This February CamInstructor.com hosted a virtual webinar event mostly dedicated to advanced MasterCAM programming.

They called it the Big Event.

I myself watched at least 2 streams. But since it was a whole day thing, only missed a few.

Luckily they published all the videos on their web site:

Check it out before the link expires or they take it down!

Often times CNC programming tutorials only teach you how to create the tool-paths and not enough attention is paid on showing how to properly hold parts being machined.

At the same time efficient workholding is an art in it self and mastering it could drastically improve shop productivity and accuracy.

Without further ado let's jump into the workflow.

Step 1. Analyze the Drawing and the Model

We would have to look at the drawing, tolerances and the CAD model to develop the machining strategy.

This particular part has tight (+/- 0.001) tolerances between the features located on the top and the bottom sides. In addition to that it has a 2.5 degree draft angle on external walls.

Thus I decided to not use the soft jaws approach and machine it in a fixture. Soft jaws are generally OK for tolerances down to +/-0.001" but because of the draft angle the part would always want to pop out of the jaws.

Read More 

1. Finished Part 2. First Op: Before 2. First Op. After 3. Machined Fixture 4. Second Op: Bearing Seat 5. Third Op: Finished Part

I came across a very educational post on Practical Machinist.

The topic-starter used over-aggressive speeds and feeds for his tiny BT30-taper machine and the retention knob (a.k.a Pull Stud) snapped causing the holder to drop lower, disengage from drive lugs and mess up the spindle bore in the process.

Just in case you don't know. Retention Knob looks like this and is used to pull the tool holder in to the spindle bore, thus holding it in place:

(Retention knob is the detail on the right)

This whole article is to remind everyone the importance of proper tool holder and retention knob maintenance.

Retention Knob Tips

• Retention knobs (according to HAAS) have service life of about 6000-8000 hours.
  That means that if a tool holder is used 3 hours a day, you should replace the knob after 8 years in service.
  For smaller BT30 knobs, you should probably replace them every 4 years.
• Retention knobs should be lightly oiled or greased (if TSC is used) once a month to lubricate the draw bar.
• There should be no visible damage or rust on the knobs.
  
• Do not exceed the maximum cutting force recommended by your machine manufacturer.
  Some of those high-helix end mills create large down-force that could in certain cases cause the knob to snap!
• Also retention knobs should be torqued to manufacturer specs and the tightness should be regularly checked. Overtightened knobs may lead to taper of the tool deforming and causing uneven contact with the spindle bore.

Tool Holder Maintenance Tips

• Keep Tool Holders clean. Especially the taper part that is matching to the spindle bore.
  Wipe them with a clean cloth. 
• Do not use sand paper to clean tool holders! Soft Scotch-brite is acceptable to clean very dirty ones.
• Repair dings and notches on the taper.
  Even an aluminum chip will cause a ding, that will create a high spot around it.
• Replace worn-out tool holders with new ones.
  Signs of ageing is uneven contact with the spindle bore and fretting (blackening of taper in certain spots)
• It is also a good idea to re-grind the spindle as well when replacing the tool holders - there are lot's of services that do that for very reasonable price.
• Like wise when a new machine is purchased, only new holders and retention knobs should be used. Using old worn out holders on a new spindle bore will lead to its premature wear and even damage.

Those are all the things I could think of at the moment.
Let me know if there is anything missing.

Have a safe and productive week!

We have many helpful articles over at HSMAdvisor Help portal. But beacuse of that very reason not many website visitors actually read any of them.
It is a pitty that most advanced users will never actually visit the help section, because they already know how to operate HSMAdvisor.

And this particular one, I believe, is too useful (I just updated it to include more info) for my customers and other machinists to keep it burried in some help section that few ever read.

So here you go:

Read More 

Being a CNC Machinist/Programmer is sometimes more than simply creating a program and machining the actual part, often times it is about creating efficient and accurate fixturing.

In this little project:

I had to machine rectangular cut-outs and drill holes through an already-turned steel ring. Then I had to part each ring to 4 equal pieces.

There were about 100 such rings that worked out to 400 pieces in total.

After drilling holes on an indexer I had to machine a fixture to hold my part through 2 remaining set-ups.

First half of the fixture consists of the expanding mandrel:

The work-piece would be mounted on it like so. A hole on the side is used to properly position it:

Read More 

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

Recently I had to machine a few pieces after turning.

Because the very top of the part was supposed to be machined off, I could not clamp through the central hole like I often do.

Decided to quickly turn an expandable washer out of aluminum and a plastic spacer that would collapse a little bit under clamping pressure and allow the part to sit firmly against the base of the fixture.

I liked this method so much I am going to do the same next time I have similar part to make.

See pics below.

Later on i will try to post some more pictures of other setups I did.

All the pieces apart Fixture, spacer, expandable washer, FH screw Workpiece mounted on

There is more than one way to skin a cat! Previously i have showed how to machine multiple pieces out of a flat plate holding only on to 0.010" thick material on the outside of the part. (here) But there is more than one way to do it. Sometimes your part is so hard to hold, that using tabs or skin is the best, or even the only way of machining something. Very often, working in prototyping, I have to make only one single part and designing and producing special fixturing is also not feasible.

Here is how you can easily machine a difficult-to-hold part from both sides without using a separate fixture:

Setup: Put or part in vise. Make sure to square off at least two sides contacting the jaws for accurate positioning and minimum distortion.

Program part normally. Perform as many operations on the first side as possible.

When machining outside profile, machine to the exact depth of your part.

Here is how your part might look after completing the first OP:Read More 

Shrink fit holders and extensions often come with a big through hole.

Its primary use is to allow the shank be knoked out from he back should the tool ever snap off. It is also used to supply coolant for CTS machines.

Unfortunately said hole affects rigidity of the holder making it more likely to chatter leaving bad surface finish and badly affecting tool life.

There is however an old trick to prevent or minimize the chatter.

All you have to do is pack that hole with some thick grease.

Don't forget to cap off the oppening so that grease does not escape when the tool is spinning.

Here are several photos of surface finish before and after grease application. All cutting parameters were exactly the same in both cases.

before. deep chatter marks after. surface finish is ideal tool in extension holder showing capped hole

I recently had to machine an aluminum mold cavity.

7 inches deep. With 5 degree wall draft and a 60 thou radius going all the way down. Roughing was not an issue, but for semi-finishing and finishing i had to manufacture these two extension holders.

Both tools have runout of less than 0.001

The one for bigger 3/8 tapered ballnose cutter is shrink fit- i mounted it using torch.

The smaller tool is a 3/32 tapered ballnose cutter from Harvey Tool.
I could not bore to correct size, and had to ream right on.
The tool is mounted with a set-screw from both sides to prevent deflection caused by unequal clamping pressure.

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