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Looking at an older Sherline CNC Mill - advice requested


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I have been considering a sherline mill (and lathe) and have come across a CNC mill that is claimed to be unused but 7 years old.  Price is pretty good.  I wasn't necessarily planning on CNC but was thinking DRO was a nice-to-have and CNC-ready was perhaps smart for future upgrade.  I will admit that I don't have any experience with machining so I will have a learning curve in any event!

 

I'm several hours away from the vendor so I'm asking him email questions before I plan t trip this weekend that would let me see the system.

 

I don't yet have model numbers but have asked for them and hope to hear back today.  I also don't know a complete set of accessories included but notably there is the rotary table.

 

One of my concerns is the vintage of the computer and software for the system.  A 7 year old EMC2 system has likely been significantly updated and a 7 year old linux box may limiting.

 

I am going to call Sherline today when its morning in CA and ask them a few questions.

 

I'm seeking advice from the forum on 

- any gotcha's I should be aware of in getting a 7 year old cnc system (e.g. change of interfaces to the stepper motors ...)

- any configuration/accessory issues I might want to check on with the vendor.

- any limitations created by having a CNC version - i.e. can I still use it completely manually?

- general advice concerning value of CNC for our hobby


Thanks all!

 

Edited by Heronguy
typo
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Doug,

 

You might check and see if it can used "manually" without the CNC parts however CNC would be much more accurate unless you'be been milling for awhile.  For "one ofs" I think it would be faster just to mill the part manually.  Where CNC shines in repetitive parts.

Edited by mtaylor
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Make certain the stepper motors have dual shafts (out each end) so you'll be able to attach handles for manual operation...otherwise you'll have no manual option.

 

I personally would be concerned about buying 7 year old computer technology to drive it.

 

As Mark mentioned above, CNC is really for repetitive operations....not one off.  But on the Sherline I think some parts of the CNC version have upgrades over the manual version, at least on new machines...if same held true for older machines it might mean a better machine for you.

 

Remember you'll spend as much in tooling as the base machine..so it will be a real plus to receive a lot of tooling accessories with the machine.

 

Good Luck!

Edited by clifforddward
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Mark and Cliff,  

 Thank you - just the kind of insight and advice I was looking for.

 

I will be a complete novice on milling but the idea of precise control over operations made CNC interesting.  As well that CNC can control multiple axes simultaneously seems to increase the range of milling that I would be able to do.(arcs, diagonal cuts).

 

i will check on the dual shafts.  I've read the Sherline site and it certainly looks promising that it will be dual shaft steppers - apparently the system was bought as a unit rather than assembled through upgrade parts.

 

 I'm also slightly off put by the computers age although since this is a dedicate machine and it appears Sherline hasn't upgraded software significantly since 2014 then it might be fine as long as the hardware keeps running and it sounds like this system hasn't been used much if at all). Vintage hardware running vintage Linux doesn't sound like too bad a combo.  I wonder about CNC systems in general.  The mill part should be good for many years.  Computer and software less longevity.  I'd hate to end up with a machine that couldn't be maintained!

 

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Doug,

 

EMC2 and Linux are open source software, you should be able to upgrade to a newer version without any cost.  I am not real familiar with either thou but I am sure an Internet search would give you all the info needed.  I use mach3 for my control software which is windows based and very popular with hobby and small shops. The important thing about both programs is they are based on old hardware platforms specifically the 25 pin parallel port.  An old computer with the parallel port on board is an advantage.  If you use a newer computer with no parallel port you will need to convert the USB signal to pulse signal for the 25 pin parallel port that goes to the stepper drivers. The timing of these signals is what allows you to control direction and speed in all directions at the same time.  You would think that it would as easy as using an USB to parallel converter but it's not.  You need special converter or a separate breakout board (such as smooth stepper).  Also just sticking in a parallel card in the computer is a hit and miss, I don't know about the new Linux platforms but the new Windows OS do not support parallel ports the way the old OS did.  Whether you have an box that plugs directly into an USB or an Ethernet port all of the stuff I just mentioned is built into the box.  From that hardware, whether in a separate box or built into a computer, this is what you connect your stepper cables to.

 

You do not need a new processor to run these programs.  I use an old Pentium 4 with Windows XP that is over 10 years old.  Will I  have to eventually upgrade, yes but not until this computer dies.  The main reason is that I would have to buy a USB motion control breakout box and reload and setup up the software.

 

Yes you can use a CNC machine manually.  There are a number of ways:  handles on the stepper shaft,. keyboard, joystick, and a pendant (MPG (manual pulse generator)).  A pendant is the easiest. All the axis, speeds, steps etc. can be controlled by this hand held unit.

