Corel help - I thought it would be simple

[Graham Taylor]

Mornin all,

I need to cut some arches from 2mm clear cast acrylic so I drew one up in Corel and cut away.

However, when I got it out of the laser the curved arch bit at the top is not as smooth as it should be - it feels uneven when you run your finger along it. Also, where the straight sides meet the blue arched bit (shown in the black circles) there is a small lip that sticks out a tiny bit but can be felt with the finger.

Arch_1.JPG

Any ideas on what I have done wrong? Does anyone have a smooth arch shape like this one they could share?

Everything else I have been cutting is smooth with no problems - its just this pesky arch.

I haver attached the file in the hope that someone can help.

Cheers all

[John Bion]

HI Graham, Try this:

Arch1.cdr

Your two vertical lines were not joined to the “base-line” and in fact overlapped the base, the two vertical lines did not quite join the two ends of the arch, so would not quite have cut at that point, giving slight sticking out “break-offs”, this drawing also resulted in 4 entry holes instead of 1. I would recommend welding this type of cut, I am not sure if you had a reason for different colours? By welding them all together you only have one entry hole. As to a rough curve, I suspect settings, I cannot comment here due to my not having a clue on your type of machine.
All the best, John

[Mike Null]

I believe I would make a rectangle to dimension then convert to curves and make the arch with the shape tool.

[Graham Taylor]

Hi John,

Thanks for the quick reply - I will giove that a go later.

I used different colours to try to show the bits I was talking about and in the one I cut it was all red.

When I said 'rough curve' I should probably have said slightly uneven like a wave rather than rough. All the straignt lines are nice and smooth and straight so I know its not the settings.

P.S. I have still not heard from the customer about that glass ornament so I assume she doesnt want to go ahead but if I do hear anything I will let you know ASAP.

Mike,

I will give that a go also.

Thanks again

HI Graham, Try this:

Arch1.cdr

Your two vertical lines were not joined to the “base-line” and in fact overlapped the base, the two vertical lines did not quite join the two ends of the arch, so would not quite have cut at that point, giving slight sticking out “break-offs”, this drawing also resulted in 4 entry holes instead of 1. I would recommend welding this type of cut, I am not sure if you had a reason for different colours? By welding them all together you only have one entry hole. As to a rough curve, I suspect settings, I cannot comment here due to my not having a clue on your type of machine.
All the best, John

[Scott Shepherd]

Graham, what speed are you cutting at? You might be going too fast for the curve.

[Jiten Patel]

Graham, have you set a correction value in the settings for the cut? This compensates if you are going too fast, so you get smooth cuts. I find with the trotec that I never get a "smooth" curve. Try using enhanced geometries too as this is meant to solve this. I never use it as I use Illustrator and it is too buggy, but it is supposed to work a charm with Corel.

[John Bion]

Exactly my thought Steve, but I know you can play with other settings on Trotecs that I cannot on my Weikes.

No problem on the ornament Graham

[John Bion]

You see, now Jiten beat me in my reply but amply proves my point about the software toys you have at your disposal

[Ruben Salcedo]

Beside the good advise that you have received regarding the graphic, I believe that your problem in the arch with cutting quality is do to your PPI resolution settings more than speed, I think you may need to up a little your PPI value, lasers in arch's or circles don't really go in a continuous line it actually pulses the beam making many little lines to form a circle, the smaller or close together the smother it will look, this means that lower PPI values will make pulses apart, higher PPI values will make pulses overlap making a more smooth cut in curves, you need to be careful not to up the values to much, if you do... it would cause melting. FYI, changing the PPI values won't affect speed, only the frequency of pulses.

[Kev Williams]

One of the things I don't like about Corel is that you can't simply pick a corner and enter ".250 radius". (If you CAN, someone show me how please!)

As for the bumps sticking out, that's a symptom of the laser slowing down to near nothing to start the curve from the straight, and then slowing down again as it gets to the next straight-- the slowing down part it's supposed to do, but the power ramp-down rate (or whatever it's called) may need adjusting...?

[Scott Shepherd]

One of the things I don't like about Corel is that you can't simply pick a corner and enter ".250 radius". (If you CAN, someone show me how please!)

What do you mean Kev? Are you using the Fillet/Scallop/Chamfer docker? If so, select the node you want to change into a radius, enter .25 and apply. Surely you're talking about something different than that? Can you clarify?

[Michael Hunter]

One of the things I don't like about Corel is that you can't simply pick a corner and enter ".250 radius".

Yes - you CAN!

Using the node editing tool, select the node(s) on the corner(s) that you wish to radius.
Now go to Fillet/Scallop/Chamfer, set the radius and click "apply".
DONE!

Note that this won't work with new rectangles - you need to "convert to curves" first and then it will work OK.

Ha! Scott/Steves post came in whilst I was writing!

[Bert Kemp]

Kev when you have the rectangle selected at the top of the screen you'll see 3 different boxes for making corner raduis click the one you want and then pick the corner you want and put in a number

One of the things I don't like about Corel is that you can't simply pick a corner and enter ".250 radius". (If you CAN, someone show me how please!)

As for the bumps sticking out, that's a symptom of the laser slowing down to near nothing to start the curve from the straight, and then slowing down again as it gets to the next straight-- the slowing down part it's supposed to do, but the power ramp-down rate (or whatever it's called) may need adjusting...?

[Kev Williams]

I do most of my editing in Casmate or Gravostyle, so I rarely if ever go near the "dockers" selection in Corel-- much appreciate the info!