CNC Program for Maloof Rocker Seat Shaping

[Richard Amabile]

Let me begin by saying that I know almost nothing about CNC machines. But, after working a long time on building a Maloof style rocker I am close to the step of shaping the seat. My son works with someone who owns a CNC and said they would be willing to try to help with the seat shaping. But, they need to start in an Auto-Cad type (DWG, IPT, DXF...) file for him to set it up.
Any help you can provide in where I might find a file already set up to accomplish this task would be greatly appreciated. As you might expect, trying to learn a program and develop a file myself is not something I am comfortable attempting.
Thanks in advance for any counsel you can provide.

[Gary Campbell]

I cant post an active link, but one of the Maloof style CNC masters, Russell Crawford, has posted his files and full instructions for his CNC version on both the Vectric and CAMheads forums. Google it up

[Richard Amabile]

Gary:

Thank you for the response and reference. I will definitely look it up.

[William Adams]

One of the easier 3D modeling programs is Moment of Inspiration --- pretty affordable by 3D standards --- it would export an STL and you'd then need to have CAM done using a 3D CAM program which would accept an STL.

If you have an iPad Pro and Apple Pencil, Shapr3D is supposed to be quite nice as well.

[Jim Becker]

I'm literally cutting chair seats "as we speak" for a local maker. While we started with a 3D scan of one of his hand-made prototypes, someone skilled with 3D CAD should be able to model a seat for your needs. There are a number of folks who have done or do this kind of work. Gary mentions Russell who has created some pretty great work. There are other modeling experts out there, including Michael Mezalick and Brady Watson (scanning expert). Brady did the scan and cleanup for the chair seats I'm producing right now and the cost was reasonable.

Of course, modeling your own is certainly possible, but be mindful of the learning curve...don't expect results "really fast". That's just the nature of the beast.

[Brad Shipton]

I would get out the hand tools and get after it if this is a one off. I doubt you will save much time after the smoke clears. If you were doing 4 or more, then my thought would be different. There is skill to the modeling and then the machining on top of it.

[Jim Becker]

I agree with you, Brad. The fellow I'm cutting seats for did them by hand previously during the design development, but now that orders are coming in, getting the general stock removal handled by my CNC saves a ton of time...and his hand-work removes any hint that the initial contours were CNC produced.

[Mark Bolton]

** repost. For some reason whenever I try to edit on my phone it just deletes..

Had just mentioned that even with a simple top view photograph, and a front view photograph, and some dimensions, in a program like Sketuchp with some free plugins you can very accurately scale the photos and generated a skinned .stl very quickly that would get you within .050" to .100" for hogging purposes.

With the pro scan and pro cleanup I would imagine youd be just about down to sanding and putting the makers own feel/hand into the part. What does shipping the part, scanning, and the cleanup cost and does it get you to within single digit tolerances?

We generate quick .stl's and go straight into carve quite often.

[Jim Becker]

With the pro scan and pro cleanup I would imagine youd be just about down to sanding and putting the makers own feel/hand into the part. What does shipping the part, scanning, and the cleanup cost and does it get you to within single digit tolerances?

I agree with the first sentence based on the cutting I've done this week. Things are close enough that the maker will largely be just refining the surface and treating edges. I worked things out via the prototypes to get the thicknesses where they needed to be so that the parts are nearly identical to the original hand-made part that was scanned. I will not say what the number was for the scanning work because every job is different and quoted thusly, but it was very reasonable, IMHO. It's easily covered by being spread across multiple units as well as with the time savings...we had the STL back in like a day from ibild's receipt of the sample to scan. There was an additional day where I requested some minor refinement of the model to make the cutting easier and more consistent. But the turnaround was lightning fast on the work. I've explored a number of discussions, both online and in person, about the cost effectiveness of subcontracting some things like this kind of modeling and based on this first experience, I absolutely agree that it saves time and money. It's rare that any one of us can be experts on everything and taking advantage of someone who is an expert on modeling and/or scanning makes sense, at least for anyone producing as a business.

