Tiny letters breaking away

[brianm]

What are some reasons letters that stand proud of the wood break away during carving. I am using end mills.

[gerry]

Soft wood, aggressive feeds & speeds. If you have to use a soft wood, sometimes it helps to use a 1# cut of shellac first. Try Zinsser Seal Coat cut 1 to 1 with denatured alcohol. This gives a 1# coat of dewaxed shellac. Thinning it will soak in and stiffen wood fibers. Dewaxed shellac is compatible with just about any type of finish. I use it to cover oil finishes before applying water-based poly.


Zinsser Seal Coat

[germanguitars]

I would use a down-spiral in case you are using an up-spiral.
More flutes take smaller bites, too.
Go a little slower if that doesn't work.
Some species of wood are more prone to shearing (cedar, redwood) than others (mahogany).

[brianm]

Thank you for the tips. I will definitely try the shellac.

If i use a down spiral will I still get a nice flat bottom in pocket? I used a upcut thinking the bottom would be smoother. I guess I can use a downcut and save my letters and sand a little more on pocket.

[gerry]

The downcut will give a nice bottom, especially if the final cut is set thin. If you are using Vcarve you can edit the passes when you setup the toolpaths.

[brianm]

I am trying to limit my passes due to time. I am doing a text on text sign 7.25 inches by 22 inches. Trying to keep it to about a 2 hour carve time.

[redwood]

The only time I will use a upcut endmill is for cutouts, usually with the edge already beveled. The only reason for using the upcut, is that it clears the chips better. A downcut endmill is the only thing I use for pocketing.

How big are your letters and how deep is your pocket? Some fonts I have to manually thicken narrow areas to limit chipping. I've learned to spot a lot of potential troublesome areas with experience and correct them ahead of time.

The city/state font on this sign was a nightmare, but eventually I got it to work.  Client liked it enough that she ordered 3 more.

[brianm]

Redwood, beautiful work! I am still learning so forgive all the questions. how come people tell me use a upcut for a smoother bottom and downcut for smoother top edge? Is this not true? Thanks.

[Deleted]

Down cut bits will be forcing the wood fibers down, since they will be supported by the wood underneath so the top edge will not have tear out. While for an up cut bit the spiral flutes will be pulling at the top edge, which will not be supported by anything so the edge will have tear out. Bit's without a spiral will have less tear out but may still have some. The problem with down cut bits is that they pack chips into confined places, the recutting of chips causes heat that can result in fires so use them where chips have good exit paths and don't leave your machine unattended. All else being equal, you can remove material faster with an up cut bit because of the improved chip clearing. There are also compression bits, that is, they are down cut at the top and up cut at the bottom so they are the best of both worlds in that chips are pushed towards the middle when doing a full depth of cut so the top and bottom edges are both clean for a single pass edge cut.

[brianm]

The attached pic is NOT my work  in pic it appears the pocket is flawless without tool marks. Is he sanding or is it possible to come out of cnc this way   wood is pine.  Thank you  

[Gary Campbell]

With over 30 years as a professional woodworker, it is highly unlikely that one could get a good finish without a good amount of sanding.  Before and between coats.  A CNC machine is not the exception.  No machine produces a finish that does not require sanding.  Especially one where the end of a rotating tool is cutting a surface.


Learning to cut with the least amount of sanding takes a lot of trial and error.  But it is what separates the men from the boys.  The time and patience required to sand projects, which may be even greater than it takes to cut and assemble them, it the price of admission to the "WOW" club.

See below, 1.5 hrs cutting time, 6 hrs+ sanding time, another 2 hrs finish sanding time.

[brianm]

Gary thanks for the info. Beautiful work. What do you use to sand? Do you use any sanding mops?

[brianm]

Gary I know people online that sell a few hundred per month of the pic i attached
They dont have time to take hours sanding.

[aluomala]

I have only be doing woodworking for a short time, and CNC woodworking even less. I am always on the lookout for "shortcuts", but I don't know if there will ever come a day where I cut something without any sanding, unless I am selling it that way (I am planning on giving discounts for unsanded/unfinished pieces, as a "DIY" way of customers saving money (and saving me hours of work), but even then I would like sand off any sharp edges, remove larger fuzzies, etc.

