HDPE cutting issues

Hello I am getting a lot of cut lines for this project. I am using a 1/4” carbide single o flute upcut. It is running 100ips on makita 1 setting. I need help with these lines it’s creating.

Check that your machine is trammed.
Try a two flute upcut with a smaller step over.
Keep feed speed up and the router a bit slower than usual.
You could be getting some lines due to a hot router bit flowing/melting the HDPE.
I listen to my spindle & run it as slowly as possible without bogging it down.

While Upcut bits are better for clearing chips, and single flute upcut are even better to create larger chips thus reducing friction and heat buildup which is great for cutting plastics. Downcut bits are better for pockets… and I think this conflict is an issue you’ll want to address in order to get the best results… you may want to use an upcut to remove the bulk of material, then swap to a downcut and remove a final pass to get a cleaner bottom of the pocket…