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Discussion Starter · #1 ·
We raise cattle and every year order custom cattle tags. With all the shortages that are happening, I decided to pick up a cheap CNC mill, create a wooden template, and cut the names into the tags and then use a permanent tag marker to fill in the slot that I made for custom tags.

I ordered a SainSmart Genmitsu 3018-PROVer. i ordered an assorted set of bits off Amazon too. Learning curve wasn't too difficult, but I spent a few days working on a single tag holder template until I got that right. I figured where my machine could cut and then made a template to do 8 tags at a time.
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I cut a hole deeper in the wood at the top to glue in a 3x12mm magnet and drop a 3x6mm magnet in the hole to help hold the tags in place.
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So far, so good.

When I actually try to cut the tags, I get a mess. the bit is not cutting the plastic out, but just melting it and making it roll and ball up. I need a different bit. I am thinking a single fluted downcut bit, but not sure. I can't seem to find one of those for the 1/8" collett that this machine has.

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what style bit were you using? most folks use a single "O" flute for cutting plastics. but you aren't cutting as much as end milling. i would try what bits you have, but also try changing your feeds and speeds. you might find it...

what is holding the tags down?
 

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Discussion Starter · #3 ·
what style bit were you using? most folks use a single "O" flute for cutting plastics. but you aren't cutting as much as end milling. i would try what bits you have, but also try changing your feeds and speeds. you might find it...

what is holding the tags down?
Thanks for answering. What is a single "0" flute?

The tags are in a recessed slot. There is a magnet in the pin hole and one glued into the board below it. Nothing else holding them down. If it wasn't working well enough, I was going to have to think of something else to hold them in place. So far, my issue is the failed cut more than the moving around.

I have played with the cutting speed and the spindle speed, but just getting different disasters.

I am using a 2mm bit from this set that is cuts flat and has a cutter on the end. Some of these bits are completely flat with no end cutter at all.

I have this set in my cart on Amazon.

 

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Discussion Starter · #4 ·
... most folks use a single "O" flute for cutting plastics. ...
I just found this, but it is the wrong shaft size for my small machine.

Amana Tool 51507 CNC SC Spiral O Single Flute, Plastic Cutting 1/4 D x 1-1/4 CH x 1/4 SHK x 3 Inch Long Down-Cut Router Bit with Mirror Finish

And I found this on Amazon.
 

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caution an up cut will tend to lift any material not securely fastened.
i would try to use a small square of double sided tape, capret tape, etc. to hold down
you may also try a v bit. i think i have seen people mention good results from a squared tip v-bit.

hopefully someone with more experience with what you are trying will show up for you...

it appears that you are melting more than cutting. i would slow rpms more and more, and/or speed up feed rate.

for just starting out you are doing well!
 

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David - Machinist in wood
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I agree that you need a downcut bit. The cut is so shallow that an O flute bit may not help much. I use an O flute to cut thicker acrylic and Plexiglas.

What feed rate are you using? This looks almost melted like @TimPa said. My first thought was that you likely need to be cutting much faster, even if you have to take lighter passes and do it twice.
 

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Discussion Starter · #7 ·
I agree that you need a downcut bit. The cut is so shallow that an O flute bit may not help much. I use an O flute to cut thicker acrylic and Plexiglas.

What feed rate are you using? This looks almost melted like @TimPa said. My first thought was that you likely need to be cutting much faster, even if you have to take lighter passes and do it twice.
David,

I had my feed rate set to 15 in/min and after the first disaster, I doubled it. Not sure the machine can really run double. Sounded faster, but not twice as fast. I am only cutting in .03 in and had the depth per pass at .015 and that didn't seem to make a difference over cutting it in one pass. I am not sure the limitation of my spindle speed, but had it set to 18100 and changed it to 10000. If 10,000 is the limit, then that change didn't do anything.

Should I set my spindle to like 3000 and my cut depth to .001 and the feed rate at max? I know this bit is the wrong one, but I sure would like to see some results.
 

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David - Machinist in wood
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Should I set my spindle to like 3000 and my cut depth to .001 and the feed rate at max? I know this bit is the wrong one, but I sure would like to see some results.
I run most jobs at 18k rpm and engraving like that at 100 ipm to 250 ipm. My machine is more robust than yours but 15 - 30 ipm is still crawling. I don't know what your max feed rate is but 0.001" is nothing. The plastic isn't accurate to 0.001" so there would be places it won't even touch, I would imagine.

What is your final (target) depth of the engraving? If it's 0.010" or less I would try it in two passes with the first being about 0.0075" and the second to clean up the final little bit. You can set Z zero 1/2" above the work piece and play with the feed rates to see how the machine works out with the faster feed rates and not waste any parts.
 