On the tolerance thing...yes, extreme tolerance is possible with the right 3D scanning setup and the right knowledge/skills for manipulating things once in the digital realm.

[Brady Watson]

I think it is relevant to note that there are always multiple paths to arrive at a finished part, but...not everyone has the same skill set or experience, so their paths are often limited. For instance, I don't own ANY carving chisels at all - have never carved anything in wood by hand (does whittling a stick count?) and do nearly everything digitally. There are many others who choose to also take this path, if for no other reason than there is comfort in an undo button!

In regards to this type of project, most seats are not very complicated or the builder, who isn't a professional woodworker or carver, has spent weeks, months or years getting the shape right, in his interpretation & expression - and they want to capture that EXACT shape and 'get it into the computer'. Quite often the issue of symmetry comes up, where one side is anatomically correct, where the other side might be a bit wonky, or a corner isn't fair or square or there are blemishes on an otherwise good part. All of these issues can be addressed by first having the model scanned and then use the data as is, or 'blueprint' the model to the customer's exact specifications.

Quite often scan data is used as a baseline for the customer to further tweak and modify the part to 'sneak up on' their final result. What's nice about having your part in digital form is that you can leverage all the advantages of 3D visualization and verify how the final result will look in relation to other components. For example, you may find it helpful to import your scanned part data into say Rhino and then construct some leg or arm parts to see how it will all look before you even cut one piece of material. You have the freedom to try different methods of joinery, styles etc to your heart's content. It's really cool to be able to do this!

In terms of costs involved etc, this is very subjective on the part to be scanned and what you need in terms of data. What I mean by that is, some are completely happy with just an STL mesh, while others have never done any 3D work and they need a little help with a video of it set up with sample toolpaths in VCP or Aspire. Furthermore, some designs really benefit from having their 2D features (holes, pockets etc) vectorized, digitally filled in and setup in relation to their 3D part to make machining faster & smoother and features sharp & true to form.

I don't believe that there is another scanning service on the planet that offers all of these services at a reasonable cost. If you've ever priced out scanning from an engineering type scanning place, you probably fell off your chair...I enjoy helping the smaller shops achieve their goals. Feel free to visit my site and send me a message. Include what you'd like to do and most importantly, send photos of the model to be scanned. After I've reviewed your project, I will send you a quote with instructions for the process. I know what it's like to be creatively 'stuck' and provide solutions to avoid that sort of thing.

[Bill George]

In the past I have used a scanning probe with my CNC to get a Digital format. It was so s l o w but it worked. Not sure if Mach3 is capable of that or I need to upgrade to a better control system as Gary suggests a Acorn, which I am really considering.

[Gary Campbell]

Centroids Acorn, and the optional Pro digitizing software will get you as good as you can get with a probed surface. That said, getting a resolution anywhere near what can be done with a scanner and software like Brady does is near impossible unless you have the ability (and upscale 3D software) to go in and edit the model to fill in the blanks and chop the peaks. And this says nothing to the time required.

Probing on a .100" grid, there are 100 points per square inch, at .010 there are 10,000 and at .002 there are 250,000 points per square inch.

Using a generous one point per second, that put the time required at somewhere between a minute and a half to almost 3 hours for the first 2 options, PER SQUARE INCH! And neither gets even close to the resolution that pros like Brady can achieve.

Higher end probes do well to locate parts, provide vectors for 2D engineering type parts to be machined from, but in todays world are seriously lacking in the ability to provide high resolution 3D scans that are anywhere near the resolution that most of our machines can cut at.

[Jim Becker]

So I'll once again vouch for the 3D scanning service...'sure made my life easier for this subcontract job!

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[Bill George]

So I'll once again vouch for the 3D scanning service...'sure made my life easier for this subcontract job!

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Is that your chair seat job? How much was the scanning and of course it needs to be shipped to them, correct?

[Bruce Page]

So I'll once again vouch for the 3D scanning service...'sure made my life easier for this subcontract job!

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What was the cut time on that? It looks great.