2 Sided Machining a Native American Flute

Our lofty goal was to have a precision blank that could be made on our CNC machine that could then be personalized on the lathe or however the student saw fit.  The problem with the blanks available is that they are fairly expensive, not customizable and the precision I was most interested in is the hole placement.  Blanks available are not already drilled for holes.  We were not aiming for a finished flute, but I wanted a proof of concept that the Slow air chamber and flute parts work, so we designed a working prototype that is actually a finished flute.  It would be easier to test a finished product.  The first test worked perfectly and the sound quality is superb, but it is royally out of tune and we are working as a class to devise a plan to create a prototype that we can move and individually tune specific holes.  With this prototype we will be able to plan each individual note and customize each student’s flute to the desired key and scale desired.

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CNC Star Wars carving the Millennium Falcon

This entire project was designed to test our ability to accurately machine 2 sides of a part.  Accurately aligning the second side to match up to the first side boggled my mind and I tended to steer students away from this.  We settled on the Millennium Falcon from Star Wars.  It has good detail on 2 sides, but we wouldn’t be able to get the detail on the edge of it.  Since most of  the detail is on the top and bottom, this seemed acceptable.  We had to make a new CNC table that easily and accurately aligns to the actual bed of the machine and has a home that can be aligned to without thought.  Here is a link to the details of the table we made.

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New CNC Routing Table

We have always loved our CNC vacuum table that came with our Multicam machine.  We have t-slots on 2 of our other machines and dread every part of holding down parts.  That was until we created our own t-slot hold downs (info available on our website here).  Since the use of these holdowns, we have not only accepted t-slots as a viable option, but have found that they offer advantages in certain situations.  The problem I have with most hold downs is the fact that they cover up some of the cutting surface.  Ours do not.

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From Solidworks to Vectric Aspire to CNC

We have known about designing boxes and cabinets in Solidworks and then cut the parts out on the CNC for some time, but we hadn’t made it happen yet.   I love this system because it takes the best of both softwares and helps create awesome work.  Solidworks handles the Assemblies so well and Vectric Aspire handles the vectors and post-processing for CNC so well.   Continue reading

T-slot CNC table hold downs

 

Holding things down on a CNC can be the most frustrating part of the entire process.  Luckily for us our main machine has a vacuum table and we use window sealant foam for the back of the wood.  This works amazingly well for parts that are not cut through.  We have had to get creative for parts that need cutting all the way through.  Our large machine has an MDF table that has T-Slots cut into it and it requires hold downs.  I have seen all sorts of solutions for this, but few solved my main concern of wanting to carve on the entire board unhindered by the hold downs.

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Depth of a V-Carve in Aspire

The V-Carve will likely be your first CNC created file.  The software does a great deal of the work and creates beautiful carves from fairly complicated designs.  Once your design is in vector form, you are ready to create a V-Carve toolpath.  It is important to understand what the software is doing for you and how it decides the depths of cut that were made.  In the simplest mathematical terms:

The depth of cut is a function of the distance between vectors and angle of chosen V-Bit.

Lets break that down a bit…

This design is what I am bringing into aspire.  This could be a font, design, scan, shapes, etc.

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Plasma cutting setup and speeds (and other data).

Take this data over with you to the Hypertherm Powermax 65 Plasma cutter.  This works with the CNC and the hand torch.  I got this from the Hypertherm Powermax 65 manual (click for the actual manual).  Some of the data is not needed for the hand torch, but needs to be inputed into the CNC controller.

1. You will need to choose your setup of Shielded (for us this is Hand) or UnShielded (for us this is CNC).

2. Choose your amperage 45 or 65 (Mostly you will do 65Amps) or if you want to use FineCut.

3. Setup the torch with the desired consumables and choose your chart link below for access to the speeds, volts height pierce delay and pierce height.

4. Manage your Kerf thickness with this chart

65 amps by hand (this is your default setup for hand plasma)

65 amp shielded setup

45 amps by hand

45 amp  shielded setup

FineCut by hand or CNC

fine cut setup

65 amps on the CNC (this is your default setup on the CNC)

65 amp unsheilded setup

45 amps on the CNC

45 unshield setup

Prepping your Vectric Aspire files for the CNC plasma

We are using Vectric Aspire for creation of vector designs and altering the vectors for quality cuts on the Torchmate.  You will be exporting a .dxf file from Aspire once done.  You will be using the torchmate software for post-processing and operating the CNC plasma

Once you have your design ready in Aspire, you need to change your vectors so that they cut right on the Plasma

Here are the issues and how you need to deal with them.

Issue #1.  The CNC plasma will cut directly on your vector lines and there is a thickness (kerf) to the cut.  The kerf thickness does vary, but we have been happy with planning for a 1/16in (.0625in) kerf.  However, you can access the real chart here.  This requires you to design things slightly larger than you need.  The offset tool in aspire has worked wonders to solve this.  We have been offsetting at about .035in depending on the requirements of the part.  For outside cuts you will need to offset to the outside.  For inside cuts you will need to offset to the inside.  We have created modeling of what the cut looks like by making a profile toolpath with a 1/16in endmill in the toolpaths tab. Another way to deal with this is to Vector design it purposefully large and grind/mill it to correct tolerances.

Screenshot 2015-04-27 10.46.06

Issue #2.  This issue is not for all cuts, but something to keep in mind.  The CNC plasma takes it’s time around corners which introduced heat to the corners of your cut.  This can be a problem if sharp precise corners are needed.  This can be solved with the Plasma loops tool.  I show the class the need for a square and this is what the toolpaths vectors look like.  As you can see the square was offset first, then the plasma loops were added.

Screenshot 2015-04-27 10.52.59

Issue #3. The plasma does not start and stop cleanly.  This means that you want the plasma to start before your part and end after your part.  These are called lead-ins.  For the above design I simply cut one of the plasma loops.  For inside circles, and any complicated designs, individual lead-ins must be added with the node editing tool.  I will create another post on dealing with just this issue as it is slightly more work.  One great feature of Aspire is the green node.  This indicates where the CNC will start cutting.  You can easily change the starting node by right clicking on desired starting node and selecting, “Make this the start node.”

Screenshot 2015-04-27 10.58.09

After this, the vector is ready for exporting as a .dxf

Screenshot 2015-04-27 10.59.44