[btu44]

Excuse me for being away for the day. There is a lot of good information here that I wanted to give a try.

Gerry, thanks for the pictures. I had stuck in my head tabs with holes in them. Then later the tabs were used to hold down the part to a threaded plate. ‘I see says the grasshopper’

I was looking at the scrapped part again. I see I was still making a relatively heavy cut after the part had been freed from the remnant plate and only the glue was holding the part. So I redid the program so the outside contour has a .005” skin holding to the plate. Then the very last operation is to cut it loose with a 1/8 chamfer mill which I think will have very low cutting forces.
Heres how it will look-



Off topic but I had a disturbing yesterday. The part was running good for awhile. So left it alone for the next tool to come up. When I came out to check, I first noticed the spindle was off but was not in the tool change position. The tool was deep in a slot but not broken…yet. The computer had a hard crash that even a CTL-ALT-DEL would not recover.
So since I had to do a PC reboot I hit the E stop button. Of course there was the clunk sound which kicked the Y axis about .100” which then broke the end. Many words followed which I will not repeat. Darn, this my 3rd ‘foxtrot uniform’ end mill for this project. A new record.(chair) At least it hit the plate instead of the part so not another scrapped part. If I had to venture a guess on why the computer crashed so hard is because the video card is failing. It’s the only reason I’ve seen so far for this hard of a crash with out the ‘blue screen of death’ on other computers I've fixed.

BAMCNC, I also have tools setup in my CAMs tool DB. Once I find out how a particular tool likes to run on the PCNC1100, I’ll update the database and that’s it for that tool. It why I can’t justify the cost of a subscription feed and speed calculator. I’d need it so rarely.

[Peter Neill]

BAMCNC,
If you have any picture examples of tab fixturing could you post them? I have only seen this way of holding a part once before.

Barry, I guess you've already seen the idea from Gerrys post, but I though a couple more pics wouldn't hurt.

[mrquacker]

Tormach made a video about it a while back.

[ame=http://www.youtube.com/watch?v=T3COWJq5pFY]SprutCAM7 Tutorial on Tabs and or Bridges - YouTube[/ame]

[BAMCNC.COM]

BTU, yeah I just used FSWizard to setup the tools, then I'll tweak from there. As for tabs, I use RhinoCam and it has tabs, but sounds like sprutcam you have to draw them?

[Spooq]

BTU, yeah I just used FSWizard to setup the tools, then I'll tweak from there. As for tabs, I use RhinoCam and it has tabs, but sounds like sprutcam you have to draw them?

I draw them in Sprut, it takes 10 seconds once you've figured out how to do it. Much quicker than mucking about trying to import geometry. I'd only do that for a complete vice or something.

Go to the 2d editing tools, draw rough rectangles where you want the tabs These don't have to be perfect, they can overlap the part or the workpiece, it's more about where they intersect with the path of the tool in the cut-out.

Go to the cut-out operation in machining, click the fixtures tab. Extrude the rectangles you added, make sure you extrude positively or negatively, depending on how you set up your Z reference.

You can add a drill operation to drill out the centers of the tabs afterwards if you want to remove a bit more material.

[Gerry Sweetland]

I draw them in Sprut, it takes 10 seconds once you've figured out how to do it. Much quicker than mucking about trying to import geometry. I'd only do that for a complete vice or something.

Go to the 2d editing tools, draw rough rectangles where you want the tabs These don't have to be perfect, they can overlap the part or the workpiece, it's more about where they intersect with the path of the tool in the cut-out.

Go to the cut-out operation in machining, click the fixtures tab. Extrude the rectangles you added, make sure you extrude positively or negatively, depending on how you set up your Z reference.

You can add a drill operation to drill out the centers of the tabs afterwards if you want to remove a bit more material.

