Arc converted to straight lines.

[TDIPower]

Just to bring this thread back to life.

I have just started to need to machine some 25mm radius arcs. When importing the DXF into VR5 it produces (and you can see this when selecting paths to machine (in/on/out of the line)) a series of short straight lines rather than a constant arc..

Pete

[TDIPower]

Bumping this as a problem again, BIG problem.

I'm now running a Microrouter PRO so have the ability to machine much larger items in school.
I have 2 GCSE exam students produce designs which require large arcs.
One is a round table top, shelf and base, each part has been machined in 2 halves giving an over all Dia of 500mm. They are meant to be a circle when put together, it machines the shape but as a series of approx. 20 x 40mm straight lines on each half.

Another student has machined his designs for bed side units which include large arcs about 1000mm dia (straight up one side 500mm and the base 260mm with the arc forming most of the other side), this is even worse and has ruined the aesthetics as the arcs are again a series of straight lines, these are about 70mm long.

What makes this even worse is the students have lasered acrylic (versa laser) to fit the machined MDF and it looks shocking because the versa laser does the job properly.

I do not have the skill/knowledge to be able to produce the G code myself to do the job properly so have had to have the student machine out the designs with this problem. As was mentioned in an earlier post, it would be nice to know at what point VR decided an ark is a series of straight lines so I can advise students in the future.

As for the students exam pieces, they are gutted but have no option now but to move forward, I suppose it will give them something to right about in the improvements/changes for commercial manufacture section and manufacturing decisions or evaluation. Had I known just how bad this issue was I would have been advice the students that although the laser can do arcs the denford kit can't.

If there is any update/upgrades on this problem PLEASE let me know....

Pete

[MAX THE MILLER]

I started this thread more than two years ago. At that time I naively thought that as I'd bought a licence for VR Milling 5 it would be a properly supported product. This clearly isn't the case and this isn't the only problem I've raised which hasn't been fixed. There's been no new software release for over a year. I have resigned myself to the fact that these problems will never be fixed.

Having to use work rounds to fix problems is bad enough for me. It must be soul destroying for someone in a educational establishment using what is supposed to be an educational machine.

EDIT. I see that version 5.64 was released at the end of last year, but there was no announcement in this section. I'll give it a try.

[TDIPower]

Ohh please post up your results.
I'm not changing now as I need to focus on getting the exam work done and preparing for the revised GCSE to start teaching in Sept (the spec only got ratified a few weeks ago and is massively different). If it works i'll move on to it too.

Many thanks

Pete

[MAX THE MILLER]

Sorry to disappoint you Pete, but the problem is still there in version 5.64.

It shouldn't be too difficult to write G Code to cut a 500mm dia semicircle. Just a G1 for the straight diameter cut and a G2 specifying the end point and arc radius for the semi-circular arc.

[TDIPower]

Max you might as well have been talking about designer hand bags or football results to me! I know it can't be that hard but I have to be able to just load a file and get the code with the kids. I can't be going in, finding the required section and altering it for every part and piece of all the kids work. I found out today it machined a series of flats on a stool designed for a child that has a round top only 250mm dia. Each flat was about 15mm long still noticeable when you mount another part that has been cut properly using the laser on to it.

Up until this problem showed its heard I have enjoyed using and working with the Denford kit over the past 16years. Going through some design stuff on Quickturn 2D design on Monday I clicked on a tab to look at the graphic system properties within the program and it lists it all in what looks like Chinese!!

Can only hope that something comes right in the end.

[TDIPower]

On another thought. I might try installing Deskproto again, I used to use it with an Old Rolland CAMM3 PNC3000. Ill give it a wiz and see if I set up the machine parameters to produce a G code file. I have done it in the past for the old micromills we used to have.

If that works I'll use that as a post processor and just use Vr5 to run the machine.

Pete

[dixonsca]

bit late now i suppose.
What CAD software are you using? I think it is the conversion to dxf that causes the problem and not VR milling. You need a CAD program that can directly output a .fnc file.

[TDIPower]

Currently use techsoft 2d design and pro desktop, just started with fusion 360 but not done any dxf from that yet
Seems a bit odd to not support DXF from something like Techsoft given the extensive use in schools.


Pete

[dixonsca]

Are you importing dxf into 2d design? it is at this point the arcs are broken into separate lines. Can you not draw in 2d design? There is a patch from techsoft that will allow you to output .fnc file directly from 2d design.

[TDIPower]

I'm using Techsoft 2D Design to do the drawings and exporting to DXF, then opening them in VR5.
Many years ago techsoft used to generate files for Denford machines as we had paid for the add on, however when Techsoft went to V1.6 and then V2 that feature was removed/no longer available.
This was very frustrating as V2 has the single line fonts (techsoft fonts) needed for V cutting/engraving text (V1 lacked this). At the time we had VR2 so the only way we could do work was to generate it in 2D V2 then copy and paste it into V1 to create the machine file. When VR5 and quick cam pro came out we bought licences for both our machines given that we were told we could just import the DXFs from Techsoft 2D into VR5. The radius into straight lines only became apparent when we got a Microrouter pro and were able to machine larger areas than on the micromills.
Is this add on you are talking of?
If this is the only way to get it to work properly I could have saved on the VR5/Quick CAM pro software/licences 5yrs ago and kept working the way I was. It has unfortunately turned out not to be what we were sold despite its advantages.

Thanks

Pete

[Denford Admin]

Hi. There is a new version of VR Milling at the address of :

https://www.denfordata.com/downloads/VRMilling_V5_67.zip

Uninstall the exisiting version first and then install this.

This versions gives greater precision on DXF imports when dealing with very shallow arcs. Previously arcs were translated into simpler polylines if they were shallow (And indistinguishable from a couple of straight cuts) however some arcs were maybe not shallow enough before they were forced to become lines. This is why the Coal Plate lost its arc to be replaced with four lines.

When the coal plate is imported now, the GCode comes out as :

Code: Select all

G0 X106.538Y100.213
G0 Z3.000
G1 Z-1.000 F5000
Y117.676
X107.867Y117.906
G17
G2 X177.975Y117.676 I34.396J-200.266 
G1 Y100.213
X106.538
G0 Z3.000
G00 Z3.000
G91 G28 X0 Y0 Z0 M05
G90
M30

So the arc is represented correctly using a G2.

And the 3D simulation gives an image of :



I hope this solves any outstanding issues. Please upload any sample DXFs if there are further issues.

[MAX THE MILLER]

Thanks for fixing the problem.

Max.