Before we run any G-Code program, we need to tell the machine where our part zero is.
A Part Zero is simply a bunch of numbers that offset the axis to give the machine a new coordinate point to work from.

Work Offsets is one of the most basic pieces of knowledge any machinist must-have.

Let us account for all the basic coordinate systems and definitions, available in a generic CNC machine

• Machine Home and (Absolute) Machine Coordinates
• Work Offset Coordinates
• Tool Length Offsets

Machine Home and Machine Coordinates: G53

Machine Coordinates (or Absolute Coordinates) is the absolute and constant representation of the machine axis position.
These coordinates never change between Machine Restarts and must remain such. In fact, there is often no way for an operator to adjust the Absolute Machine Axis Home position.

Machine Home is simply that magical place where all Machine Coordinates should become Zero.

To Home the Machine is to start a machine operation, that will move all Axis to their soft limit position where X, Y, and Z-axis reading will be set to zero.

Homing must be done every time you restart your machine. Without it machine does not know where is the position of its table or spindle.

When homed your machine coordinates will read X=0 Y=0 and Z=0 and it is going to look like this:

The point where Machine X and Y intersect is called Table Home Position and the one where the Machine Z-axis starts from is called Spindle Home.

Now, there is no agreement between machine tool manufacturers on where the machine home should be.

One of the most versatile ways of clamping irregular -shaped parts is with use of soft jaws.

In this one I had to machine a triangular-shaped part from two sides.

It is going to be some sort of a part holding jaw for a robot.

So step one: Machine one side of the part in vise. hold on to 1/8" of stock. So make sure to cut your part on a bandsaw oversize.

Step Two: Bolt soft jaws to your vise and machine a pocket using outside contour of your part.

Be sure to relieve corners.

Step three: Clamp your part in the soft jaws and machine the second side of your part.

One important thing to consider is: this method is not very accurate. depending on the size and a shape of your part you may be able to hold it within 0.001" though.

See attached photos of the steps below.

1. Machine one side 2. Machine pocket in soft jaws 3. Clamp the part 4. Machine the second side

Whats New:

• Update Notification Added
  (when a newer version is available you will see a notification on the bottom of the HSMAdvisor window)
• Number of Flutes and Corner Radius now display on the Tool Drop-Down list

Whats Improved:

• Chamfering tools improved significantly. Almost everything has been redone and works very solid.
• High Feed Mills Tool Display has been changed and internal model has been improved.
  Tip Diameter now specifies the maximum Diameter of the mill.
• A typo has been fixed in the material list. Now It displays 15-5 Stainless steel instead of 15-8

Here is how  Update Notification looks:

Since you will be downloading this very update it will say you are up to date.
But next time i upload something, you will know right away!

Also Big changes happened to chamfering tools:

Another week - another HSMAdvisor update!

Yesterday i uploaded a newer version. You can download it already.

Major change is only one: I have finally come around to implementing a Turning surface finish calculator.

After selecting any Turning Tool type, a "Scallop" button on Comp. panel will open a separate Turning Surface Finish dialog.

As usual you can change the units of measure by clicking "Units in/mm" label in top right corner.

Default units will be the units of chipload.

Also a corner radius is needed for calculator to work.

Changing Feed per Rev. or Corner Rad. values changes Surface Finish and Scallop and vise-verse

After you click "Apply", proper feed override is applied to the final result to get the surface finish you desire.

Aside from this new feature a couple of things got improved and fixed as well

• First of all, i believe i have finally fixed a plagues that most of software running under Windows:
  Scaling issues under DPI greater than 96 were addressed and i think from this point on i should get much fewer reports about things being cropped off in wrong places.
  Still, if something looks odd on your system, please let me know!
• A new "Stickout" column was added to the Tool Drop-Down List
• Turning Cuts with mixed in/mm data saved in them used to have conversion issue.
  It has been fixed in this update.
• Also collapsing panels that used to close when another panel is being opened now operate independently.
  Many people as it turns out like ot have ALL of the panels expanded at the same time.

A few days ago one of FSwizard:PRo users questioned me over how FSwizard works.

The way SFM calculates seemed off to him.

As a result i made a quick sketch for him, that i thought i would share here.

Omar was asking me how come SFM seemed wrong for a 1" dia ball-nose cutter when making shallow depth cuts.

The sketch above shows exactly why.

