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Discussion Starter · #1 ·
Help! I built a machine after watching YouTube videos and reading online. I got it to run a program, and tried to carve an inlay. I am using a brand new 30 degree 1/4 inch bit, on a spindle running at 12000RPM at 60IPM feed rate. I'm carving in half inch mahogany. I've tried several times to carve the wood, and it always rips the wood to bits. What am I doing wrong?

I've posted the image from Aspire, and the actual carving.

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David - Machinist in wood
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My problem is that it's taking too much material. Some of the fine lines are tearing out of the wood.
If you aren't able to control that in your CAM software then just set the Z height 1/8" above the work piece for the first pass and then lower it on a subsequent pass (or 1/16", whatever works).
 

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Are you using the vcarve toolpath in Aspire? I not referring to the bit you are using, but to the toolpath you are selecting. Mahogany can be a bear owing to its grain structure. I do inlaid coasters and use a 60° V bit with a pointed tip. Keep in mind that, if you are using the vcarve toolpath, Aspire will cut as deep as it needs to in order for the bit to touch both lines in the carved out portion. That means, if you do not set a clearing depth, with a 30° bit, things can get very deep. It also means that your depths will not be consistent.
 

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Discussion Starter · #8 ·
Are you using the vcarve toolpath in Aspire? I not referring to the bit you are using, but to the toolpath you are selecting. Mahogany can be a bear owing to its grain structure. I do inlaid coasters and use a 60° V bit with a pointed tip. Keep in mind that, if you are using the vcarve toolpath, Aspire will cut as deep as it needs to in order for the bit to touch both lines in the carved out portion. That means, if you do not set a clearing depth, with a 30° bit, things can get very deep. It also means that your depths will not be consistent.
Yes, I am using the Vcarve toolpath in Aspire. My first attempt was with a 90 degree bit, it also tore out terribly, and I didn't like the looks of the carving. I couldn't test fit it because my machine wasn't dialed in yet and I was having some drift in my Y axis, so the sizes did not line up. I switched to a 30 degree bit hoping the tearout would diminish, but it hasn't. I will acquire a 60 and try again, but if the 30 AND the 90 both had tear out, I am concerned for the 60 as well. Every failed attempt costs me another $7.80 in wasted mahogany, so I'm hoping for a sure fix. My gut is telling me it's a feeds and speeds issue, but I don't know which way to go on that. The spindle is maxed out at 12,000 rpm.

The bits I have been using are 2 fluted bits. Would a 4 flute make a difference? My bits are a solid single milled bit, would a composite bit make a difference?
 

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Mike
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You don't say what size the carving area is so it is hard to tell how much material should be left. Using the 30 degree v-bit will make it easier for the narrow parts to chip off because there is not much material left to backup the fragile portions. Will this be an epoxy inlay? If so trying using a 90 degree or 60 degree bit so there will be more material left under the narrow places and you will also save a little bit of epoxy.
 
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Discussion Starter · #10 ·
You don't say what size the carving area is so it is hard to tell how much material should be left. Using the 30 degree v-bit will make it easier for the narrow parts to chip off because there is not much material left to backup the fragile portions. Will this be an epoxy inlay? If so trying using a 90 degree or 60 degree bit so there will be more material left under the narrow places and you will also save a little bit of epoxy.
This is the male part of a 6" tall inlay. I tried carving the female piece out of Poplar, it didn't fare any better. I'm experimenting on the (more expensive) mahogany thinking it's hardness would hold the detail better, but it's apparently brittle when it comes to the fine details, But the soft poplar did the exact same thing.
 

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Discussion Starter · #11 ·
The entire carving has a clearance program using a 1/4 end mill, and a detail cut using the V-bit. My first attempts, I ran the clearing program first, on the attempt in the pic I only ran the V-bit portion.
 

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You say the top speed of your spindle is 12000 rpm so what kind of CNC are you using. That might be the problem. Your CNC might have too much flex to do v-carve inlays or other precise work.

I would use a 60-degree v-bit and hardwoods or if using softwoods I would stabilize it before carving. You might also use the blanks that were messed up to do some test cuts to see if you can adjust your feed rate for a better cut since you can't use higher speeds with your spindle.
 

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Discussion Starter · #13 ·
You say the top speed of your spindle is 12000 rpm so what kind of CNC are you using. That might be the problem. Your CNC might have too much flex to do v-carve inlays or other precise work.

I would use a 60-degree v-bit and hardwoods or if using softwoods I would stabilize it before carving. You might also use the blanks that were messed up to do some test cuts to see if you can adjust your feed rate for a better cut since you can't use higher speeds with your spindle.
I built it myself. I've spent 3 years getting it to stabilize. I started with the cheapest parts I could find and learned as I replaced almost all of them with higher quality parts.
 

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Can you post pictures of your CNC?

One other thought I have is your depth of cut, are you trying to cut full depth in one pass or are you using more than a single pass for the full depth?
 
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Discussion Starter · #15 ·
Can you post pictures of your CNC?

One other thought I have is your depth of cut, are you trying to cut full depth in one pass or are you using more than a single pass for the full depth?

I think I set the program to cut 0.2 with a start depth of 0.1. I measured the actual cut and found it to me 0.335. It runs in 2 passes.

When I built the thing, I was hoping to do thick stock, so I made the gantry really high. I then discovered that that acted like a fulcrum and the spindle was a lever, it would put too much pressure on the spindle and it would seize up. So I added 4 inches of base and eliminated that problem. The Z and Y axis run on a 12MM ball screw, while the X axis runs on an 8MM screw with 12mm rails. I started with all 8MM, and replaced them as they proved to be less than adequate for the job.
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What clutter in the background? That is clean compared to what mine looks like right now.

There may be some looseness in your machine that is giving you some of your problems but you can check that by doing some test cutting.

I would say do test cutting with your bits to determine what speeds and feeds to use with your system. Don't try to take off too much at a time(add enough passes so you get a good clean cut), use small stepovers. Make sure you are within the chip loads for the bits you are using(you want chips not dust). Then change the cut depths, feeds, and speeds in the database for the bits so when they are chosen again they will cut as you want them to.

If you find that your machine just won't do v-carve inlays then you could make sure the pocket cuts cleanly and do epoxy inlays. You might have to do a little vector editing to get what you want but they will look good when finished. You could also look at using the standard inlay pocket toolpath and a small endmill, then epoxy for the inlay.
 
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Discussion Starter · #18 ·
What clutter in the background? That is clean compared to what mine looks like right now.

There may be some looseness in your machine that is giving you some of your problems but you can check that by doing some test cutting.

I would say do test cutting with your bits to determine what speeds and feeds to use with your system. Don't try to take off too much at a time(add enough passes so you get a good clean cut), use small stepovers. Make sure you are within the chip loads for the bits you are using(you want chips not dust). Then change the cut depths, feeds, and speeds in the database for the bits so when they are chosen again they will cut as you want them to.

If you find that your machine just won't do v-carve inlays then you could make sure the pocket cuts cleanly and do epoxy inlays. You might have to do a little vector editing to get what you want but they will look good when finished. You could also look at using the standard inlay pocket toolpath and a small endmill, then epoxy for the inlay.
I didn't really start on inlay work till I was getting perfect pockets. This one is .45 inches deep, 5 passes with a 1/4" mill end. Nice chips coming off of it where I had sawdust before. (The dark spot is a knot)
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