Finish Pass Question: Recessed Areas

[courtney2018]

Hi everyone!

I'm still getting used to my Buddy. I was cutting some foam yesterday and when it got to the finish pass it didn't do quite as I expected.

Some background - I will be mainly building electric guitars. Electric guitars have recessed areas for pickups, the neck, and sometimes have recessed areas for a tremelo. These recessed areas all have vertical walls.

When I created the finish pass I choose Raster in X. The problem that I'm seeing is that there are small sharp bumps where the bit moved over to cut the next pass and cut into the foam these sharp bumps. In the X direction it's a smooth surface as you'd expect, but not in the Y direction. I would've thought it would go around the recessed areas to make all the vertical walls smooth, like the roughing pass does, but that's not what happened.

So I'm asking to see what is the solution to this problem. Granted, I can Raster in Y after doing so in X, but that's time consuming and some of these areas are curved. Plus, the roughing pass does exact what I'd like the finishing pass to do.

I have a couple of potential solutions. One is to create a "roughing pass" using my finishing bit but leave no maching allowance. Although it's technically a roughing pass, it would be my finishing pass. My other idea is to take some of the ShopBot toolpath language that is in the roughing pass and put it into my finishing toopath - G-Code Circles. The only problem I see with that is the numbers associated with the G-Code Circles may be specifically for my roughing bit (1/2"). My finishing bit is 1/4".

I'm sure someone has experienced the same problem. Can anyone give me some guidance on this please?

Thanks in advance!

[srwtlc]

Courtney,

In the same pocket toolpath window that you used to make the raster pocket, there is a place to choose first, last, or no finish pass. I'm guessing that yours was left at "No" finish pass.

[courtney2018]

Hi Scott,
What you're talking about is on the roughing toolpath window. The "profile" was set to "last". But that's for the roughing toolpath. The finish toolpath window doesn't have that. My only options there are the rapid clearance gap, raster angle, and a check-button to add another raster path 90 degrees to the first. I had my raster angle set to "Along X". I'm I missing something?

[tmerrill]

Courtney,

It sounds like you are using a 3D toolpath to perform simple pocket cutting. Since you posted this under Partworks, I assume you are doing the 3D toolpaths in another program and importing them into Partworks.

Unless you have a good reason for wanting to do everything with 3D toolpaths, I recommend setting up and using Pocket toolpaths. A pocket toolpath will allow you to set up your profile pass as Scott pointed out, and there is no need for a rough or finish toolpath.

If you need to use 3D toolpaths, let us know what software you are using to create your 3D toolpaths and someone can probably guide you in the right direction to prevent the rough edge. I can tell you how to do it in Aspire, but I assume you don't have Aspire if you are using Partworks.

Tim

[srwtlc]

Courtney,

I assumed that you were using PartWorks, but it sounds like you're trying to use PartWorks3D. As Tim stated above, it would be better to use PartWorks for the kind of pocketing you're wanting to do. Take a look at that program instead and you should find the kind of pocketing toolpath (vertical wall) that you want.

[courtney2018]

Yea, I'm using PartWorks3D because there are some 3D contours in the guitar body on the front and back. Is there a way to break up the model into pieces and use PartWorks2D and 3D when it's necessary? What I mean by that is use 2D to do the outline of the guitar, neck pocket and recessed areas for the pickups and tremelo and then use 3D for the contours on the front and back. If so, that wouldn't be so bad, but as I know how to use the program now, if I do a toolpath it's for the entire model, not specific area.

I guess I could find where in the 3D toolpath code it's telling the ShopBot to do the contours, cut that out and paste it into the 2D toolpath file. Would that be a reasonable solution?

[courtney2018]

I just looked at the PartWorks (2D). I exported my model out as a .dxf, but it won't load up for some reason. I don't know anything about .dxf files, but my guess is that Lightwave (my modeling software) is creating a .dxf file that is slightly different than what PartWorks is wanting. As a result it won't load. Looks like I may have to use PartWorks3D only.

[tmerrill]

Courtney,

It would be hard to cut out the pocket sections of code in the toolpath file. I would think that's a pretty large file with thousands of lines of instructions.

