Delete ramps/lead-ins or fewer parts?

[Chuck Keysor]

On the layout that is shown in the attachment, it looks like it will have loose parts come flying out! I hadn't realized my lead-ins and ramps would cut away so much of my stock.

I have to make a total of 34 arches, of which 7 are on this one board. Will it be a problem if I delete the ramps and lead ins, or will I have to keep those, and spread my arches farther apart so that I don't create loose parts?

I laid this out with the Toolpath Template function, noted in an earlier post. So I don't think I can manually go and tweak ONLY the offending ramps and leads.

The profile toolpaths are to be cut with a 1/4" end mill. The material is 1" thick Douglas fir.

I have never cut such a part before, so any advice will be greatly appreciated!

Thanks, Chuck

[gc3]

I've cut many files like this using a 6mm LH flute bit with no tabs or DC bit packs chips into kerf parts don't move

[ssflyer]

I do this type of cutout with a 1/4" downcut, w/o tabs, but leave a 0.005" skin, Z-Zero from the table, to keep it consistent. Of course your spoilboard needs to be flat...

The downcut bit packs sawdust/chips into the kerf and holds the pieces in place well.

Keep your ramps and loose the tabs. I also generally use a spiral ramp for my cutouts.

After my cuts, I can take my pocket knife and separate, cleanly.

[Chuck Keysor]

Thank you Gene and Ron. So, by using a 1/4" down cut bit and a bottom "onion skin" layer, I need not worry about having cut my "remnant tree" into unstable fragments at key points...... I assume that others agree with your assessments, since no one has chimed in to the contrary. I guess that is a passive endorsement!

Well I'll report back with my results. But I do tend to be overly cautious. It is one thing for me to be stuck at the simulation stage, but it is another when I contemplate messing up actual wood! Thanks, Chuck

[Chuck Keysor]

Ron, I went back to my arch project to begin editing. The first change I tried to make was to use "Spiral" ramps. The selection button for that option is grayed out. I can only choose between "Smooth" and "Zig zag" ramps.

I tried changing other parameters and selections, to see if I could enable the "Spiral" ramp option. But I could not.

Any suggestions? Thanks again, Chuck

[coryatjohn]

Have you considered using double sided tape in key areas? That might save some unintended destruction when a part rips loose.

[Chuck Keysor]

John, the little I experimented with double sticky tape before, I was not very happy, as things shifted, and I messed up my spoil board (I guess I spoiled it....)

My thinking now, is to take scrap wood, and glue it onto each side of my stock. Then I can spread things out providing a sound remaining "tree", while keeping all the good clear wood in the original piece of stock. Since I don't have to make that many blanks, this seems OK to me for learning. Of course, if I had a functional vacuum, I wouldn't have to mess with this......

Thanks, Chuck

[ssflyer]

Hi Chuck,

Do you still have Lead In's specified on the toolpath? Spiral ramps are not available with Lead In applied.

[Chuck Keysor]

Hello Ron. Yes, I have ramps and lead-in specified. What do I loose by getting rid of the lead-ins? I frankly am not experienced in this yet. I simply assumed it would be best to have lead-ins and ramps. What do I loose by dumping the lead-ins, and what is the extra value in a spiral ramp compared to the other options? Thanks for the follow-up,,,, Chuck

[ssflyer]

Hi Chuck,

I do use lead-ins, occasionally, but don't usually. A spiral ramp will cut progressively deeper as it goes and the passes are set with the pass depth.

Here's an excerpt from the help file:

"Continuous spiral ramp moves are only available when the toolpath does not include lead in moves.
This option ramps into the material over the complete circumference of the profile pass. The angle is automatically calculated to ramp from the start point to full depth over the perimeter distance around the job.
The rate at which the cutter ramps into the material is determined by the Pass Depth specified for the cutter. For example, Spiral Profiling 0.5” deep with a cutter that has a Pass depth of 0.5 or greater will spiral down in 1 pass. Editing the Pass depth to be 0.25” results in the 2 spiral passes around the profile. "

It just seems to hold the piece better to me, when you are packing the kerf with a downcut. Give it a try on a test piece and see what you think!

[Chuck Keysor]

Hello Ron. Thanks for the info on the spiral ramping. I had just a hazy (and wrong) idea of what spiral ramping was. Now that you have explained it, it makes total sense and I will revise my toolpath designs accordingly.

Maybe that shows the danger of hazy notions. The entire CNC world for me is full of hazy notions. Some are right, probably most are wrong, but I don't get to discover what is really what without first trying to actually do something, and then having something go wrong, or getting some specific pointers from someone. Then a specific hazy notion can be corrected and solidified, or if actually right, then simply solidified.

So thanks again for contributing to my education! Chuck