Hi Spoog,
How do you tell SC that the geometry you have picked for a the drill op that it is not a fixture anymore? Does the drill op ignore fixtures?
I'm away from the shop so I can't play with it now to see for my self.
Thanks,
Gerry

[Spooq]

Hi Spoog,
How do you tell SC that the geometry you have picked for a the drill op that it is not a fixture anymore? Does the drill op ignore fixtures?
I'm away from the shop so I can't play with it now to see for my self.
Thanks,
Gerry

That's why you just set it on the operation you need it for. You might need to untick "and fixtures from last op" on the next op as well, haven't got it in front of me either.

[Steve Seebold]

Easy way. Cut the slots first, then have a program stop (M0). Add 4 screws in the slots in each part, then profile the outside.

[btu44]

Good stuff here, especially the StrutCAM video. When I have time I think I’ll watch them all and try and apply the techniques to MasterCAM.

It looks like if an un-interrupted outside chamfer is needed, either the parts in the plate need to be glued down, or the parts need to be separated and then use soft jaws.

I tried the hot glue method yesterday. It held very strong but as tbaker2500 said, it was a bear to remove the residue. I had the heat them to 380 F and wipe the parts off. Felt like playing hot potato. I’m happy with the result. The chamfer is very even on both sides of the part and the finish has no scuffs or scratches.


You know I was thinking. You guys notice as the years go by. First you learn your first CNC machine and the learning curve is high. But it gets easy and the next machine is easier than the first. Then you start setups. After a little while, that gets easy and you stop breaking cutters. Then there’s CAD/CAM, this really can be difficult to learn but after a few years you get comfortable with it. The point I’m making is it seems fixturing never seems to get any easier. Some parts are simple and others, like sand castings, are not. Just wondering what you long time machinist think?

[kevinro]

I just started using Vetric Cut2D about two weeks ago. It allows you to setup tabs very easily. The rendering below are tabs in a .5" thick aluminum 6061. The sprocket is a #25 with a hub. The sprocket part is about .09" thick and the tabs are .0325" thick and .0325" wide. Holds the part very nicely. I am milling the sprockets with a .125" bit. Removing the sprocket from the fixture can be done by just pushing it out the bottom.

I have been surprised as just how small of a tab I can get away with on a lot of operations. They are usually pretty small and can be removed in 2 strokes of a file.

[AiR_GuNNeR]

btu44,
What size endmill are you using to cut the long slotted parts out?
By the way, I love my .22 cal S410E.
Eric

[SCzEngrgGroup]

Good stuff here, especially the StrutCAM video. When I have time I think I’ll watch them all and try and apply the techniques to MasterCAM.

It looks like if an un-interrupted outside chamfer is needed, either the parts in the plate need to be glued down, or the parts need to be separated and then use soft jaws.

I tried the hot glue method yesterday. It held very strong but as tbaker2500 said, it was a bear to remove the residue. I had the heat them to 380 F and wipe the parts off. Felt like playing hot potato. I’m happy with the result. The chamfer is very even on both sides of the part and the finish has no scuffs or scratches.


You know I was thinking. You guys notice as the years go by. First you learn your first CNC machine and the learning curve is high. But it gets easy and the next machine is easier than the first. Then you start setups. After a little while, that gets easy and you stop breaking cutters. Then there’s CAD/CAM, this really can be difficult to learn but after a few years you get comfortable with it. The point I’m making is it seems fixturing never seems to get any easier. Some parts are simple and others, like sand castings, are not. Just wondering what you long time machinist think?

I still think you could do those a lot more quickly and easily using screws rather than glue. Worst case, you have to make up clamp plates that are the same shape as the parts, with tabs that locate in the slots to align them precisely. Cut the slots, screw the clamp plates down, and there's no change of losing alignment, since you haven't cut them from the plate yet. Then cut the outside profile. With aluminum clamp plates, you won't mar the surface of the parts at all. I do this all the time, and it works perfectly, even with rather small screws - I routinely hold parts down with as few as two 10-24 Allen screws, even for pretty heavy milling with a 1/2" endmill. Never once had one come loose. It would save a lot of time gluing and cleaning up afterwards. If you need to chamfer the edges, either make the clamp plates slightly smaller around the outside than the parts, to allow room for the chamfer tool, or cut a partial outer profile (maybe going only half-way through), do the chamfer, put the clamp plates one, then finish the outside profile. With a good power drill/driver, installing removing the screws takes just seconds.