Did you design the 3D file yourself or get it from another source?

Best solution is to modify the 3D file like you suggested in a 3D design program to ignore the pockets. Then the 3D would only do the body contours. Then you could easily program the pockets in 2D and either run that file before the 3D one or after.

Tim

[courtney2018]

Hi Tim,
Yes, I designed the model myself in Lightwave.

The problem with doing two seperate models deals with tabs. I have a body blank that's much bigger than the model and the tabs keep the guitar attached to the blank until it's all finished and then I'll cut the body out.

There's not a way to create tabs in exactly the same spot that I know of. The program will record the z location of the tab, it's width and height, but not the x and y location. If it did I could do two models like you're suggesting with tabs in exactly the same location.

What I did today was create a roughing pass with my finishing bit with no material allowance in hopes that it would get rid of the sharp bumps. It didn't do as great a job as I would've hoped. Granted, it's styrofoam, but in the middle of the body where the recessed areas are I would've thought it would get rid of those bumps. I recorded what lines in the ShopBot file that were responsible for cutting the outer shape of the body and the recessed areas. I can cut that out and paste it into my finishing file. I don't believe it's going to be good enough though. I don't see why this has to be this difficult.

[tmerrill]

Unfortunately, I believe the difficulty is coming from Lightwave. I've never used Lightwave, but what you are trying to do would be pretty easy in Aspire, for example. Not sure if an option for you would be to convert the lightwave model to a more standard format and get someone to set it up for you in Aspire or similar program. Even if you just had the 3D body, you could import it into Partworks, then position and toolpath the recesses using Partworks.

Found this on the Vectric forum. Might be of interest:

http://www.vectric.com/forum/viewtopic.php?f=13&t=4487&p=29908&hilit=lightwave# p29908

[srwtlc]

I don't know anything about Lightwave, but would it be possible to draw the needed rectangle at the proper location (X and Y) and export/save as a .dxf or .eps that you could then load into PartWorks.

Another thought is if you save the file that you are using in PartWorks 3D and use the import vectors in PartWorks 2D to import the .v3d file, you should be able to draw a rectangle for the pocket then and toolpath it.

[myxpykalix]

I don't believe the problem is with lightwave. A 3d file is a 3d file, a model is a model. The cutting strategy is what i believe is the problem.
What is your step overs and step downs?
Are you using tapered bits or straight bits?
A tapered bit will rub the sidewalls and create the ridges you describe.
If you want to send me the .lwo object or whatever file let me check it out.
Lightwave saves (sometimes) in several pieces or objects. Sometimes the textures that are saved within the lightwave object influence the finish cut. Do you have any textures applied to the surface?
Also check out what type of surface attributes may be associated with the file. Much of surface attributes we do not need like reflection, specularity, ect. but may influence the model.

Also check the resolution that the model was created at. Also the tolerences that the model was saved at.

[gene]

Is there a way to do an offset vector of say .o2 and put it as the finish pass to clean up the bumps?

[khalid]

Jack.. very good questions.. i also need to know the step-over values.. Also i want to know whether he is using end mill or ball nose cutter for that rough pass....

[tmerrill]

As I read Courtney's first post, he indicated everything was fine except for the vertical walls in the recesses. This would indicate a good bit selection and stepover.

With proper settings, a tapered bit will not create ridges in the sidewalls. The sidewalls will be smooth but at the angle of the bit, not vertical.

For a finish toolpath, Partworks ignores the stepdown value for the bit and only calculates a single pass. That is why you never see your finish pass cut any area twice. So the stepdown setting is a non-issue.

My comment about Lightwave was poorly worded and was not intended to slight the program.

And if anyone thinks a 3D model is a 3D model and only cutting parameters separate good results from bad results, well....

The link I posted for the Vectric forum thread shows a prototype guitar body modeled in Lightwave and cut in Cut3D (Partworks 3D). That person doesn't seem to be having the same issues, so perhaps Courtney can contact him off-line and discuss techniques.

Tim

Gene, that is one of the options Aspire gives you. Using a separate 3D modeling program to create the model then trying to cut it with a program only designed for setting 3D toolpaths would make this hard to do.

