How to get rid of Tool Marks in MDF

[bd007]

I have been using my JGRO for cutting 1/2" mdf but I am getting tool marks mainly going around curves, straight cuts are not that bad. Does anyone have any tips/tricks for getting smoother cuts around curves? Should I try increasing the router rpm, I'm afraid I may start burning the wood?

I am using turbocnc with an Onsrud 1/8" upcut spiral with .125" depth per cut. My router is a 1-1/2 hp peak craftsman with a HF speed control.

Thanks

[joecnc2006]

Originally Posted by bd007 I have been using my JGRO for cutting 1/2" mdf but I am getting tool marks mainly going around curves, straight cuts are not that bad. Does anyone have any tips/tricks for getting smoother cuts around curves? Should I try increasing the router rpm, I'm afraid I may start burning the wood? I am using turbocnc with an Onsrud 1/8" upcut spiral with .125" depth per cut. My router is a 1-1/2 hp peak craftsman with a HF speed control. Thanks

This is called (Chatter) What is your feedrate and microstepping, Alot of times its the machine not being tight enough, meaning movement at the cutting bit..... I got this more from my cheaper built DIY machines until I built my double rail system, which made everything alot more tighter, Also your piperails may cause the chatter if they are not smooth enough.

[Tom Brown]

Joe, did you paint your pipe rails?

As I recall, you just used bare galvenized.

[bd007]

Joe, Thanks for the reply. I am cutting at ~15ipm. I am at work so I can't check the microstepping but I believe it is set to 1/4, I am running the hobbycnc board with 127 oz motors.

Looks like I really need to get started on machine #2. I really like your 2006 model. I would like to build one similiar to yours and Lionclaw's setup.

[joecnc2006]

Originally Posted by Tom Brown Joe, did you paint your pipe rails? As I recall, you just used bare galvenized.

no did not paint them but do a very light sand from time to time where rollers roll over.

[Rance]

bd007,

It seems you are saying "Tool marks" but are describing resolution. The two are different. If your straight cuts are smooth but curves are jagged, then I'd say you probably don't have enough resolution in your steps.

On the other hand, imagine that your Z axis is canted 5 degrees. Then plane the surface of a board. You'll see swirl marks. This is truely "Tool marks". Am I making sense?

Rance

[bd007]

Hi Rance,

The straight cuts are not perfectly smooth but it is a lot better than the curves. How can I increase/check the resolution? Is it the microstepping that Joe was referring to?

I am running 5/16 -18 threaded rod.

[spalm]

My guess would be that this problem is caused by excess flex. Just my gut feeling. This is a JGRO isn't it? Watch and feel the pipe rails while it is going around corners. They should not move. Try going slower.

Steve