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

Due to the current situation with lack of N95 masks in the stores I resorted to 3D print a pair for me and my wife.

I also made the designs freely available on thingiverse: https://www.thingiverse.com/thing:4264883

Here is the description of the project:

High airflow Respirator mask in 3 sizes: Large, Medium and Small.

Large works for a large male face. 125mm height*
Medium for a smaller male face. 115 mm
Small works for a female or a 10 y/o kid face. 105mm height.

*I measure face height from chin to the centre of the nose bridge.)

Designed to take 1 or 2 55mm cotton pads into each of 3 filter housings.
Install filter medium into the bottom of the cap and screw on to the mask body.

Make sure to print 3 caps for each mask as well. Caps are the same for all mask sizes.

Used white window insulation sticky cord on the inside to add cushion and improve insulation.

Had to also use a file and fine sanding paper to make sure the mating surfaces on the mask body are smooth and do not have any air gaps.

Disclaimer: I designed and printed this for me and my family. It has not been tested, and although I designed with safety in mind, I do not claim it can prevent any infections or viruses. Use at your own risk. PLEASE be careful when testing: different cotton pad brands have different density and 2 pads per filter may cause difficulty breathing! Please make sure to remove the filters and sanitize the mask and caps after each use.

The models are designed in Fusion 360.

Parts printed on Creality Ender 3S Printer with the following settings:

• Layer Thicknss: 0.2mm
• Infill: 20%
• Filament Material: PLA
• First Layer Speed: 35mm/s
• Wall Speed: 75mm/s
• Support: everywhere
• Support Speed 75mm/s
• Support Density: 1 line at 5%

1 mask plus 3 caps takes about 14 hours to print at: 75mm/s.

Please wash your hands and stay safe.

We will get through this!

Cap Size:0.55 MB Large Mask Size:3.29 MB Medium Mask Size:3.79 MB Small Mask Size:3.78 MB

On the heels of the previous post.

YouTuber Breaking Taps has just published another of his interesting videos:

In it he is testing various High-Speed Machining techniques on his benchtop CNC router.

Also it is mentioned that HSMAdvisor does not seem to like those small high-feed cutters: at some point some calculated values become negative.

This is a legitimate criticism and it actually happens because default cutting depth of 0.024" becomes too large for the 0.24" Lakeshore high feed and mill and an actual Flute length of 0.015" must be entered in order to get proper values:

With actual 0.015" flute length entered the recommended speed and feed values are now in the safe end of the ballpark suggested by the manufacturer.

Task added to the issue tracker!

Just found a very good video of testing a table-top gantry router cutting mild steel.

YouTuber named "Breaking Taps" used speeds and feeds generated by HSMAdvisor to get a starting point.

To see where exactly he was in the calculations I decided to reproduce all of cuts in HSMAdvisor.

A couple of assumptions i made:

1. Tool Type: Solid End Mill. It is not recommended to use the HP/Roughing tool type on such light machines, so i assumed this is the tool BT used.
2. Tool Stick-out looked like about 3/4" so I used that number.
3. Material was set to A36 Hot rolled steel.

Test 1) Minute 4:52

Good, slow and very safe starting point.

Test 2) Minute 6:20

Twice as aggressive as before, but we can still push it further.

Test 3) Minute 7:10

Here we can see the lack of machine rigidity starting to show. But at 65% feed rate it is still alive.

Test 4) Minute 8:30

This last test did not go well at all.

The machine has finally hit its limit and the endmill broke at all S&F overrides at about 100%

Was this fault of the software? Not really!

If that were a heavier machine, the last cut would not even be considered that difficult.

Here is a full slotting cut on a Matsuura VMC:

And here is the calculation that was done using HP/Roughing End Mill tool type:

If i were using the "Solid End Mill" tool definition, i would have to dial the feed override to 176% to match the 45ipm feed rate!

So what can users of light machines do in order to not break taps end mills?

First of all make sure the spindle torque curve is built and enabled in your machine profile settings.

The easiest solution is to de-rate the spindle. There is "Warning at" level in machine profile settings. Set that to 50% for starters and it should save you from exceeding the machine's capabilities.

Overall this was a great test of this little machine's capabilities and of the great help that software like HSMAdviasor can lend in discovering them.

Please head over to Breaking Taps YouTube account and subscribe.

The 2020 New Year's Holiday sale will end this weekend!111!!!

Merry Christmas and Happy Holidays, everyone!

Let this new year be more productive with HSMAdvisor.

To kick it off let us start it with a massive 30% off for all products in HSMAdvisor store ONLY!

FSWizard now has ISO Fits and Tolerances calculator.

Best of all - it is available in all versions. Free and PRO alike!

https://FSWizard.com

Because the latest version of MasterCAM 2020 was just released last month, we too had to create an updated version of HSMAdvisor plugin.

As usual you can get it here: https://hsmadvisor.com/?page=HSMAdvisor_for_MasterCAM

There were quite a few changes on the back end, but users would not notice any of them, so why bother with proper release notes?

Just download, install and enjoy!

Do not forget to tell you MCam-loving friends about HSMAdvisor!

Cheers!

This major and long overdue update brings customizable virtual keyboard layout (in settings) and new updated style that feels more native to both iOS and Android than what we had before.

See screenshots.

Cheers!

Screenshot_2019-06-06-00-06-25~2.png Screenshot_2019-06-02-19-49-34~2.png Side By Side