty nice little cnc hobby machine and will handle steel, although slowly. A little larger than the Taig, quite a bit larger than the Sherline and I have never seen a kx1 but have seen the x1 mico mill which is a bit smaller.
Many kits and plans for the x2 mini mill.
Here's a couple early parts I made with my x2 mini mill -
A 303 stainless flywheel, and a model engine connecting rod , and a shot of my old mini mill that I learned a lot with.
http://i109.photobucket.com/albums/n48/S_J_H/misc/Stevie167.jpg
http://i109.photobucket.com/albums/n48/S_J_H/misc/Stevie113.jpg
http://i109.photobucket.com/albums/n48/S_J_H/misc/Stevie115.jpg

Steve

macona
01-22-2009, 12:57 AM
I have been putting new controls in a sherline cnc lathe at work and am actually surprised how well the thing is put together. But the KX1 looks like it has a lot more mass which is always good. But it depends on what you are doing.

I have build or rebuilt 4 cnc machines now. One thing I learned. I HATE STEPPERS!

John Stevenson
01-22-2009, 03:35 AM
I have build or rebuilt 4 cnc machines now. One thing I learned. I HATE STEPPERS!

Steve made a good quote when he said he jumped in without knowing anything about CNC.
Now without trying to start a stepper / servo war all I want to say is steppers, whilst I admit are inferior to servo's, at least allow a beginner to achieve his goal cheaply.

All to often I have seen a beginner jump in at the highest spec level and loose heart because of problems encountered with servo's, a problem that with more experience he could have overcome.

Remember most people only have email and forums for help, not many can call on someone to actually look over a system and check it out.

A decent designed stepper system running within it's limits does not loose steps and I can prove that.

I have a big Beaver CNC machine here same size as a Bridgeport Series II, it was built with steppers from new.
It also shares some mechanical parts from the manual range of machines they made, that includes dials in from of the stepper motor couplings.

I have one job that I do that involves peck drilling over 11,000 holes with a 2.5mm drill.

If I take a note of the readings on the dials at the start when the job is finished they read exactly the same.

motorworks
01-22-2009, 05:03 AM
Steppers:

I have a lathe I converted about 7-8 years ago that I used steppers.
The lathe has a 11" swing
I have a 6" 3 jaw chuck on it.
I had to make 8 large bushings this week.
The material is sae 660 bronze ID 3" x 6.125" OD x 4.5" long (app 37lbs)
Put the reverse jaws on the chuck and rough bored each
(the bore only had to be rough as there were others things to do)
Ran all 8, bronze all over the place.
Out of curiosity I checked each and found that they all were within a 0.001"
Not bad for 600oz-in steppers

eddie

vincemulhollon
01-27-2009, 12:17 PM
The Sherline and the KX1 from Made In China Inc.

Pros and cons of each based on actual experience?


I own several sherline and Chinese manual machine tools and have converted a sherline mill to CNC.

Sherline stuff is generally smaller and lighter and Chinese stuff is generally bigger and heavier.

Sherline stuff in general wins on fit and finish, they look great and work great right out of the box with no rebuilding needed. Chinese stuff is generally best considered a parts kit, the oil comes with added sand, the paint is applied with a spatula sometime missing spots and sometimes getting paint on the ways, and you'd be wise to check dimensions and parallelism and concentricity on all parts.

Chinese electric motors are known to go up in smoke and their electronics are well known to occasionally just smoke for no reason. The Sherline stuff has a nearly perfect reputation for reliability except that the thermal cutout freaks people out since it has no visible indicator that it overheated.

Sherline manual to CNC conversion is pretty much "bolt together out of the box" with a couple exceptions... The Z axis ways and screw are pretty much manual or CNC specific (you replace the Z axis rather that bolt something on), and the stepper motor mounts need motor shafts that are slightly shorter than usually supplied by motor manufacturers.

As for the Z axis, if you're buying a new axis and screw, may as well go to A2Z CNC and buy an extra tall CNC model rather than a standard length CNC model. Its a simple ten minute bolt on job.