One bonus, if you want to look at it that way, is the "rustic" art trend that is still ongoing. I carved a sign similar to the one brianm posted, and I used a 45degree cutting path (to simulate rough cut lumber)to cut out the pocket, and scraped that area little with a blade, and did minimal sanding. I also roughed up the finish (it hurts a little to do that after I took care NOT to do it (out of habit)) while I was finishing it, to make it look aged. So, sometimes being too refined is a negative

I do a lot of detail work and one tool that I bought that was worth the money (it is an expensive system) is the Micro-Make MicroLux powered sander (link). Be aware you HAVE to buy the transformer (another $90), but if you use their other tools, the transformer is used for all. The only modification that I made is using heavy duty hook-loop (aka Velcro) pads on the pieces, since PSA sandpaper in the finer grits is hard to find (here in Canada anyway). I have a damaged finger, and my hand seizes up pretty quickly (as well as carpal tunnel) from gripping sandpaper too tightly, so this tool has come in handy quite a bit lately.

Attachments:

[gerry]

You might be able to cut the sandpaper with a drag knife in your CNC.  

[brianm]

Very nice sign! What bits did you use? Are you impressed with the micro sander? Seems like a must in the CNC world. 😁

[Deleted]

Mar 20, 2018 12:35:26 GMT -5 Gary Campbell said:

With over 30 years as a professional woodworker, it is highly unlikely that one could get a good finish without a good amount of sanding.  Before and between coats.  A CNC machine is not the exception.  No machine produces a finish that does not require sanding.  Especially one where the end of a rotating tool is cutting a surface.


Learning to cut with the least amount of sanding takes a lot of trial and error.  But it is what separates the men from the boys.  The time and patience required to sand projects, which may be even greater than it takes to cut and assemble them, it the price of admission to the "WOW" club.

See below, 1.5 hrs cutting time, 6 hrs+ sanding time, another 2 hrs finish sanding time.

I don't even want to think about any projects that would require 6+ hours of sanding....YUK. (Better you than me.)

[aluomala]

Mar 20, 2018 21:20:24 GMT -5 brianm said:

Very nice sign! What bits did you use? Are you impressed with the micro sander? Seems like a must in the CNC world. 😁

Thanks. I used a upspiral 1/4" endmill and a 30degree .03" width v-tip insert blade for the Amana InGroove system to carve around the letters (the .03" flat tip leaves a nice flat area around the letters, instead of a ton of tiny ditches that you get with standard v-tips.

I like the micro sander, with the caveat that you have to modify the plastic shaped pieces with Velcro (unless you can find a source for PSA (pressure sensitive adhesive) sandpaper that goes into the finer grits (better than 150grit)). Initially, I cut out about 20 pieces of each shape, and then quickly realized it's easy to lose track of what grit each piece is unless you use a colour coding system, or each grit is coloured differently. What I do now is just cut a few pieces for what I need at the time and work that way. One downside is that some of the smaller heads don't hold the sandpaper very well (lack of surface area for the velcro to grip onto). I (unsuccessfully) tried superglue, but it doesn't work with the fuzzy velcro pieces. I would recommend buying extra packs of the heads, so that you can have multiples of each size at the ready (so you can swap them out when they wear out, rather than mess around with changing the pieces of sandpaper).

I am always looking for something better to do the sanding, since it is the bane of my existence. Sanding mops are OK, but you have to be careful with them (you can lose sharp edges in a hurry). I don't use Dremel style sanding equipment anymore, since it is too hit/miss, and you can make catastrophic mistakes in a few seconds. I'm slowly realizing that good old elbow grease needs to be used more than I would like. One quick tip before I forget: if you go to hobby stores (Micheal's, Hobby Lobby, etc) look for plastic paint pallette spatulas (link) like the one on the left (diamond shape). Put some velcro on the bottom, throw some sandpaper on there, and you can get into nooks and crannys a lot easier. The stuff I do (military badges) have a lot of small triangular shaped areas, and that gets in there nicely and you won't create a groove like you do if you fold sandpaper into a flat "U" shape. I just need to find smaller ones than I already have and then I'm good to go.

Allan

[redwood]

Like the rest of you, I'm not particularly fond of sanding, I am constantly on the look for sanding help. Unfortunately, I've yet to find the perfect solution, despite spending lot's of money and effort in my search. Tooling marks seem to be greatly reduced when pocketing with the grain. That wasn't done in the sign I posted earlier.