[tmerrill]

Courtney,

I've re-read your posts a couple of times and think I have a better understanding of what you are trying to do and the software you own to get it done. It sounds like you have Lightwave for 3D modeling, Partworks3D for generating 3D toolpaths, and Partworks for the remainder.

If I were you, I'd change my approach as follows. Here are the major steps, most of which are covered by tutorials if you need extra help.

First, modify your Lightwave model to only be the body with contours. This appears to be the only 3D part of the process. Ignore all recesses.

Second, import the guitar body into Partworks 3D and calculate your 3D roughing and finish passes.

Third, start a new project in Partworks 2D and import the guitar body with toolpaths. Now you can create and position vectors where the recesses will be and use the simple pocketing tool in Partworks to create the toolpaths for these. Actually you would have to create two projects in Partworks (or use layers), one for the top and one for the bottom, and set up a simple indexing system for flipping the body while maintaining alignment. I still don't quite understand your post about tabs, but there are a couple of ways to hold the body in place until all cuts are done.

There are tradeoffs, but you could possibly use the same bit for your roughing pass and the pocket cuts. Therefore, only two bits (and one bit change) would be required per side.

Also, as I envision the contoured body with smooth flowing lines, you could probably use a 1/4" or larger ball nose bit for the finishing path which will help reduce machining time. You would still need a small stepover to ensure a smooth finish.

If this change in workflow interests you, I'd be happy to add more details.

Tim

[courtney2018]

Thanks everyone for helping out.

My bit is straight, not tapered, down-sprial end mill bit. The step over isn't the problem. These sharp bumps are going to be present to some degree no matter how small the step over.

I choose a 1/4" bit because I want the radius between walls of 90 degrees to each other to be 1/4".

I probably should look into the 2D version a bit more. I tried looking at it last night and got the impression that after building my model in 3D I would have to use PartWorks2D to re-build these recessed areas. That's a duplication of work. These recessed areas aren't all at the same depth, so I would have to go back, measure the depth and dimensions of everything and redo all of this in PartWorks2D. That kinda turned me off. Maybe that's the only way to do it? If so and it proves to be faster, then that's how I'll do it, but it still doesn't change how the finish pass is done. The finish pass will still plunge down at the end of each small pass which creates these sharp bumps all along the vertical wall.

What I did last night was spent some time learning ShopBot's toolpathing language. I took the toolpath generated on the finish pass and deleted everything except the contour toolpath. I then edited that so that the bit wouldn't plunge down beside the vertial wall. Yea, it took some time, but I got exactly what I wanted.

I tried messing around with PartWorks2D, but I definitely don't know that program or how to re-draw the recessed areas and how to specify the depth. I'm sure there's a tutorial on that though.

As for Lightwave, I'm not messing with surface attributes. Everything in that regard is default. The resolution of my model isn't what I would call extremely high, or a high-polygon count. I would think it's a medium poly count. The way that my model looks in the contoured areas and how the results look on the styrofoam (just the contoured areas and not the vertical walls during the finish pass) I'm very happy with the resolution. There's just a small amount to clean up with the palm sander and I would be doing that anyway. So I think the resolution is just right. My problem has to do with how PartWorks3D generates toolpaths for the finish pass. Seems like you should be able to tell it to only do certain areas and treat vertical walls like it's treated during the roughing pass. At the end of the roughing pass it goes back and does a perfect trace along all vertical walls where there are through-holes. I think the same should be true for the finish pass. It seems that PartWorks3D is restrictive in this regard and gives the user very limited customizable options. This is why I opened up the toolpath file and edited out everything except the contoured area.

Gene, I would love to do an offset vector. I wouldn't do 0.020"...maybe between 0.005" and 0.010". How do you do that in PartWorks3D?

Oh, one last thing, I'm probably the only girl on the forum. :o)

[tmerrill]

Sorry!

Tim

[courtney2018]

No problem Tim! :o)

[khalid]

Courtney..can you post the picture of the cut.. I usually use upcut spiral bits with good results.....

Thanks

[courtney2018]

Yes. I'm off to run errands now, but I'll post a pic when I return.

[robtown]

I don't use aspire or partworks3d, but can it not import vectors?

