Double-sided machining and introduction

[renklint]

Hi everyone.
Let me introduce myself. I do woodworking for hobby and built myself a Copycarver to do some 3d-carving. Every once in a while I drop by here and I'm just amazed about your willingness to help each other out. If I ever will come around to bying a CNC-router, it has to be a shopbot, since I've never heard of a machine that has this kind of forum participation.

I have a question about wether it is possible to make a double-sided cut. I understand that some softwares give you the ability, but if I wanted to cut something like this:

8012

would it be possible to reposition my board with the other side up when it's time to cut the other side?

And what about this kind of objects?

8013

Could you machine everything but the undercuts, and then flip it over and do the rest?

Lars Renklint

[scottcox]

Short answer is "YES".

You'll have to build a jig to hold it while you carve the bottom. I would use Vectric's Cut3D program for this.

[renklint]

Thanks for the reply.

I see when I look at my illustrations that it's not very clear whether it's solid wood, mdf or something else. My thought was some sort of sheet-material, so when I flip it over it would still be attached to the sheet. I guess my question is: do you just zero all axes again on the other side or would you have to make some other kind of arrangement to make things line up perfectly.

/Lars

[scottcox]

Most likely not, but it would depend on the toolpath strategy, the hold-down method and the software used.

Also consider that material like MDF varies in thickness from sheet to sheet. Sometimes that matters, sometimes not, but it's good to recognize it before you decide on a toolpath strategy.

[cmagro]

Lars,

An actual example of what I think you mean.

8014
8015
8016

This a a handrail easing, blank is just held by two clamps on a scrap piece of wood squared with the bot first. Nothing fancy...takes about 20 minutes for the entire piece...chop end off on miter saw....band saw the excess and about 2 minutes of sanding.

Though I wrote the program myself for this I have Cut 3d and know it would do this quite well. My program allows the bit to follow the shape of the curve though so I think might be faster since there is not so much up and down movement.

As far as your second shape I have attempted to make climbing easings (you may have seem those things on fancy staircases) using my indexer but good old fashion craftmanship is my choice there. Indexer does work well though and when time allows I will have those programmed as well.


Christian

[cmagro]

Lars,

Forgot to answer your other questions.

In may case I flip the wood blank over...line it up and reclamp it...and then I DO re-zero the bit(s). This whole process takes just a minute.

And as far as lining up...I just place three register lines on the scrap block..the one in the center is the X Zero point. The wood blank gets lined up with that when flipped.


Christian

[renklint]

Thank you Scott, I will have a look at some softwares and see what the alternatives are. Now I know that it's possible.

Christian thank you for posting images, I went ahead and took a look at your website - very beautiful staircases. Most of the time it's easier to understand a picture than an explanation, but bear in mind that I'm new to this and don't own a shopbot yet. The way I understand it you've written a program that will let you follow a curve with a special router bit, not a spiral cutter. So as I understand it, you're able to do the undercutting in the sides of the handrail with that bit and don't have to rotate your workpiece. Or have I misunderstood you?

Edit: Yes, I have misunderstood. I just see in the third picture that this piece have been cut from both sides.

/Lars

[cmagro]

Lars,

Nothing near that complicated. The easings are made using a 1/4" round nose bit..if at all possible use inexpensive off the shelf so if (I mean when) they break just grab another one and keep working.

Program reads the profile and whatever path I create (this is done in AutoCAD) and automatically creates the toolpaths. I actually have it draw the bit locations so I can go into the drawing and relocate the bit so it fits right where I want it. The toolpath is actually created based on the tip of the bit. If I relocate the bit...the path is updated. One push of a button and bot file is outputted.

I use this method for a LOT of stuff...it lets me do custom work very quickly. I do turnings this way too.


8017
8018

I can also control whether or not to flip the start and end points of each path which would make the bit go batk and forth and not go down the path...lift up...back to the start etc.

I cannot do undercutting of any kind.

Hope this helps.

Christian

[henrik_o]

Hejsan Lars!

Yes, another Swede here. And you just got really, really lucky: not only am I Swedish, I also happen to have a Shopbot (PRS Alpha 120-60-14), I like visitors (bring kaffebröd!) and my workshop is less than an hour’s drive from where you are. (I take it that it’s Grillby, from looking at your homepage – beautiful work you’re doing)

So, what do you say? Want to come over for a live demonstration? If you want to cut a test part, we could set that up: as long as you have a decent 3D file we can look over it and probably toolpath it. If you want it cut in a special material, bring that with you, otherwise we have plenty of blanks in the scrap bins.

You can email me or call me, my mail is in my profile and you can get our phone number plus directions for getting here from our homepage; www.mobelhantverk.se (http://www.mobelhantverk.se) ; if you call and someone else answers ask for Henrik. Our business hours are 08 to 18, but you can usually reach me by phone from 07 to 20.

[renklint]

Hej Henrik!

That was a really generous offer. I will endeed bring something to go with the coffee and come over to your shop.
I'll get in touch.

Lars