 

What also is important is the spindle speed.  Getting something up to 10000 rpm is nice especially since you will be using smaller cutters.  

 

I should say I don't own the Sherline I have a Taig CNC mill, but all these hobby type CNC machine are all basically the same.  They use steppers, stepper drivers, control software (almost alway EMC2 or mach3), and a PC.  You also need software to draw you part and software to generate g-code.  Note Fusion is free for non commercial use. 

 

I am by no means an expert.   My son has his own small engineering and CNC manufacturing business, so when he needs the extra help I operate one of the large mills (these are not hobby mill but the principle is the same) so this gives me some practice at what not to do.  If I get in trouble I just find him that's the nice thing about being free help, but I have learned a lot by helping and watching him trouble shot.

 

Don

 

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Loads of useful info Don.  Thanks.  I've been researching Sherline CNC since this opportunity came up and am aware of the parallel port vs USB issue.  Standard Sherline CNC packages do support manual feed through dual axis stepper motors.   One significant difference with your Taig mill would be the max spindle speed.  Sherline quotes 70-2,800 rpm whereas Taig offers 1,100 to 10,000.  I wonder what the advantage of the low spindle speed might be (you've already stated what the advantage of the high spindle speed is)

 

The folks from Shoreline also think there is no problem upgrading to more recent LinuxCNC software.

 

I'm hoping to drive down to see the equipment this weekend - with luck it will be suitable.

 

 

 

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Well the plot thickens.  

 

The mill itself was shipped to a distributor in 2008 so it is a bit older than the 7 years.  It must have been subsequently upgraded to CNC. So far I don't know if it used Sherline sourced parts or 3rd party.  Sherline updated their drivers in 2009 so it is really important for me to determine if the CNC electronics are the newer ones. I also have to check that the stepper motors have compatible plugs if I ever need to upgrade the driver box. I'm preparing myself with spec sheets so I can look at the system carefully when I get down to see it.  

 

Turns out the mill is the 8-direction version which offers more adjustments than I expect I'll ever need.  Bit bigger bed though and since bench space isn't a constraint I can be happy about that.

 

I must compliment Sherline rep for their friendly advice.

 

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Doug,

 

Speeds and feeds for milling whether manual or CNC can be tricky.  It depends on many factors material, bit size, spindle speed, feed rate and the bit type (carbide, HSS, number of flutes) whether drill, end mill etc. and chip clearance.  Check out some speed and feed calculators online to give you some ideas.

 

The the short answer for the slower rpm is you can use HSS bits to cut hard material such as stainless or tool steel.  If you switch to a carbide bit you can increase your spindle speed and feed rate without burning up the bit and get a good finish. In our hobby work we usually work with softer materials such as wood, brass, plastic etc. so the slower speeds aren't as important. You also have to keep in mind many of these calculators may assume you are using a coolant which you will not be using.  

 

A easy visual of this is using a hand router.  Move the router to fast it starts tearing out and leaves a rough surface, to fast and you burn the wood and bit. 

 

Keep in mind we are doing this for a hobby to have fun.  In the end you will probably use the higher end of the spindle speed with some carbide bits and adjust you feed rate to match.  

 

Don

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  • 2 weeks later...

The mill arrived home last night!  I went to inspect it the previous week and found it was as described - the mill was in pristine condition - never cut into material - and a nice collection of accessories.  The gentleman selling it had hoped to use it to learn CNC programming but had trouble even turning on the computer so it just wasn't the thing for him.  He has a Sherline lathe (not CNC) in his shop that does look well used so it was the programming aspect that thwarted him.

 

I've got a programming background (though no machining background) so I imagine I'll be OK.  My main concern is that learning machine may impact time in the shipyard itself - I think it will be a while before this new tool plays a useful role in my modelling efforts

 

There are gems out there - I think I found one!

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Glad to hear all has worked out for you Doug...I look forward to hearing of your progress using the Sherline mill.  I've had several machining friends who tried to venture into CNC with small mills who got overwhelmed by the programming side of things...sounds like you will have success since you already have that background, picking up the machining skill set is an easily achievable proposition.

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I'll let you know what my experiences are.  I'll be keen to figure out how to make best use of it for ship modelling. Drilling a straight line of holes for a pin rail sounds so very pedestrian but I've thought that having an x-y table for that would be handy.  Now I can probably spend an hour setting up the mill and have the computer turn out a matched pair! Oh boy!

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  • 1 month later...

What software are you using?

 

I'm debating converting my Sherline to CNC or buying something like a Shapeoko or Nomad from http://carbide3d.com/.  I think the potential for using CNC mills is huge for creating high quality parts but modeling and building the tool paths is a skill just like any other.

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  • 3 weeks later...
On 2017-10-13 at 11:05 AM, Ben752 said:

What software are you using?

