CNC Milling

Setup of Shop to Final Product


Sherline 8580 NexGen

Copyright © 1988-2021 by Abbott Analytical Products. All Rights Reserved.


Purpose of Document

This document traces the movement of one user down the learning curve. That movement centers on increasingly complex and challenging projects. It forms a book-of-knowledge regarding the CAD/CAM/CNC process. It serves as a bread-crumb pathway for the author. It is presented without warranty.

Constructive, helpful feedback is welcomed.

Lessons Learned

On the Positive Side

1. Projects:

The Sherline CNC products and available OpenSource make it possible to enter the CAD/CAM/CNC environment with a minimal expenditure of funds. Coupled with over ten years of direct experience with Linux/Ubuntu and software engineering it was possible to successfully complete an array of increasingly more complex and challenging projects during the first calendar year of ownership.

Brass Nameplate: Early prototype.

Heart Shape Message Early prototype run.

Box/Lid: Implemented pockets and pads.

Through-Wire Fishing Lure: Improved Lures: Draft/Part: Incorporated Revolving about Axis, Through-Wire Channels.

Fishing Lure Mobile: Inexpensive, Simple, Quick Gift for Fishing Cabin.

Projects Lost In The Woods

Simple Fishing Lure: Prototype executed in scrap wood

Waterline Fishing Lure: Extending original fish lure design.

Bezier Surface Fishing Lure: Increasing complexity of surface/shape. Terminated

Using Bezier Surface for Fishing Lure: Implemented via Draft/Sketch/Part to saw dust.

Realistic Fishing Lure: Simple/Elegant Lures: Draft/Part: Lofting, Mirror, Rotate to saw dust.

2. Related Side Projects:

2.1> Fixtures:
To support several of the projects shown above, aluminum hold down strap fixturing was created. Two types: slotted and spaced holes were milled. Both are index near the "first hole" using three "dibbits". The slotted version proved to be more useful. The raw aluminum strap stock was purchased at a bigbox store. But a better local source (a scrap metal dealer) of raw stock was found . The specific dealer, JD Rcyclers in Durham, had a great selection and good prices for aluminum, steel, and brass. Several pieces of scrap aluminum and steel were found to be "milled" to tolerances well beyond the user's current skill level. These pieces have been helpful in fixturing.

2.2> Spindle Tachometer:
A spindle tachometer was developed. The tachometer was composed of an Arduino, a light/grey sensor, wire cabling between the Arduino/sensor/PC-USB, and a a modified mill holder . The driving program was loaded to the Arduino before going to the mill. A mill holder was masked/modified to provide a clear breakpoint between the white and black demarcation. Then the modified end mill was installed (less any end mill bit) on the spindle per normal. The sensor was then placed as near as feasible and parallel to the "white" strip on the modified end mill holder. The Arduino was powered. At that point a GtkTerm was invoked and configured to "sync" with the Arduino tachometer. Once the GtkTerm - tachometer were communicating, the mill spindle could be measured for various rotary settings.

The device helped to verify specific rpm reference point on spindle rotary speed switch. Once a set reference rpm-s was visually set various rpms relative it were set. An old Starrett RPM and stop watch provided a rough validated check.

2.3> Axis Movement Controllers:
2.4> 3D probe experience:
2.5> Electronic Touch Pad:
A yellow/green led touch pad was created. It uses the PC 25D Parallel port as a power source supporting software was acquired from AskJerry Frankenlab CNC #20 Probes. The schematic is based upon the concept of inverting a digial signal. The actual electronic design was based upon the schematic shown and parts on hand at the shop. The other twist was the usage of the PC 25D Parallel to provide 5VDC and ground. A user can invest a great deal of time and effort searching the Internet, installing the touch pad with new LinuxCNC pyVCP buttons. But under a working approach, the user can invoke the touchplate.ngc from LinuxCNC just like any other and "monitor" the yellow-green transition at the instant of touch. Bottom-line a new user's time might be better used making saw dust/swarf. At a beginner's skill level and modest project complexity, this device has not yet been helpful.

3. Shop Lessons:

General shopwork/technique continues to improve.

4. Focus on Doing:

Focus on making sawdust and metal swarf rather than puttering around with various accessories. Otherwise adequate CAD/CAM/CNC/skills can not be developed.

On the Negative Side

  1. Sherline Nex Gen CNC 8580 was a reality purchase. The first choice was Tormach 770. That is a real CNC. Visits to owners of Tomach 770 were very revealing. The size, footprint, power, and cost were the adverse side of the Tormach coin.

