[photomankc]

Hey, when you cut your parts out from the interior of the bar like that, are you leaving some material at the bottom of the slot to hold it in? Kinda looked like it in those photos. How much do you leave if so and how do you then remove it? I ask because I have done a few things that didn't work too good. Skimming away the back caused it to chatter like mad, leaving in holding tabs made for really hard to remove blemishes on the sides, but I don't trust a big part to drop out without jamming up or bouncing at the end and gouging.

[hoss2006]

Hey, when you cut your parts out from the interior of the bar like that, are you leaving some material at the bottom of the slot to hold it in? Kinda looked like it in those photos. How much do you leave if so and how do you then remove it? I ask because I have done a few things that didn't work too good. Skimming away the back caused it to chatter like mad, leaving in holding tabs made for really hard to remove blemishes on the sides, but I don't trust a big part to drop out without jamming up or bouncing at the end and gouging.

I add some 3d tabs with vcarve to hold the part so it doesn't cut all the way thru.
The max depth is set to the stock thickness so it may leave a wafer of flash sometimes.
They pop out pretty easy then just have to sand off the flash.
Hoss

[photomankc]

Ah I just wasn't seeing them in the other angle. You are putting in wider tabs. I'll give that a try. Wide but thin would be easier to file away. Mine were tall but narrow.

[dugpits]

Hey, when you cut your parts out from the interior of the bar like that, are you leaving some material at the bottom of the slot to hold it in? Kinda looked like it in those photos. How much do you leave if so and how do you then remove it? I ask because I have done a few things that didn't work too good. Skimming away the back caused it to chatter like mad, leaving in holding tabs made for really hard to remove blemishes on the sides, but I don't trust a big part to drop out without jamming up or bouncing at the end and gouging.

Hey photoman -

I work for a defense company, and we almost exclusively use the "picture frame" method of cutting off parts made from hogouts. In fact, I was told by my lead NC guy to NEVER let the parts fall out because it can ding the part and damage the cutter. In fact, we never let ANY part of the stock fall off – even the excess – because it can damage the cutter and have a negative influence on the rest of the part. But...I've seen plenty of videos of guys completely cutting a part through on their home machines with no problems so what do I know…

For tabbing, our method is to rough and finish the profile down. We never finish at the same depth as a roughing pass - always come back up a thou or 2 so we are only cutting with the side, makes a better finish and less chatter.

Do this all the way down to leave .030 all the way around the part. Then do 1 pass that roughs out the part leaving tabs - staying .020-.030 off the wall, then finish that wall again coming back up 1 or 2 thou off the floor. FWIW, if I remember correctly (haven’t been a NC programmer for a couple of years) our tabs are usually around ½ - ¾ wide depending on size of the part. We go all the way through the part, not net like Hoss is doing - because we pretty much always used a cutter with a corner radius - most often .030 radius.

Example, cutting a 1” thick part. Profile wall leaving .030 wall. Finish wall leaving .001 floor. Continue doing this process as your machine depth (per pass) allows down to .970 deep. Take 1 pass through the part, ramping up and then back down on the pass to leave tabs as desired, leaving .015-.030 on the wall. Again finish the wall leaving .001-.002 on floor.

A few .030 tabs around a part are surprisingly strong. On relatively small parts I will come back in with a 1/8" endmill (zero corner radius) and take 3 x .005" passes staying about .004-.005 off the wall to reduce at least some of the tabs to .015 (occasionally .010). If you get a tab thinner than that, the cutter sometimes sucks it up and whacks the whole thing off – never had a problem with a 1/8 endmill though except in thin stock like 1/8 where the stock actually flexed up.

I have no idea how easy/hard that is to program on the software you use – I was using the high dollar stuff that the company could afford. (Unigraphics NX)

Sorry for the novel..just my 2 cents worth.

-Doug

[photomankc]

No I appreciate the info. CamBam isn't quite that sophisticated in its strategy but I could easily implements parts of what you are talking about. Even if the program is more complicated the fixturing is way easier to cut from oversized stock than something that requires creative holding to get around its perimeter.

[hoss2006]

Yeah, I take several roughing passes than leave .010 stock with the tabs then a finish pass to size full depth
sometimes using the same tabs, sometimes removing some or all the tabs.
I always mount the stock on some sacrificial material or round ally spacers.
Depends on the part but some can be cut through and just leave a little burr at the corner of the part.
Hoss

[Titaniumboy]

I add some 3d tabs with vcarve to hold the part so it doesn't cut all the way thru.
The max depth is set to the stock thickness so it may leave a wafer of flash sometimes.
They pop out pretty easy then just have to sand off the flash.
Hoss

I wonder if you've ever done a video on how you make the parts coming off the CNC mill nice-looking. I've just run the as-cut parts over a bench belt sander, but have never taken the next step into any kind of polishing.

