CNC Milling, etc.

[reinhardtjh]

So the milling bug is biting again and I've been reading and re-reading old threads like:

     Recommendations on bench top mill and laser cutter...
     How to mill incredibly small slots in a milling machine

I have a ways to go with this.  I'm probably looking at very late this year or early next year for actually purchasing.  I'm just looking around for good information.

The one post by @Andrew Hutchinson is great, just chock full of information about milling in general.  https://www.therailwire.net/forum/index.php?topic=28735.msg304598#msg304598

What I'm really interested in is things like Bryan is doing in his post:

Max — I figured you were thinking of milling a mold for casting purposes.  Brass will work just fine, so that eliminates the need of a coolant system.  K&S McMaster-Carr has the most reasonable prices on brass bar stock.

Yes, you can do what you want regarding milling spoked hubs.  But start with larger diameter end mill bits to remove the bulk of the material, then follow with smaller diameter bits for the fine detail.  That saves time and materials (in the form of non-broken micro bits).

Also — if this is for a one-off (or two-off, etcetera) project, use wax block instead of brass.  That saves a ton of stress-wear on the mill bits, and the wax holds the detail perfectly as long as you don't leave it out in the sun on a hot day.











My RPO and Diner wax molds were milled with the following bits in this order:  .055 flat head, .040 flat, .020 flat, .010 flat, .005 flat, .008 round head (for rivets - dip the head ½ the diameter, raise, move, repeat).

If you're going to do injection-molded plastic, then brass is the way to go for runs that aren't going to be tens-of-thousands of copies.  All the American Limited core-kit tooling was milled into brass plates.

So I'm wondering exactly what kind of setup Bryan has.  The Sherline seems to be pretty much what I am looking for.  I don't see a need for cutting anything harder than brass or maybe aluminium once in a while.  For the CNC part I'd be looking at the wax or MDF materials for molds or patterns.

So how is the accuracy?
The precision?
What kind of backlash do you have in the mechanism?
Did you do anything special to the setup in preparation for cutting N scale items?
   Or is it in the G-Code?

The other part of me also wonders if 3D printing isn't good enough now for producing the flat side patterns?  Is the Shapeways FXD okay for that?  Or maybe one of the other printing services.

[crrcoal]

Taig is the one Ive been eying up for some time. Might pull the trigger this fall.

http://www.cartertools.com/

[Chris333]

I have a Taig lathe. Everyone says Sherlines are much better, but also cost more.

[bbussey]

So I'm wondering exactly what kind of setup Bryan has.  The Sherline seems to be pretty much what I am looking for.  I don't see a need for cutting anything harder than brass or maybe aluminium once in a while.  For the CNC part I'd be looking at the wax or MDF materials for molds or patterns.

Standard Sherline 2000 with the FlashCut CNC interface and a surplus Windows XP workstation. It took a while for me to get it calibrated but the Sherline and FlashCut tech support is very good. Yes, G-code. The advantage of the machineable wax molds and resin castings is that the castings are of injection-molded plastic quality.

[reinhardtjh]

Taig is the one Ive been eying up for some time. Might pull the trigger this fall.

http://www.cartertools.com/

I've had that link bookmarked for a couple years as I researched and drooled over milling machines. 

I have a Taig lathe. Everyone says Sherlines are much better, but also cost more.

I narrowed the choices down to between the Taig and the Sherline.  The Taig seems more rugged, but everyone I have seen post says the Sherline works for the things they do.  As I mentioned before, I'm interested in wax, MDF mostly for master patterns.  I also want to machine frames for DCC so zamak/zinc as well.  Probably some brass. I can't see myself doing any cutting for injection molding, but from what I have read you can make small run molds from aluminum which the Sherline can cut. Maybe slowly.  The big thing I see different is like Peteski mentioned in one of the other threads I listed and that is that with the Taig you must build your own fixtures most of the time. With the Sherline it seems most are available, if you want to pay the price.  And as Andrew mentioned, model railroaders tend to lose interest making parts that are non-hobby related.  Making tools/fixtures to make models is not my prime area of interest.  Although I realize that some will need to be made.

[reinhardtjh]

Standard Sherline 2000 with the FlashCut CNC interface and a surplus Windows XP workstation. It took a while for me to get it calibrated but the Sherline and FlashCut tech support is very good. Yes, G-code. The advantage of the machineable wax molds and resin castings is that the castings are of injection-molded plastic quality.

Thanks Bryan.  Do you note any flexing in the Z column when working with the harder materials?
The Flashcut CNC package is highly regarded.  I assume you have the stepper motor version rather than the servo?
   Is it noisy?  Mine would go in the basement of our house.

[peteski]

I had a Sherline since mid 80s (from Micro-Mark) and I never really looked at Taig.  Looking at the photos of Taig, to me it looks like Sherline is more rugged (if that is what you are after). The Taig drive also seems more antiquated that Sherline's. Sherline looks to be more professionally made where Taig seems like more of a home-made machine.

My Sherlines are not CNC but I do have digital readout which made huge difference in making machining easier. No more counting dial revolutions.    Sheline also has excellent support and oodles of accessories.  The modular construction is also a huge plus.  Originally I had a lathe and then I bought a vertical column to be able to convert my lather into a mil and back to lathe.  Many years later I bought the XY table and adding my vertical column I was able to have a mill setup. I was still swapping the headstock/motor  between the mill and lathe. Then few years later I bought another headstock/motor and now I have a a complete mill and complete lathe.  I was able to spread the purchase over many years.  One headstock has a standard pulley set while I added a high speed pulley on the other one. Again. I can mix and match which headstock I use on which machine. It is all modular construction and swapping things are as easy as loosening one screw.  Of course throughout the years I made several upgrades too. Like changing the old AC motor to the current high-torque DC motor and adding the digital readout.