  2. The Sherline CNC implementation is not as complete as it should be.

II Lessons Learned Focused on Sherline 8580 CNC Milling:

1> The Sherline CNC is blind, dumb, and lame. But for the price it works well. Various project designs have moved from conception/CAD to gcode/CAM actual CNC mill runs. The various projects were executed in in balsa wood, soft pine, plexiglass, aluminum, and thin sheet brass The Sherline cuts were executed as specified in the design. Minor latency issues infrequently arose. But not to an annoyance level.
1.1> The specific designs executed to a suitable level of repeatability.
1.2> Milling operations with multiple tooling changes were a challenge. One operation had three tooling changes. This three tool milling process was accomplished by breaking the milling process into three separate gcode programs with three separate the tooling height settings performed manualy.
1.3> Acquiring tool height, tool change-overs during the cutting process, and usage of tool setters on the Sherline was challenging. A good, repeatable mill tool height process finally evolved.
1.3.1> Reached a comfort level using 1-2-3 mill blocks to set the Z axis to 1 inch above the work piece. That point will serve as the "zero" for the tool measurement.
1.3.2> Evolved a workable technique for setting tool heights. That technique used a height gauge such as the Wixwy Digital Height Gauge to measure the distance from zero" to the contact edge along the bottom of the spindle' headstock.
1.4> Moving a design from CAD to pyCAM/HeeksCNC/FreeCAD to produces gcode for the Sherline CNC mill requires only a minimum of actual adaption to perform suitably.
1.4.1> FreeCAD permits preambles and postambles. This can be propagated across projects. Setting-up similar preamble/postambles was not attempted in pyCAM or HeeksCNC.
1.4.2> A user can employ gcode user defined variables and o-codes flow control syntax. This allows looping, scaling, etc. within the NGC.
1.5> Sherline ships a largely useless set of software.
1.5.1> The Ubuntu operating system that Sherline ships is downlevel and beyond the long term support/expiration date. DO NOT Upgrade Ubuntu without a full image backup and rigorous testing of OS and critical applications!!!!! There are plenty of pathways to negotiate this issue. Just be cautious.
1.5.2> Sherline ships its NexGen 8580 with the operating system, LinuxCNC, and its working machines already installed. But there is no "Installation Disk" or pathway to an installation ISO file that can located within the Sherline Web pages. Their "CNC Instructions" specifically identifies this missing "Installation Disk" as a critical component required to install or reinstall the CNC software bundle. Sherline's does ship an "Instructions & Utilities" CD with the 8580. But it contains MS Windows software that probably is useless under the Ubuntu operating system unless the user has WINE installed.
1.5.3> But the user can rectified the poor state of the shipped software.> Employ a tool such as Clonezilla to make/restore system images. The Clonezilla tool can be downloaded from the site. For the Sherline 8580 NexGen you will need the Clonezilla i686-pae 32 bit version. Do backups at least monthly. In this manner, even without the Sherline "Installation Disk" you can rebuild your machine to the exact same state of the last system image.> Sherline ships its CNC with the "mini" version of the LinuxCNC GUI (graphical user interface). The "mini" version of CNC is a largely useless and highly restricted version of LinuxCNC.> Do not change LinuxCNC GUI until a full backup of the "linuxcnc" folder is secured!!!The typical user should consider employing the improved, fuller featured, extend-able LinuxCNC GUI "axis" version.> Do not change the configurations (*.ini, *.var, *. tbl, *.hal, xml, pref) before creating backup copies.> Do not change the *.hal files before creating backup copies. Features like a physical, working Emergency Stop switch and Probe (both available with the DPP Extender box) will need to have tweaks made to *.hal files. These changes added a whole new dimension to the mill. The Home and Limit switches have not yet been added. But those additions will also require *.hal files changes.> Depending on the user's comfort level and body of knowledge, the Internet provides a fantastic resource for increasing the "usefulness" of the Sherline CNC. The Internet has at least three "nice" software add-ons for the LinuxCNC "axis" version that greatly enhance the "probe" experience and and usefulness.> Sherline provides no upgrade path for OS, LinuxCNC, or its CNC machines. What you receive is what you have for the life of your CNC. You can work around this by staying abreast of Ubuntu and LinuxCNC upgrades. Test your new installs on a simulator and make plenty of system image backups. Take a couple days to do your image backups, installs, test, and verifications. Do not rush.
1.5.4> The poor state of Sherline's software is not a major issue. One can voice the opinion that the poor state is balanced with the risk involved. If the software fails or behaves abnormally, the loss is probably limited to a couple of thousand dollars or a few hours of time. The Sherline CNC is a hobby/prototype/entry-level machine. It is like a Smart Phone app you buy for $1.99. "You get what you pay for." If you want 911 service when you need it. Do not depend upon the $1.99 app.
1.5.5> Sherline software support is limited to FAQ and a poor set of web pages. Do not expect to find the answer to any challenging question. Try google-ing Ubuntu and LinuxCNC specific question instead. From google-ing and the initial Sherline 8580 NexGen mill configuration setups, you should be able to manually rebuild a working system.
1.6> Prior to purchasing local CNC owners (Tormach 770 and Sherline 5800 with DRO) were visited and polled about their experience. CNC users indicated work piece hold-down and end-mill employment had been their second and third biggest challenges to far. (Tool height/tool table is the biggest.)
1.6.1> Tooling plates and holding steps are useful in making solid progress down the learning curve. The the shop vises sold by the two CNC vendors were reported (and confirmed for Sherline's) as also being useful in the initial learning phase.
1.6.2> The scrap dealers and hardware stores have been good sources for preliminary projects (raw stock and fasteners). Shelf sections and container stores have been good Plexiglas sources for small quantities. Purchasing small, store-able quantities of shelving makes stock handling easier.
1.6.3> There are never enough end-mill holders and a couple of blanks might also be helpful.
1.6.4> A benchtop bandsaw with a table miter handles 60-80% of stock material gross cutting so far.
1.6.5> A more a aggressive power bandsaw has proven handy for rough cutting aluminim and steel. A local demonstration with a base of the SWAG table with a foot switch and miter was awe inspiring. They can be purchased separately or from SWAG.
1.6.7> A small benchtop drill press has provided flexibility and utility for preparing tooling fixtures and stock hold down.
1.6.8> Searh pawnshops and craig's list for equipment opportunities.