By the way, since no one has asked and you haven't said, what the heck are the parts you've shown in the pictures going to do?

Titaniumboy

[hoss2006]

I use the belt/disc sander for a lot of the deburring / tab removal.
If it needs more I sand it flat with emery paper on a small surface plate.
Sometimes it goes to the powdercoating station, my craftsman powdercoater and toaster oven on the kitchen table.
Those parts are for the newer power drawbar.
Hoss

[photomankc]

Yeah, I take several roughing passes than leave .010 stock with the tabs then a finish pass to size full depth
sometimes using the same tabs, sometimes removing some or all the tabs.
I always mount the stock on some sacrificial material or round ally spacers.
Depends on the part but some can be cut through and just leave a little burr at the corner of the part.
Hoss

I have some 3/4" aluminum blocks I use for that purpose as well. Since I carefully and lovingly matched thier heights I don't like to sacrifice them much though! I got away dropping parts several times but had one that bounced just wrong and buh-bye end-mill so I figured I'd pressed my luck enough.

I need a belt/disk sander. I slump a little every time I think about haveing to hand file and sand off the tab left-overs so I mostly tried to avoid using them. I guess I just need to suck it up.

Thanks for all the good info. Sounds like I just need to tweak a few things in how I do it...... and break down and purchase a sander.

[hoss2006]

I have a good 6x48 US made machine similar to this I got used from work.
Can't get to it so I got this little guy from HF, works pretty well.
Combination 4" x 36" Belt / 6" Disc Sander
Hoss

[hoss2006]

Here's those parts put together, the PDB 2 base.
Much shorter than the previous model, gotta make little knobs for the shoulder screws like on the other.
The socket screws are just to hold these parts together for a test fit, they'll be studs attached to the air cylinder as well.
Everything went together beautiful, now to coat these pieces.
Hoss

[hoss2006]

mmmm, candy red translucent.
Hoss

[diyengineer]

mmmm, candy red translucent.
Hoss

Gorgeous.

Did you prep the surface with any conversion coating etc? Where those hex head bolts contacted the coating did you get any cracking? Just wondering.

[BobWarfield]

Frickin' sweet--that candy red looks good enough to eat!

Which brand of candy red did you use, Hoss? Wondering what their color selection looks like. I have to try some of that someday soon.

Thanks also for the tidbits on the tabbing. I like that approach vs dropping out parts. Also, the tip to pull the cutter up a few though for the finishing pass so it won't cut on the bottom is excellent.

Best Regards,

Bob Warfield

[hoss2006]

Gorgeous.

Did you prep the surface with any conversion coating etc? Where those hex head bolts contacted the coating did you get any cracking? Just wondering.

Thanks,
just sanded and washed with soap and hot water the night before.
no cracking, these are just temp bolts ad finger tight.
Hoss

[hoss2006]

Frickin' sweet--that candy red looks good enough to eat!

Which brand of candy red did you use, Hoss? Wondering what their color selection looks like. I have to try some of that someday soon.

Thanks also for the tidbits on the tabbing. I like that approach vs dropping out parts. Also, the tip to pull the cutter up a few though for the finishing pass so it won't cut on the bottom is excellent.

Best Regards,

Bob Warfield

Thanks,
I use Columbia Coatings, been itching to try some copper translucent too.
Translucent Colors
Hoss

[cncmoose]

mmmm, candy red translucent.
Hoss

Beautiful work Hoss!

I got a PC gun from Caswell plating that is still in the box. I'll have to take it out and give it a shot.
Moose

[hoss2006]

Go for it, makes a very nice, smooth, tough surface.
It's cool watching it in the oven turn from a dull powder to a shiny glass like surface.
Hoss

[rwskinner]

I thought about this some as well and I like the belt/ chain concept. The only thing that really bothers me about it is unpredicatable slop/ droop/ backlash in the drive system and chain.

The Z-Bot looked pretty neat but I noticed they aren't around anymore...?

I'm headed out to make more parts for the ATC here.


Richard

I had a idea for a ATC that uses a chain or belt setup Each tool goes into a holder that's attached to the link. Keeps you from having to have a huge circumference and helps eliminate clearance issues, and would allow you to add or remove additional links/tools.

[Simon C]

Love how the PD2 mount looks like a "H" for Hoss.

I realy gata try some powdercoating sometime. your parts look awesome.



regards
Simon