Bad finish

[Tinny]

Hi all,

I have a problem outputting a program which follows a spline toolpath. The finish will be facetted i.e. a series of flats in stead of a nice curve.

I also get the same finish when using a side and face cutter ( its like a dovetail form with radius ) with a surface contour finish, spiraling down a cylinder. I need to improve the finish but how?

 

Many thanks in advance

[Gary]

Is it a surface toolpath or a contour toolpath. Did you try filtering or if a wireframe tightening the linerization tolerance.

[Storkman]

Splines will give you a series of short lines, sometimes filtering helps. If not try curve fitting arcs to your helical moves.

[BernieT]

I'm assuming you have Ver 9.1

 

Try setting the 'Linearization Tolerance' to .0002 or so. Splines are cut as short line segments like Storkman says and the smaller the tolerance, the shorter the line segments. Filtering to .0004 with Arcs on should also smooth the toolpath. I also like to set the 'Roll Cutter around corners' to None.

 

For surfaces set the 'Total Tolerance' settings to 2/1 ratio with Filter Tol .0004 and Cut Tol .0002 with Create Arcs On.

 

HTH

[Tinny]

I am indeed running v9.1 We have X but are waiting for a modified cimco post.

 

BernieT when I tighten the tolerances as suggested MC crashes. We get this problem quite often. I gather your pc's run happily if set to this tolerance? If so then maybe there is another setting we have to change.??

[smokey_44]

Try changing the spline into lines and arcs for whatever you are doing and you will get good results then , I have found that using splines just sucks ,linea ands arcs give you nice curves and no facetting.

 

 

Dave

[Tinny]

Hi,

The toolpath based on a spline is not a huge problem now. It is the surface contour toolpath using the helix option. When I tighten the tolerances to less than 0.02 then MC crashes. MCX does not crash but will refuse to generate a toolpath nci. I tried the settings suggested by BernieT but it took 2 1/2 hours to do the toolpath but crashed at the end!! My MC reseller is looking into this but I thought I would tap into the knowledge on this forum. I cant post the file because it is sensitive but I will try to recreate it.

[BernieT]

Are you working in metric?? My suggestions are for inches.

[Dan_AKA_ROY]

That would be problem if working those tolerances in metric, Bernie! I think Tinny is from Nottingham, England, so you're probably right.

 

You could copy your design to another level and try breaking that spline into lines using the Modify/Break/Mny pieces function. When selecting either By Error or Length, make sure you make the lines small enough. Try toolpathing it then and if it doesn't work any better you still have your original spline.

[Müřlıń®]

Tinny,you could create edge curves on the trimming boundary of the cylinder.

 

Then, break your spline that makes the cylinder into a couple pieces so you can draw a 2-d, 3-point arc and recreate the cylinder.

 

Extrude the cylinder surface and then trim to the boundary you just made.

 

I have to do stuff like this all the time...works for me...

 

Hint....when a surface renders slowly, you have a lot of math going on in the entity.

 

I will most always do what the others have said and recreate the spline as arcs and lines. Slight non tangencies will not be noticible after machining.

 

Just a thought...

[Ocean Lacky™]

Regarding the computer crashes......how much RAM?

[Tinny]

Thank you all for your support. Yes I am from Nottingham, England. And yes we always use metric now. ( I myself was brought up using a proper measuring system - Inches ) I have tried re-creating the surface, and It no longer crashes. I have 1 gig of ram, another workstation has 2 gig and both have the same problem.

 

I have tried re-running the same toolpath with a filter tol. of 0.01 ratio 2:1 and get much better surface finish results.