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Posts from — April 2014

Stepper Motors: Improving Performance – The Chopper Drive, Rail Voltage vs. Motor Inductance, Wiring Configurations

Excellent Resource on why one would use an 80V DC Power Supply with a 5V DC Stepper Motor, and the most common bipolar motor wiring configurations.

Selene – Stepper Motor Voltages Explained

Selene – Stepper Motor Wiring Configurations

 

April 23, 2014   Comments Off on Stepper Motors: Improving Performance – The Chopper Drive, Rail Voltage vs. Motor Inductance, Wiring Configurations

Excellent Post of the Costs of Supporting Hobby Level CNC and A Guide to CNC (from a moldmaking perspective)

April 23, 2014   Comments Off on Excellent Post of the Costs of Supporting Hobby Level CNC and A Guide to CNC (from a moldmaking perspective)

An Excellent Overview on the Scope of CNC Machining Toolpath (Design, CAD Drawing, CAM generating, Controller)

I was researching general hobby level CAD/CAM, and out popped this blog post. Having spent many an hour doing research on the subject, it struck me this is as good or better a write up as I could do.

THMSblog on CAD/CAM

 

 

April 23, 2014   Comments Off on An Excellent Overview on the Scope of CNC Machining Toolpath (Design, CAD Drawing, CAM generating, Controller)

General CNC Wood/Metal/Plastic/Composites Router Bit Information

Several decent links:

– This from the Fab Academy: Router Bit Basics

– Decent basic description of the material types used in the above: Onsrud Cutter Tools (toolssxp.com)

– AmanaTool.com’s description of various cutters: CNC Router Bits

 

Cutting MDF/Plywood/Laminates:

 – MDF is abrasive due to glue content and should be cut with at least carbide cutters. HSS will die very quickly with MDF, plywood and other similar materials.

  – Using a Compression Endmill is best on laminates. It cuts both up and down, which leaves both surfaces clean, but is designed so that it is done in ONE pass. If the machine cannot manage a single pass, another style of bit needs to be used.

– Next best is straight flute cutters. Upcutting alone (for good-one-side plywood would leave the bottom side clean, much better for clearing chips, but will mar the top surface and require extra cleaning up. In addition, an upcutting spiral bit can also (with aggressive feeds) actually pull the work material off the table if it is not secured well enough.

– A downcutting bit would save the top of the material, but risks re-cutting the chips and damaging the lower side.

– According to some sources, Plywood likes to splinter when cutting in climb milling, so conventional is better. Having said that, I have seen representatives state that one should do a test cut, and see which is a cleaner cut (the waste material or non-waste), and adjust the cutting method to accommodate that. In my own recent use, I had a better finish in climb (Home Depot 1/2 inch SPF plywood; had lots of voids). This site states Climb Milling is better with wood. *shrug*.

– It is said that high speed steel with cut smoother than carbide, but as with anything, that depends on feed rates, condition and type of tool; I have used straight flute carbide and had (to me) acceptable finish on plywood (conventional worked better with that bit, as climb caused splintering)

– Several sources state the same methodology should be used in wood as metal; use a rouging tool to remove the bulk of the material at a high rate of speed, and use a finishing tool to complete the job. This will extend the life of both tools, but will require more than one pass, and possibly more than one Gcode session.

April 22, 2014   Comments Off on General CNC Wood/Metal/Plastic/Composites Router Bit Information

Clamping Tips

Found these reading various forums, and thought they were significant enough to keep track of. In no particular order or sort:

– Spherical Clamping Washers: Clamp nut or cap screw is evenly loaded and clamping pressure is uniform, and square to the machine table.

– Insert newspaper between the mill table and the work-piece. It’s said to significantly increase the frictional resistance of work-piece shifting.

April 20, 2014   Comments Off on Clamping Tips

Mini-Mill

Having worked with lathes in the past (both metal and wood), and having bought, used and then sold the TAIG lathe to my former workplace (they have lovely CNC turning machines, but they can’t work any stock less than 1″. I made the case, they agreed, and it paid for itself quite well) I realized that while a lathe is very important, it can only do round things (imagine that)!

In actuality, the TAIG was a little undersized for the usages I had in mind, and the former company wouldn’t hear of anything more expensive (no matter the rationale). A case could be made for a mini-mill as well (there were no manual mills, only the Mazak and Haas Vertical Machining Centres), but I knew they wouldn’t go for it.

 

As such, since I’d already decided I wanted (needed? it’s so vague) one, I started research into various units.

