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Tools to improve spline to polyline interpolation resolution
SolverHeath
Member Posts: 8 PRO
Hello community, I'm getting accustomed to OnShape. A task I'm presently struggling with is figuring out how to increase the resolution of spline to polyline interpolation when exporting a part profile as a .dxf or .dwg file. I've never encountered this problem before as my former CAD solution provided fine control over polyline resolution. All I can find in OnShape is a checkbox to "convert splines to polylines" on the export screen (see attached).
THIS HAS A MATERIAL IMPACT
Trusting OnShape would preserve my geometry during export has been extremely costly. Both the absence of controls and the lack of visibility into how OnShape degrades the resolution of curves resulted in a customer rejecting an entire lot of CNC thermally cut parts from numerous sheets of 12 ga steel sheet. The customer rejected the parts due to the curves being jagged, rather than smooth as shown in the model, which they reviewed and approved. It was a reasonable expectation that OnShape would preserve my edge geometry when exporting files. However, as OnShape degraded my file, and provided no indication their software would do that, my business has been negatively affected in a significant way. The waste from that single lot rejection cost more than three years subscription to OnShape!
So, I require visibility into how OnShape is changing/degrading the quality of my files during export. Does anyone know where the settings are to control how OnShape interpolates splines to polylines? Where are these controls? I've dug through the product documentation. I've done several keyword searches. Not finding any actual solutions. The bottom line is my bottom line. I'm a small business owner and must be able to control polyline resolution. This is a crucial part of quality control. And please, do not suggest I install poorly supported or documented scripts. And please, do not suggest I go buy or use other programs to correct what OnShape is fumbling. Any suggestions that remotely sound like an excuse for a lack of product maturity is honestly not helpful. Please, add the functionality, enhance the functionality, or tell me where the functionality already exists, please!
Lastly, please NO down votes. If I provide actual criticism of OnShape features that don't work (yeah, I may say I think they suck, is that being rude?) or that are costing me resources (yeah, I live in the real world where time and money are limited and matter), well, that is constructive feedback!
Comments
I'm sorry to hear about the scrapped parts. I see you have created a support ticket, but you are right, there is no way currently to increase the spline to polyline resolution. I presume your machine controller can't take splines?
I feel the pain. However, are you sure the issue is onshape? I have had a few thousand parts cut over the years with thermal cutting methods and have noticed that the machine's price (which influences the quality of the components) has a direct effect on this issue.
I have had many parts cut on lasers that cost over a million dollars (not mine machines) and have no complaints, but I have seen this issue show up on the same part when cut on a ten-thousand-dollar job shop plasma.
I would go back to the company that cut it and ask them to at least share the burden. I obviously don't understand the entire project scope, so disregard useless information.
Thanks for jumping in. I read your periodic marketing emails! Thank you for sharing those.
I operate a Boss Table WHC-Pro 10 table. It's controlled by Flashcut CNC hardware and software (v10 Premium) and has NEMA 34 750W AC Servo Motors. This machine's controller can handle splines. However, when parts require higher resolution I contract the cutting to other shops with high-definition plasma cutters, waterjet machines, or laser cutters. In the case mentioned in my opening post the shop I outsourced CNC laser cut parts to operated a Mazak Laser. This shop's controller requires polylines. I've had this same shop laser cut many part profiles generated from from spline to polyline interpolated .dwg/.dxf exports in the past. In this case I assumed OnShape would preserve the curve geometry as my previous CAD program did. Assumptions get people in trouble, and in this instance my assumption got me in trouble. I'm proactively trying to mitigate a costly situation like this from occurring again, hence the reason for my post.
Good questions Wayne. In this case I am sure the jagged edges are a result of how OnShape interpolates splines to polylines when exporting .dxf/.dwg files. I exported the same profile with and without the box checked and then imported both files into Flashcut CNC 10 Premium. As Flashcut can handle splines it visually verified the edge geometry is jagged with the interpolated splines as polylines file,
My old CAD program provided tools to set tolerances when interpolating splines as polylines for .dxf/.dwg exports. A couple years back I got a handle on what this meant (fractals) and developed some workflows to manage the quality control across the main shops I work with for part cutting. Trying to understand what I can do to mitigate future, similar occurrences.
I agree that we should have proper control over how splines are converted to poly lines. I've made the case a various points and with various CAD systems that on-screen surface tessellation and edge drawing needs high resolution to do real work. I've also had a lot of pain in the past going between PCB layout packages and mechanical CAD where the PCB packages couldn't handle splines.
However, we're in 2024, not 1994. If I were you, I would push on your supplier(s) to modernize their controllers, or I would find different suppliers.
As an industry, we shouldn't be stuck with such primitive limitations.