As for the typical stepper shaft being too long, you'll probably be grinding flats on the shafts using a dremel, so realize you'll be using a cutoff wheel to slowly cut the end of the shaft to length. Take breaks to let it cool, wrap the bearings so no dust gets in there, etc. You could probably buy steppers with the correct length but it's easier to buy based on NEMA size, torque, and shaft diameter rather than throwing length in the mix. I would imagine if you bought sherline model steppers they would simply bolt on, but if you just buy off the shelf third party steppers like I did, you'll spend an hour with your dremel tool.

Other sherline challenges include no formal official way covers and no formal or official limit/home switch mountings and no spindle encoder. You can most certainly add way covers, switches, and spindle encoders but you're on your own and there are probably as many unique solutions as there are owners of CNC sherline mills. Since practically all users want them I have no idea why sherline has never come out with them. A2Z CNC sells the stuff that sherline users want but sherline won't sell, I wish they (or some other manufacturer) would provide well designed way covers, limit switches, and spindle encoders.

You can increase capacity by buying the A2Z CNC bolt on X Y and Z axes. I bought the longer A2Z CNC Z axis and it looks great, works great, ten minute bolt on job to install.

The Sherline will be less rigid, but thats OK in a non-production line CNC, since you can just reduce depth of cut or feed and take more and slower passes, etc. After all, the CNC controller never gets bored, and there is usually no tight time schedule in home machining. A zillion light passes on a manual machine is quite annoying, however on a CNC that only means more time to enjoy your beverage while watching the machine do the work.

I have not personally had dealings with customer support in the USA or china. Both Sherline and Chinese have local english speaking dealers, but only the Sherline has an onshore production line. Very much like foreign vs domestic cars it's on average going to be easier to get repair parts from the domestic manufacturer.

Finally the KX1 is absolutely huge and expensive. You could buy a Sherline CNC mill and CNC lathe and a new computer for the cost of the KX1 alone.

macona
01-28-2009, 05:13 AM
Steve made a good quote when he said he jumped in without knowing anything about CNC.
Now without trying to start a stepper / servo war all I want to say is steppers, whilst I admit are inferior to servo's, at least allow a beginner to achieve his goal cheaply.

All to often I have seen a beginner jump in at the highest spec level and loose heart because of problems encountered with servo's, a problem that with more experience he could have overcome.

Remember most people only have email and forums for help, not many can call on someone to actually look over a system and check it out.

A decent designed stepper system running within it's limits does not loose steps and I can prove that.

I have a big Beaver CNC machine here same size as a Bridgeport Series II, it was built with steppers from new.
It also shares some mechanical parts from the manual range of machines they made, that includes dials in from of the stepper motor couplings.

I have one job that I do that involves peck drilling over 11,000 holes with a 2.5mm drill.

If I take a note of the readings on the dials at the start when the job is finished they read exactly the same.

If one uses the Gecko servo drives you can put together a servo driven system for about a comprable price to a servo . The price of the drives are about the same at $114 a piece. Get an old DC permanent magnet motor and slap a cheap encoder from USDigital on it and away you go.

Once you find the limits of the machine yes, the machine wont loose steps. What I dont like about steppers is there is no feedback at all. If something happens and it does stall a motor the machine will happilly carry on from where it stalled none the wiser. With a servo drive the control constantly monitors follow error. If the follow error exceeds a programmed limit it sends a fault signal to the control and you can have the machine stop.

Also I believe you get a better performing machine for the money with servos. Servos dont have the torque drop off that steppers do and are able to run at much higher speeds than a stepper. My mill when running off something like a SmoothStepper can easily do 400ipm rapids at a theoretical minimum resolution of a fraction of a tenth. The motors are running at 2000 RPM at that speed.

Lastly is the noise!

But its easy enough to convert to servo later on and sell your drives and motors on ebay!

Heres the little Sherline CNC training lathe I just finished redoing the controls for. It had its own control built in and talked to a PC through the serial port. But the company went out in '95 so I installed a SmoothStepper and a new stepper drive. I also added a spindle sensor while I was at it so we can do threading. Need to put a better spindle speed control in though.

http://portlandtechshop.com/index.php/tools-and-equipment/6-machine-shop/57-smi-cnc-training-lathe