On the left part we see a cutter engaged into the material to the depth equal to its corner radius.
At that depth the maximum effective diameter is achieved. So an old good RPM=4xSFM/Dia formula would apply.

But at shallower depths, effective diameter of the cutter is reduced.

At 0.1" depth of cut, effective diameter would only be around 0.6"

In fact it goes to zero at the very centre. So a higher RPM will be required to achieve the recommended cutting speed.

In the same thread i also explained how DOC/WOC balancing works.

So if you are interested - read on.

Here is the thread http://zero-divide.net/index.php?page=forums&shell_id=170&article_id=4590

In this tutorial we are going to explore different options and techniques when programming cutter movement.

Lets begin with a simple part shown in a drawing below.

Basically it is a rectangular piece 4.00x2.00
For the purpose of simplicity lets make the depth of our profile (z- dimention) 0.75"

We are going to use a 0.5" dia endmill, again because it is a very common size and is easy to do basic math with.

I took a liberty of puting locations for our part/toolpath, so it is easy to extract numbers from the drawing just by looking at it.

Notice the green rectangle. This rectangle represents the path that the center of the tool will have to take to produce the part with required dimentions.
The thing is: because endmills have certain diameter, the center of the tool must be always offset by its radius.

There are two ways of doing that.

HEM is a relatively new term.

It means High Efficiency Milling. It only became available when constant tool engagement toolpahs became almost standard on most of the CAM software.

Unlike HSM that utilizes chip thinning effect, HEM relies on much larger widths of cut and thus chip thinning does not occur. What gives it its name is much higher material removal rate that would normally be possible.

When you are machining a pocket you are most often only milling at about 50% WOC. But nevertheless you need to calculate speeds and feeds based on the fact that the very first move and every corner will be full slotting action. Which means that the whole pocket needs to be machined at lower feedrate.

HEM uses constant engagement toolpths to make sure that this never happens and that Width of Cut remains optimal. Tool never needs to make a full slot so you can ramp up the feedrate as if you were doing outside profiling.

Here is a video of a 1/2" 3 flute endmill machining a 5/8" deep pocket in aluminum at full depth. Normally this pocket would have been machined in 2 steps at 150 inches per minute.

Using Constant Tool Engagement toolpaths we can go full depth at 0.175" stepover and 275 inches per minute.

The advantage of this method is obvious- Higher Productivity.

HEM is not ideal for all cases and each application merits its own method of machining, but its always nice to know more than one way to do your job.

Lately there have been a lot of really interesting HSM topics on PracticalMachinist forums.

In one of them a guy who owns his own resharpening business posted a video of his endmill milling a block of D2 hardened to over 60 RC.
The forum topic is located here First try on D2 62Rc(video)

Here is his post so you know what we are talking about:

In the ensuing discussion i posted my own take on how and why HSM works

HSM works in many ways.

1) Reduced cutting time per edge per revolution allows it to cool down more.
2) Chip thinning allows to increase chipload (advancement per tooth per revolution)
3) Increased depth of cut combined with shallow radial positively affects deflection. Tool bends less as it is more rigid towards the tool holder.
4) Higher cutting speed actually reduces cutting forces as heat generated in the cutting zone makes it easier to shear off a layer of metal. Yet because the time of contact is so small, most of the heat is carried away with the chip.
5) Higher RPM also allows to get rid of hot chips faster thus further reducing heat transferred to the tool.
6) Higher feedrate actually reduces relative cutting speed.
7) At high axial engagements more than one flute is in contact with the workpiece at different points along the axis of the tool. This too helps combat vibrations and chatter.
8) You are using more of the tool than just its tip, so technically you can do more work with one tool before it gets dull.
9) lastly it looks cool as hell and is very impressive. Whenever we know visitors or bosses are coming we try to make sure some HSM is going on even if application does not merit that
I am not sure if the air that is moved by the endmill is doing much, but i suspect he didn't mean exactly that.

I have been asked to create a tutorial on how to work with the tool library, so here it is.

myCut Tool Database is quite a unique thing.

It not only contains all of your tools, but also each and every tool can have multiple operations or "Cuts" attached to it.

Everything is very simple.

Database contains Libraries

Libraries contain Tools

And Tools contain Cuts

Each entity behaves according to specific rules and "knows" specific kind of data.

Please read more to learn how it all works.