That research showed the following paths:

Micro-Mills (Printed Circuit and Jewelry suitable units; TAIG, Sherline)

Taig Tools Machines

Sherline Machines

– I’d decided these were too small for my likely uses; first rule of machine tools: get as BIG a working area as you can imagine needing realistically.  These were accurate, but not big on envelope.

– Both of these machines are NOT new, have loyal followings, and plenty of experience. I had no complaints about the TAIG lathe, and the parts can be interchanged. As a bonus, they could be purchased in “turnkey” CNC configurations!

– When looking at work envelopes, for the price, I decided I wanted more envelope and power.

Mini-Mills (Re-branded Chinese units of varied quality) (I say re-branded due to their being only two manufacturers at the time, and several machines of differing name)

– Here’s where I learned the term “Snowflake Mill” also known as “no two alike”. I saw them represented all over the planet; Europe, Australia, USA.

US Re-Worked Mini Mills (ones made to a US manufacturer’s specifications- Re-worked Chinese machines, or ones built to US company specifications

– At the time of my research, one company making these, Little Machine Shop (rebranded SEIG SX2, SX1, SX3 built to their specifications)

Mini-Mills (European Brands)

– Reported excellent (example: the Proxxon brand) but really not economical to obtain in Canada.

 Proxxon Mills

Macro Mills (IH Clones, the X/SX 3 series, RF-45 and clones, Refurbished Bridgeport machines)

MD001 Milling Machine

Craftex Brand Milling Machines

– These are what I was being steered towards by professional machinists, but the costs were a bit high for my starter position ($3000 and up), they were very heavy/took up a lot of room.

Entry Level Manual/CNC-Ready/CNC Equipped (LMS 3501, Tormach 770/1100, Novakon Torus/Pulsar, etc.)

Novakon Machines

The droolworthy Tormach Machines

LMS 3501 CNC Machine

– Fantastic machines, ones a professional would use, or a serious hobbiest. However, prices, mass, work envelope, and power requirements were all equally impressive.

– Don’t misunderstand; Rigidity, and therefore weight, are critical the larger the workpieces to be handled/amount of material removed/speed of operations. You want a bigger work area? That costs, in money, material and weight.

 

I was looking for a mill of moderate size, at the upper limit of one man portability, reasonable work area, reasonable accuracy (hobbyest), well supported/understood and potentially upgrade-able to CNC.

 

With those in mind, plus much research from those in the know, I decided on the Little Machine Shop LMS 3960 Mini-Mill. This variant comes with a solid column, which increases the rigidity, prevents it from being knocked out of tram when an oops occurs, and most machine operations can be done without the tilting column.

This image is what it looked like after the addition of an Air Spring modification; as of this writing (19th Apr 2014), they sell this included as the 3990 model. The Air Spring modification solves some of the head nod issue, give some extra travel, and carries the head weight MUCH better than the torsional spring normally mounted.

 

480.3990

As a humorous aside, not long after I purchased it, I could have paid for the mill with a job I was offered, if only the head would tilt (would save the person from purchasing a trunnion table)…

 

Here’s an example of a tilting model (the LMS 3900, I believe) with a CNC kit on it

xcqKpfKpRHGrKCcY

April 20, 2014   Comments Off on Mini-Mill

Extrusion Head for CNC

Well, Why not? You’ve most of the machine there!

Well, some people believe you’ll have accelerated wear on expensive ballscrews in localized areas, and the speeds will never approach those of a lightweight machine (throwing all that heavy cast iron Mini-Mill table/High Speed Spindle Gantry Style mount around…)

 

Links

Rockcliff Machines – Spyder 3D print Head Attachment

April 20, 2014   Comments Off on Extrusion Head for CNC

Drag Knife, Tangential Knife

Oooh! Sharp Objects! *coughs*

A Drag Knife. Name is fairly descriptive of its purpose. The Spindle drags the knife behind it, cutting through the surface material. The material has to be fairly thin (think X-Acto style blades) in order for this to work properly (having said that, some styles take a utility/boxcutter blade)

 

Thicker material you say? Plunge serrations needed? Enter the Tangential Knife.

Instead of freely rotating, a much stouter knife blade is held by a stepper motor, which is motion controlled to drag the blade through heavier materials.

Links

WidgetWorks Drag Knife (for Vinyl)

Tormach’s Spring Loaded CNC Drag Knife (Carbide Blade, made by WidgetWorks 🙂 )

Rockcliff Machine – Drag Knife (three carbide blades, each of differing angle)

Donek Tools Drag Knife

VIDEO – Platform CNC, Making and Using a Drag Knife (YouTube)

www.damencnc.com – Tangential Knife (NOT inexpensive)

Rockcliff Machines Project – Stepper Driven Tangential Knife

 

 

April 20, 2014   Comments Off on Drag Knife, Tangential Knife

CNC Plotting

Let’s re-invent the wheel, while we’re at it!