Regards,
Ray L.

[btu44]

btu44,
What size endmill are you using to cut the long slotted parts out?
By the way, I love my .22 cal S410E.
Eric

I am using a 1/8" 3 flute to a depth .300". I should have used a 1/4" 3 flute because the 1/8" took to long.
Yea, I really like my .22 S410 E also. Some of my freinds think it's a toy till they see the 1.6" group at 100 yards (no wind). Having the Tormach, I made a picatinny rail for it. There wasn't enough scope eye relief me.

I still think you could do those a lot more quickly and easily using screws rather than glue. Worst case, you have to make up clamp plates that are the same shape as the parts, with tabs that locate in the slots to align them precisely. Cut the slots, screw the clamp plates down, and there's no change of losing alignment, since you haven't cut them from the plate yet. Then cut the outside profile. With aluminum clamp plates, you won't mar the surface of the parts at all. I do this all the time, and it works perfectly, even with rather small screws - I routinely hold parts down with as few as two 10-24 Allen screws, even for pretty heavy milling with a 1/2" endmill. Never once had one come loose. It would save a lot of time gluing and cleaning up afterwards. If you need to chamfer the edges, either make the clamp plates slightly smaller around the outside than the parts, to allow room for the chamfer tool, or cut a partial outer profile (maybe going only half-way through), do the chamfer, put the clamp plates one, then finish the outside profile. With a good power drill/driver, installing removing the screws takes just seconds.

Regards,
Ray L.

Ray,
I agree, your technique is good for holding long plate parts. I have large tooling plate I bolt down to the mills table for just this purpose. It has dowel and threaded holes all over it from various projects.
Here I'm trying different ideas to make it easier and quicker to do 1 or 2 small parts. And so far I haven't found quicker than you idea.
I have a book, Metalworking - Sink or Swim by Tom Lipton. He talks about Dop Wax, maybe the same thing Steve mentioned. I think I'll try that next time. If that has it's own issues than I'll go back to hold down plates or soft jaws.

Barry

[SCzEngrgGroup]

Ray,
I agree, your technique is good for holding long plate parts. I have large tooling plate I bolt down to the mills table for just this purpose. It has dowel and threaded holes all over it from various projects.
Here I'm trying different ideas to make it easier and quicker to do 1 or 2 small parts. And so far I haven't found quicker than you idea.
I have a book, Metalworking - Sink or Swim by Tom Lipton. He talks about Dop Wax, maybe the same thing Steve mentioned. I think I'll try that next time. If that has it's own issues than I'll go back to hold down plates or soft jaws.

Barry

I find I end up making a lot of simple fixtures - Seems like every part has some challenge to holding it. I have a number of pieces of scrap, usually 3/8" or 1/2" plate that I'll use, over and over, for these, even if I'm only making one parts. Some of these plates look like Swiss cheese at this point, they've been used so many times, for so many different parts. But I find making these typically takes just a few minutes, and saves time overall.

Regards,
Ray L.

[mrquacker]

This might be relevant: Holiday Trivets: A CNC Gift Idea - CNCCookbook CNC Blog CNCCookbook CNC Blog

[btu44]

This might be relevant: Holiday Trivets: A CNC Gift Idea - CNCCookbook CNC Blog CNCCookbook CNC Blog

That is a very interesting option. Maybe make several different size trays, filled with the alloy at the ready...thanks.

Here's some pics of how this project is going.

Drilling a turners cube corner.


Turners cube mobile. Here I'm finding the balance point before drilling.


Barry

[Spooq]

That is a very interesting option. Maybe make several different size trays, filled with the alloy at the ready...thanks.

Here's some pics of how this project is going.


Barry

Nice one, this has inspired me to make another one of these