Rotex RO 150, more like a bucking bronco

[unknown user]

I recently purchased a RO 150 and have been attempting to sand with it. I've noticed that thing will jump around for no reason, does not matter if it is on rotex or eccentric mode, tried using multiple grits. I've watched a few sanding videos from "Sedge" and I think I am supporting the rear correctly. I'm using a light touch to let the tool do the work.

Scenario 1 - Sanding 1x6 whitewood common softwood board from the orange place. Occasionally I get to a sopt where the sander will jump in a random direction. Clean area, no knot or other oddity in that section. Just going lightly with the grain.

Scenario 2 - Sanding 1x4 cedar in addition to the random jumping, occasionally i'll get an odd vibration which makes it feel like the sander is jumping / bouncing. Going back to the area adding a bit of pressure to the top of sander, it still feels like it wants to jump.

I've experienced this on several boards. Using 60, 80 & 120 grit. Adjusting speed from 6 to 4. Adjusted grip and pressure, nothing seems to work. Odd that it is just random.

What do y'all think im doing wrong?

 

[rvieceli]

You are most likely lifting an edge of the pad causing the opposite edge to dig in and set the sander out of control. It’s not hard to do even if you think you don’t.

For most sanders, it’s usually just mindless moving the thing around the piece. The Rotex sanders require a bit of concentration and attention.  Feed rate is also important. Not too fast and not too slow. You need to be in control of the sander all the time.

There’s a good video floating around with one of the Festool folks taking a piece of walnut from 80 to about 5000 on a rotary mode. Perhaps someone will post it

Ron

 

[rvieceli]

Found it!

Notice how he changes his stance when using the sander. Feet get wider and pulls the elbows in for better control.


Ron

 

[Alanbach]

Unless I missed it, no one has mentioned vac setting. You must reduce vac pressure for these sanders not to bite the workpiece and cause all that jumping around.

Secondly, years ago a woman from Germany with Festool taught me a little trick. Move your right arm under the vac hose and then move your arm back to grab the back of the sander. This causes the hose to wrap around your arm and makes it almost impossible for the sander to “heel” which is a number 1 cause of bucking.

 

[unknown user]

Unless I missed it, no one has mentioned vac setting.

I should have mentioned I did try with the suction set to minimum and even opened the port on the host connection.

 

[unknown user]

Found it!

Notice how he changes his stance when using the sander. Feet get wider and pulls the elbows in for better control.


Ron

Thank you! I tried adjusting a bit and it still jumps around, just not nearly as bad. I suppose I need to work on technique.
Worked on a new 1x4 cedar board running through the grits 60, 80, 120, wiping down between grit changes, and am noticing some swirles only near the top and bottom edges, the center appears to be nice and smoothe. I'm guessing user error is still an issue.

For additional troubleshooting, I sanded the same board with my ETS 125, no issue. It does like to jerk a little when going over a know but I would think that is normal given change of density in material.

 

[Sparktrician]

[member=80384]unknown user[/member],  have you ever used a 18-24" floor buffer?  You must carefully balance the buffer on its brush before grabbing the grip switch.  If you fail to balance the buffer, it will throw you across the room and sit there laughing at you.  The RO sanders are just like that.  You must balance them carefully before turning them on and keep them balanced while on the material.  As was noted earlier, the vacuum must be reduced.  Additionally, remember the phrase, "let the sander do the work".  Do not push the sander down into the material.  Let just the weight of the sander be all the pressure that is used.  Also, if you've not heard this before, it's best to hold the sander back at the power cord and vacuum hose connect points to give you a better fulcrum.  I hope this helps.

 

[unknown user]

[member=7493]Sparktrician[/member] Old memories from night shift at the grocery store 

Something I just noticed, these boards are cupping. I layed a straight edge across the grain and shined a light. In some places there seems to be gaps between .5-1mm. I'd have to run the sander again but I seems like the sander was jumping around the areas where the board was not completely flat.

 

[unknown user]

I found this video. Around the 30 minute mark he goes into technique for the rotex. Similar to what [member=3192]rvieceli[/member] posted.