Rounding outside corners? without holddowns?

[myxpykalix]

I finished routing the inside of this african mahogany, now the customer has decided he wants a radiused outside edge for this piece...ok

what i would do is take the square deminsion raduis the corners to what he wants but heres my problem. I use mechanical clamps to hold down this material and the toolpaths when created would do a continual outside perimeter pass for the radiusing and my clamps will be in the way.

Is there a way to measure from my center 0,0 and tell it to only radius the corners? And in doing so won't it leave a lip at the edge of the beginning of the cut?

[Gary Campbell]

Jack...
Using the rectangular outline vectors, apply proper radius fillets to corners. Node edit out the staight line vectors between them and set start points. Toolpath outsode vectors and check start points. Set high safe Z to miss your clamps.

Part 2: Not if you are good?

[srwtlc]

Along with Gary's suggestion, depending on your software, you could either program a slight circular approach/depart to each corner or draw it in.

Is this blank already to size? If it is, be warned of tear out as it rounds the corner. A climb cut may do better. If it was me, and it was to size already, I'd just draw the desired radius with a compass or something that was the right size, cut the corner off proud of the line with a jig saw (hand held) and then belt sand the corners to the line with a hand held belt sander along with a light pass along the edges. Sort of old school, but not everything has to be done on the bot. ;)

[myxpykalix]

Gary if i read it right then make a toolpath based on the pic here right? for all 4 corners.

Scott you may be right in that it isn't worth ruining the expensive wood when the customer can round the corners himself.

[knight_toolworks]

one work disc sander. a perfect tool for the job. or a bigger belt sander. mark the corners and sand away.

[steve_g]

In pre shopbot days … we would have used a radius template and a bearing router bit. Maybe an acceptable solution here.

[robtown]

Can you screw it to a pc of MDF or melamine (from behind) that is larger and hold the MDF or melamine down safely outside the cut area?

[gundog]

If you want to do it on the bot I would draw the profile with radius corners and copy it and make 4 copies, then with some node editing leave yourself an overlap and 1 corner to each of the four copies.

Make 4 tool paths and use the lead in and lead out function. Hold the part by all but the one corner and the amount of staright line you left cut one then move one clamp to the area you just cut and cut the next just work your way around the piece by never moving more than one clamp at a time. You can do the whole perimeter that way and not leave a line the lead in and lead out really helps not leaving a start and stop point. Make sure to use a safe Z that can travel over the clamps to the cut area.

Mike

[maxheadroom]

In all the time it's taken to make, and read responses to this post, you could have:

1. Marked the radius on each corner and sanded to the line, either by hand, belt sander, or edge sander.
2. Made a router jig - on the router - clamp the two together and route the corners.
3. Cut the corners with a jig saw and sand.

This is an excellent example of how easily we can all over think the simplest solution.

What's most efficient, spending an hour - or more - to figure out how to do it on the 'bot', or do it by hand?

Using hand tools and or standard shop tools found in most shops, longer than affordable CNC's have been on the market, allowed me to think of other ways to complete a job, rather than rely entirely on one machine. How many one off parts do people make on the CNC that could be completed in a fraction of the time by other means??

Do it on the CNC just because you can? Not!!

[feinddj]

I agree that this might be a situation where its easier to accomplish by hand.
Depending on the radius, use a router and a roundover bit of the right size at 90 degrees to the table top. However if you are dead set on the bot, instead of doing a four corners at once, why not make a jig and clamp set that you can use to round one corner, then turn the piece, round the next, etc.

[curtiss]

As I have slept a few times since I was told the answer...

WHEN is the best time to use a "CLIMB cut" and with what type of bit ??

.......I used to know the meaning of life but I forgot to write it down...

[gc3]

Shaper.

May need to make a ply jig.

That is what I did for these panels for the stile/rail tounge.

2 hrs max setup and cut.

Done.

Sometimes the Bot process will slow you down.

[myxpykalix]

file all cut, customer happy. That was a quick $100.00 for a couple hours work.