When I was a kid, plotters were the first printers I was exposed to (computer wise). I was in awe of them.

Well, I’ve got this CNC machine, just sitting around…

Two types of tools I’ve found for this job:

– Drag Pens

– Spring Loaded Pens

The drag pens, due to the build angle, automatically swivel to follow the movement of the spindle, and are (as far as I can tell) used on large, flat surfaces. The Spring Loaded Pens, on the other hand, have flexible Z axis movement under either a controlled weight or spring pressure, allowing the pen to move over irregular surfaces (cylinders, rough work).

Like the Spring Engravers, a mix of people building their own, and purchasing. One turn-off for me on the spring loaded I found for purchase is you are locked into their pens. Having said that, the company has been around for eight years or so, so not exactly a huge risk.

The best DIY spring loaded takes a simple click pen, and modifies it! Cost? The click pen *grin*

 

Links

WidgetWorks Coilover Pen Holder, Thick Line (they nominally stock a thin line as well, but seem to be out at the moment)

Shopbot Forum Posting on the WidgetWorks unit

RockcliffMachine Drag Pen – Video of it HERE

 

The aforementioned Click Pen DIY

DIY Coil Over Pen for Plotting, by Grunblau Design (makers of my drool worthy next acquisition: Platform CNC)

Solsylva.com – DIY Pen Holders (Shows how to use a wooden block and dowel for a drag pen, and a compass, good thinking)

Floating Weight Style DIY for Sharpie Markers (Practical Machinist) – (Zip file with drawing at the bottom)

 

Example of (assumed) overkill (I think this was meant for a gantry type CNC): Artsoft Link to Forum Post, and in the same thread, the aforementioned Click Pen Modification

 

PIC 1_HCIR PIC 2_HCIR

 

April 20, 2014   Comments Off on CNC Plotting

Engraving – Drag, Rotary, Burnishing, Laser

It’s the same thing all over. Got a hammer? Start looking for nails…

Hey! I’ve a CNC mill! What can I do with it? *shakes head in shame*.

Engraving. CNC. Cool.

CNC engraving requires (what a shock) research.

Rotary Engraving

This involves having a high speed cutter remove material from a surface (speeds in the 10 000 RPM range and above; hello High Speed Spindle project!) Naturally, the feeds and speeds are dependent on tool geometry and material being worked. It can work on metal, wood, plastics, generally without worries. The tool bit can be held rigid, in a spring loaded holder (for uneven surfaces) or a nose collar.

Example Spring Loaded Holder and Engraving Bits

805243SONY DSC

Drag Engraving

This involves use of a diamond or carbide tipped tool to be dragged across the surface to be marked. I understand it’s typically slower than a rotary method, but can have very good results on softer materials.

Burnishing

Similar tools are used, either Carbide or Diamond, and the tool is spun at a high rate of speed, simultaneously removing a surface layer of material and polishing the underlying. This is used to engrave glass, I’m told. Have to try it out!

Laser Engraving

Can be done on a variety of materials, and apparently has overtaken all other forms in engraving shops as a primary tool. However, it can generate noxious fumes from the material being worked, apparently has issues with certain colors and types of metals, cannot be done all surface treatments, and can require a stand along machine (unless you make a DIY laser attachment for your CNC mill, hmm).

Links

Engravers Journal (2009) Rotary is still in –  Very informative article on the above methods

Antares, Inc – Makers of fine engraving tools, AND very informative factsheets

Antares, Inc – on Burnishing

2Linc.com – CNCZone’s multiple mention for spring loaded engraving (for purchase, not DIY)

WidgetWorks highly regarded Drag Engraver (they have both 1/4″ and 1/2″ shanks; 1/4″ linked)

MrRace’s manufactured take on such

Dezign Shack’s DIY Version (there are several links out there for such)

Tormach Drag Engraver (I hear very good things about Tormach in general)

Zen Toolworks on CNCZone, discussing a home made variant

The following links are straying a bit away from Mini-Mill CNC, but good for the high end. Here’s a ahem, low end example: Fun of DIY – Raspberry Pi DVD Laser

TweakieCNC – LASERS!

Build Log – Home Laser

Tweakie CNC – Low Powered Laser

 

 

 

April 19, 2014   Comments Off on Engraving – Drag, Rotary, Burnishing, Laser