2> Mounting tooling:
2.1>Collet/Chucks: The 3/4-16 nut technique for removing drill collet/chucks works well.
2.1.1> A set of suitable 3/4-16 slim nuts purchased at a local nuts and bolts store, Weller on Alwin Court just East of Atlantic Avenue in Raleigh. They also have an excellent supply of fastener hardware.
2.1.2> The technique was employed for removing the DPP probe and the extended length router bit (see wooden box/lid T19). The technique worked exactly as demonstrated by other users.
2.1.3> Sherline sells a similar product to the nut that is round and uses Tommie Bars.
2.1.4> For the collet/chuck retaining bolt, a small block of wood with a drilled hole is used in concert with light taps from a jeweler's brass hammer. Place the block over the head of the bolt such that the drill hole cups the bolt head. Then place a small piece of scrap wood on the mill plate/table such that this scrap protects where the bit will fall. Then lightly tap the block.
2.2> End Mills:
2.2.1> Spraying lightly (Ballistol Multi-Purpose) the interior threads of the End Mill Holders prior mounting has been very helpful.
2.2.2> When a stuck End Mill Holder needs a "break" to loosen,> Place a bounce pad/wood scrap directly under the Spindle housing. Then remove the end mill bit from the End Mill Holder.
2.2.2.> Place a large bolt like item parallel to the spindle shaft such that it is adjacent to the spindle housing. That bolt then becomes an excellent pry/force point for the spindle's Tommie bar.> Then place a Tommie Bar through "both holes" of the Spindle's Head Stock. Once inserted rotate the Spindle's HeadStock Tommie bar toward the pry/force point until they "touch".> Insert a bolt with washer all the way through the End Mill Holder and lock with a washer and nut.> Shim with brass stock as deemed needed to protect surfaces of housing and/or End Mill Holder.> Secure and tighten the clamping jaws of an adjustable wrench around the End Mill Holder's Bolt/Nut.> From looking down from above the spindle rotate by pulling the wrench clockwise toward the pry/force point.> Prior to using this leverage scheme and the Ballistol lubrication bending Tommie bars was a common event.
2.3> Spindle 3/4-16NF Maintenance:
2.3.1> Hanson/Iwrin manufacures 3/4-16NF die part number 6860ZR die for re-threading which might prove useful in maintaining a servicable external thread on the spindle. The die can be purchased for any hardware store or big box lumber company.
2.3.2> Follow guidance of lubrication of the spindle thread with Ballistol, sequence of half turn/back-off a quarter turn, inspect/test with an end mill holder. Avoid using anything more than channel locks and a Tommie bar. The mill's spindle is ready when the end mill holder can be installed with modest hand pressure before locking down with Tommie bars at teh sholders of the spindle.