 

I'm debating converting my Sherline to CNC or buying something like a Shapeoko or Nomad from http://carbide3d.com/. I think the potential for using CNC mills is huge for creating high quality parts but modeling and building the tool paths is a skill just like any other.

 

I’ve experimented a bit with FreeCAD and downloaded VisualCAD from MECSoft but not really gone far with either.  Although I’m very comfortable with g-code programming I’m finding CAD concepts a bit foreign.  

 

So so far I’ve used the mill to prototype a coppering nail jig and a mast supports for the Essex crossection I’m building now.  In the process I ran into some problems with the mill -seems like the backlash on both x and y axes was of the order of 30 to 40thou!

 

I finally  found the time to disassemble the slide and re-lubricate the mill.  Now the backlash is better although still more than I’d expect.  I have to rerun my code examples to see if the results are good enough for my modelling needs.

 

Although I haven’t done much with CNC I think it going to be really useful. I’m glad I got the CNC version!

 

 

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Yea, 30-40 thou is way off!  One thing I found on my manual Sherline, is to check the spacing between the lead screw bracket on the slide and the hand wheel (I'm assuming this can still happen with how the stepper attaches).  I had a gap on mine that was contributing a fair amount of backlash.  Fixing it was as simple as adjusting loosening the set screw and pushing the hand wheel flush and tightening again.

 

If the machine is really worn, the brass nuts inside of the slides are replaceable as well but it's a more involved process.  I'd try replacing the brass anti-backlash nuts first.  When I first received my machine, the prior owner had really tightened the gibs and it was causing the anti-backlash nut to not do its job effectively.  Tapping them loose and lubricating/cleaning them appropriately was all I needed.

 

I probably sound like a broken record but try Fusion 360, it's free for hobbyists.  I find the parametric approach makes the most sense to me.

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12 hours ago, Thistle17 said:

Doug there is a "kit" in the catalog that allows one to retro older mills. P/N 5011U for the inch version. I found it in the book Sherline Accessories Shop Guide. The book is loaded with how to info as well. The metric one is 5111U.

Joe

The mill I bought already has the newer backlash locks.  I tried just adjusting them to take out backlash the feed screw would just bind up if I tightened the backlash nut.  Taking the slide right off and lubricating and repositioning everything made a reasonable improvement but still in the 10 thou range.

 

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8 hours ago, Ben752 said:

Yea, 30-40 thou is way off!  One thing I found on my manual Sherline, is to check the spacing between the lead screw bracket on the slide and the hand wheel (I'm assuming this can still happen with how the stepper attaches).  I had a gap on mine that was contributing a fair amount of backlash.  Fixing it was as simple as adjusting loosening the set screw and pushing the hand wheel flush and tightening again.

 

If the machine is really worn, the brass nuts inside of the slides are replaceable as well but it's a more involved process.  I'd try replacing the brass anti-backlash nuts first.  When I first received my machine, the prior owner had really tightened the gibs and it was causing the anti-backlash nut to not do its job effectively.  Tapping them loose and lubricating/cleaning them appropriately was all I needed.

 

I probably sound like a broken record but try Fusion 360, it's free for hobbyists.  I find the parametric approach makes the most sense to me.

 

As I mentioned just above, I've got the backlash down to around 10thou.  May be good enough for my purposes??  I gather from various commentaries on Sherline that I should expect to get 2-3 thou so I still have a long way to go.  I was somewhat surprised that both the X and Y axis backlash were so large given that the machine was effectively unused previously.  

 

I looked at Fusion 360 briefly and it is certainly well recommended.  I guess I'm a skeptic when software companies offer free for now access to their products. That being said I haven't made any significant commitment to the others and the Fusion 360 tutorials look extensive and useful.  

 

I'm a dyed-in-the-wool Mac user but I was so frustrated with FreeCAD tutorials (because the mouse gestures were much more convenient that the equivalent mac-mouse option) that I went and purchased a used windows laptop so I could run PC versions.  One toe over to  the darkside!

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1 minute ago, Thistle17 said:

Hard to communicate this way Doug but I will try. If you have not already done this look at page 120, the Backlash Upgrade procedure, in the manual mentioned prior. It also refers to Page 11 in the mill assembly instructions to facilitate the adjustment, if that helps.

Joe

 I haven't got the Sherline Accessories Shop Guide - I guess I should order one.  I wonder it the same description as found on line in the tech note "Adjusting Backlash on Sherline handwheels"  It is an 11 page  document with colour photos of steps involved - The release date on it is 3/31/17 so it is certainly up-to-date!

 

I've done a search through Sherline, Youtube, and Google for information various ideas on backlash.  Found a couple of useful links.

 

 

 

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