Haas polar coordinate machining speed issue

[haas1FD6Q9]

Reference.

https://forums.autodesk.com/t5/fusion-manufacture/problems-with-c-axis-machining-using-the-haas-umc7... 

I am currently performing polar coordinate machining on a Haas UMC-750. While the machining method itself is fine, I have a question regarding issues with adjusting the machining speed.

The image above is the NC data of the toolpath I posted. The machining is performed as the C-axis rotates from a larger diameter to a smaller diameter. In the NC file, the speed is slower at the larger diameter and faster at the smaller diameter.

In the machine settings, the maximum speed for the X, Y, and Z axes is 6000, while the C-axis is set to 2000.

I believe there are two issues.

First, I think the speed should increase when the diameter is larger and decrease when the diameter is smaller.

(I might have misunderstood this part. When acceleration and deceleration are involved, I understand that the speed should change according to the diameter, specifically increasing when the diameter is larger and decreasing when the diameter is smaller.)
Second, the speed exceeds the limit I have set.

Is there any solution to this issue?

[a.laasW8M6T · Accepted solution]

Hi

Depending on this setting:

The code will be using Inverse Time feed if its unchecked, or DPM  feed if it is checked.

Inverse time is preferable and it often has odd looking feed rates as the F value is not how fast the axes should move but (The inverse of) how long they should take to move the programmed distance.

https://www.haas.co.uk/resources/better-techniques/control-features/inverse-time-feed-mode-g93/

This should explain the numbers you are seeing.

Hope that helps.

[haas1FD6Q9]

When the option is turned off in the settings, G93 appears, but when the option is turned on, it doesn't.

When the option is enabled, the feed rate uses G93, meaning the machine adjusts the speed according to G93 (though I don't fully understand it yet) rather than the typical G98 speed we use. If the option is disabled, can I understand that the CAM adjusts the feed rate instead?

[a.laasW8M6T]

Hi

Hi

yes with G93 Fusion just needs to calculate how long a particular move should take, the Machine controller then works out how fast to move each axis. This is an older method of defining multi axis feeds and is largely superseded by TCPC(G234 on haas).TCPC take a Linear feed and figures out the axis motions

In most multi axis stuff it will be output using TCPC but for this case using POLARMODE it is output using DPM or Inverse time.

For DPM the feed is calculated by the post processor to determine the correct feed rate to move the rotary/linear axes to achieve the effective linear feed.

When you combine rotary and linear feed rates they  again can look faster than expected as there is a Weighting between how the controller interprets the linear and rotary components of the Feed command.

This is why its better to use G93 Inverse time and let the controller deal with the calculations

[haas1FD6Q9]

Yes, I think I understand now. Currently, I'm struggling with acceleration and deceleration issues. I didn't encounter this type of problem on other FANUC machines, but it seems to be a specific issue with Haas. I’ll need to study more and work on resolving this issue. Thank you for your response.