For me Sherline is the machine to own.  I was saddened to see that Micro-Mark stopped carrying Sherline and replaced it with a larger, Chinese-made machines.

Fun Fact:  Walthers carried the Sherline brand (I don't know if they still do).  For a while I was ordering Sherline accessories from Walthers, through my local model RR hobby shop at a decent discount!  Sadly, that hobby shop has been gone for a while (not because they were giving discounts on Walthers orders). 

[bbussey]

Thanks Bryan.  Do you note any flexing in the Z column when working with the harder materials?
The Flashcut CNC package is highly regarded.  I assume you have the stepper motor version rather than the servo?
   Is it noisy?  Mine would go in the basement of our house.

No flexing that I can see, but the hardest material I cut is brass. I also bought the non-digital version, because I figured I didn't need it due to the FlashCut CNC enhancements. That makes it tougher to calibrate, and I would get the digital version of I had a do-over. But other than that, no complaints. And it's not as if the machine has to be calibrated regularly. Usually, only on setup and if it is moved. Yes, stepped version.

Not as noisy as you would think. Most of the noise comes from the actual milling of brass with larger diameter bits. Otherwise, it's not an issue. I have it in a spare room adjacent to the laundry room, so a basement location would be more than adequate.

[bbussey]

And fortunately, you still can get the Sherline products direct if necessary.

[reinhardtjh]

Bryan,

  One other question.  You bought the Model 200 mill. Do you feel that it has benefits over the model 5400?  Do the additional directions help? Or did they add to the calibration tasks?  Or was the 2000 chosen for it's slightly larger working area?

[bbussey]

John — I don't recall specifically.  I don't remember the XY table size having to do with the model number, but I could be wrong.  I wanted have have an XY table length (at the time) that was large enough to cut brass tooling for passenger car sides.  I bought the machine under the recommendations of the late Bob Fingerle of American Limited, as that was what he used.  I also learned the basics of milling from him.  So my recollection is that I bought the minimal configuration of what I needed to start that endeavor, before the passenger car sides market collapsed.

I also had bought Bob-Cad software, which converted STL files generated by SolidWorks (and other 3D modeling programs) into G-code, which then was utilized by FlashCut to operate the Sherline.  I've since abandoned the Bob-Cad interface, as writing G-code is not difficult and I can write it manually more efficiently than the Bob-Cad was generating.

[bbussey]

This is a pic of the tooling for the 10-6 County series fluted car sides. The brass was cut on a Sherline. The steel mold base and injection pins/ports were cut and added by the late John Parker of San Juan Car Company back then. But this is an example of the two-part mold-cutting capability of the Sherline.

[reinhardtjh]

This is a pic of the tooling for the 10-6 County series fluted car sides. The brass was cut on a Sherline. The steel mold base and injection pins/ports were cut and added by the late John Parker of San Juan Car Company back then. But this is an example of the two-part mold-cutting capability of the Sherline.

Thanks Bryan. That's really helpful to see.  I don't know if I'd ever get that advanced since I'm not likely to need more than a few of anything, but you never know.

And if Bob Fingerle recommended the Model 2000, who am I to second guess?


The DRO option looks interesting.  I looked at Sherline's documents for it.  I'm not positive it could be added to a CRC mill though.  I have to read through the installation instructions again to get it all in my head.  Looks like if it does work, it could be added afterwards fairly easily.

[Sokramiketes]

I also had bought Bob-Cad software, which converted STL files generated by SolidWorks (and other 3D modeling programs) into G-code, which then was utilized by FlashCut to operate the Sherline.  I've since abandoned the Bob-Cad interface, as writing G-code is not difficult and I can write it manually more efficiently than the Bob-Cad was generating.

Now I understand more why you were trying to get center points for each rivet out of SW... are you using any tricks to generate portions of the code, or writing all the tool paths for a pocket strictly by keyboard?

[Andrew Hutchinson]

With a turret head the Sherline 2000 mill could be considered overkill and it is less rigid than the other models Sherline sells but it does allow the user to fine tune the Z axis as needed. No question that the Taig is a more rigid mill, whether that matters depends on the scope of the projects intended. I don't think it will given reinhardtjh's stated interests. The pictures posted by Bryan confirm what can be done with the Sherline machine. Last year I  picked up a used 2000/A2Z servo mill. It came with DeskCNC sold through IM Service. It's been a vertical learning curve for me as I am a confirmed luddite (just got my first cellular phone last week) but it is pretty cool when everything works out. I never ran it with the stock screws but I was told they were troublesome in comparison to the A2Z package that replaced the originals.

For me personally the biggest question is what to do about CAD/CAM/CNC software when you're trying to run as fast as possible away from MS Windows. Getting three out of three is difficult for me on Linux with my lack of computing skill. Bryan's nod to hand-bombing code speaks to his skill set but that gets really tricky around organic shapes and ball ended cutters. I know it will get better with time as my abilities  improve but at the moment it is a bit frustrating.

Not totally on topic, but this guy's blog might be of interest to some:

 http://cnc-for-model-engineers.blogspot.ca/

Andrew Hutchinson