3> To make real progress the serious user must have a good knowledge of Linux/Ubuntu/Debian and LinuxCNC.
3.1> It seems the Sherline intellectual property is hidden.
3.1.1> The distribution disk is mis-labeled or appears to just be a "brochure" for Sherline. But it is really a hidden restore disk. If your system crashes and needs a rebuild, you need that knowledge.
3.1.2> The actual Sherline CNC distribution is probably designed to be extremely limited. To increase usefulness and to reach a comfortable level of user friendliness and productivity additional third party software should be installed. Ubuntu Software Center, Calculator, System Monitor, Shutter, Meld, Geany, Disk Utilities, pyCAM, heeksCNC, FreeCAD, OpenSCAD, Blender, Veusz, Clonezilla, and Nautlis are strongly recommended OpenSource applicaitons that a serious user should consider installing
3.1.3> During early development Sherline employed a LinuxCNC setup wizard, stepconf. The stepconf wizard matches the physical hardware with the virtual software elements of LinuxCNC. Masking that complexity is what a users pays Sherlien to do. But the Sherline CNC folder is a menagerie of configuration files that some how work properly once the "ini" file is adjusted for the user's specific lathe or mill. Do not mess around with the LinuxCNC stepconf wizard until a full backup of the exisiting linuxcnc folder is secured. Only then, instead of creating a new stepconf, try modifying an existing one by selecting it and renaming the "new" machine stepconf file. That will create a separate, independent stepconf, separate launch icon, and a separate folder specifically for the "new" machine.
3.2> Sherline did not provide an installation CD or a downloadable installation ISO with their CNC mill bundles like the 8580 shipped during the end of October 2017.
3.2.1> When asked, their technical support suggested that a request be made to Sherline Sales. Sherline Sales response to the request was quick. The installation CD that was received contained a Live OS for installing Ubuntut 12.04 LTS and LinuxCNC v2.6. These are both down level and need of updating.
3.2.2> The installation CD has no instructions. But If one is familiar with Ubuntu the install can be achieved with a minimum of trial and error.
3.2.3> My original CNC 8580 was shipped during the transition period when Sherline was cutting-over from Debian 7.11 to Ubuntu 12.04. There is no easy upgrade path in this instance. So all prior user content that existed in Debian environment had to be manually migrated to Ubuntu -or- lost.
3.2.4> The installation process once the decision to proceed was made was straight forward but tedious. Below is a description of the resulting upgrade:
1> Simulator: IBM Think Center Model 8114-D1U with 1T Drive.
2> CNC PC/Controller: ARS with upgraded 1T Drive in a standalone role.
3> Contents of both machines:
  • Ubuntu 12.04
  • LinuxCNC 2.8
  • Geany
  • Meld
  • Shutter
  • Qjoypad and PyPar2 for logitech GamePad F310
  • XFBurn
  • System Monitor Profiler
  • 3.2.5> Notes of interest:> Upgrading to 2.8 Pre forces change to each *.ini of prior versions -or- results in LinuxCNC error message. But the upgrade from 2.6 to 2.7 if desired is seamless.> Notes and images regarding the upgrade are available in a zip file. The contents of that zip file are shown in the image shown below.> The Abbott Help Desk can be contacted clicking here. Personal telephonic help or remote desktop support can be arranged by scheduling though the Help Desk. Extended help/support cost may be chargeable to the requester.
    4> The Sherline 8580 CNC does have a few issues to consider.
    4.1> The Sherline CNC mill has no direct control of the spindle's speed or direction.
    4.1.1> This missing primary CNC feature is well camouflaged in the sales and marketing material.
    4.1.2> A feasible work-around appears to be available. But experimenting with this aspect will have to wait until the equipment is outside of its warranty period. With LinuxCNC controlling the specific parallel connector pins and using a similar approach the DPP took with their Extender box, a level of spindle control should be obtainable.
    4.2> Mill oilers are a bit weak and need constant, regular monitoring
    4.2.1> The XY saddle oiler works well. But to check and refill requires that the mill's tooling table must be loosened and moved. May be an extended plug cap for the tooling table is the answer. An extended plug would allow access to the XY saddle fill plug. But it would be messy checking and filling.
    4.2.2> The Z oiler requires constant monitoring, refilling, and cleaning because it leaks down the vertical column. That means that the Z axis drops plenty of oil on the tooling plate. Keep paper towels handy.
    4.3> Latency issues arose, but were infrequent enough to not risk jeopardizing projects or time to investigate.
    4.4> Backlash issues have been anticipate but not experienced.
    5> The typical user should find that the effort and potential of the Sherline 8580 NexGen are worth the expense.
    5.1> The mill is highly modular and portable.
    5.1.1> The mill disassembles into bundles that can be carried from my lab to my shop. The movement involves a flight of stairs.
    5.1.2> The modularity of the Sherline CNC products gives them plenty of flexibility in meeting a user's changing interest, environment, and opportunities.
    5.2> The mill is designed with a large portion of standard or parts that are manuafacture-able.
    5.2.1> With the high modularity and portability the brass tube bearing that protects the y axis leadscrew and mounting post are vulnerable. But suitable brass tubing was found locally and adapted to replace the bent piece.
    5.2.1> The Sherline mills use many standard nuts, bolts, router bits, etc. that are readily available in the bigbox sotres, some hardware stores, better blade/router shops, and Internet shopping.

    Please send comments or questions using e-mail. (Last update: January 11, 2021 tar)