[brianm]

Aluomala thank you for the great info. I have Vcarve Pro, how would I program It to carve around letters with vbit and endmill everywhere else? Thanks again!

[brianm]

Would you happen to know the part number for the 30 degree bit you use? I couldn't find it anywhere. Thank you.

[aluomala]

Mar 22, 2018 17:28:27 GMT -5 brianm said:

Aluomala thank you for the great info. I have Vcarve Pro, how would I program It to carve around letters with vbit and endmill everywhere else? Thanks again!

I use Aspire, so I'm not sure of the process for VCPro.

Allan

[aluomala]

Mar 22, 2018 17:37:10 GMT -5 brianm said:

Would you happen to know the part number for the 30 degree bit you use? I couldn't find it anywhere. Thank you. 

Here's the link to the Amana website (link). You have to buy the holder (1/4" or 1/2" shank, or metric) and then the replacement blades, whether as a kit, or separately. The one I used was RCK-363 (I bought the kit, AMS-210, initially and then bought extra blades as required).

There are pro's/con's to this system:

Pro's

1) In the long run, it CAN be cheaper to buy replacement blades, vice destroying a $30+ carbide bit and having to replace the whole thing.

2) A very good selection of different replacement blades, particularly the flat-tipped v-bits, which I didn't have any success finding in a stand-alone bit (I have read of DIY solutions, like grinding the tip down on a stand v-bit to achieve the flat bottom, but that is a little more than I want to chew off with my limited skills/shop/budget.

Con's

1) Expensive to start off, and you will unlikely use some of the blades that come in the kits, so you might be better off buying the tool body and any blades that you think you would likely use.

2) There is a maximum RPM speed on the tool body (1/4" shank tool body is 24,000 RPM) so if you don't have a variable speed router (i.e bottom end laminate router) you can't SAFELY use this. I forgot to turn down the RPM's on my VS Bosch Colt router, and the tip size was effected (affected?!?), and consequently my cut was off considerably (the tip was flung out by centrifugal force, and wasn't .03" anymore, but substantially bigger..... I'm not an engineer, or smart for that matter, but that is my best guess at what occured)

3) It doesn't replace regular bits completely. For example, you couldn't use the 30degree tips for deep routering (creating joints for example) since the tool body would interfere with the cut. It is designed for engraving/etching, etc.

4) It isn't as cost effective as other options, such as buying 1/8" shank 30degree bits from eBay, such as Drillman1. I bought 10 of those for $50, so they are cheap enough that you won't cry if you break one (I broke 3 of the Kyocera 1/4" 30degree bits in 2 days, because my touch off puck on my NWA PirahnaFX had a loose wire and was intermittenly working... I got a 5 pack of those from Drillman1 for about $60 (with shipping) so it wasn't that traumatic (compared to a $30+ bit).

So, all in all, it's not a bad system to have, but not 100% neccesary.

TL;DR version: It's a want, not a need.

Allan

[redwood]

Mar 22, 2018 17:28:27 GMT -5 brianm said:

Aluomala thank you for the great info. I have Vcarve Pro, how would I program It to carve around letters with vbit and endmill everywhere else? Thanks again!

For this process, there is no difference between Aspire and V-Carve Pro.  I V bit on the vectors and I pocket outside the vectors.  I don't usually V carve the letters to the depth of the pocket.

[Deleted]

Mar 22, 2018 17:28:27 GMT -5 brianm said:

Aluomala thank you for the great info. I have Vcarve Pro, how would I program It to carve around letters with vbit and endmill everywhere else? Thanks again!

The process for all of the Vectric tools is the same. Make one tool path with the letters using the Profile Toolpath and set the depth and offset to get what you want or form a double outline so that you can use the V-Carve Toolpath. You'll also need to do your other toolpaths with whatever bits and have them stop at some offset to the letters which can be done with an offset or by creating another set of vectors that are the letter's outlines with an outward offset. It isn't that hard, you'll just have to go back and forth perhaps between the generation of vectors and toolpaths and check the simulation plots for areas that may need a little tweaking.

[redwood]

By the way, for small letters, I will finish any pockets with a 1/16" endmill, as long as they are no deeper then around 1/4".