Soft/Stable Movement for Parallelogram Mount with Wheel + Printhead

[mc_09]

TL;DR

Designing a parallelogram-mounted printhead that prints onto concrete. Adding a 6" polyurethane wheel to maintain a 0.25" gap and allow smooth movement. Looking for advice on how to prevent vibration/slamming when the wheel contacts the surface — considering springs or dampers, but open to better ideas. Need specific hardware recommendations and mounting tips.

I'm a design engineer, but admittedly not very experienced in mechanical systems. I'm currently working on a project where I need to add smooth, soft movement to a parallelogram mount that supports a printhead. I could really use some guidance from more mechanically savvy folks.

Project Overview:

• The printhead is mounted to a parallelogram-style arm and will be printing downward onto a sheet of concrete
• I'm planning to add a 6" diameter polyurethane wheel (labeled Part E in blue) to allow for a smooth transition as the printhead engages with the concrete surface
• The wheel should keep a consistent 0.25" gap between the printhead and the top of the concrete.
• The wheel will likely be mounted using an adapter plate (Part D in yellow), which connects to the back of the printhead and also supports the wheel

What I need help with:
1. Stabilizing the Mechanism:

• When the wheel hits the concrete and lifts the printhead, I want to avoid any rattling or vibration in the mounting.
• I'm worried about the printhead "slamming down" if the joints are loosened to allow adjustability.
• Ideally, I want some form of damping or soft control when the wheel engages with the concrete

2. Ideas I'm Considering:

• I was thinking of adding springs to absorb shock and provide controlled lift/drop but I’m unsure where to mount them or if this is the best option.
• Open to alternative suggestions

Please provide specific hardware suggestions – part numbers, Amazon/McMaster-Carr links, or product names.
I've labeled all the parts (A–E) for easier reference in the comments/discussion.
Thanks in advance! Happy to provide sketches or more details if needed.

EDIT: I uploaded a back side image a bit more refined

 

[jrmichler]

Search dashpots in McMaster-Carr. Dashpots are designed to slow something down for a soft landing. You will need some sort of bracket on your adaptor plate and another bracket on the fixed part of the assembly. If you sketch something up, and provide the drop distance and moving mass, we can help you select the right part. Here's a link: https://www.mcmaster.com/products/dashpots/.

For those not familiar with McMaster-Carr, they are an essential resource for anybody who is looking for information on small mechanical parts.