# Part marking - HDPE plastic parts



## vandomme2 (Jun 11, 2012)

I tried to mark 8x8in plastic parts (3-dog handles) with the character string uturnhandles.com along a curve using VCarve Pro but don't get acceptable results.
Text height is 0.20-0.25in, text depth is approx. 0.04-.08in. I tried 60deg V-bits first, then 1/16 and 3/32in straight bits, with several solid line and true font fonts. 

V-bit results look better but still not very good, not readable enough and it feels rough to the touch.
I'll try 30deg V-bits next. Probotix Nebula CNC spindle speed 13,000- 16,000, feed approx 60ipm. 

Any recommendations? Are Diamond Drag bits better for this kind of small lettering on thermoplastics = soft plastic?


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## MEBCWD (Jan 14, 2012)

Paul not having pictures to see your results makes it hard to give you an answer but small lettering is often problematic. Using v-bits would probably be the best way to go but I also recommend making the lettering as large as possible. 

One more thing to look at would be just using "uturnhandles" because most people would search using what is written on the item and that would lead to your site, your YouTube videos, your Amazon listing and other places listing your handles. 

It looks like you might be able to go with Arial Black 3.5 to 4.0 long by 0.4 high using a 90 deg v-bit. You will probably still have some clean up around the edges because of the soft plastic maybe a quick touch with a torch or fine sand paper.


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## Job and Knock (Dec 18, 2016)

I suspect that you may be attempting to machine with a single pass. When I used to run an industrial CNC router (Biesse Rover) we did quite a few jobs in HDPE (350 to 1000 grade) and found that with the lower (softer) grades it was almost always necessary to make a primary cut 0.1 to 0.2mm shallower than the final cut and then finish with a final cut to full depth. Sometimes it was necessary to run the final cut in reverse so as to obtain a climb cut. This approach is necessary with the softer HDPE plastics as well as some grades of nylon, polypropylene, etc because the plastic will compress on the first (roughing) cut, springing back after the cutter has passed. The result can be unevenness of surface as well as some roughness. Maybe worth taking a look at although it does involve extra time and effort in programming


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