Month: February 2024

Posted on by — Leave a comment

CNC Routing: PVC Sintra

CNC Routing: PVC Sintra

A customer recently asked me how fast (feed rate) they could push a 1/4″ Amana Single O Flute bit (51404) on 1/8″ PVC Sintra. They were running at 200 IPM and wanted to speed up the process. My recommendation was that they could use a different bit that would quadruple their feed rate. However, they had a stockpile of bits and wanted to use them up first.

Since I had the Amana 1/4″ Single O Flute bit (51404) and 1/8″ PVC Sintra, I did a quick test and found out that they could double their feed rate without losing too much quality. I first started out at 200 IPM / 22,000 RPM / Climb Cut and started ramping up from there.

PVC Sintra 200 IPM / 22,000 RPM / Climb Cut
200-IPM / 22000RPM / Climb Cut

Next up was 300 IPM / 22,000 RPM / Climb Cut.

PVC Sintra 300 IPM / 22,000 RPM / Climb Cut
300 IPM / 22,000 RPM / Climb Cut

You may notice that these pictures look the same and that’s because the quality wasn’t much different. Since this turned out well, I tried 400 IPM / 22,000 RPM / Climb Cut.

PVC Sintra 400 IPM / 22,000 RPM / Climb Cut
400 IPM / 22,000 RPM / Climb Cut

I ended off at 500 IPM / 22,000 RPM / Climb Cut because the material was beginning to move. You can see striations on the edge of the material. It’s possible that with extra hold down this could have cut better. Extra hold down may include a vacuum hold down enhancer, tabs, double sided tape, or something else. If you want to cut any faster than 300-400 IPM, I would recommend using a different bit. Feel free to reach out with any questions.

PVC Sintra 500 IPM / 22,000 RPM / Climb Cut
500 IPM / 22,000 RPM / Climb Cut

All in all, you can definitely cut faster than 200 IPM without losing too much quality in this case. However, the next test would be tool life. Just because a tool can cut faster doesn’t mean it will last as long as it could. Make sure to pay attention to this when trying out new feeds and speeds as I was not able to along with this test.

When orders are placed, they will be double checked to ensure no errors were made and customer follow up will take place during the same day (unless an order is made after hours). If products are available, which most of them are, they will be shipped out the same day. If they are not available, a lead time will be provided. Feel free to reach out for any assistance with our website or anything else regarding CNC routing and knife cutting.

CNC Tooling Shop, a division of Specialty Machinery Inc.

Email: tooling@cnctoolingshop.com

Hours: 8:00 AM to 5:00 PM (EST)

Phone: (616) 502-7277

Greg Smolka (Author)

CNC Tooling & Application Manager

Here to help with tooling recommendations (bits, knives, collets, tool holders, maintenance kits, torque stations, etc.) and cutting recommendations (feeds/speeds, tips/tricks, # of passes, etc.).

Contact Info: greg@cnctoolingshop.com

Posted on by

Why are my CNC bits breaking?

Why Your CNC Bits Are Breaking

Every so often, I’m asked the question “Why are my CNC bits breaking?” and then the process of elimination begins. There are an array of issues that could be causing this to happen. Here are the most common:

  1. Incorrect feed/speed
  2. Dull bit
  3. Bad vacuum/hold-down
  4. Debris in collet/tool holder
  5. Bad collet

Incorrect Feed/Speed

First off, the feed/speed or feed rate and spindle speed are often the culprit. Bits can break at too high or too low of both the feed rate and spindle speed. It’s important to find the correct mix of feed/speed that meets your quality requirements. The easiest solution for this is to call me at (616) 502-7277. On a daily basis, I’m trouble shooting and offering starting points on how to cut a specific material for my customers.

Dull Bit

Most operators know this, but a dull CNC bit is far more likely to break than a new sharp one. Instead of the dull bit cutting through the material, the pressure is pushing through it until it no longer can. In this case, a smaller diameter tool will break before a larger one will. Pay attention to the cut quality and sound coming from the tool when a new tool is cutting vs. a used one. This way you can spot a dull tool before it breaks or sacrifices too much quality.

Poor Vacuum/Hold-Down

Bad material hold-down can very easily break a bit. Vibration or material movement is the enemy. The hold-down could be bad because of vacuum problems, lack of milling the spoil board, vacuum pressure leaking out the side of material, etc. Do whatever you have to do to keep material held in place. Some people use tape, down-spiral bits, or vacuum enhancers to further decrease movement. Again, do everything in your power to keep material held in place.

Debris In Collet/Tool Holder

If tool holders and collets are not properly cleaned, debris can build up and cause the tool holder to be off balance. When your CNC machine is cutting material out of balance, you face a decrease in tool life, spindle life, and cut quality. This can easily be a reason why your bits are breaking. Remember that collets and tools holders are consumables and should be replaced in a reasonable time-frame. See a recent article, I wrote, with more detail on tooling maintenance HERE.

Bad Collet

Like I mentioned above, collets are consumables. Depending on use, collets have a 90 day life. When you break a bit near the collet, they should also be replaced because they can damage the collet to where it no longer holds a bit correctly. Think of a collet as a spring. If a spring is compacted together for 90 straight days, it will no longer be the spring it once was. Therefore, your CNC bits are not being held as tight and balanced as they need to be. Find collets on our webstore HERE

Greg Smolka (Author)

CNC Tooling & Application Manager

Here to help with tooling recommendations (bits, knives, collets, tool holders, maintenance kits, torque stations, etc.) and cutting recommendations (feeds/speeds, tips/tricks, # of passes, etc.).

Contact Info: greg@cnctoolingshop.com