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Purple Heart Wood - Questions for Carving

PostPosted: Mon Aug 06, 2018 3:18 pm
by xoneeleven
Has anyone had good results carving on Purple Heart wood?

We tried carving a model we acquired from Design and Make, with terrible results.

The grain on the purple heart was long, and very stiff. The stiffness caused the grain to break off in long, skinny pieces.
The cutting direction was "with" the grain.

Has anyone here tried carving on Purple Heart wood? If so, what results did you have, and do you have any tips for carving it?

Thanks...

Mark

Re: Purple Heart Wood - Questions for Carving

PostPosted: Mon Aug 06, 2018 3:30 pm
by Mobius
I can't say I've every had a problem. I love using purple heart for V-inlays as it is so dense and holds detail nicely.

The obvious answer here is to not cut with the grain. Try running the job at a shallow angle across the grain, say 10º. Haven't tried it myself but you may get both benefits of cutting with the grain, but enough lateral movement to prevent tearing.

Re: Purple Heart Wood - Questions for Carving

PostPosted: Mon Aug 06, 2018 3:47 pm
by mtylerfl
xoneeleven wrote:...

The grain on the purple heart was long, and very stiff. The stiffness caused the grain to break off in long, skinny pieces.
The cutting direction was "with" the grain...


Could be a number of factors. Depth per pass set too deep, and/or stepover set too wide would be among the first things to consider. I prefer cutting (3D carving) with the grain and have never had a problem.

Re: Purple Heart Wood - Questions for Carving

PostPosted: Mon Aug 06, 2018 3:57 pm
by xoneeleven
Mobius wrote:I can't say I've every had a problem. I love using purple heart for V-inlays as it is so dense and holds detail nicely.

The obvious answer here is to not cut with the grain. Try running the job at a shallow angle across the grain, say 10º. Haven't tried it myself but you may get both benefits of cutting with the grain, but enough lateral movement to prevent tearing.



We will try cutting against the grain, next. Hopefully the results will be better.

We are using good quality bits, and using a CNC Calc for feeds and speeds.

Thanks for the tip

Re: Purple Heart Wood - Questions for Carving

PostPosted: Mon Aug 06, 2018 4:03 pm
by xoneeleven
mtylerfl wrote:
xoneeleven wrote:...

The grain on the purple heart was long, and very stiff. The stiffness caused the grain to break off in long, skinny pieces.
The cutting direction was "with" the grain...


Could be a number of factors. Depth per pass set too deep, and/or stepover set too wide would be among the first things to consider. I prefer cutting (3D carving) with the grain and have never had a problem.


Hello Mike,
I am pretty sure we have dialed in the correct depth and stepover.

One thing we did notice, is the bit got very hot during the finish cut (the bit is an Amana 46282, 5.4 deg tapered ball nose).
Perhaps the bit life ended while cutting this piece. We have replaced this bit with a fresh one and will cut against the grain on the next run.

Mark

Re: Purple Heart Wood - Questions for Carving

PostPosted: Mon Aug 06, 2018 4:41 pm
by scottp55
Mark,
You may still want to post a screenshot of the feeds/speeds you're using(the edit box in the actual toolpath).
Calculators don't always give the best info for your machine/bit/and material.
scott

Re: Purple Heart Wood - Questions for Carving

PostPosted: Mon Aug 06, 2018 5:08 pm
by xoneeleven
scottp55 wrote:Mark,
You may still want to post a screenshot of the feeds/speeds you're using(the edit box in the actual toolpath).
Calculators don't always give the best info for your machine/bit/and material.
scott


Here are the feed/speed details

bit feed and speed.jpg
Screenshot

Re: Purple Heart Wood - Questions for Carving

PostPosted: Mon Aug 06, 2018 6:30 pm
by Rcnewcomb
I'd use a 10% stepover and increase the plunge rate to match the feed rate.

Re: Purple Heart Wood - Questions for Carving

PostPosted: Mon Aug 06, 2018 7:26 pm
by xoneeleven
Rcnewcomb wrote:I'd use a 10% stepover and increase the plunge rate to match the feed rate.


Thanks

We will make the adjustments and check the results.

Mark

Re: Purple Heart Wood - Questions for Carving

PostPosted: Tue Aug 07, 2018 4:25 am
by dhellew2
Other possible considerations:
Use a spiral bit, better yet use a 3-flute spiral bit
Check out www.cuttingtoolsource.com

I typically use an 8% stepover but then again I mostly use very small bits.. ie 1mm
If the bit is getting too hot there are 3 basic reasons:
1. feed rate
2. rpm
3. dull bit

Good luck,
Dale

Re: Purple Heart Wood - Questions for Carving

PostPosted: Tue Aug 07, 2018 2:17 pm
by scottp55
Yep, Randall got it:)
The plunge feed was slowing EVERYTHING down, which resulted in the excess heating of the bit.
Should be better now.
scott

Re: Purple Heart Wood - Questions for Carving

PostPosted: Tue Aug 07, 2018 6:29 pm
by Xxray
I have made dozens of 3d models with PH and never had a problem, has always been one of my favorite woods to work with. Usually comes off the table so nice it barely needs any sanding.