Can you not import your 3d model and then "lay" your vectors on top of the model to do pocket and profile cuts?

I recently did a sign that incorporated 3d carving of a model done in 3dsmax, and used vectors to pocket around my 3d carving. This was wayyyyyy more efficient than 3d carving all of the sign.

I made all my vectors in 3ds max so they matched up with the 3d model exactly. Worked like a charm.

[courtney2018]

Rob, I definitely need to talk to you or Tim about this. "Wayyyyyy more efficient" is what I'm looking for. Smarter, not harder. I just don't know how to do what you're talking about.

Pics up in a few moments.

[courtney2018]

For some reason the upload attachment function isn't working so I posted links to the pics.

This is what the front of the body looks overall. The only contour (3D part) of the front if thw arm rest that you see towards the bottom right of the model.

http://img178.imageshack.us/img178/8586/dsc00410wa.jpg

Here's a closer shot of the lower horn. You can see where the finishing bit plunges down beside of the vertical wall, comes up and then over the model to the other side where it plunges again. The bit plunging down like that is what is causing my sharp bump problem which you can see on this pic. This is after I took the same 1/4" bit and did a "rough pass" on it with no material allowance (set to 0.000"). I did that hoping that it would clean up the sharp bumps, but it didn't.

http://img178.imageshack.us/img178/2933/dsc00411s.jpg

Here's a closer shot of the pickup cavity which is what I was calling a recessed area. It's not a hole all the way through. Just a recess. The finishing pass plunges here as well and causes the sharp bumps.

http://img178.imageshack.us/img178/550/dsc00412us.jpg

Here's a shot of the trem cavity. You can see that the wall to the right is smooth because it is in line with the X-axis and I was doing a X-raster for the finish pass. However, on the adjacent wall you can see the sharp bumps.

http://img178.imageshack.us/img178/1600/dsc00413p.jpg

[jerry_stanek]

have you tried the offset cut where the cutter runs around rather than back and forth.

[tmerrill]

Courtney,

This may be a long shot and it's hard to know without being able to watch your machine cut, but if you read Brady's information here about setting your control software up you might try some of his 3D settings and run another test cut. A lot quicker than a redesign at this point. In particular, read what he says about SCS (slow corner speed) and banging into a vertical wall.

http://www.talkshopbot.com/forum/board-admin.cgi?action=quick&do=print&HTTP_REFERER=29/26478&postindex=61433

If you feel comfortable trying this, just keep good notes so you can return the settings to factory later on. If you see a change (good or bad) it may point us in the right direction. If you don't see any change, then we are back with your model and the software settings.

Tim

PS you play a mean guitar!!! (or however you youngsters would say it nowadays)

[dana_swift]

Courtney.. loved the photos.. makes it much easier to see what you are getting!

Looking good. Try switching to some cheap wood and see what you get in the cavities. What the photos looks like to me is a lot of the foam effects. Wood gives a better finish than foam, plus you get to get all your feed rates figured out.

The advise on using 2D cutting for those pockets is right on. 3D the outside, then 2D the pockets. While the body is still in the same setup, just run the other file on it. You will get better results in the cavities, and much better control, as each cavity can get custom cut parameters.

D

[courtney2018]

Jerry, where do you set that at?

Tim, just looking at the link I'm not sure this is going to help. See, I first did a rough pass with a 1/2" bit that left 0.010" of material. I then did the finish pass with a 1/4" bit and did a raster in x-direction. So at the end of each pass it plunges down beside the vertical wall to take off the remaining 0.010" that was left after the rough pass. So it plunges down, moves off the wall, moves to a different y, then continues in x until it hits the wall taking off another 0.010", moves up and then over the model to the other side where this repeats. The space between each y is the sharp bump.

Really, to use the finish pass and not have these sharp bumps I would have to use a stepover so small that it would take a ridiculous amount of time to finish it. I can't imagine moving over 0.005" or 0.010" for each pass. All that is needed is for there not to be a plunge at the end of each pass. Instead go around the model like the roughing pass does.

Thanks for the mean guitar bit. :o)

[tmerrill]

Courtney,

Don't be too quick to eliminate the 3D settings. Looking at the pictures I see one possible explaination being an alternating issue between passes.

