@StevenPaxman Here’s a direct link to the Dewalt 611 instruction manual:
The component that is impacted by run time is the motor brushes. The manual states:
For your continued safety and electrical protection, brush inspection and replacement on this tool should ONLY be performed by a DEWALT factory service center, a DEWALT authorized service center or other qualified service personnel.
At approximately 100 hours of use, take or send your tool to your nearest DEWALT factory service center or DEWALT authorized service center to be thoroughly cleaned and inspected. Have worn parts replaced and lubricated with fresh lubricant. Have new brushes installed, and test the tool for performance.
Any loss of power before the above maintenance check may indicate the need for immediate servicing of your tool. DO NOT CONTINUE TO OPERATE TOOL UNDER THIS CONDITION. If proper operating voltage is present, return your tool to the service station for immediate service.”
The brushes are considered a wear part by Dewalt and they sell replacements.
As for speed Dewalt publishes the no load speed on the 1-6 settings ranges from 16,000-27,000 RPM. For my X-Carve I keep it on the #1 setting and use the formula:
Feedrate=Spindle speed x chip thickness x number of flutes on the bit.
I adjust the depth per pass based on how smooth the Carve is. You are going for good bit engagement. Too slow will cause rubbing, create too much heat, and wear your bit. Too fast will cause the machine to move faster than the material can be removed by the cutting edges.
You want to be in the “Goldie locks Zone” not too slow and not too fast.
Last night I was using a this bit to cut letters from 2" thick insulation foam from Home Depot.
My depth per pass was 2", feed rate was 224, chip thickness was .007", and I had the Dewalt on #1.
Dust collection is really important on a long Carve. Sawdust can clump up and cause friction which generates heat. Enough sawdust can actually impede the motion of the machine if it gets impacted between the bit and material. This is a reason you want to monitor the machine and should consider the new Dust Control System if you plan on doing long carves frequently.
Long story short you should always monitor your machine. With properly maintained brushes, proper speeds and feeds, the Dewalt can handle a 5-6 hour carve safely.
The new X-Carve has a number of upgrades that make it perform better than the first version on long carves. These include:
X-Controller. Inside the box is a large heat sink that pulls heat away from the stepper drivers. The gshield doesn’t have a heat sink. It also has four stepper drivers that are 4amps each while the gshield has 3 drivers that are 1.5amps each. On the Y axis one of those is driving two stepper motors so you are only getting .75amps per motor. As the drivers on the gshield get hot on a 5 hour carve you could lose a step. On the X-controller given the increased power, increased number of drivers, and heat sink the chance of this happening is much lower.
On the first X-Carve the motor pulleys had set screws. On the new one they are permanently mounted. The set screws can be a source of skipped steps if they loosen due to vibration on a long Carve. On the new X-Carve they will not loosen.
The new X-Carve has locking hardware and eccentric spacers. On the 2015 X-Carve you can replace the hardware or use locktite to prevent it from loosening from vibration both options work.
The belt sleeves on the new X-Carve prevent the belts from slipping. With the 2015 version you need to make sure your belts are secure. You can use a zip tie in place of the belt sleeve to give extra security. It’s important to check the belts before starting a long carve.
Those are factors I would think about. I’d be interested in hearing from others who run long carves to hear if they have any other experiences to share.