How to mill these on the bot?

[drodda]

I am trying to come up with a way to mill these chip holders on my bot in a table top.
http://www.regalpokertables.com/picts/laser1.jpg
I currently do them on a drill press but figred one of you knowledgeable people on here would know the math to get this done on the bot. The ends of the chip ares need to be flat and not radiused as the chips lean on them and need to stack tight up against it. As usual any help would be greatly appreciated.

-D

[Brady Watson]

Dave,
The only thing I can think of off the top of my head is to use a 2" ball and machine along vector on one part, and then inlay that into the surrounding part...or more asthetically correct, pop it in from the bottom.


5113

Of course, depending on the depth of the pocket, you could cheat the corner with a 1/16" cutter, getting it very, very close to a true square corner. Aside from rotating the piece and getting it like you do on the drill press, or doing an inlay, I don't see how you could easily get a sharp inside 90° corner.

-B

[drodda]

Thanks Brady,

Do you think a spiral downcut bit moved in a 3-d arc perpendicular to the rounded groove would leave a sharp corner? I had already thought of the inlay idea that you are talking of but I was thinking of making them tapered on the back and the cutting the pocket for the inlay tapered to match to get a tight almost seamless joint. The only issue is the chatter that I am currently getting might make it tougher. The radius of the grooves is 39mm or little less than 1-5/8" and I mill them 9/16" deep. Right now I am using the forstner bit and then glueing a cap on one end.

[Brady Watson]

Dave,
No. This is what the part would look like using a 1/4" downcut moving only in a 3D arc:


5114

Notice that you still have internal radii using a straight bit...just like you would get with an inside profile cut. There is no way around that. Also notice the jagged 'scales' caused by the flat bottom bit.

"The only issue is the chatter that I am currently getting might make it tougher."

What do you mean you are getting chatter? Where? On what kinds of cuts?

Tighen up the gantry, CHECK THOSE PINIONS!!! and check the rails for wear. Make the tool aircut something that has to move some distance. Take the time to listen to the tool...how do the pinions sound? Listen to the v-rollers riding on the rails...Does it sound like they are riding on something bumpy? Place you hand on the X car. Is it vibrating? Pinions don't last forever...they are consumables. Replace them & set your motor tensioners to 3.5 turns. Check the rails and deburr as necessary. Use a file or sandpaper and some steel wool...it makes a HUGE difference.

-B

[drodda]

I think my bot is getting tired and needs a tune up badly. I am really busy and have not had a chance to shut down long enough to calibrate and tune it.

It makes more noise while traveling than it used to and it also vibrates if you put your hand on it while it is moving. I clean the rails with emry cloth about every other week and this always seems to help. I have been cutting alot of cherry these days and the edge is very chattered? If that is even a word. Where do I get replacement pionions? Is this a shopbot part only or can you just order them from somewhere? I have been wanting to upgrade the alpha to the new gantry. Is this upgrade available from shopbot yet? I would love to covert the v-bearings to a linear bearing setup. I keep thinking that when I have time I will (list is too long to post), you get the idea though.

Phone does not stop ringing long enough to play with the setup right now. Do you need to replace all four pinions or just the x and y ones?

Once again Brady I appreciate your time. I realize that time is hard to come by sometimes.

-D

[Brady Watson]

Dave,
Get them from ShopBot. They are cheap and a NECESSITY not a 'maybe someday' maintenence item. Buy a spare set too & keep them in your spares kit. You will want to replace at the very least the X & Y pinions, and check for slop in the Z & adjust the horizontal v-rollers on the Y car and the v-rollers that hold the t-rail on the Z. New pinions, clean/deburred rails and properly adjusted v-rollers will make your machine cut like it did when new...which is how it should be maintained always. Take time to 'sharpen the saw' if you catch my drift...

No dice on the new gantry yet. I wouldn't expect an upgrade to be available until late summer...but I don't work for SB, so I don't know for sure.

-B

[drodda]

Brady,

Just ordered the pinions but did not get a spare set as they said they were not going to used on the upgrade and I am hoping the upgrade will be here soon. Thanks for the help.

[dmidkiff]

Brady, and Dave,

I have been asked to cut something similar for a company making a game table. The table is round and the chip holder follows the curve. Could this shape be done with a 1/4" or 1/8" ball nose? Or could you use a box core bit for the main body of the cut and then "square" the ends with one of the above bits?

Thanks,
Dave

[Brady Watson]

Dave,
There's lots of ways to do it...the challenge comes if you want the part to be 1 solid piece. If you can make it in separate pieces (as shown above) you'll initially spend more time engineering it, but in the end you'll have a better looking product in my opinion.

-B

[dmidkiff]

Brady,

They want the table in one solid piece. The end user will actually have two tables. When flipped over it will become a dining table. I have spent some time today with the drawing and think that I have everything drawn correctly. I will show the drawing to my client tomorrow and if he gives the OK, I will need help with the toolpath.
Since the table is 60" dia. I have asked him to bring table it 2 pieces. I will not decide on my center for indexing until I see the parts and I would also appreciate a quick check of the drawing from some veteran eyes because of the time and material that my client will have tied up.

I just tried to upload the DXF. It was drawn in Vector9 and imported into VCP. I just did final ajustment to the chip holder, to get it to 1.625" as Dave said above.

I see it did not post. OH well.

[mrdovey]

Dave...

I've done something similar - take a look at the photos at this page (http://www.iedu.com/DeSoto/panel_saw/index.html). You'd want to use a small (1/8") ball end mill for a finishing pass, but most of the material could be hogged out with a 1" round nose.

...Morris

[dmidkiff]

Morris,

That looks like what I need, however I will have to lift out of slot and start a new one about 1/2" away.

That is an interesting panel saw design. Does the lumber give problems with movement?

Here is the DXF that I tried to upload last night. If anyone is interested in taking a look at the file for accuracy and helping with toolpath please respond to this or email from my profile. We can make some arrangements for payment. I would like to use VCP for the toolpath.

Thanks in advance,
Dave
Well, Now I am not only hampered with dialup but the file is too big. Some days are diamond and some are coal. So if there is any interest I will email the file to you.
Dave

[mrdovey]

Dave (M)...

Lifting out of slot is easy - JZ,3 :-)

The panel saw design was Q&D and intended to get the job done with a minimum of materials. I haven't had any problems with SPF squirminess in the couple of years I've had it in the shop - but I did (sorta) go overboard on the fasteners...

Since I didn't have any of the neat 3-D tools for producing the toolpath, I did my usual: brushed up my analytic geometry and wrote an SBP program to do all the cutting. All that's needed is to calculate the endpoints for each cut, move the cutter to the starting point, and use an M2 command to make the cut.

I'd use a 1" round nose to hog out the center portion of all of the chip holders, then chuck up a 1/8" ball mill to square up the ends. If you're feeling AR about radii, you could add a third round of cutting using a 1/32" end mill (that'd shrink the radii to 1/64"), but I doubt you'll find that necessary. Do all the cutting with each size cutter at the same time or you'll make yourself crazy with all the bit changing (DAMHIKT)

What's VCP?

...Morris

[dmidkiff]

Morris,

VCP is V-Carve Pro. It is easier for me to use than Part Wizard and Vector for the tool path. The drawing tools are limited but I here that is about to change. My math skills are not up to that. It would be torture.

Dave