Picture this - the bit is moving from right to left and reaches the vertical wall. Horizontal motion will stop and the Z will plunge the bit straight down, giving you one vertical cut. Now the bit continues to move right to left in the recess until it reaches the other vertical wall. Now horizontal motion should stop the bit and the Z moves it back up out of the recess. But what if the right to left movement overshoots a little, then you will have a vertical dimple. Now the opposite will happen when the bit moves in the next pass from left to right, giving you that alternating pattern.

If this is what's happening, you are actually getting overshoot on both stops where motion changes from pure horizontal to pure vertical and back, so the distance between the top and bottom of the ridges would be twice as large.


Tim

[jerry_stanek]

I don't have Partworks I use Aspire and Vcarve pro mostly. It is in the flat area clearance in Aspire and In partswizard it is in the create tool path.

[courtney2018]

Tim, that's precisely what's going on! I wouldn't have thought that it would overshoot though. That really doesn't make sense to me. If the toolpath is supposed to follow the model then what the toolpath is doing next to a vertical wall is actually violating the model. So changing the Slow Corner Speed will eliminate that?

I just cut the back of my model and turned out pretty good. I had edited the finish pass file so that the two contours on the back were in seperate files with no plunging at all. Turned out really well.

I'm going to try the SCS setting next and see what I get.

[tmerrill]

Yes, please try another cut using a different setting for SCS. That's the only way to be sure.

Its not the software doing this. With a new machine you may still need to do some adjustments and fine tuning. It's a piece of machinery and we all went through it.

If your machine does have any looseness in it, you would see it in this case as the control system says stop but enertia takes over. A softer setting in SCS may help.

Let us know.

[robtown]

What I see is a fairly normal thing in 3d cutting.

Are you using a ballnose bit definition? (it will have a small stepover, you need that for 3d carving)

Are you doing you 3d carving as raster or offset?
(raster will go back and forth in either x or y axis, offset will do a circular cut. If raster make sure you do it in both x and y)

All of your pockets and your outside profile need to done with pocketing and profile cutting. I'd guess you're adding 30% or better to the cutting time by not doing this.

Is your foam held down securely?

I can't really tell, but is the entire face of your guitar body domed? if not you should only be doing the sloped corner there with 3d carving. Does Partworks 3d or Aspire have "machine selected vectors" as an option when setting up a 3d carve?

It's been many years since I used lightwave, but it should be able to take your profile curves that you used to create your guitar body, and export them as an .ai or .dxf, unless you did the whole thing by deforming primitives. (I'm guessing you did it by lofting or extruding drawn shapes...)

I've got a full day, but I'll try to get some of the stuff posted that I recently learned on my "scary flourish" sign. (I posted a pic of the flourish up on show and tell here a few weeks back.)

[courtney2018]

Hi Rob, I saw your scary flourish which was quite cool.

My bits are all end mills. I'm doing a raster in x. In PartWorks3D the only option that you have is to raster in X, Y, 45deg. or 135deg., and then you have the option of rastering again 90deg. to one of those four choices. Where can you specify it to raster in circular cuts? This is why I took the entire finish pass and deleted everything but the contour part and eliminated all the plunge commands. I also created a "roughing pass" with my finish bit that would leave no material allowance, so it would actually be the final pass on the model.

This gives me the kind of finish that I want, but the time to set all this up is high.

Yesterday when I did the contours on the back I had deleted everything but the contour toolpaths. There were two contours to do: one for the tummy contour and one for the neck heel contour. Combined it took about 8min. to do. So, while I can edit the toolpath to do this it takes alot of time.

Foam was definitely held down securely and guitar is flat on both sides. To my knowledge PartWorks3D doesn't have "machine selected vectors". That's a PartWorks2D command.

I tried exporting my model out of Lightwave as a .dxf which is the only file that would be readable to PartWorks2D. PartWorks2D wouldn't read it in. How convenient.

The model was constructed by starting off with a primitive, dividing many, many times and moving points around to match the drawing.

[myxpykalix]

Courtney,
go to: http://www.okino.com/conv/conv.htm and look up "PolyTrans" (not sure what versions out now) mine is from the 90's but this will convert your .lwo files into any number of formats including .3ds or .stl which you should be able to load into most programs.

