Another part for the scrap bin

[walnotr]

This is not a big mistake, blunder or boo boo, but it is another day in the life of using a light weight CNC mill to make parts. Having a CNC mill is very empowering in that complex parts are taken from design to reality. The down side is once the "go" button is pushed, you better hope everything is planned out correctly and the set up is right. The photo below is my first attempt at the rear bearing housing for the Whittle V8 I'm trying to make. A not too close of an examination will reveal something changed during to course of running the part. So far, the only thing I have been able to figure out is the machine lost steps because I mistakenly set up a climb mill operation and overwhelmed the steppers. All is not lost though. I have a couple of practice parts for the flip side of the housing and I did get the bore diameter for the bearing "spot on" without having to fret about ruining the part!

Sometimes the glass just has to be half full of lemonade. :big: :big:

Steve C.

 

[lee9966]

For a complex part like that where I really don't want anything going wrong I sometimes cut it first in plastic wood, the stuff used for house trim. It can be glued together easy to make whatever block size needed. And it's cheap!


http://www.lowes.com/pd_238343-99999-282608003_4294815781_40?productId=3195345&pl=1&currentURL=/pl__4294815781_40_?identifier=

 

[kvom]

Been there, done that, broke the endmill. :

 

[shred]

Moving a feature after generating a toolpath does that for me in BobCAD sometimes.

 

[walnotr]

Well, it turned out the climb mill did overwhelm the little Taig mill. After adjusting the gcode I got this part. It is almost right if you don't count the over sized holes (wrong drill in the index)and the wrong hole pattern in the lower half of the part. Funny how those things can slip by you when one looks at a drawing so long. I hope I don't run out of material before I get this thing right! At least I'm getting plenty of practice and finding out what works and what doesn't. ;D

The flip side

It does look pretty though. :big: :big:

Steve C.

 

[SAM in LA]

Steve,

Looks good to me. I can't imagine making a part that complex with my old 3 in 1.

I'm looking forward to following your build.

SAM

 

[shred]

I do a lot of test parts in plastic and wood when trying to CNC something complicated. The machinable wax looks ok too, but a little more expensive.
Those don't help so much for feeds-and-speeds though.

 

[mu38&Bg#]

I like servos to avoid lost steps. I have huge servos on my little mill. While it machines well and is capable of high speeds it only causes more trouble when you screw up. I broke a 1/4" carbide endmill not too long ago when it couldn't keep up with the feedrate I programmed. Just after I started with this machine I had a problem with a connection on an axis and crashed it into the end of travel. I ended up having to replace the angular contact bearing pair on the ball screw in the slide. I got away cheap because a wrecked ball screw would have been as much as I paid for the set of X-Y slides. I'm drawing the Whittle in Solidworks. I need to make some cylinders and cranks from scratch before I attempt that one.

My box of scrap parts and endmills continues to grow.

Lowes around here doesn't stock that plastic wood. Somebody must sell it. I saw a pickup trucked loaded with the stuff the other day.

Greg

 

[kc5ezc]

The cheapest machinable wax we have found is to melt paraffin 3 parts and 1 part number 4 plastic together.
We get the plastic from large (5 gal) water bottles that are delivered to various offices. Usually you can get the driver to save them for you. May have to entice him with a beverage.
This stuff works very well for us.
John Burchett
in Byng OK