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Discussion Starter · #9 ·
I run most jobs at 18k rpm and engraving like that at 100 ipm to 250 ipm. My machine is more robust than yours but 15 - 30 ipm is still crawling. I don't know what your max feed rate is but 0.001" is nothing. The plastic isn't accurate to 0.001" so there would be places it won't even touch, I would imagine.

What is your final (target) depth of the engraving? If it's 0.010" or less I would try it in two passes with the first being about 0.0075" and the second to clean up the final little bit. You can set Z zero 1/2" above the work piece and play with the feed rates to see how the machine works out with the faster feed rates and not waste any parts.
I just looked up the specs and the maximum spindle speed for this one in stock form is only 9000RPM. There is no listing for IPM, so I don't know.

The maximum thickness of my plastic is only .056 - .062 They don't seem to be consistent. I have my cut depth set to .03

These tags that I have been testing on are gold. The 3 brands of cattle tags are 5-6 months out on getting more and the mounting buttons are sold separately. Tag and button combo if available are north of $1.50/ea. I have about 50 tags and no way to mount them. Searching ebay this week and found some no name tags. 100 with buttons for $21.49 so I now have some cheaper ones to test with. They are a different shape so I have to create a new wooden template.
 

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David - Machinist in wood
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The maximum thickness of my plastic is only .056 - .062 They don't seem to be consistent. I have my cut depth set to .03
That's engraving about half the thickness of the part. That seems awfully deep to me.
 

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Welcome to the forum, Kirk.
 

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Discussion Starter · #13 · (Edited)
So, I am getting closer. I ordered a set of bits that are single flute.

I used the 2.5 mm bit and my settings were:
Cut depth .015 in
feed 30 in/min
depth per pass .05 in
Spindle speed 3000 RPM

I am not melting plastic, but there are feathers of plastic around the edges that aren't removed. It takes a while with a needle nose pliers to pull loose all the little pieces from the edge.

I have tried cutting it all in one pass, or up to 3 smaller passes. I have slowed down and sped up the spindle. These results are all similar.

I tried to melt the filaments off with a heat gun, but that is counter productive because they melt into the channel that I am wanting to have cleared out. I have tired using a jitterbug and a belt sander, but these little filament seem to hang on pretty tight. I am going to try a wire brush next.

What else should I try? I am wasting expensive tags that are out of stock everywhere.

Thanks.
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I came in late for this topic. I have cut and engraved many sheets of PVC material. My suggestion is similar to the others, but one simple suggestion I didn’t see was try running the program twice. On the second pass it will generally clear out what looks to be the melted chips. As for fast, easy hold down I use vacuum. So long as the material you are cutting is not porous it will hold down tight. Second choice is double sided tape as previously mentioned. I’ve used single flute straight and “v” bits for the engraving with good success. No need to purchase a laser module, you already have what you need to make the tags. If you go with the laser be cautious of possible dangerous out gasses.
 

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Discussion Starter · #16 ·
I came in late for this topic. I have cut and engraved many sheets of PVC material. My suggestion is similar to the others, but one simple suggestion I didn’t see was try running the program twice. On the second pass it will generally clear out what looks to be the melted chips. As for fast, easy hold down I use vacuum. So long as the material you are cutting is not porous it will hold down tight. Second choice is double sided tape as previously mentioned. I’ve used single flute straight and “v” bits for the engraving with good success. No need to purchase a laser module, you already have what you need to make the tags. If you go with the laser be cautious of possible dangerous out gasses.
I don't know what kind of plastic this is, but it is quite a bit more flexible than PVC. With my jig, I am not having problems with it holding down using my template. I have tried cutting twice, but that doesn't seem to help. What is a single flute v bit?

is this what you are talking about?
Font Parallel Rectangle Wood Drawing

Do they make a bit like this with a flat tip?
 

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Discussion Starter · #17 ·
A friends wife is an IT person at a school. They have a 30,000 dollar cnc mill/laser. She did this today in about a minute with the laser. Unfortunately, she is about to leave that job. Font and layout are not what I want, but the results are exactly what I wanted. Still making me think I need the laser module for the 3018. Of course that module is probably junk compared to the school cnc.
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The cheap Chinese mills are very frustrating. You get what you pay for. Plastics usually need a fast ipm to keep plastic from melting. If your machine cannot go faster slow down router. On your machine not sure how much slower your spindle can go.

Recommend you send machine back or sell it.

If you can use a cnc try Shapeoko, xcarve or oneinfinity for hobby class machines.

If you need these on a recurring basis just hire someone to make them. Sign shops have cnc and laser machines.
 

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I'd go with a laser as you can get a decent laser for around $500, and your jig would work well for what you're trying to do. Might take a little more time than a $30K machine. Plastic that thin can flex while being cut.
 
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