[robtown]

I don't have access to partworks, so I can't be of much help there.

Maybe something you could do is make a "slab" in partworks 3d that simply carves the taper in the corner, Then overlay your pocket and profile vectors.

It's a little daunting at first because you are dealing with a little bit of a leap of faith (since none of the toolpath programs I work with will allow you to see your 3d model and the vectors overlaid together), but you just need to have a good understanding of 3d space and make sure if your model is at position x and position y that you lay your vectors down in the same location. One thing that helps with non rectangular shapes is to draw a box around it and export that box with your vectors.

If you are using a 24" x 18" x 2" slab to start out with, then draw a 24" x 18" box around your guitar model (2d rectangle, not 3d box) then when you have your profile vectors ready for export, you export the box as well. This way when you set your slab up for carving, and have the lower left corner at, say, 1,2, when you import your 2d vectors you can place the lower left corner of the rectangle at 1,2 and it should line up correctly.

Hope this makes some sort of sense, I have it down to a science in my head, but it's a dark scary place in there, and sometimes it's hard to actually get coherent thoughts out of there...

Here's some pics of what I would do in max for this project. For the face I would do a slab with a tapered corner, and draw 4 vectors (and my rectangle for indexing to the slab), then export the 3d model and the 2d vectors seperately.

Then just make sure if your slab is situated and x1 and y1 (lower left corner) , that you place your vectors at Lower Left corner x1 and y1.

There's no need to output and carve this particular piece as entirely a 3d model. But you do need to really understand your 3d space, which you should have a good grip on based on your LW skillz...

Hope I've made sense...

4447

4448

[courtney2018]

Jack, thanks for the link, but I'm not going to spend $300 for something that I don't know is going to work. I can't even get PartWorks2D to open a .dxf file.

I can import the toolpath vectors into PartWorks2D that PartWorks3D creates. I don't think you can edit them there so that's pretty much useless.

If I could bring my model into PartWorks2D as a .dxf file the outline of the model and all the recessed areas would come in as vectors. That would be great, but that's not happening. So it looks like I'm stuck editing the toolpath files out of PartWorks3D. I don't see any other way to do it.

I guess I need to call Vectric to see what's up with their import function.

Anybody see another work around for this?

What I did today before lightening storms moved in is adjust the Ramp settings that Tim mentioned. Before I did a finish pass I made a roughing pass with my 1/2" bit leaving 0.010" left. I then used my 1/4" bit and made another roughing pass with no material allowance. I then used the same bit to do a raster in X. I colored the vertical walls on the outside of the guitar with a marker to see if the bit was cutting into the foam during the plunge operation. Some areas it did and some it didn't. In the areas that it did it looked like it was just enough to take the marker off. So the changed ramp settings helped. In the recessed areas there were still sharp bumps but that's because the stepover is too large. I would have to use a very small stepover to eliminate the bumps and that's not pratical. What I need is for it to trace those recessed areas like the roughing pass does. Looks like that's where PartWorks2D would come into play, but I can't get my model in there.

One thing I noticed in PartWorks2D was when I imported my vectors in and looked at the 2D drawing space my model is shaded in different whites, greys and black. Is there a way to delete my toolpath vectors and use the grey-scale image of my model to cut it that way?

[tmerrill]

Courtney,

First, the Vectric program is working as designed. It will import a 2D .dxf file but not the 3D .dxf that you have. If you want to check with them directly, please contact Mark or Tony at support@vectric.com (mailto:support@vectric.com). They are already aware of this thread.

To do everything in one program, you would need something like Aspire. But you don't have Aspire, so Vectric has done a great job developing a process that may not be as direct and streamlined, but lets you get the job done. And you have the programs to do this already.

Please take a few minutes to view the third tutorial from the bottom on this page. I think it will help a lot!

http://www.vectric.com/WebSite/Vectric/support/vcpro_tutorials.htm

Realize that Partworks = V-Carve Pro and Partworks 3D = Cut3D. The programs are the same, just the Partworks named ones only ship with the ShopBot post processors.

Tim